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Nov 2009

Volume 27, Issue 6, pp. 1255-1399

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Analysis of controlled mixed-phase (amorphous+microcrystalline) silicon thin films by real time spectroscopic ellipsometry

N. J. Podraza, Jing Li, C. R. Wronski, E. C. Dickey, and R. W. Collins

J. Vac. Sci. Technol. A 27, 1255 (2009); http://dx.doi.org/10.1116/1.3212893 (5 pages) | Cited 4 times

Online Publication Date: 14 September 2009

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Engineered thin films consisting of periodic arrays of silicon microcrystallites in a hydrogenated amorphous silicon host matrix have been prepared by plasma-enhanced chemical vapor deposition where the hydrogen dilution of silane is modulated in multiple cycles. These types of films have been guided by a phase evolution diagram, depicting the deposition conditions and film thickness at which the material exhibits amorphous, microcrystalline, or mixed-phase (amorphous+microcrystalline) characteristics, developed for intrinsic Si:H prepared with varying H2 dilution on unhydrogenated a-Si:H. Real time spectroscopic ellipsometry (RTSE) has been used in situ to noninvasively determine the phase evolution of the resulting hydrogenated mixed-phase (amorphous+microcrystalline) silicon thin films and corroborated with dark-field transmission electron microscopy. Such tailored microstructures are of growing interest as components of thin film photovoltaic devices, and RTSE is shown to be a key technique for structure verification.
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68.55.ag Semiconductors
81.15.Gh Chemical vapor deposition (including plasma-enhanced CVD, MOCVD, ALD, etc.)
81.30.Dz Phase diagrams of other materials
85.60.-q Optoelectronic devices
68.37.Lp Transmission electron microscopy (TEM)
07.60.Fs Polarimeters and ellipsometers

Characterizations of Ga-doped ZnO films on Si (111) prepared by atmospheric pressure metal-organic chemical vapor deposition

Yen-Chin Huang, Zhen-Yu Li, Li-Wei Weng, Wu-Yih Uen, Shan-Ming Lan, Sen-Mao Liao, Tai-Yuan Lin, Yu-Hsiang Huang, Jian-Wen Chen, Tsun-Neng Yang, and Chin-Chen Chiang

J. Vac. Sci. Technol. A 27, 1260 (2009); http://dx.doi.org/10.1116/1.3212895 (6 pages) | Cited 3 times

Online Publication Date: 14 September 2009

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Gallium-doped ZnO films were grown on p-Si(111) substrates by atmospheric pressure metal-organic chemical vapor deposition (AP-MOCVD) using diethylzinc and water as reactant gases and triethyl gallium (TEG) as a n-type dopant gas. The structural, electrical, and optical properties of ZnO:Ga films obtained by varying the flow rate of TEG from 0.56 to 3.35 μmol/min were examined. X-ray diffraction patterns and scanning electron microscopy images indicated that Ga doping plays a role in forming microstructures in ZnO films. A flat surface with a predominant orientation (101) was obtained for the ZnO:Ga film fabricated at a flow rate of TEG = 2.79 μmol/min. This film also revealed a lowest resistivity of 4.54×10−4 Ω cm, as measured using the van der Pauw method. Moreover, low temperature photoluminescence (PL) emission recorded at 12 K demonstrated the Burstein Moss shift of PL line from 3.365 to 3.403 eV and a line broadening from 100 to 165 meV as the TEG flow rate varied from 0.56 to 2.79 μmol/min. This blueshift behavior of PL spectra from ZnO:Ga films features the degeneracy of semiconductor, which helps to recognize the enhancing of transparency and conductivity of ZnO films fabricated by AP-MOCVD using Ga-doping technique.
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81.15.Gh Chemical vapor deposition (including plasma-enhanced CVD, MOCVD, ALD, etc.)
73.61.Ga II-VI semiconductors
78.66.Hf II-VI semiconductors
78.55.Et II-VI semiconductors
78.20.Ci Optical constants (including refractive index, complex dielectric constant, absorption, reflection and transmission coefficients, emissivity)
72.80.Ey III-V and II-VI semiconductors
68.55.ag Semiconductors
61.72.uj III-V and II-VI semiconductors
68.55.Ln Defects and impurities: doping, implantation, distribution, concentration, etc.

