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Nov 1989

Volume 7, Issue 6, pp. 3147-3380


Preparation of superconducting Y–Ba–Cu–O thin films

M. Leskelä, J. K. Truman, C. H. Mueller, and P. H. Holloway

J. Vac. Sci. Technol. A 7, 3147 (1989); http://dx.doi.org/10.1116/1.576329 (25 pages) | Cited 10 times

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The preparation of YBa2 Cu3 07−x high critical temperature superconducting thin films is reviewed. Thin films have been grown by many techniques, including sputtering, electron beam evaporation, laser ablation, spray pyrolysis, molecular‐beam and epitaxy (MBE). Stoichiometric films with high Tc and Jc have been obtained using each of these methods. The choice of substrate significantly affects the superconducting properties, and among the numerous substrates studied MgO, ZrO,2 and SrTiO3 yield best results. This review outlines the various deposition techniques, the effect of postdeposition annealing and the subsequent film–substrate interactions.
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74.70.-b Superconducting materials other than cuprates
74.78.-w Superconducting films and low-dimensional structures
81.15.Cd Deposition by sputtering
81.40.Ef Cold working, work hardening; annealing, post-deformation annealing, quenching, tempering recovery, and crystallization

Phase‐selective chemical vapor deposition of boron carbide by nucleation control on patterned substrates

U. Jansson, J.‐O. Carlsson, L. C. Markert, and J. E. Greene

J. Vac. Sci. Technol. A 7, 3172 (1989); http://dx.doi.org/10.1116/1.576330 (4 pages) | Cited 1 time

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During film growth by chemical vapor deposition (CVD), the phase deposited can sometimes be controlled by the choice of substrate material. This concept can be employed to obtain phase‐selective CVD, i.e., the simultaneous selective deposition of different phases on different regions of a patterned substrate. In this paper, differential nucleation behavior is used to obtain phase‐selective deposition of metastable tetragonal boron carbide and rhombohedral B13 C2 on a patterned substrate consisting of adjacent regions of amorphous boron carbide and Mo, respectively.
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81.15.Gh Chemical vapor deposition (including plasma-enhanced CVD, MOCVD, ALD, etc.)
82.65.+r Surface and interface chemistry; heterogeneous catalysis at surfaces

Plasma enhanced chemical vapor deposition using forced flow through hollow cathodes

Frank Jansen, Dan Kuhman, and Charles Taber

J. Vac. Sci. Technol. A 7, 3176 (1989); http://dx.doi.org/10.1116/1.576331 (7 pages) | Cited 4 times

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The application of hollow cathodes to the deposition of thin films from molecular gases is discussed. Precursor gases are decomposed in glow discharges created in the hollow cathode tubes while a laminar viscous gas flow is maintained through the tube towards a substrate. Either the substrate or another structure external to the hollow cathode, such as a coaxial tube, may function as the anode. Deposition rates up to 30 μ/min are observed for a‐Si:H. These high‐deposition rates are attributed to the high power density in the plasma combined with the efficient transport of the radicals to the substrate. A coaxial hollow cathode arrangement allows the deposition of insulating films by a direct current process. The unusual properties of amorphous silicon and silicon nitride films deposited with these electrode structures are discussed.
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81.15.Gh Chemical vapor deposition (including plasma-enhanced CVD, MOCVD, ALD, etc.)

Plasma enhanced chemical vapor deposition of HgTe–CdTe superlattices

L. M. Williams, P.‐Y. Lu, S. N. G. Chu, and M. H. Ross

J. Vac. Sci. Technol. A 7, 3183 (1989); http://dx.doi.org/10.1116/1.576332 (5 pages)

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Plasma enhanced chemical vapor deposition was used to grow epitaxial layers of cadmium telluride and mercury telluride from metalorganic compounds. High deposition rates were obtainable for both of the materials, and the plasma allowed epitaxial growth to occur at temperatures that were markedly lower than those required for the standard metalorganic deposition processes. Properties of the mercury telluride and cadmium telluride will be presented. Superlattices were grown at 150 °C that had 70 Å thick mercury telluride layers.
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81.15.Gh Chemical vapor deposition (including plasma-enhanced CVD, MOCVD, ALD, etc.)

