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Mar 2010

Volume 28, Issue 2, pp. L1-381

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X-ray photoelectron spectroscopy study of polyimide thin films with Ar cluster ion depth profiling

T. Miyayama, N. Sanada, M. Suzuki, J. S. Hammond, S.-Q. D. Si, and A. Takahara

J. Vac. Sci. Technol. A 28, L1 (2010); http://dx.doi.org/10.1116/1.3336242 (4 pages) | Cited 7 times

Online Publication Date: 11 March 2010

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X-ray photoelectron spectroscopy depth profiling of polyimide thin films on silicon substrates using an Ar cluster ion beam results in an extremely low degradation of the polyimide chemistry. In the range from 2.5 to 20 kV, a lower cluster ion energy produces a lower sputter induced damage to the polymer and results in an improved polyimide to silicon interface width. The sputtering rates of the polyimide are found to increase exponentially with an increase in the Ar cluster ion energy.
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79.60.Fr Polymers; organic compounds
82.80.Pv Electron spectroscopy (X-ray photoelectron (XPS), Auger electron spectroscopy (AES), etc.)
79.20.Rf Atomic, molecular, and ion beam impact and interactions with surfaces
61.82.Pv Polymers, organic compounds
82.65.+r Surface and interface chemistry; heterogeneous catalysis at surfaces
61.80.Jh Ion radiation effects
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Modifying the composition of hydrogen-terminated silicon nanoparticles synthesized in a nonthermal rf plasma

Jason Holm and Jeffrey T. Roberts

J. Vac. Sci. Technol. A 28, 161 (2010); http://dx.doi.org/10.1116/1.3276451 (9 pages) | Cited 3 times

Online Publication Date: 14 January 2010

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Hydrogen-terminated silicon nanoparticles were synthesized over a broad range of conditions in a continuous flow, nonthermal rf plasma. The effects of three operating parameters—rf power, reactor pressure, and hydrogen flow rate—were examined in terms of their effects on particle crystallinity, size, and surface composition. Silicon-hydrogen composition was characterized in situ by Fourier transform infrared spectrometry, and particle structural morphology was examined with a transmission electron microscope. Amorphous or crystalline particles could be synthesized by appropriately adjusting the operating parameters. Over the majority of settings examined, the minimum power required to produce discrete crystalline particles was ∼ 20–30 W. Depending on the parameter settings, particles also exhibited hydrogen coverage ranging from predominantly monohydride (SiH) functional groups to more complex compositions of higher hydrides. Particles with the highest proportion of surface SiH bonds were consistently synthesized in the smallest diameter (4 mm i.d.) tube reactor.
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81.16.-c Methods of micro- and nanofabrication and processing
81.07.Bc Nanocrystalline materials
78.67.Bf Nanocrystals, nanoparticles, and nanoclusters
52.77.-j Plasma applications
61.46.Df Structure of nanocrystals and nanoparticles ("colloidal" quantum dots but not gate-isolated embedded quantum dots)
78.30.Am Elemental semiconductors and insulators

Photoconduction in silicon rich oxide films obtained by low pressure chemical vapor deposition

J. A. Luna-López, M. Aceves-Mijares, J. Carrillo-López, and A. Morales-Sánchez

J. Vac. Sci. Technol. A 28, 170 (2010); http://dx.doi.org/10.1116/1.3276781 (5 pages) | Cited 1 time

Online Publication Date: 14 January 2010

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Photoconduction properties of silicon rich oxide (SRO) thin films were studied under different illumination conditions. In the past, Al/SRO/Si structures showed a high photocurrent in spite of the fact that an opaque Al layer was on the active area. In order to elucidate this observation, new Al/SRO/Si structures were tested, but this time they were also measured horizontally. SRO thin films were deposited on silicon wafers by low pressure chemical vapor deposition technique using SiH4 (silane) and N2O (nitrous oxide) as reactive gases at 700 °C. 1%–12% silicon excess was used. Structures with a single SRO layer and with a double layer were fabricated in order to have a barrier to isolate the silicon from the active SRO layer. The results show that all structures have a higher current when light shines on them than when they are in the dark. It is proposed that the photocurrent is produced in the SRO bulk, and an explanation for these observations is given.
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72.40.+w Photoconduction and photovoltaic effects
68.55.A- Nucleation and growth
73.40.Qv Metal-insulator-semiconductor structures (including semiconductor-to-insulator)
81.15.Gh Chemical vapor deposition (including plasma-enhanced CVD, MOCVD, ALD, etc.)

Coexistence of epitaxial Ta(111) and Ta(110) oriented magnetron sputtered thin film on c-cut sapphire

S. Gnanarajan, S. K. H. Lam, and A. Bendavid

J. Vac. Sci. Technol. A 28, 175 (2010); http://dx.doi.org/10.1116/1.3276801 (7 pages) | Cited 1 time

Online Publication Date: 14 January 2010

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Epitaxial Ta films were grown on c-cut and r-cut sapphire substrates using magnetron sputtering. X-ray diffraction measurements indicate that the Ta films grown on c-cut sapphire substrates have two different crystal orientations. Low vacuum base pressure produced films with the (111) plane parallel to the basal plane after an initial (110) plane growth phase, whereas high base pressure resulted in the growth of (110) plane parallel to the basal plane with three azimuthally oriented domains coexisting. The superconducting critical temperatures Tc of the films grown on c-cut substrates were found to be slightly higher than those for the films grown on r-cut substrates. The x-ray photoelectron spectroscopic data show oxygen content in the high vacuum base pressure deposited films and a difference in the valance band with different Ta surface planes.
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81.15.Cd Deposition by sputtering
79.60.Bm Clean metal, semiconductor, and insulator surfaces
62.50.-p High-pressure effects in solids and liquids
74.78.-w Superconducting films and low-dimensional structures
74.70.Ad Metals; alloys and binary compounds (including A15, MgB2, etc.)
74.62.Fj Effects of pressure

Comparison of compressive and tensile relaxed composition-graded GaAsP and (Al)InGaP substrates