Effects of Si capping layers on the properties of ultrathin Co/Ir(111) films

J. S. Tsay, Y. C. Liou, C. M. Chen, and W. Y. Chan

J. Vac. Sci. Technol. A 27, 1266 (2009); http://dx.doi.org/10.1116/1.3222909 (5 pages) | Cited 1 time

Online Publication Date: 14 September 2009

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Surface compositions and annealing effects for ultrathin Co/Ir(111) films influenced by Si capping layers have been investigated. On the surface of Co/Ir(111) films, Si adatoms are chemically active in the formation of Co–Si interfaces. Low-energy electron diffraction observations reveal that Si–Co interfaces is disordered in the long range. From sputtering profiling measurements, alloy formations occur at the interfacial layers, while pure cobalt remains on the Ir(111). After depositing submonolayer silicon on Co/Ir(111), the relative easy axis of magnetization in the polar geometry is mainly attributed to the positive interface anisotropy of the Co/Ir interface. The formation of nonmagnetic Co–Si compounds plays a dominant role in reducing the effectiveness of magnetic layers. Below 500 K, the interdiffusion of Si into the underlying Co layer occurs. Further interaction of Si atoms with Co layers and interdiffusion at the Co–Ir interface are observed at higher temperatures. This causes no detectable magnetic hysteresis after annealing up to 800 K.
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75.70.Ak Magnetic properties of monolayers and thin films
75.60.Ej Magnetization curves, hysteresis, Barkhausen and related effects
75.30.Gw Magnetic anisotropy
66.30.Ny Chemical interdiffusion; diffusion barriers
81.40.Gh Other heat and thermomechanical treatments
68.43.Mn Adsorption kinetics

Kinetic modeling of the effect of electron beam pulse duration on abatement of carbon tetrafluoride using O2 as an additive gas

Susumu Kato, Isao Okuda, Eiichi Takahashi, and Yuji Matsumoto

J. Vac. Sci. Technol. A 27, 1271 (2009); http://dx.doi.org/10.1116/1.3224880 (4 pages)

Online Publication Date: 14 September 2009

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The abatement mechanism of carbon tetrafluoride (CF4) in atmospheric-pressured argon using O2 as an additive gas under electron beam irradiation and the effect of the pulse duration of electron beams on the abatement were studied by using a kinetic model. About 99% of 1000 ppm CF4 is abated for pulse duration from 0.1 to 10 μs and an input energy density of 0.85 J/cm3. The abatement of CF4 decreases to about 70% when the pulse duration becomes longer than 10 ms. This is because the decomposition of CF4 and other products by reaction with activated species and the composition of products by chemical reactions coexist.
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61.80.Fe Electron and positron radiation effects

Effect of magnetic field strength on deposition rate and energy flux in a dc magnetron sputtering system

Samuel D. Ekpe, Francisco J. Jimenez, David J. Field, Martin J. Davis, and Steven K. Dew

J. Vac. Sci. Technol. A 27, 1275 (2009); http://dx.doi.org/10.1116/1.3222874 (6 pages)

Online Publication Date: 21 September 2009

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Variations in the magnetic field strongly affect the plasma parameters in a magnetron sputtering system. This in turn affects the throughput as well as the energy flux to the substrate. The variation in the magnetic field in this study, for a dc magnetron process, is achieved by shifting the magnet assembly slightly away from the target. Measurements of the plasma parameters show that while the electron density at the substrate increases with decrease in magnetic field, the electron temperature decreases. The cooling of the electron temperature is consistent with results reported elsewhere. The deposition rate per input magnetron power is found to increase slightly with the decrease in magnetic field for the process conditions considered in this study. Results suggest that the energy flux to the substrate tends to show a general decrease with the shift in the magnet assembly.
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81.15.Cd Deposition by sputtering
52.25.-b Plasma properties

Time of flight secondary ion mass spectroscopy studies of poly(allyl methacrylate-g-dimethylsiloxane) copolymers using cryogenic sample handling techniques: Effects of hydration on surface chemical structure and surface chain length distribution