Plasma polymerization by magnetron glow discharge. II. Effect of magnetic field on chemical characteristics of plasma polymers of tetrafluoroethylene revealed by electron spectroscopy for chemical analysis

K. Sato, Y.‐S. Yeh, and H. Yasuda

J. Vac. Sci. Technol. A 7, 3188 (1989); http://dx.doi.org/10.1116/1.576333 (9 pages) | Cited 1 time

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Plasma polymerizations of tetrafluoroethylene (TFE) by magnetron glow discharges were investigated by varying the magnetic field of a magnetron electrode system. Polymer deposition rates at two strategically selected positions in the electrode space and chemical characteristics of deposited films revealed by electron spectroscopy for chemical analysis (ESCA) were studied as functions of a magnetic field. It was found the presence of a magnetic field influences the spatial distribution of deposition rates and chemical characteristics of the deposited polymers. The intensity, width, and the relative location of the intense glow (in the form of a ring) with respect to the electrode surface vary with the magnetic field strength and the discharge voltage. Because the intense glow is highly localized (only in a ring shape adhering close to the electrode surface), the remaining glow discharge, which fills the majority of the interelectrode space, becomes a weak, but uniform field for plasma polymerization. This situation is similar to the tail‐flame portion of a rf tubular reactor. In the presence of a magnetic field in the range investigated and at a relatively low level of discharge wattage, plasma polymerization yields films with three‐dimensional networks comprised of relatively long segments and lesser amounts of quaternary carbons. The overall characteristics of plasma polymers, however, are similar to those formed without a magnetic field.
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82.35.-x Polymers: properties; reactions; polymerization
81.15.Gh Chemical vapor deposition (including plasma-enhanced CVD, MOCVD, ALD, etc.)
82.80.Pv Electron spectroscopy (X-ray photoelectron (XPS), Auger electron spectroscopy (AES), etc.)

Growth of PbTe/Pb1−xMnxTe quantum well structures by molecular‐beam epitaxy

H. Clemens, P. C. Weilguni, U. Stromberger, and G. Bauer

J. Vac. Sci. Technol. A 7, 3197 (1989); http://dx.doi.org/10.1116/1.576334 (3 pages) | Cited 4 times

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PbTe/Pb1−xMnxTe (x≤0.03) structures were grown from PbTe, Te, and Mn sources with in situ control of the growth mode using reflection high energy electron diffraction. As a substrate material cleaved (111) oriented BaF2 was used. The period of multiquantum well structures was determined by high–angle x‐ray diffraction patterns. Mobilities in excess of 2×104 cm2/Vs were observed at temperatures T>30 K.
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81.15.Hi Molecular, atomic, ion, and chemical beam epitaxy
73.21.-b Electron states and collective excitations in multilayers, quantum wells, mesoscopic, and nanoscale systems

Novel 〈110〉 growth processes in vacuum evaporated calcium fluoride films on 〈001〉 silicon

A. R. Srivatsa, J. Narayan, F. Radpour, and R. Singh

J. Vac. Sci. Technol. A 7, 3200 (1989); http://dx.doi.org/10.1116/1.576335 (5 pages) | Cited 2 times

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Novel microstructures in calcium fluoride films deposited by vacuum evaporation were observed on 〈001〉 silicon substrates as a function of deposition temperature. The microstructure consists of two sets of 〈110〉 oriented crystallites on the 〈001〉 silicon. A set of {110} planes in each of these two kinds of crystallites is aligned with a set of {110} planes of silicon, leading to a film morphology with mutually perpendicular, elongated, rodlike features running along a 〈110〉 direction of each set of crystallites. Both scanning electron microscopy and transmission electron microscopy were used to examine these features. The growth of this microstructure is discussed in the context of a combination of 〈110〉 textured growth and ‘‘planar‐matching epitaxy.’’
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81.15.-z Methods of deposition of films and coatings; film growth and epitaxy
68.55.-a Thin film structure and morphology