M. J. Mori, S. T. Boles, and E. A. Fitzgerald

J. Vac. Sci. Technol. A 28, 182 (2010); http://dx.doi.org/10.1116/1.3290762 (7 pages) | Cited 6 times

Online Publication Date: 14 January 2010

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The authors present a comparison of metal organic chemical vapor deposition grown compositionally graded metamorphic buffers, which enable virtual substrates with very high quality crystal lattices with lattice constants from 5.45 to 5.65 Å (threading dislocation density, ρt, around 104 cm−2). The structures, grown on GaP or GaAs, consist of graded In-fraction InGaP and AlInGaP or graded P-fraction GaAsP. They show that surface roughness and locally strained regions of phase separation (branch defects) limit misfit dislocation glide velocity and escalate threading dislocation density. High surface roughness and branch defects in (Al)InGaP lead to the lowest quality virtual substrates we observed, with ρt of around 3×106 cm−2. In contrast, graded mixed-anion films of GaAsP avoid branch defects and minimize surface roughness, giving superior defect densities, as low as 104 cm−2 at useful lattice constants halfway between that of Si and Ge. Tensile graded GaAs1−zPz layers yield the smoothest films (0.78 nm rms in a 5 μm scan) with the lowest defect densities but are subject to cracking when graded beyond z = 0.5 with a graded layer thickness of <10 μm. Compressive graded GaAsP yields excellent ρt values (3.3×105 cm−2) with very thin buffers (1.3 μm). The accelerated grade rate of the compressive buffers increases crosshatch roughness, which along with the higher defect density of GaP substrates, accounts for the higher defect density compared to tensile GaAsP on GaAs substrates.
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81.15.Gh Chemical vapor deposition (including plasma-enhanced CVD, MOCVD, ALD, etc.)
82.33.Ya Chemistry of MOCVD and other vapor deposition methods
61.72.Ff Direct observation of dislocations and other defects (etch pits, decoration, electron microscopy, x-ray topography, etc.)
61.66.-f Structure of specific crystalline solids
68.35.B- Structure of clean surfaces (and surface reconstruction)
68.55.-a Thin film structure and morphology

Fast and smooth etching of indium tin oxides in BCl3/Cl2 inductively coupled plasmas

H. B. Andagana and X. A. Cao

J. Vac. Sci. Technol. A 28, 189 (2010); http://dx.doi.org/10.1116/1.3280919 (4 pages) | Cited 1 time

Online Publication Date: 19 January 2010

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The etching characteristics of evaporation-deposited indium tin oxide (ITO) films in BCl3/Cl2 inductively coupled plasmas have been studied. High etch rates >200 nm/min were obtained at large BCl3/Cl2 gas flow ratios and high rf chuck powers, suggesting that the etching process is limited by sputter desorption of InClx and SnClx compounds. The addition of a small amount of CF4, which acts as reducing agent, increased the etch rate by 30% and resulted in very smooth etched surfaces. It has also been found that the material crystallinity has a pronounced influence on ITO etch rate. ITO films annealed at 500 °C exhibited the maximum etch resistance.
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81.65.Cf Surface cleaning, etching, patterning
52.77.Bn Etching and cleaning
81.40.Ef Cold working, work hardening; annealing, post-deformation annealing, quenching, tempering recovery, and crystallization
68.43.Nr Desorption kinetics
81.15.-z Methods of deposition of films and coatings; film growth and epitaxy

Influence of the magnetron on the growth of aluminum nitride thin films deposited by reactive sputtering

G. F. Iriarte

J. Vac. Sci. Technol. A 28, 193 (2010); http://dx.doi.org/10.1116/1.3280174 (6 pages) | Cited 1 time

Online Publication Date: 19 January 2010

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Aluminum nitride (AlN) thin films deposited on high-vacuum systems without substrate heating generally exhibit a poor degree of c-axis orientation. This is due to the nonequilibrium conditions existing between the energy of the sputtered particles and the energy at the substrate surface. The application of substrate bias or substrate temperature is known to improve the adatom mobility by delivering energy to the substrate; both are hence well-established crystal growth promoting factors. It is well known that low sputtering pressures can be used as a parameter improving the growth of highly c-axis oriented aluminum nitride films at room temperature even without applying bias voltage to the substrate. Generally, the use of high pressures implies thermalization of particles within the gas phase and is considered to increase the energy gap between these and the substrate surface. However, in later experiments we have learned that the use of high processing pressures does not necessarily implies a detriment of crystallographic orientation in the films. By measuring (for the first time to the author’s knowledge) the full width at half maximum value of the rocking curve of the 0002-AlN peak at several positions along the 100 mm diameter (100)-silicon wafers on which aluminum nitride thin films were deposited by reactive sputtering, a new effect was observed. Under certain processing conditions, the growth of the AlN thin films is influenced by the target magnetron. More precisely, their degree of c-axis orientation varies at wafer areas locally coincident under the target magnetron. This effect should be considered, especially where large area substrates are employed such as in silicon wafer foundry manufacturing processes.
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68.55.ag Semiconductors
81.15.Cd Deposition by sputtering
68.43.-h Chemisorption/physisorption: adsorbates on surfaces
62.50.-p High-pressure effects in solids and liquids
71.20.Nr Semiconductor compounds

In situ observation of change in surface atomic arrangement of Sc–O/W(100) system during phase transition at high temperature

T. Nagatomi, Y. Nakanishi, and Y. Takai

J. Vac. Sci. Technol. A 28, 199 (2010); http://dx.doi.org/10.1116/1.3281475 (8 pages)

Online Publication Date: 19 January 2010

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In situ observation of low-energy electron diffraction (LEED) patterns during the phase transition of the Sc–O/W(100) surface at high temperature was performed to investigate the correlation between the surface atomic arrangement, coverage of surface atoms, and work function during the phase transition. For this purpose, a LEED system enabling LEED observation at high temperatures of 1500–1900 K was developed. The temperature dependence of the intensity of diffraction spots was measured, and the Debye temperatures were estimated for relevant surfaces. The changes in the intensity of diffraction spots during the phase transition were found to correlate with the changes in the coverage of surface atoms and work function. The present results revealed that surface phenomena such as surface segregation, oxidation, oxygen desorption, and diffusion of ScO complexes predominate the surface properties of the Sc–O/W(100) system.
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64.70.K- Solid-solid transitions
61.05.jh Low-energy electron diffraction (LEED) and reflection high-energy electron diffraction (RHEED)
81.65.Mq Oxidation
68.35.Dv Composition, segregation; defects and impurities
66.30.H- Self-diffusion and ionic conduction in nonmetals
82.65.+r Surface and interface chemistry; heterogeneous catalysis at surfaces