Daniel J. Hook, Lu Chen, Paul L. Valint, and Joseph A. Gardella

J. Vac. Sci. Technol. A 27, 1281 (2009); http://dx.doi.org/10.1116/1.3224878 (8 pages) | Cited 1 time

Online Publication Date: 21 September 2009

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A series of amphiphilic graft copolymers having a poly(allyl methacrylate) [poly(AMA)] backbone and polydimethylsiloxane (PDMS) side chains were studied by time of flight secondary ion mass spectroscopy (ToF-SIMS) in both hydrated and dehydrated states using cryogenic sample handling methods. Both the copolymers and the PDMS macromers used for grafting to the acrylate backone were synthesized using anionic methods, yielding copolymers with a tightly controlled molecular weight distribution and a tightly controlled PDMS graft chain length in a polymer brush surface configuration. The effects of hydration on surface chemical structure and graft length distribution at the surface were examined. Low mass ToF-SIMS studies provided direct structural evidence that the polymer surface reorganized between hydrated and dehydrated states. High mass ToF-SIMS (1000–5000 Da) studies detected oligomeric ion distributions of the PDMS macromer graft at both air and water exposed interfaces, but with a greatly decreased ion yield at the water exposed interface. This marks the first time that detection of high mass oligomeric ion distributions from water exposed (frozen) interfaces has been reported. The chain length distribution of PDMS at the surface was determined and no statistical difference in surface graft length distribution was detected between hydrated and dehydrated copolymers. The effects of polymer bulk structure and composition on graft length distribution at the surface were also examined. High mass ToF-SIMS (1000–5000 Da) results indicated that shorter chain lengths were more prominently represented in distribution of graft chains at the surface, regardless of polymer bulk structure, composition, or hydration condition. This is the first report of quantitative and high mass ToF-SIMS study of the effect of water absorption on polymer surface structure in both hydrated and dehydrated states, with control of the polymer structure and composition.
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79.20.Rf Atomic, molecular, and ion beam impact and interactions with surfaces
68.35.bm Polymers, organics
82.30.-b Specific chemical reactions; reaction mechanisms
61.41.+e Polymers, elastomers, and plastics

Mechanisms for plasma etching of HfO2 gate stacks with Si selectivity and photoresist trimming

Juline Shoeb and Mark J. Kushner

J. Vac. Sci. Technol. A 27, 1289 (2009); http://dx.doi.org/10.1116/1.3231480 (14 pages) | Cited 3 times

Online Publication Date: 21 September 2009

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To minimize leakage currents resulting from the thinning of the insulator in the gate stack of field effect transistors, high-dielectric constant (high-k) metal oxides, and HfO2 in particular, are being implemented as a replacement for SiO2. To speed the rate of processing, it is desirable to etch the gate stack (e.g., metal gate, antireflection layers, and dielectric) in a single process while having selectivity to the underlying Si. Plasma etching using Ar/BCl3/Cl2 mixtures effectively etches HfO2 while having good selectivity to Si. In this article, results from integrated reactor and feature scale modeling of gate-stack etching in Ar/BCl3/Cl2 plasmas, preceded by photoresist trimming in Ar/O2 plasmas, are discussed. It was found that BCln species react with HfO2, which under ion impact, form volatile etch products such as BmOCln and HfCln. Selectivity to Si is achieved by creating Si–B bonding as a precursor to the deposition of a BCln polymer which slows the etch rate relative to HfO2. The low ion energies required to achieve this selectivity then challenge one to obtain highly anisotropic profiles in the metal gate portion of the stack. Validation was performed with data from literature. The effect of bias voltage and key reactant probabilities on etch rate, selectivity, and profile are discussed.
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52.77.Bn Etching and cleaning
81.65.Cf Surface cleaning, etching, patterning
85.40.Hp Lithography, masks and pattern transfer
85.30.Tv Field effect devices
77.22.Ch Permittivity (dielectric function)

Development of copper-alloy Matsumoto–Ohtsuka-type vacuum flanges and its application to accelerator beam pipes

Y. Suetsugu, M. Shirai, M. Ohtsuka, T. Nishidono, K. Watanabe, Y. Suzuki, M. Tsuchiya, A. Yonemoto, K. Sennyu, and H. Hara