Pressure controlled feeding system for vacuum flash evaporation

V. Fuenzalida, N. Beltrán, C. Grahmann, and M. Pérez

J. Vac. Sci. Technol. A 7, 3205 (1989); http://dx.doi.org/10.1116/1.576336 (3 pages)

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An automated feeding system for flash evaporation of powder in high vacuum has been developed. It is controlled by the system pressure and gives a nearly constant mean evaporation rate. The device is tested by evaporating ceramic powder (BaTiO3) with a base pressure of 2×10−4 Pa and a peak pressure of 1.4×10−3 Pa.
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81.15.Gh Chemical vapor deposition (including plasma-enhanced CVD, MOCVD, ALD, etc.)
81.15.-z Methods of deposition of films and coatings; film growth and epitaxy
07.90.+c Other topics in instruments, apparatus, and components common to several branches of physics and astronomy (restricted to new topics in section 07)
81.05.Je Ceramics and refractories (including borides, carbides, hydrides, nitrides, oxides, and silicides)

Computer‐controlled, three‐electron‐gun, multisubstrate evaporator for the preparation of multilayer thin films

X. K. Wang, H. Q. Yang, K. C. Sheng, B. Davis, R. P. H. Chang, and J. B. Ketterson

J. Vac. Sci. Technol. A 7, 3208 (1989); http://dx.doi.org/10.1116/1.576337 (5 pages) | Cited 1 time

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We have developed a novel multisource electron‐beam evaporator to prepare high‐quality multicomponent, multilayer thin films. The essential parts of the evaporator consist of three electron guns, a shutter turntable, and a multisubstrate turntable; the latter can be loaded with up to 20 substrates. A very attractive feature of the system is the implementation of computer control over the movement of the stepping motors. The two turntables are driven by separate stepping motors with optical encoders, and are used to: (i) position a selected substrate over a specified electron gun, and (ii) gate the flux for a desired time. With a suitable programming of the movement of the stepping motors, up to 20 different thin films, with individually tailored layers deposited sequentially from the three sources, can be prepared in a single run. The deposition rate and the sublayer thickness of the three constituents of a multilayer film are individually monitored by three film deposition controllers which communicate directly to the computer and the electron‐gun power supply. Predictable and reproducible deposition of thin films is accomplished by accurate, digital control of the deposition process. High‐quality films of YBaCuO have been prepared with this system.
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81.15.Rs Spray coating techniques
06.60.Sx Positioning and alignment; manipulating, remote handling

Blazed grating formation in a hollow cathode etcher

M. Gross, Y. Wu, and C. M. Horwitz

J. Vac. Sci. Technol. A 7, 3213 (1989); http://dx.doi.org/10.1116/1.576338 (4 pages)

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Blazed gratings with well‐defined facet angles can be etched in a modified hollow cathode reactive sputtering system. Electric field distortion and metal compound deposition are combined to give asymmetrically etched, controlled‐angle structures. The grating blank is scanned past the active discharge area to form a large‐area sample with uniform properties. Computer models of the etch and deposition processes agree with our experimental data in showing that blaze angles of ∼25° with apex angles of <90° are possible using this method.
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81.65.-b Surface treatments
81.15.Cd Deposition by sputtering
02.60.-x Numerical approximation and analysis

Monte Carlo simulation of thin‐film deposition in a rectangular groove

M. J. Cooke and G. Harris

J. Vac. Sci. Technol. A 7, 3217 (1989); http://dx.doi.org/10.1116/1.576339 (5 pages) | Cited 11 times

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The deposition of a thin film in a rectangular groove has been simulated by a Monte Carlo method, taking into account collisions in the gas phase, desorption, and surface mobility. The model shows that conformal coating is best achieved by a low sticking coefficient.
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85.40.Bh Computer-aided design of microcircuits; layout and modeling

A kinematic model of surface evolution during growth and erosion: Numerical analysis