Oxygen plasma damage to blanket and patterned ultralow-κ surfaces

J. Bao, H. Shi, H. Huang, P. S. Ho, M. L. McSwiney, M. D. Goodner, M. Moinpour, and G. M. Kloster

J. Vac. Sci. Technol. A 28, 207 (2010); http://dx.doi.org/10.1116/1.3281525 (9 pages) | Cited 3 times

Online Publication Date: 19 January 2010

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Oxygen plasma damage to blanket and patterned ultralow-κ (ULK) dielectric surfaces was investigated by examining the effect of plasma species and dielectric materials. Blanket ULK films and patterned structures were treated by O2 plasma in a remote plasma chamber where the ions and radicals from the plasma source can be separately controlled to study their respective roles in the damage process. The plasma damage was characterized by angle resolved x-ray photoelectron spectroscopy, x-ray reflectivity, and Fourier transform infrared spectroscopy. Studies of the angle dependence of oxygen plasma damage to blanket ULK films indicated that damage by ions was anisotropic while that by radicals was isotropic. Ions were found to play an important role in assisting carbon depletion by oxygen radicals on the blanket film surface. More plasma damage was observed with increasing porosity in ultralow-κ films. Probable reaction paths were proposed by analyzing the reaction by-products. Plasma damage to the sidewall of low-κ trenches was examined by electron energy loss (EELS) analysis. The depletion depth of carbon was found to be related to the penetration of radical species into the porous dielectric and the distribution at the sidewall and trench bottom was affected by the trench pattern geometry, i.e., the aspect ratio, which can be correlated with the electron potential distribution and subsequent trajectory of ions. Vapor silylation was applied for dielectric recovery of trench structure and the result was examined by EELS. The trimethylchlorosilane was found to be effective for recovery of the sidewall carbon loss. The recovery was better for loss induced by radical O2 than by hybrid O2 and the difference was attributed to the surface densification by ions limiting the mass transport of vapor chemicals.
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77.55.Bh Low-permittivity dielectric films
79.60.Bm Clean metal, semiconductor, and insulator surfaces
52.50.Dg Plasma sources
78.20.Ci Optical constants (including refractive index, complex dielectric constant, absorption, reflection and transmission coefficients, emissivity)
79.20.Uv Electron energy loss spectroscopy
78.30.Hv Other nonmetallic inorganics

Rapid thermal annealing of ZnO thin films grown at room temperature

Young Rae Jang, Keon-Ho Yoo, and Seung Min Park

J. Vac. Sci. Technol. A 28, 216 (2010); http://dx.doi.org/10.1116/1.3290759 (4 pages) | Cited 6 times

Online Publication Date: 19 January 2010

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The authors successfully obtained high quality ZnO thin films by growing them at room temperature (RT) and postannealing by rapid thermal annealing (RTA). The thin films were grown by pulsed laser deposition on Si (100) substrates at RT, and RTA was performed under various temperatures and ambient conditions. Based on the UV emission to visible emission ratio in RT photoluminescence (PL) spectra, the optimum film was obtained at annealing temperature ∼ 700 °C in an ambient of Ar, N2, or O2 at 0.1 Torr, while the optimum annealing temperature was above 1100 °C in the air ambient at atmospheric pressure. The morphology and structure of the films in different RTA conditions were investigated by using field emission scanning electron microscopy and grazing incidence x-ray diffraction, and were discussed in conjunction with the PL data.
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61.72.Cc Kinetics of defect formation and annealing
81.15.Fg Pulsed laser ablation deposition
68.55.ag Semiconductors

Experiences from nonevaporable getter-coated vacuum chambers at the MAX II synchrotron light source

A. Hansson, E. Wallén, M. Berglund, R. Kersevan, and M. Hahn

J. Vac. Sci. Technol. A 28, 220 (2010); http://dx.doi.org/10.1116/1.3281432 (6 pages)

Online Publication Date: 20 January 2010

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Vacuum chambers coated with nonevaporable getter (NEG) materials have been used in straight sections of synchrotron light sources for the past 10 years. The MAX II storage ring, where four NEG-coated insertion device vacuum chambers and three NEG-coated dipole vacuum chambers have been installed, is the first synchrotron light source to also use NEG-coated dipole vacuum chambers. In connection with the installation of the latest two NEG-coated dipole chambers in April 2009, the evolution of the pressure and lifetime-limiting effects in MAX II has been determined from measurements with movable scrapers. The results have been compared with results from scraper measurements done in 2003, before any NEG-coated vacuum chambers were installed in the storage ring. Less than three months after the installation of the latest dipole chambers the vacuum system in MAX II was performing well with a pressure already lower than the pressure measured in 2003.
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29.20.db Storage rings and colliders
29.20.dk Synchrotrons
29.27.-a Beams in particle accelerators
41.75.Fr Electron and positron beams
07.30.Kf Vacuum chambers, auxiliary apparatus, and materials

Etch mechanism of In2O3 and SnO2 thin films in HBr-based inductively coupled plasmas

Kwang-Ho Kwon, Alexander Efremov, Moonkeun Kim, Nam Ki Min, Jaehwa Jeong, MunPyo Hong, and Kwangsoo Kim

J. Vac. Sci. Technol. A 28, 226 (2010); http://dx.doi.org/10.1116/1.3294712 (6 pages)

Online Publication Date: 21 January 2010

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The investigations of etch characteristics and mechanisms for both In2O3 and SnO2 thin films in the HBr-based inductively coupled plasmas were carried out. The etch rates were measured as functions of gas mixing ratio (0%–100% Ar), input power (400–700 W), and gas pressure (4–10 mTorr) at fixed bias power (200 W) and gas flow rate [40 SCCM (SCCM denotes cubic centimeter per minute at STP)]. Plasma parameters and composition were determined using a combination of plasma diagnostics by double Langmuir probe and global (zero-dimensional) plasma model. The correlations between the behaviors of etch rates and fluxes of plasma active species allow one to infer both In2O3 and SnO2 etch mechanisms as the transitional regime of ion-assisted chemical reaction, which is controlled by neutral and charged fluxes together.
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81.65.Cf Surface cleaning, etching, patterning
52.77.-j Plasma applications
52.70.Ds Electric and magnetic measurements

Measurement of adsorption isotherms in the gas phase on native titanium dioxide surfaces by quartz crystal microbalance technique