J. Vac. Sci. Technol. A 27, 1303 (2009); http://dx.doi.org/10.1116/1.3237149 (7 pages) | Cited 2 times

Online Publication Date: 6 October 2009

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The possibility of employing copper-alloy Matsumoto–Ohtsuka-type flanges in a vacuum beam pipes with complicated apertures for a particle accelerator is experimentally studied. Copper-alloy flanges can mitigate the heating problems arising as a result of high-intensity beams more efficiently than stainless-steel flanges. Baking of beam pipes up to a temperature of 200 °C was acceptable with copper-alloy flanges. Moreover, direct electron-beam welding to a copper beam pipe became available, which made the manufacturing easy. In this study, several beam pipes with copper-alloy flanges were installed in the KEKB B-factory positron ring, and the performance was investigated using the high-intensity beams.
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89.20.Bb Industrial and technological research and development
89.20.Kk Engineering

Effects of pulsed sputtering frequency on the uniformity of Al:ZnO’s transparent conductive oxide properties for solar cell applications

Wonkyun Yang and Junghoon Joo

J. Vac. Sci. Technol. A 27, 1310 (2009); http://dx.doi.org/10.1116/1.3242421 (6 pages) | Cited 8 times

Online Publication Date: 6 October 2009

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Bipolar pulsed magnetron sputtering is used to deposit Al doped ZnO (AZO) on a glass substrate for a transparent conducting oxide in a solar cell structure. A 5×25 in.2 AZO target was sputtered by 50–250 kHz bipolar pulsed dc power supply to deposit a 400×400 mm2 area by swinging back and forth. Sheet resistance, surface morphology, and optical transmittance were measured at different positions on 16 witness samples (small glass slides) to evaluate uniformity. In the thickness of 800 nm, the average value of sheet resistance was 30 Ω/◻ and the average resistivity was 2.1×10−3 Ω cm. Transmittance was 50%–80% over the visible range. The nonuniformities of thickness, transmittance, and resistivity in the 400×400 mm2 area were 5.8%, 0.8%, and within 9.5%, respectively.
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81.15.Cd Deposition by sputtering
68.35.bg Semiconductors
61.72.uj III-V and II-VI semiconductors
84.60.Jt Photoelectric conversion
73.61.Ga II-VI semiconductors
68.55.ag Semiconductors

Zn-doped CuAlS2 transparent p-type conductive thin films deposited by pulsed plasma deposition

Ming Yang, Yinghua Wang, Guifeng Li, Zhan Shi, and Qun Zhang

J. Vac. Sci. Technol. A 27, 1316 (2009); http://dx.doi.org/10.1116/1.3244565 (4 pages) | Cited 4 times

Online Publication Date: 14 October 2009

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CuAl0.90Zn0.10S2 thin films were deposited by pulsed plasma deposition. The dependence of structural, surface morphology, electrical, and optical properties of the films on substrate temperature was investigated. X-ray diffraction patterns reveal that the film be amorphous structure. The electrical properties are sensitive to the substrate temperature. A typical sample with conductivity of 50.9 S cm−1, carrier mobility of 3.13 cm2 V−1 s−1, carrier concentration of 1.41×1019 cm−3, and average transmission of 74% in visible range of 400–700 nm was obtained. A transparent p-CuAlS2:Zn/n-In2O3:W heterogeneous diode was also fabricated and exhibits rectifying current-voltage characteristics. The ratio of forward current to the reverse current exceeds 80 within the range of applied voltages of −3.0–+3.0 V and the turn-on voltage is approximately 0.5–0.8 V.
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68.55.ag Semiconductors
52.77.Dq Plasma-based ion implantation and deposition
81.15.-z Methods of deposition of films and coatings; film growth and epitaxy
85.30.Kk Junction diodes
78.66.Jg Amorphous semiconductors; glasses
73.61.Jc Amorphous semiconductors; glasses

Dry-etching properties of TiN for metal/high-k gate stack using BCl3-based inductively coupled plasma