I. V. Katardjiev

J. Vac. Sci. Technol. A 7, 3222 (1989); http://dx.doi.org/10.1116/1.576340 (11 pages) | Cited 2 times

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A concise and critical review of the basic ideas of the kinematic model of surface evolution during growth and erosion is presented. Further generalization of a recent development based on the Huygens principle of wave‐front propagation is briefly discussed. Numerical analysis and consequent numerical procedures based on the generalized kinematic model are also presented. A number of simulation examples of surface evolution are given to illustrate the advantages and capabilities of the numerical method.
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81.10.Aj Theory and models of crystal growth; physics and chemistry of crystal growth, crystal morphology, and orientation
02.60.-x Numerical approximation and analysis

Polymer surface reactivity enhancement by ultraviolet ArF laser irradiation: An x‐ray photoelectron spectroscopy study of polytetrafluoroethylene and polyethyleneterepthalate ultraviolet treated surfaces

M. Chtaib, E. M. Roberfroid, Y. Novis, J. J. Pireaux, R. Caudano, P. Lutgen, and G. Feyder

J. Vac. Sci. Technol. A 7, 3233 (1989); http://dx.doi.org/10.1116/1.576341 (5 pages) | Cited 5 times

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We have investigated by x‐ray photoelectron spectroscopy (XPS) the surface of two polymers [polytetrafluoroethylene and polyethyleneterepthalate (PTFE) and (PET)] which were previously submitted to pulsed UV radiation delivered from an excimer laser (ArF: λ=193 nm). Treatments realized under different gaseous atmospheres allow us to point out mechanisms leading to several chemical transformations at the polymer surface. In the case of PTFE, the high‐fluence irradiations produce defluorination with surface oxidation. The latter is mainly due to air moisture. The deposition of some ablated fragments on the surface has also been observed. For PET, the major modifications are produced below the ablation threshold. They are characterized by severe deoxidation due to the loss of CO and CO2. The irradiations under oxygen and nitrogen atmospheres show the possibility of grafting new functionalities at the polymer surface.
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61.80.Ba Ultraviolet, visible, and infrared radiation effects (including laser radiation)
79.60.Jv Interfaces; heterostructures; nanostructures

The effects of O2 plasma treatments on the surface composition and wettability of cold‐rolled aluminum foil

Brian R. Strohmeier

J. Vac. Sci. Technol. A 7, 3238 (1989); http://dx.doi.org/10.1116/1.576342 (8 pages) | Cited 7 times

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The effects of oxygen plasma treatments on the surface composition and wettability of cold‐rolled aluminum foil have been examined using x‐ray photoelectron spectroscopy (XPS or ESCA) and contact angle measurements. Results have shown that oxygen plasma treatments have two main effects on the surface composition of cold‐rolled aluminum: (i) Residual carbon contamination is removed efficiently, and (ii) the thickness of the aluminum oxide surface layer is increased. The removal of residual carbon species via plasma treatments results in a significant improvement in the foil wettability. The wettability of plasma treated cold‐rolled foil has been shown to be as good as, or better than, that of the best annealed foils. However, it was found that the wettability of plasma treated foils can degrade with time following treatment, which is apparently due to the adsorption of airborne carbon species and other contaminants. Oxygen plasma treatments also cause additional aluminum oxide to grow on the metal surface. The composition of this additional oxide is similar to that of the native passivation oxide. The thickness of the aluminum oxide layer has been shown to increase with both the plasma rf power and/or the plasma exposure time.
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81.05.Bx Metals, semimetals, and alloys
68.08.Bc Wetting
68.55.Nq Composition and phase identification

Dependence of oxygen redistribution on titanium film thickness during titanium silicide formation by rapid thermal annealing