A. Marx and W. Langel

J. Vac. Sci. Technol. A 28, 232 (2010); http://dx.doi.org/10.1116/1.3294716 (6 pages) | Cited 1 time

Online Publication Date: 22 January 2010

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The surface of air exposed titanium dioxide is known to be significantly covered with hydrocarbons, which modify the properties of titanium based materials such as used for human implants. The n alcohols are among the most important organic contaminants in the ambient atmosphere with typical partial pressures of 5×10−3 Pa [50 ppb (parts per 109)]. The authors measured adsorption isotherms of H2O and n alcohols up to butanol in the pressure range of 10−6–1000 Pa in a UHV chamber with a quartz crystal microbalance. The crystals were covered by physical vapor deposition titanium layers passivated in oxygen atmosphere. Significant adsorption was observed in the pressure range equivalent to atmospheric contamination. The data were fitted by sums of Brunauer, Emmett and Teller (BET) isotherms with a spectrum of adsorption energies ranging from the evaporation enthalpies of about 40 to 100 kJ/mol. Due to the high energy contributions, significant coverage of TiO2 by n alcohols is already possible at their typical partial pressures in air.
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68.43.Mn Adsorption kinetics
64.70.fm Thermodynamics studies of evaporation and condensation

Metal-organic chemical vapor deposition of aluminum oxide thin films via pyrolysis of dimethylaluminum isopropoxide

Benjamin W. Schmidt, William J. Sweet, Eric J. Bierschenk, Cameron K. Gren, Timothy P. Hanusa, and Bridget R. Rogers

J. Vac. Sci. Technol. A 28, 238 (2010); http://dx.doi.org/10.1116/1.3294718 (6 pages) | Cited 1 time

Online Publication Date: 22 January 2010

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Metal-organic chemical vapor deposited aluminum oxide films were produced via pyrolysis of dimethylaluminum isopropoxide in a high vacuum reaction chamber in the 417–659 °C temperature range. Deposited films contained aluminum, oxygen, and carbon, and the carbon-to-aluminum ratio increased with increased deposition temperature. Aluminum-carbon bonding was observed in films deposited at 659 °C by x-ray photoelectron spectroscopy, but not in films deposited at 417 °C. The apparent activation energy in the surface reaction controlled regime was 91 kJ/mol. The O/Al and C/Al ratios in the deposited films were greater and less than, respectively, the ratios predicted by the stoichiometry of the precursor. Flux analysis of the deposition process suggested that the observed film stoichiometries could be explained by the participation of oxygen-containing background gases present in the reactor at its base pressure.
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68.55.A- Nucleation and growth
81.15.Gh Chemical vapor deposition (including plasma-enhanced CVD, MOCVD, ALD, etc.)
82.30.Lp Decomposition reactions (pyrolysis, dissociation, and fragmentation)
82.80.Pv Electron spectroscopy (X-ray photoelectron (XPS), Auger electron spectroscopy (AES), etc.)
61.66.Bi Elemental solids
61.66.Dk Alloys

Tribological and mechanical properties of nanocrystalline-TiC/a-C nanocomposite thin films

J. Musil, P. Novák, R. Čerstvý, and Z. Soukup

J. Vac. Sci. Technol. A 28, 244 (2010); http://dx.doi.org/10.1116/1.3294717 (6 pages) | Cited 6 times

Online Publication Date: 27 January 2010

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This article reports on interrelationships between x-ray structure, mechanical properties, coefficient of friction μ, and wear coefficient k of ∼ 3000 m thick nc-TiC/a-C nanocomposite films sputtered using unbalanced magnetron from a composed C/Ti target (∅ = 100 mm); here nc and a denotes the nanocrystalline and amorphous phase, respectively. It is shown that (1) μ and k of the nc-TiC/a-C nanocomposite film strongly depend not only on its hardness H but also on its effective Young’s modulus E∗ = E/(1−ν2); here ν is the Poisson s ratio, (2) the nc-TiC/a-C nanocomposite films with C/Ti>1.5 and the ratio H3/E∗2 (characterizing the resistance of film to plastic deformation) ranging from ∼ 0.2 to ∼ 0.3 exhibit the lowest values of μ and k, and (3) μ increases with increasing load L of the testing ball. The main result of this investigation is the finding that the achievement of the lowest value E∗ at a given value of H is of key importance in the formation of films with the lowest values of coefficient of friction μ and wear coefficient k.
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68.60.-p Physical properties of thin films, nonelectronic
81.40.Jj Elasticity and anelasticity, stress-strain relations
81.40.Lm Deformation, plasticity, and creep
81.40.Pq Friction, lubrication, and wear
62.23.Pq Composites (nanosystems embedded in a larger structure)
81.07.-b Nanoscale materials and structures: fabrication and characterization

Etching of SiO2 in C4F8/Ar plasmas. I. Numeric kinetics modeling and Monte Carlo simulation in a three-dimensional profile simulator

Wei Guo and Herbert H. Sawin

J. Vac. Sci. Technol. A 28, 250 (2010); http://dx.doi.org/10.1116/1.3290760 (9 pages) | Cited 4 times

Online Publication Date: 2 February 2010

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In this article, the etching kinetics of SiO2 in C4F8/Ar plasmas was modeled and calculated in a three-dimensional (3D) Monte Carlo profile simulator. The kinetics models were developed using the numerical integration of the rate equations with mass balance constraints for a planar surface and iteratively solved to determine the rate coefficients by least squares regression. The assumptions including the well mixed surface layer and equal reactivity of similar species were used to simplify the reaction scheme. Initially, etching yields of SiO2 in multiple CFx+ beam scattering experiments were fitted to determine the rate coefficients associated with ion-induced etching and sticking coefficients of the neutrals. The reaction set and the initially fitted rate coefficients were then adjusted using numerical integration of the set of rate equations to steady state and least squares regression of the model coefficients to fit SiO2 etching in C4F8/Ar gas plasma. The etching yield was modeled over a wide range of neutral-to-ion flux ratios, ion energies, and ion bombardment angles with good agreement with the experimental results. The surface composition was modeled to evaluate the fundamental reaction set and the parameters such as the sticking probability. The kinetics was then incorporated into the 3D cell-based profile simulator with Monte Carlo flux calculation. Similar etching yields were obtained for SiO2 planar surfaces using either the profile simulator or the numerical integration of the set of rate equations over a wide range of plasma conditions and for off-normal ion bombardment, thereby verifying the Monte Carlo solution of the set of rate equations within the 3D profile simulator.
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61.43.Bn Structural modeling: serial-addition models, computer simulation
81.65.Cf Surface cleaning, etching, patterning
68.35.Dv Composition, segregation; defects and impurities
02.70.Rr General statistical methods