Dong-Pyo Kim, Xue Yang, Jong-Chang Woo, Doo-Seung Um, and Chang-Il Kim

J. Vac. Sci. Technol. A 27, 1320 (2009); http://dx.doi.org/10.1116/1.3244567 (6 pages) | Cited 3 times

Online Publication Date: 14 October 2009

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The etch rate of TiN film and the selectivities of TiN/SiO2 and TiN/HfO2 were systematically investigated in Cl2/BCl3/Ar plasmas as functions of Cl2 flow rate, radio-frequency (rf) power, and direct-current (dc) bias voltage under different substrate temperatures of 10 and 80 °C. The etch rate of TiN films increased with increasing Cl2 flow rate, rf power, and dc-bias voltage at a fixed substrate temperature. In addition, the etch rate of TiN films at 80 °C were higher than that at 10 °C when other plasma parameters were fixed. However, the selectivities of TiN/SiO2 and TiN/HfO2 showed different tendencies compared with etch-rate behavior as a function of rf power and dc bias voltage. The relative-volume densities of Ar (750.0 nm), Cl (725.2 nm), and Cl+ (386.6 nm) were monitored with an optical-emission spectroscopy. When rf power increased, the relative-volume densities of all studied particles were increased. X-ray photoelectron spectroscopy was carried out to detect nonvolatile etch by-products from the surface, and nonvolatile peaks (TiClx bonds) in Ti 2p and Cl 2p were observed due to their high melting points. Based on the experimental results, we can conclude that the TiN etch is dependent on the substrate temperature when other plasma parameters are fixed. This can be explained by the enhanced chemical pathway with the assistance of ion bombardment.
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68.55.aj Insulators
52.77.-j Plasma applications
79.60.Dp Adsorbed layers and thin films
78.55.Hx Other solid inorganic materials
64.70.dj Melting of specific substances
78.66.Nk Insulators

Modeling of the angular dependence of plasma etching

Wei Guo and Herbert H. Sawin

J. Vac. Sci. Technol. A 27, 1326 (2009); http://dx.doi.org/10.1116/1.3231450 (11 pages) | Cited 4 times

Online Publication Date: 22 October 2009

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An understanding of the angular dependence of etching yield is essential to investigate the origins of sidewall roughness during plasma etching. In this article the angular dependence of polysilicon etching in Cl2 plasma was modeled as a combination of individual angular-dependent etching yields for ion-initiated processes including physical sputtering, ion-induced etching, vacancy generation, and removal. The modeled etching yield exhibited a maximum at ∼ 60° off-normal ion angle at low flux ratio, indicative of physical sputtering. It transformed to the angular dependence of ion-induced etching with the increase in the neutral-to-ion flux ratio. Good agreement between the modeling and the experiments was achieved for various flux ratios and ion energies. The variation of etching yield in response to the ion angle was incorporated in the three-dimensional profile simulation and qualitative agreement was obtained. The surface composition was calculated and compared to x-ray photoelectron spectroscopy (XPS) analysis. The modeling indicated a Cl areal density of 3×1015 atoms/cm2 on the surface that is close to the value determined by the XPS analysis. The response of Cl fraction to ion energy and flux ratio was modeled and correlated with the etching yields. The complete mixing-layer kinetics model with the angular dependence effect will be used for quantitative surface roughening analysis using a profile simulator in future work.
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81.65.Cf Surface cleaning, etching, patterning
52.77.Bn Etching and cleaning
61.72.jd Vacancies
79.60.Bm Clean metal, semiconductor, and insulator surfaces
68.47.Fg Semiconductor surfaces
68.35.B- Structure of clean surfaces (and surface reconstruction)
68.35.Dv Composition, segregation; defects and impurities

Ferroelectric polarization dependent interactions at Pd–LiNbO3(0001) interfaces

Mosha H. Zhao, Dawn A. Bonnell, and John M. Vohs

J. Vac. Sci. Technol. A 27, 1337 (2009); http://dx.doi.org/10.1116/1.3248268 (6 pages) | Cited 1 time

Online Publication Date: 22 October 2009

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A combination of Auger electron spectroscopy and temperature-programed desorption was used to characterize the growth and interaction of Pd films with positively and negatively terminated ferroelectric LiNbO3(0001) surfaces. The growth mode of vapor-deposited Pd layers at 300 K was found to be dependent on the direction of the ferroelectric polarization with layer-by-layer growth occurring on the negative (c−) surface and particle formation occurring on the positive (c+) surface. The Pd metal layers were also found to be more thermally stable on the c− surface relative to the c+ surface. These results provide another example of how the polarization orientation in ferroelectric materials affects adsorption and reaction on their exposed surfaces.
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77.22.Ej Polarization and depolarization
77.84.Ek Niobates and tantalates
77.84.Cg PZT ceramics and other titanates
79.20.Fv Electron impact: Auger emission
68.43.Mn Adsorption kinetics
68.43.Vx Thermal desorption
68.55.A- Nucleation and growth
82.65.+r Surface and interface chemistry; heterogeneous catalysis at surfaces