S. W. Kang, John S. Chun, and S. C. Park

J. Vac. Sci. Technol. A 7, 3246 (1989); http://dx.doi.org/10.1116/1.576343 (5 pages)

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Silicidation of titanium (Ti) thin films sputter‐deposited onto (100) oriented single‐crystal silicon (Si) was performed by rapid thermal annealing (RTA) at temperatures of 500–800 °C. Auger depth profiling shows that, when exposed to air, the Ti films take in oxygen atoms independently of Ti thickness. During RTA the oxygen tends to be redistributed uniformly throughout the Ti film near the onset of silicide formation. As silicide formation progresses, the redistributed oxygen is expelled by the advancing silicide front. For 50 nm Ti thickness, the oxygen driven from the TiSi2 is confined at the surface of Ti film and the silicide growth is almost stopped even though there remains unreacted Ti. For 100 and 200 nm Ti thicknesses, before the oxygen driven from the TiSi2 is confined at the surface a second silicide layer starts growing at the surface. The oxygen driven from the both silicides is buried where the two silicide fronts meet. The depth of the buried oxygen peak was found to be dependent on the annealing temperature and on the Ti thickness: The peak tends to penetrate deeper for higher temperatures and for thicker Ti films. Also, it was found that amorphous silicon (a‐Si), which is sputter‐deposited sequentially on Ti film without breaking the vacuum, is quite effective in forming oxygen free and homogeneous TiSi2 by preventing oxygen infiltration into Ti film.
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81.15.Cd Deposition by sputtering
81.40.Ef Cold working, work hardening; annealing, post-deformation annealing, quenching, tempering recovery, and crystallization

Surface composition and structure changes in GaAs compounds due to low‐energy Ar+ ion bombardment

H. J. Kang, Y. M. Moon, T. W. Kang, J. Y. Leem, J. J. Lee, and D. S. Ma

J. Vac. Sci. Technol. A 7, 3251 (1989); http://dx.doi.org/10.1116/1.576344 (5 pages) | Cited 9 times

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We have carried out an experimental study of the surface composition and structural changes of GaAs under Ar+ ion sputtering using Auger electron spectroscopy (AES) and reflection high‐energy electron diffraction (RHEED). The Auger results show that preferential sputtering of As atoms takes place in the GaAs compound and that such a composition change with depth occurs in a simple exponential form with Ga enrichment on the top surface layer. The grown surface undergoes a C(4×4) reconstruction, and after Ar+ ion sputtering this GaAs(001)–C(4×4) structure disappears resulting in an amorphous halo. But the characteristic surface which has a superlattice of (011) on GaAs (001) was found after sputtering and postannealing.
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81.15.Cd Deposition by sputtering
68.65.-k Low-dimensional, mesoscopic, nanoscale and other related systems: structure and nonelectronic properties

Pulsed laser induced effects on the HgCdTe surface

C. N. Afonso, M. Alonso, J. L. H. Neira, A. D. Sequeira, M. F. da Silva, and J. C. Soares

J. Vac. Sci. Technol. A 7, 3256 (1989); http://dx.doi.org/10.1116/1.576132 (9 pages) | Cited 11 times

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Laser annealing of mercury cadmium telluride (MCT) is interesting from both physical and practical perspectives. We have investigated the behavior of nominal Hg1−xCdxTe(x=0.2) wafers under pulsed laser irradiation and analyzed the role of some of the laser beam parameters. Rutherford backscattering spectroscopy (RBS), auger sputter depth profiling (SDP), and scanning electron microscopy (SEM) have been used to achieve a general picture of the process and to characterize the compositional, morphological, and order–disorder changes produced by the laser irradiation. We report the first depth profiles of laser treated MCT by both RBS and Auger SDP techniques. Significant differences are found when compared with results for other annealing methods. A Te‐rich layer is observed at the surface. The Hg deficient region is found a few tens of monolayers below the top of the surface with the maximum depletion at 18–30 nm. At this depth, small increases of Hg concentration are detected in the surrounding nonirradiated areas. Thermal and compositional changes are discussed taking into account that laser irradiation produces the melting of surface and near‐surface regions and a consequent liquid phase epitaxial regrowth.
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81.40.Ef Cold working, work hardening; annealing, post-deformation annealing, quenching, tempering recovery, and crystallization
61.80.Ba Ultraviolet, visible, and infrared radiation effects (including laser radiation)

Variation in GaAs surface oxide desorption temperature as a function of shuttered aluminum oven temperature