Etching of SiO2 in C4F8/Ar plasmas. II. Simulation of surface roughening and local polymerization

Wei Guo and Herbert H. Sawin

J. Vac. Sci. Technol. A 28, 259 (2010); http://dx.doi.org/10.1116/1.3290766 (12 pages) | Cited 2 times

Online Publication Date: 2 February 2010

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In this article the SiO2 surface morphology in C4F8/Ar plasma etching was simulated using a three-dimensional Monte Carlo profile simulator. The complete surface kinetics model was previously developed, incorporated, and tested for accuracy within the simulator as reported in the companion paper [ Guo et al., J. Vac. Sci. Technol. A 28, 250 (2010) ]. The simulated planar surface roughening at ion incidence angles from 0° to 82° and flux ratios of 5 and 20 were compared to the experimental results that were etched in reactive ion beam experiments and characterized by atomic force microscopy. Distinctively different patterns were obtained with varying ion incidence angle. The surface remained smooth at normal ion incidence up to 45° off-normal and transformed to striations perpendicular to the ion beam at 60°–75°. The transverse striation was explained with the local curvature dependence based on the sputtering theory. The surface became smooth again at grazing angle of 82°. The simulated transition of surface morphology was qualitatively consistent with the experimental observations. Surface composition was mapped out to disclose the roughening mechanism. At low flux ratio, the surface composition indicated the formation of polymer islands around the roughened area. Greater polymer formation on the shadowed edge of features and enhanced the roughening, in agreement with the micromasking mechanism proposed previously based on other experimental observations. At high flux ratio, the simulation showed a higher extent of polymerization with a uniform distribution. The surface passivation together with other factors led to a smooth surface. The simulated polymer distribution provided insights to the surface roughening process.
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52.77.Bn Etching and cleaning
81.65.Cf Surface cleaning, etching, patterning
82.35.-x Polymers: properties; reactions; polymerization
68.35.B- Structure of clean surfaces (and surface reconstruction)
68.37.Ps Atomic force microscopy (AFM)

Sr flux stability against oxidation in oxide-molecular-beam-epitaxy environment: Flux, geometry, and pressure dependence

Y. S. Kim, Namrata Bansal, Carlos Chaparro, Heiko Gross, and Seongshik Oh

J. Vac. Sci. Technol. A 28, 271 (2010); http://dx.doi.org/10.1116/1.3298880 (6 pages) | Cited 4 times

Online Publication Date: 2 February 2010

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Maintaining stable fluxes for multiple source elements is a challenging task when the source materials have significantly different oxygen affinities in a complex-oxide molecular-beam-epitaxy (MBE) environment. Considering that Sr is one of the most easily oxidized and widely used elements in various complex oxides, we took Sr as a probe to investigate the flux-stability problem in a number of different conditions. Source oxidation was less for higher flux, extended port geometry, and unmelted source shape. The extended port geometry also eliminated the flux transient after opening a source shutter as observed in the standard port. We also found that the source oxidation occurred more easily on the crucible wall than on the surface of the source material. Atomic oxygen, in spite of its stronger oxidation effectiveness, did not make any difference in source oxidation as compared to molecular oxygen in this geometry. Our results may provide a guide for solutions to the source oxidation problem in oxide-MBE system.
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81.15.Hi Molecular, atomic, ion, and chemical beam epitaxy
81.65.Mq Oxidation
81.10.Dn Growth from solutions

Etching studies of silica glasses in SF6/Ar inductively coupled plasmas: Implications for microfluidic devices fabrication

L. Lallement, C. Gosse, C. Cardinaud, M.-C. Peignon-Fernandez, and A. Rhallabi

J. Vac. Sci. Technol. A 28, 277 (2010); http://dx.doi.org/10.1116/1.3298875 (10 pages) | Cited 4 times

Online Publication Date: 2 February 2010

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To fabricate microlaboratories, commercially available silica glasses represent a good alternative to the expensive quartz or fused silica substrates. Therefore, the authors have here investigated the behavior of four of them—Vycor, Pyrex, D263, and AF45—in SF6 and SF6/Ar inductively coupled plasmas. Using Vycor, a material close to pure SiO2, as a reference, they demonstrated that the etch rate negatively correlates with the global content in metallic oxides. However, no such clear trend was found for the surface roughness and they hypothesize that the large asperities (>500 nm) sometimes observed might be due to local variation in the glass surface composition. Furthermore, investigations on the influence of the plasma conditions (i.e., source power, dc self-bias, gas mixture, and pressure) on the etch rate, surface chemistry, and surface morphology, as well as positive ion current and fluorine concentration measurements, enable them to unravel an ion enhanced chemical etching mechanism, where stronger ion assistance is needed when more metallic oxides are present. By increasing the ion to neutral flux ratio, they consequently could, for all the materials, reduce the surface roughness to less than 5 nm while maintaining etch rates around 150 nm/min. These conditions have further been used to optimize pattern transfer experiments.
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81.65.Cf Surface cleaning, etching, patterning
52.77.Bn Etching and cleaning
81.16.-c Methods of micro- and nanofabrication and processing
68.35.bj Amorphous semiconductors, glasses
68.35.Ct Interface structure and roughness

Surface-charging effect of capacitively coupled plasmas driven by combined dc/rf sources

Quan-Zhi Zhang, Wei Jiang, Shu-Xia Zhao, and You-Nian Wang

J. Vac. Sci. Technol. A 28, 287 (2010); http://dx.doi.org/10.1116/1.3305537 (6 pages) | Cited 4 times

Online Publication Date: 5 February 2010

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The surface charging effect in hybrid dc/rf capacitively coupled plasmas is investigated by particle-in-cell/Monte Carlo simulations with an equivalent-circuit module. When the thickness of the dielectric is fixed, the self-bias dc voltage induced by the charge accumulated in the dielectric first increases and then decreases with increased dc voltage. The ratio of electron-to-ion charge flowing into the dielectric increases from −1.195 to −2.582. Increasing the dc voltage results in the number of high-energy ions bombarding the dielectric decreasing. The average electron energy at the dielectric decreases to the minimum value at the biggest self-bias dc voltage in the beginning and then rapidly increases. While fixing the dc source with thickening the dielectric, the self-bias dc voltage rises, but the charge ratio decreases. The average electron energy decreases monotonically and the ion-energy distributions (IEDs) at the dielectric are shifted toward the higher energy region. The results imply that the applied dc voltage may increase the electron flux and average energy to the dielectric at the cost of reduced etching rate, which may mitigate the notching effect. The applied dc voltage can also serve as a tool to modulate the ion IEDs. At the same time, a thicker dielectric will require higher applied dc voltage.
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73.40.-c Electronic transport in interface structures
52.65.Pp Monte Carlo methods
77.84.-s Dielectric, piezoelectric, ferroelectric, and antiferroelectric materials