UV detection based on a ZnO/LiNbO3 layered surface acoustic wave oscillator circuit

Ching-Liang Wei, Ying-Chung Chen, Jiun-Lin Fu, Kuo-Sheng Kao, Da-Long Cheng, and Chien-Chuan Cheng

J. Vac. Sci. Technol. A 27, 1343 (2009); http://dx.doi.org/10.1116/1.3222916 (4 pages) | Cited 2 times

Online Publication Date: 28 October 2009

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This study elucidates the combination of an oscillator circuit with a high-frequency amplifier, a matching network, and a layered surface acoustic wave device for detecting ultraviolet (UV) light. The oscillator circuit shows an excellent performance with the resonance frequency of 109.34 MHz and phase noise of −107.137 dB at 100 kHz. The frequency shift that is caused by the interaction between the acoustic wave and carriers upon excitation by UV light in the ZnO thin film is discussed. The frequency variation of the oscillator steadily increases with the intensity of the UV light. An extreme frequency shift of 63.75 kHz was observed as the UV light intensity reached 1250 μW/cm2.
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43.58.Wc Electrical and mechanical oscillators
85.60.Gz Photodetectors (including infrared and CCD detectors)
84.30.Ng Oscillators, pulse generators, and function generators

Synthesis and hydrogen gas sensing properties of ZnO wirelike thin films

Nguyen Le Hung, Eunseong Ahn, Seongyong Park, Hooncheol Jung, Hyojin Kim, Soon-Ku Hong, Dojin Kim, and Chanyong Hwang

J. Vac. Sci. Technol. A 27, 1347 (2009); http://dx.doi.org/10.1116/1.3244563 (5 pages) | Cited 7 times

Online Publication Date: 28 October 2009

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The authors investigated the hydrogen gas sensing properties of the ZnO wirelike films synthesized by two consecutive steps: thermal oxidation of sputtered Zn metallic films in dry air. Structural characterization revealed that the authors synthesized polycrystalline wurtzite ZnO films of a wirelike structure with a width of less than 100 nm and a length of several micrometers, possibly consisting of a chain of ZnO nanocrystallites with a mean granular size of 15 nm. It was found from the gas sensing measurements that the ZnO wirelike films exhibited a maximum sensitivity, defined as a ratio of the change in conductance upon exposure to H2 gas in dry air over the conductance in dry air, ΔG/Ga, of 283% to 200 ppm H2 gas at a temperature of 200 °C, indicating quite a possibility of much reduction in the operating temperature of the ZnO-based H2 gas sensors. The ZnO wirelike film sensors showed a fast response to hydrogen gas in comparison with conventional ZnO films. These results suggest that the ZnO wirelike films can be used as the gas sensing materials for low-cost and high-performance gas sensors.
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81.05.Dz II-VI semiconductors
07.07.Df Sensors (chemical, optical, electrical, movement, gas, etc.); remote sensing
73.61.Ga II-VI semiconductors
68.55.ag Semiconductors

Transmission electron microscopy specimen preparation perpendicular to the long axis of high aspect ratio features

R. B. Irwin, A. Anciso, P. J. Jones, A. L. Glenn, B. L. Williams, S. Sridhar, and S. Arshad

J. Vac. Sci. Technol. A 27, 1352 (2009); http://dx.doi.org/10.1116/1.3248271 (8 pages) | Cited 1 time

Online Publication Date: 28 October 2009

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A new variation of transmission electron microscopy (TEM) specimen preparation is introduced. By thinning a tall high aspect ratio structure perpendicular to the long dimension (i.e., from the side) rather than from perpendicular to the short dimension (either the top or the bottom), it is possible to obtain a more uniformly thin TEM specimen over the entire long dimension of the structure. This article will describe the rational for this variation in specimen preparation. The necessary modifications of four different specimen preparation methods (in situ lift-out, traditional H-bar, ex situ lift-out, and tripod polishing) will be discussed and images of specimens obtained by both of these first two methods will be shown. Additional potential advantages and other applications of this specimen preparation method will be covered.
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06.60.Ei Sample preparation (including design of sample holders)
07.78.+s Electron, positron, and ion microscopes; electron diffractometers