K. J. Kuhn and G. A. Pubanz

J. Vac. Sci. Technol. A 7, 3265 (1989); http://dx.doi.org/10.1116/1.576133 (4 pages) | Cited 3 times

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A variation in the thermal desorption temperature of surface oxides as a function of shuttered aluminum oven temperature has been observed for GaAs substrate material prepared for molecular‐beam epitaxy (MBE) using two different wet‐etch processes. A novel temperature calibration technique was developed to determine the absolute thermal desorption temperature. The observed thermal desorption temperature with a cool shuttered aluminum oven displayed no variation and was consistent with the currently accepted value of 582 °C. However, experimental results indicate that the thermal desorption temperature with a hot shuttered aluminum oven is substantially greater (630–650 °C) than the currently accepted value. It is suggested that aluminum species present on the shutter desorb and react with the surface gallium oxide to form a more refractory surface oxide.
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68.35.Md Surface thermodynamics, surface energies
07.20.Hy Furnaces; heaters

Effect of carburization on diffusion and desorption properties of a La–Mo system

G. Sreenivasa Rao, C. V. Dharmadhikari, and A. S. Nigavekar

J. Vac. Sci. Technol. A 7, 3269 (1989); http://dx.doi.org/10.1116/1.576134 (6 pages)

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The effect of carburization on diffusion properties of a La–Mo system has been investigated using Auger electron spectroscopy in conjunction with Ar+ ion sputtering. Both bulk and grain boundary diffusion is investigated: The former increases by one or two orders of magnitude after carburization, depending on the temperature, whereas the latter shows decrease by the same order. The grain boundary diffusion coefficients of La in Mo–C are approximately only two orders of magnitude higher than the corresponding bulk values in contrast to five orders of magnitude in the case of La in Mo. The results suggest that the carburization causes drastic changes in defect and morphological structures both in the grain and at the grain boundaries of molybdenum. The isothermal desorption of La from polycrystalline Mo–C is also investigated and yields values 2.56 eV and 3.0×108 s−1 of activation energy and pre‐exponential factors, respectively. Comparison of the present results with that of clean La–Mo system is used to elucidate the role of carbon in the performance of a La–Mo cathode.
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68.03.Fg Evaporation and condensation of liquids
68.43.Mn Adsorption kinetics
81.40.-z Treatment of materials and its effects on microstructure, nanostructure, and properties

Infrared analysis of film growth on the silicon surface in room air

J. E. Olsen and F. Shimura

J. Vac. Sci. Technol. A 7, 3275 (1989); http://dx.doi.org/10.1116/1.576135 (4 pages) | Cited 11 times

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Two infrared internal reflection spectroscopic techniques are used to analyze the composition of the film that grows on hydrophobic silicon at room temperature. A conventional internal reflection technique with a silicon internal reflectance element shows that the silicon surface adsorbs hydrocarbons from the atmosphere. A modified internal reflection technique showed <0.2 nm of SiO and SiO1.5 on the silicon surface one month after a hydrofluoric acid strip. Compared to the rate of contamination, the rate of silicon oxidation at room temperature is considered negligible.
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68.55.-a Thin film structure and morphology
78.30.Hv Other nonmetallic inorganics

Adsorption of CO, O2, and H2O on GaAs(100): Photoreflectance studies

E. G. Seebauer

J. Vac. Sci. Technol. A 7, 3279 (1989); http://dx.doi.org/10.1116/1.576136 (8 pages) | Cited 3 times

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Adsorption of CO, O2, and H2O on semi‐insulating GaAs(100) has been examined with photoreflectance (PR). This work represents the first use of PR for quantitative adsorption measurements on semiconductors. In PR, the laser‐induced change in surface reflectance is monitored as a function of wavelength. The resulting spectra are sensitive to changes in both the surface potential and the nature of surface states. Results at the E1 (3.0 eV) and E0 (1.4 eV) transitions are complementary to each other. Sticking coefficients S were obtained from E1 data for these gases, and S at low coverage was found to increase in the order CO≪O2<H2O. S decreases by at least four orders of magnitude for all the gases as saturation is approached. The results suggest that oxygen has two binding states that fill sequentially. Gas adsorption generally improves the communication between isolated surface states and the bulk.
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68.03.Fg Evaporation and condensation of liquids
68.43.Mn Adsorption kinetics
77.22.Ch Permittivity (dielectric function)