Amorphization of Si(100) by Ar+-ion bombardment studied with spectroscopic and time-resolved second-harmonic generation

P. M. Gevers, J. J. H. Gielis, H. C. W. Beijerinck, M. C. M. van de Sanden, and W. M. M. Kessels

J. Vac. Sci. Technol. A 28, 293 (2010); http://dx.doi.org/10.1116/1.3305812 (9 pages) | Cited 2 times

Online Publication Date: 5 February 2010

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The surface and interface sensitive technique of optical second-harmonic generation (SHG) has been applied spectroscopically and time-resolved before, during, and after low energy (70–1000 eV) Ar+-ion bombardment of H-terminated Si(100). The photon energy range of the fundamental radiation was ℏω = 0.76–1.14 eV. Besides physical sputtering of the silicon, ion bombardment of crystalline silicon damages and amorphizes the top layer of the sample and thereby creates a layered structure of amorphous silicon (a-Si) on crystalline silicon. The SHG radiation, which is sensitive to the Ar+-ion flux, ion energy, and the presence of reactive gas species, originates from the top surface of the sample and from the interface between a-Si and c-Si. From a comparison with the SHG results obtained at a fundamental radiation of ℏω = 1.3–1.7 eV, it is concluded that the SHG radiation during and after creation of this structure dominantly originates from the tails of electronic transitions in the E0′/E1 energy region rather than from silicon dangling bonds.
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42.65.Ky Frequency conversion; harmonic generation, including higher-order harmonic generation
61.43.-j Disordered solids
71.55.-i Impurity and defect levels
61.80.Jh Ion radiation effects
61.82.Fk Semiconductors
81.05.Cy Elemental semiconductors

TaN metal gate etch mechanisms in BCl3-based plasmas

Denis Shamiryan, Andrey Danila, Mikhail R. Baklanov, and Werner Boullart

J. Vac. Sci. Technol. A 28, 302 (2010); http://dx.doi.org/10.1116/1.3280170 (4 pages)

Online Publication Date: 9 February 2010

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TaN is a potential candidate for metal gates. BCl3-based plasma is used to pattern metal gates because it has a high selectivity over Si substrate and capable of etching metal oxides (native oxides on metal gates and high-k dielectrics). During metal gate etch in inductively coupled plasma reactor, the authors found that the TaN metal gate profile depends on the composition of BCl3-based plasma. Pure BCl3 results in an undercut of TaN. The undercut can be avoided by addition of 5% O2, further increase in O2 concentration (until 10%) does not change the TaN profile. When N2 is added to BCl3 plasma, first the undercut disappears (at about 6% of N2) and then a slope appears as N2 concentration increases further (toward 10%). It was found that the profile is controlled by a film deposited from BCl3-based plasma. In the case of pure BCl3 plasma, the film consists of B (50%), Cl (30%), and O (20%). When 5% of O2 is added, no film is observed, but strong BO and BO2 peaks appear in the plasma emission spectra. When 5% N2 is added to the BCl3 plasma, again a film is deposited, but it contains less Cl (18%). Based on our research, the authors propose the following etch mechanism to explain the observed profile notching/footing. In pure BCl3 plasma, a B- and Cl-containing film is deposited on the sidewalls of the gate. Cl from this film will react with TaN producing an undercut. When O2 is added, no film is formed and the TaN profile is straight as B apparently reacts with O in the gas phase, forming volatile BOx species. Further increase of O2 content does not change the profile as no film is formed. When N2 is added to BCl3, a film is formed but in this case N replaces Cl and the film becomes passivating leading to a straight TaN profile. As more N2 is added, the film passivates TaN more efficiently leading to a sloped profile.
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52.77.Bn Etching and cleaning
81.65.Cf Surface cleaning, etching, patterning
52.77.Dq Plasma-based ion implantation and deposition
81.15.Jj Ion and electron beam-assisted deposition; ion plating
68.55.A- Nucleation and growth

Quantum turbulence at room temperature

C. Llaguno and A. Muriel

J. Vac. Sci. Technol. A 28, 306 (2010); http://dx.doi.org/10.1116/1.3294720 (3 pages)

Online Publication Date: 9 February 2010

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The authors explain the multilevel turbulent nitrogen data of a Hinkle pipe experiment at 25 °C using the Muriel molecular theory of turbulence and the quantum rotational energy spectrum of nitrogen. As a result, they generalize the scope of quantum turbulence at superfluid helium temperature to include room temperature turbulence data for nitrogen.
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05.30.Ch Quantum ensemble theory
03.65.-w Quantum mechanics
47.27.-i Turbulent flows

Self-bias voltage diagnostics for the amorphous-to-microcrystalline transition in a-Si:H under a hydrogen-plasma treatment

A. Hadjadj, N. Pham, P. Roca i Cabarrocas, and O. Jbara

J. Vac. Sci. Technol. A 28, 309 (2010); http://dx.doi.org/10.1116/1.3305719 (5 pages)

Online Publication Date: 18 February 2010

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The authors demonstrate the possibility of using self-bias voltage on the radio-frequency electrode of a capacitively coupled deposition system as a diagnostic tool to detect the amorphous-to-microcrystalline silicon transition during the exposure of a-Si:H thin films to a hydrogen plasma. This is achieved by combining self-bias voltage (Vdc) and kinetic-ellipsometry measurements, which provide real-time information on the film properties. On intrinsic and n-type a-Si:H films, the hydrogen-plasma exposure results in the formation of a hydrogen-modified layer, which is accompanied with a decrease in the absolute values of Vdc, until a plateau corresponding to the nucleation and the growth of the microcrystalline layer occurs. On p-type a-Si:H, the amorphous-to-microcrystalline transition is characterized by a rapid increase in the absolute values of Vdc. This particular trend is ascribed to the effects of boron on both the solid and plasma phases.
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64.70.kg Semiconductors
68.55.ag Semiconductors
81.65.-b Surface treatments
52.77.-j Plasma applications
78.66.-w Optical properties of specific thin films