Structure and properties of ZrN doped diamondlike carbon films prepared by pulsed bias arc ion plating

H. K. Li, G. Q. Lin, and C. Dong

J. Vac. Sci. Technol. A 27, 1360 (2009); http://dx.doi.org/10.1116/1.3248274 (5 pages)

Online Publication Date: 28 October 2009

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ZrN doped diamondlike carbon composite films with different compositions were deposited on cemented carbide substrates at different nitrogen flow rates by pulsed bias arc ion plating. Scanning electron microscopy results show that the film surfaces were all uniform, smooth, and dense. X-ray photoelectron spectroscopy reveal the C contents are more than 60%, the N content increases, and the Zr content decreases with increasing nitrogen flow rate. The Raman spectra indicated that the deposited films were diamondlike carbon. X-ray diffraction results suggested that a ZrN crystalline phase was also present in the films. The hardness and elastic modulus were closely related to the composition and structure of the films and decrease with increasing nitrogen flow rates, principally due to the increase in the sp2 content and the decrease in the ZrN crystalline phase.
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68.60.-p Physical properties of thin films, nonelectronic
78.66.Nk Insulators
78.30.Hv Other nonmetallic inorganics
79.60.Dp Adsorbed layers and thin films
62.20.de Elastic moduli
81.40.Jj Elasticity and anelasticity, stress-strain relations
62.20.Qp Friction, tribology, and hardness
81.40.Np Fatigue, corrosion fatigue, embrittlement, cracking, fracture, and failure
81.15.Jj Ion and electron beam-assisted deposition; ion plating
61.72.up Other materials

Analysis of carbon in SrTiO3 grown by hybrid molecular beam epitaxy

Bharat Jalan, Joël Cagnon, Thomas E. Mates, and Susanne Stemmer

J. Vac. Sci. Technol. A 27, 1365 (2009); http://dx.doi.org/10.1116/1.3253355 (4 pages) | Cited 6 times

Online Publication Date: 28 October 2009

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Secondary ion mass spectroscopy (SIMS) was used to investigate carbon impurity concentrations in stoichiometric SrTiO3 films grown by a hybrid molecular beam epitaxy approach that uses an effusion cell to supply strontium, a rf plasma source for oxygen and a metal organic titanium source (titanium tetra isopropoxide). The carbon concentration in the films was measured as a function of growth parameters. At sufficiently high growth temperatures (>800 °C), the films contain a few ppm of carbon. The challenges in accurately quantifying low carbon concentrations are discussed. A carbon-containing contamination layer is detected on the surfaces of SrTiO3 substrates and air-exposed films by SIMS and in scanning transmission electron microscopy. The contamination layer could be removed by high-temperature predeposition oxygen plasma cleaning.
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81.15.Hi Molecular, atomic, ion, and chemical beam epitaxy
68.55.aj Insulators
61.66.Bi Elemental solids
61.66.Dk Alloys
79.20.Rf Atomic, molecular, and ion beam impact and interactions with surfaces
52.77.-j Plasma applications
68.37.Ma Scanning transmission electron microscopy (STEM)

Effects of type of reactor, crystallinity of SiC, and NF3 gas pressure on etching rate and smoothness of SiC surface using NF3 gas plasma

A. Tasaka, H. Yamada, T. Nonoyama, T. Kanatani, Y. Kotaka, T. Tojo, and M. Inaba

J. Vac. Sci. Technol. A 27, 1369 (2009); http://dx.doi.org/10.1116/1.3222938 (8 pages) | Cited 1 time

Online Publication Date: 29 October 2009

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Polycrystalline β-SiC and single-crystalline 4H-SiC surfaces were etched by reactive ion etching (RIE) using NF3 gas plasma. A smooth surface was obtained on the polycrystalline SiC after RIE at NF3 gas pressures of 2 and 10 Pa for 10 min, and neither spikes nor pillars were formed on it. On the other hand, some pillars were formed on the single-crystalline SiC surface by RIE at NF3 gas pressures of 2 and 10 Pa. Though the absence of carbon-rich regions and SiOx on the outermost surface before etching was confirmed by x-ray photoelectron spectroscopy and Raman analysis, x-ray diffraction analysis revealed that graphite crystallites were present in the single-crystalline SiC bulk. It was concluded that the graphite crystallites acted as masks and the pillars grew up from the graphite crystallites in the single crystalline SiC during RIE.
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81.65.Cf Surface cleaning, etching, patterning
78.68.+m Optical properties of surfaces
61.66.Fn Inorganic compounds
78.30.Hv Other nonmetallic inorganics
79.60.Bm Clean metal, semiconductor, and insulator surfaces
52.77.Bn Etching and cleaning