Differential optical reflection spectroscopy of thin TiSi2 films on Si(111)

M. Tanaka, P. E. Schmid, A. Piaggi, and F. Lévy

J. Vac. Sci. Technol. A 7, 3287 (1989); http://dx.doi.org/10.1116/1.576137 (4 pages)

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The microstructures of thin TiSi2 films with nominal thicknesses of 2.4 to 10.8 nm on Si(111) substrates have been estimated in situ. The change of normal incidence optical reflectance was measured in the course of film formation. Surface roughness was monitored by diffuse light scattering. It is an important factor in the analysis of the optical properties. The reflectivity is calculated on the basis of a three‐parameter model which accounts for both structural and compositional fluctuations. The values of the parameters agree with the results of electron microscopy studies on TiSi2 films of ∼100 nm. The method presented gives quantitative estimates of coverage, in contrast with Auger electron spectroscopy which suffers from an excessive surface sensitivity.
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68.55.-a Thin film structure and morphology
78.20.Ci Optical constants (including refractive index, complex dielectric constant, absorption, reflection and transmission coefficients, emissivity)

Low‐retardance fused‐quartz window for real‐time optical applications in ultrahigh vacuum

A. A. Studna, D. E. Aspnes, L. T. Florez, B. J. Wilkens, J. P. Harbison, and R. E. Ryan

J. Vac. Sci. Technol. A 7, 3291 (1989); http://dx.doi.org/10.1116/1.576138 (4 pages) | Cited 24 times

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We describe a low‐strain, Suprasil quartz window assembly for ultrahigh vacuum applications that require high transmittance and/or low retardance over a wide spectral range. The assembly mounts on a 2 (3)/(4) in. Conflat flange. The window can be heated externally to 400 °C to remove typical molecular‐beam‐epitaxy growth deposits, thereby eliminating a major source of inaccuracy in optical pyrometry and allowing high‐light fluences to be transmitted with minimal attenuation. Retardations at 459 nm (2.5 eV) of four unmounted Bellcore windows ranged from 0.05° to 0.3° while retardations of properly mounted windows were <0.5°. These retardations could be reduced an order of magnitude by applying small counterstresses, thereby allowing highly accurate real‐time growth data to be obtained by polarization‐sensitive optical techniques such as reflectance‐difference spectroscopy or spectroellipsometry.
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42.79.Fm Reflectors, beam splitters, and deflectors
42.79.Ls Scanners, image intensifiers, and image converters
07.30.Kf Vacuum chambers, auxiliary apparatus, and materials

Cross‐sectional transmission electron microscopy/electron beam induced current investigations on as‐grown and hydrogen‐passivated, gas‐assisted solidified polycrystalline silicon

C. H. Chu, C. Y. Sun, and H. L. Hwang

J. Vac. Sci. Technol. A 7, 3295 (1989); http://dx.doi.org/10.1116/1.576139 (6 pages)

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Gas‐assisted‐solidified (GAS) polycrystalline silicon was developed for low‐cost solar cells. The as‐grown and hydrogen‐passivated samples were investigated by the electron beam induced current (EBIC) technique and cross‐sectional transmission electron microscopy (XTEM). The shallow penetrated EBIC line profiles across the grain boundaries were used to monitor the effects of hydrogen passivation, and the results were correlated with those revealed by the XTEM. All the samples after hydrogen passivation have reduced EBIC line profile contrast and grain boundary recombination velocities. But the thickness of the damaged layer observed from XTEM is 100 and 200 nm for 10 and 60 min passivation, respectively. Dislocations, defect clusters, thin amorphous layers, planar cracks, and bubbles were observed in the hydrogen‐passivated samples. The near surface damaged areas were investigated by the 15 keV electron beam and resulted in the reduction of minority carrier diffusion length.
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84.60.Jt Photoelectric conversion
81.10.Fq Growth from melts; zone melting and refining