Combinatorial characterization of transparent conductive properties of Ga-doped ZnO films cosputtered from electron cyclotron resonance and rf magnetron plasma sources

Housei Akazawa

J. Vac. Sci. Technol. A 28, 314 (2010); http://dx.doi.org/10.1116/1.3328053 (8 pages) | Cited 7 times

Online Publication Date: 24 February 2010

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The simultaneous sputtering of ZnO and Ga2O3 by electron cyclotron resonance and rf magnetron plasma sources produced Ga-doped ZnO (GZO) films with continuously varying Ga concentration over the substrate surface. Combinatorial evaluation of electrical and optical properties of GZO film grown on silica glass substrate without heater annealing enabled identification of minimum resistivity (0.5 mΩ cm) at a Ga2O3 content of 5.5 wt % with an optical transmittance of 90% in the visible wavelength. The monotonically decreasing mobility that was associated with increasing carrier concentration as Ga2O3 content was increased indicated that conduction was governed by ionized impurity scattering. Above the critical Ga2O3 content (6 wt %), carrier concentration decreased since excess Ga atoms that were incorporated beyond the solubility limit at Zn sites hindered large crystalline domains from forming. The ZnO (002) x-ray diffraction peak was suppressed and peaks assigned to Ga2O3 were observed at high Ga2O3 content. The optimum Ga2O3 content shifted to 3.5 wt % at a deposition temperature of 200 °C and 2.5 wt % at 300 °C, and the minimum resistivity was further decreased to 0.28 mΩ cm at 200 °C. However, the resistivities at these elevated temperatures were incredibly high both at the lower and higher side of the optimum Ga2O3 content.
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81.15.Cd Deposition by sputtering
66.70.-f Nonelectronic thermal conduction and heat-pulse propagation in solids; thermal waves
81.05.Dz II-VI semiconductors
61.72.uj III-V and II-VI semiconductors
78.66.Hf II-VI semiconductors
73.61.Ga II-VI semiconductors
72.80.Ey III-V and II-VI semiconductors

Plasma kinetics of Ar/O2 magnetron discharge by two-dimensional multifluid modeling

C. Costin, T. M. Minea, G. Popa, and G. Gousset

J. Vac. Sci. Technol. A 28, 322 (2010); http://dx.doi.org/10.1116/1.3332583 (7 pages)

Online Publication Date: 4 March 2010

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Multifluid two-dimensional model was developed to describe the plasma kinetics of the direct current Ar/O2 magnetron, coupling two modules: charged particles and neutrals. The first module deals with three positive ions—Ar+, O2+, and O+—and two negative species—e− and O−—treated by the moments of Boltzmann’s equation. The second one follows seven neutral species (Ar, O2, O, O3, and related metastables) by the multicomponent diffusion technique. The two modules are self-consistently coupled by the mass conservation and kinetic coefficients taking into account more than 100 volume reactions. The steady state is obtained when the overall convergence is achieved. Calculations for 10% O2 in Ar/O2 mixture at 2.67 and 4 Pa show that the oxygen excited species are mainly created by electron collisions in the negative glow of the discharge. Decreasing the pressure down to 0.67 Pa, the model reveals the nonlocal behavior of the reactive species. The density gradient of O2 ground state is reversed with respect to all gradients of the other reactive species, since the latter ones originate from the molecular ground state of oxygen. It is also found that the wall reactions drastically modify the space gradient of neutral reactive species, at least as much as the pressure, even if the discharge operates in compound mode.
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52.25.Dg Plasma kinetic equations
52.25.Fi Transport properties
52.40.Hf Plasma-material interactions; boundary layer effects
52.65.-y Plasma simulation
52.80.Hc Glow; corona
82.33.Xj Plasma reactions (including flowing afterglow and electric discharges)

Effects of working pressure on physical properties of tungsten-oxide thin films sputtered from oxide target

I. Riech, M. Acosta, J. L. Peña, and P. Bartolo-Pérez

J. Vac. Sci. Technol. A 28, 329 (2010); http://dx.doi.org/10.1116/1.3333423 (5 pages) | Cited 1 time

Online Publication Date: 4 March 2010

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Tungsten-oxide films were deposited on glass substrates from a metal-oxide target by nonreactive radio-frequency sputtering. The authors have studied the effect that changing Ar gas pressure has on the electrical, optical, and chemical composition in the thin films. Resistivity of WO3 changed ten orders of magnitude with working gas pressure values from 20 to 80 mTorr. Thin films deposited at 20 mTorr of Ar sputtering pressure showed lower resistivity and optical transmittance. X-ray photoelectron spectroscopy (XPS) measurements revealed similar chemical composition for all samples irrespective of Ar pressure used. However, XPS analyses of the evolution of W 4f and O 1s peaks indicated a mixture of oxides dependent on the Ar pressure used during deposition.
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81.15.Cd Deposition by sputtering
73.61.Ng Insulators
78.66.Nk Insulators
79.60.Bm Clean metal, semiconductor, and insulator surfaces
68.55.A- Nucleation and growth

Model for aspect ratio dependent etch modulated processing

Peter J. Gilgunn, J. Fernando Alfaro, and Gary K. Fedder

J. Vac. Sci. Technol. A 28, 334 (2010); http://dx.doi.org/10.1116/1.3305716 (13 pages)

Online Publication Date: 5 March 2010

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A time-multiplexed, anisotropic, inductively coupled plasma Si deep reactive ion etch process is characterized in terms of the Si macroload, cross-wafer spatial variation, local pattern density, and feature size. The process regime is established as neutral flux limited, in which material transport occurs in the molecular flow to transition flow regimes. For this process regime, a semiempirical, unified analytic model and a numeric model are developed using the Dushman and Clausing vacuum conductance correction factors, respectively, in the Coburn and Winters model of aspect ratio dependent etching. The experimental reaction probability for etching of Si by F was found to be 0.24 for Dushman’s factor and 0.22 for Clausing’s factor. Each model is validated to ±10% against experimental depth data for microdonut and trench test structures and match each other to within 10% for depths of up to 160 μm. The observed depth range is 64 μm at a depth of 160 μm.
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85.85.+j Micro- and nano-electromechanical systems (MEMS/NEMS) and devices
81.65.Cf Surface cleaning, etching, patterning
81.16.Rf Micro- and nanoscale pattern formation
52.77.Bn Etching and cleaning
07.10.Cm Micromechanical devices and systems

Characterization of worn Ti–Si cathodes used for reactive cathodic arc evaporation