Simulation of gas flow through tubes of finite length over the whole range of rarefaction for various pressure drop ratios

S. Varoutis, D. Valougeorgis, and F. Sharipov

J. Vac. Sci. Technol. A 27, 1377 (2009); http://dx.doi.org/10.1116/1.3248273 (15 pages) | Cited 14 times

Online Publication Date: 29 October 2009

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The rarefied gas flow through circular tubes of finite length has been investigated computationally by the direct simulation Monte Carlo method. The reduced flow rate and the flow field have been calculated as functions of the gas rarefaction, the length-to-radius ratio, and the pressure ratio along the tube. The gas rarefaction, which is inversely proportional to the Knudsen number, is varied from 0 to 2000, i.e., the free-molecular, transitional, and hydrodynamic regimes are embraced. A wide range of the length-to-radius ratio, namely, from 0 corresponding to the orifice flow up to 10 representing a sufficiently long tube, has been considered. Several values of the pressure ratio between 0 and 0.7 have been regarded. This pressure range covers both gas flow into vacuum and into a background gas. It has been found that the rarefaction parameter has the most significant effect on the flowfield characteristics and patterns, followed by the pressure ratio drop, while the length-to-radius ratio has a rather modest impact. Several interesting findings have been reported including the behavior of the flow rate and other macroscopic quantities in terms of these three parameters. In addition, the effect of gas rarefaction on the choked flow and on the Mach disks at large pressure drops is discussed. Comparison of some of the present numerical results with available experimental data has shown a good agreement.
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47.45.-n Rarefied gas dynamics
47.60.Dx Flows in ducts and channels
47.11.Mn Molecular dynamics methods

Preferential growth of helium-doped Ti films deposited by magnetron sputtering

Lei Zhang, L. Q. Shi, Z. J. He, B. Zhang, and L. B. Wang

J. Vac. Sci. Technol. A 27, 1392 (2009); http://dx.doi.org/10.1116/1.3253087 (8 pages)

Online Publication Date: 29 October 2009

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The authors present a study on the influence of the bias voltages on the preferred orientation and microstructure of helium-doped Ti films. The films were deposited in a vacuum chamber by both direct-current magnetron sputtering and electron-cyclotron-resonance plasma-aided magnetron sputtering (ECR-PMS) methods. The preferred orientation and microstructure of the films were analyzed by x-ray diffraction (XRD) and transmission electron microscopy. They found that the preferred crystal orientation of helium-doped Ti films was controllably varied from (002) to (100) orientation by increasing the bias voltage (i.e., ion bombardment current and energy). The dominant bombardment effect on the orientation was from the Ar ions of the anode sheath in the magnetron sputtering plasma, and He bombardment also showed a slight influence on the orientation transformation at low trapped-helium content in the crystal. The XRD peak broadening of helium-doped Ti films prepared by ECR-PMS is much more serious than for conventional magnetron sputtering even at low helium concentrations. It is believed that asynchronous bombardment from He ions in the ECR plasma area and Ar ions in the deposition plasma during film growth significantly decreases the mobility of Ti adatoms on the surface and enhances the growth of helium-induced defects, thus increasing the crystal disorder and influencing the crystal orientation transformation. On the contrary, the sequential bombardment of He and Ar particles can decrease helium-dissolution produced defects and improve crystallization.
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81.15.Cd Deposition by sputtering
76.40.+b Diamagnetic and cyclotron resonances
81.15.Jj Ion and electron beam-assisted deposition; ion plating
52.77.Dq Plasma-based ion implantation and deposition
68.43.-h Chemisorption/physisorption: adsorbates on surfaces
68.55.-a Thin film structure and morphology
64.70.kd Metals and alloys
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