J. Q. Zhu, A. Eriksson, N. Ghafoor, M. P. Johansson, J. Sjölén, L. Hultman, J. Rosén, and M. Odén

J. Vac. Sci. Technol. A 28, 347 (2010); http://dx.doi.org/10.1116/1.3330767 (7 pages) | Cited 5 times

Online Publication Date: 5 March 2010

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The microstructural evolution of Ti1−xSix cathode surfaces (x = 0,0.1,0.2) used in reactive cathodic arc evaporation has been investigated by analytical electron microscopy and x-ray diffractometry. The results show that the reactive arc operated in N2 atmosphere induces a 2–12 μm thick N-containing converted layer consisting of nanosized grains in the two-phase Ti and Ti5Si3 cathode surface. The formation mechanism of this layer is proposed to be surface nitriding and redeposition of macroparticles formed during the deposition process. The surface roughness of the worn Ti1−xSix cathodes increases with increasing Si content, up to 20 at. %, due to preferential erosion of Ti5Si3.
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82.45.Fk Electrodes
81.15.Kk Vapor phase epitaxy; growth from vapor phase
68.47.-b Solid-gas/vacuum interfaces: types of surfaces
68.37.-d Microscopy of surfaces, interfaces, and thin films

β-Ga2O3 growth by plasma-assisted molecular beam epitaxy

Min-Ying Tsai, Oliver Bierwagen, Mark E. White, and James S. Speck

J. Vac. Sci. Technol. A 28, 354 (2010); http://dx.doi.org/10.1116/1.3294715 (6 pages) | Cited 2 times

Online Publication Date: 10 March 2010

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The authors demonstrate the heteroepitaxial and homoepitaxial growth of single crystalline β-Ga2O3 by plasma-assisted molecular beam epitaxy. Phase-pure (math01) and (100) β-Ga2O3 thin films were grown on c-plane sapphire and (100) β-Ga2O3 substrates, respectively. Based on the homoepitaxial results, detailed information is reported on the dependence between the β-Ga2O3 film quality and various growth parameters. At an optimized growth temperature of 700 °C, a growth relationship between growth rates and increasing gallium fluxes was established at a fixed oxygen pressure. A three-dimensional columnar growth with a relatively high growth rate was measured at a low gallium flux while a terrace surface morphology with a reduced growth rate was observed as the gallium flux increased. The gallium flux played an important role on both surface morphology and growth rate. We associated the decreasing growth rate with increasing gallium flux with the formation of gallium suboxides monitored by quadrupole mass spectrometry. The formation and desorption of volatile gallium suboxides limited the resulting growth rate of β-Ga2O3 growth.
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68.55.aj Insulators
81.15.Hi Molecular, atomic, ion, and chemical beam epitaxy
68.35.B- Structure of clean surfaces (and surface reconstruction)
68.43.Nr Desorption kinetics
52.77.Dq Plasma-based ion implantation and deposition

Surface loss rates of H and Cl radicals in an inductively coupled plasma etcher derived from time-resolved electron density and optical emission measurements

G. A. Curley, L. Gatilova, S. Guilet, S. Bouchoule, G. S. Gogna, N. Sirse, S. Karkari, and J. P. Booth

J. Vac. Sci. Technol. A 28, 360 (2010); http://dx.doi.org/10.1116/1.3330766 (13 pages) | Cited 8 times

Online Publication Date: 11 March 2010

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A study is undertaken of the loss kinetics of H and Cl atoms in an inductively coupled plasma (ICP) reactor used for the etching of III-V semiconductor materials. A time-resolved optical emission spectroscopy technique, also referred to as pulsed induced fluorescence (PIF), has been combined with time-resolved microwave hairpin probe measurements of the electron density in a pulsed Cl2/H2-based discharge for this purpose. The surface loss rate of H, kwH, was measured in H2 plasma and was found to lie in the 125–500 s−1 range (γH surface recombination coefficient of ∼ 0.006–0.023), depending on the reactor walls conditioning. The PIF technique was then evaluated for the derivation of kwCl, and γCl in Cl2-based plasmas. In contrast to H2 plasma, significant variations in the electron density may occur over the millisecond time scale corresponding to Cl2 dissociation at the rising edge of the plasma pulse. By comparing the temporal evolution of the electron density and the Ar-line intensity curves with 10% of Ar added in the discharge, the authors show that a time-resolved actinometry procedure using Ar as an actinometer is valid at low to moderate ICP powers to estimate the Cl loss rate. They measured a Cl loss rate of ∼ 125–200 s−1 (0.03 ≤ γCl ≤ 0.06) at 150 W ICP power for a reactor state close to etching conditions. The Cl surface loss rate was also estimated for high ICP power (800 W) following the same procedure, giving a value of ∼ 130–150 s−1 (γCl ∼ 0.04), which is close to that measured at 150 W ICP power.
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52.77.Bn Etching and cleaning
81.65.Cf Surface cleaning, etching, patterning
82.37.Np Single molecule reaction kinetics, dissociation, etc.
52.80.-s Electric discharges
52.40.Hf Plasma-material interactions; boundary layer effects
52.70.Kz Optical (ultraviolet, visible, infrared) measurements

Surface modification of phyllosilicate minerals by fluorination methods

Alain Tressaud, Christine Labrugère, Etienne Durand, Hélène Serier, and Larisa P. Demyanova

J. Vac. Sci. Technol. A 28, 373 (2010); http://dx.doi.org/10.1116/1.3328826 (9 pages) | Cited 1 time

Online Publication Date: 11 March 2010

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The effect of fluorination on various types of phyllosilicate minerals has been investigated. Two different fluorination techniques have been used: direct F2 gas and cold radio frequency plasma involving c-C4F8 or O2/CF4 mixtures. The modifications of the surface composition and properties have been followed mostly by x-ray photoelectron spectroscopy (XPS). Depending of the fluorination reagents, a reactive etching process involving M-F bonding occurs (direct F2 gas; O2–CF4 rf plasma) or a carbon fluoride deposition takes place (c-C4F8 rf plasma). In the case of F2-gas treated minerals, Si 2p XPS signal accounts for the presence of fluorinated Si environments.
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81.65.Cf Surface cleaning, etching, patterning
82.80.Pv Electron spectroscopy (X-ray photoelectron (XPS), Auger electron spectroscopy (AES), etc.)
79.60.-i Photoemission and photoelectron spectra
52.77.-j Plasma applications
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