Image processing of multispectral x‐ray photoelectron spectroscopy images

P. L. King, R. Browning, P. Pianetta, I. Lindau, M. Keenlyside, and G. Knapp

J. Vac. Sci. Technol. A 7, 3301 (1989); http://dx.doi.org/10.1116/1.576140 (4 pages) | Cited 2 times

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A new direct imaging photoelectron microscope has been demonstrated at the Stanford Synchrotron Radiation Laboratory. Data are obtained in the form of spectrally resolved images with a lateral resolution of <5 μ. The microscope produces a series of projected images with 64×64 picture elements. These images are recorded digitally and represent a very large data set. Image statistical methods have been used to reduce and present the image information.
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81.65.-b Surface treatments
07.60.Pb Conventional optical microscopes
42.30.Va Image forming and processing

A versatile spectrometer system for quantitative surface and in‐depth analysis with secondary ion and secondary neutral mass spectroscopy, Auger electron and x‐ray photoelectron spectroscopy

P. Sander, M. Altebockwinkel, W. Storm, L. Wiedmann, and A. Benninghoven

J. Vac. Sci. Technol. A 7, 3305 (1989); http://dx.doi.org/10.1116/1.576141 (7 pages) | Cited 1 time

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Recently, secondary neutral mass spectrometry (SNMS) has proved to be a fast and accurate technique for quantitative surface and bulk analysis of trace elements and multicomponent materials. The lack of sufficient chemical information urges the need of combination of this method with complementary analytical techniques such as secondary ion mass spectroscopy (SIMS), Auger electron spectroscopy (AES), and x‐ray photoelectron spectroscopy (XPS). We describe a fully computerized surface analytical instrument, in which electron‐beam SNMS, SIMS, AES, and XPS have been implemented for the first time in the same UHV system. We particularly discuss aspects of depth resolution, as obtained with each of the methods, and the need of a flexible computer‐based control and data acquisition system for reliability and flexibility of the analytical instrumentation. Typical applications to depth profiles of multicomponent semiconductor materials include analysis of amorphous hydrogenated carbon (a‐C:H) layers on germanium and of copper contacts on mercury cadmium telluride (CdxHg1−xTe).
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07.75.+h Mass spectrometers
82.80.Pv Electron spectroscopy (X-ray photoelectron (XPS), Auger electron spectroscopy (AES), etc.)
81.70.-q Methods of materials testing and analysis

Ethylene π species on bare and cesiated Pt(111) surfaces

M. B. Hugenschmidt, P. Dolle, J. Jupille, and A. Cassuto

J. Vac. Sci. Technol. A 7, 3312 (1989); http://dx.doi.org/10.1116/1.576142 (5 pages) | Cited 5 times

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The adsorption of ethylene on bare and cesiated Pt(111) surfaces has been investigated by means of thermal desorption spectroscopy and ultraviolet photoemission spectroscopy, at temperatures ranging between 37 and 800 K. On the bare Pt(111) surface, a new π‐bonded C2H4 species has been observed at T<52 K. It is believed to be nearly undistorted with respect to the gas phase molecule. At T>52 K, it transforms into di‐σ C2H4 and then into ethylidyne (∼300 K). Conversely, cesium preadsoption gives rise to reversibly adsorbed π‐bonded ethylene, meanwhile it inhibits the usual reaction path (di‐σ species leading to ethylidyne). Furthermore, valence‐level binding energy shifts induced by cesium adatoms have been shown to be consistent with the theoretical picture of the electrostatic potential surrounding adsorbed alkali elements.
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68.03.Fg Evaporation and condensation of liquids
68.43.Mn Adsorption kinetics

Oxygen reactive ion etching mechanisms of organic and organosilicon polymers

Charles W. Jurgensen and Anne Rammelsberg

J. Vac. Sci. Technol. A 7, 3317 (1989); http://dx.doi.org/10.1116/1.576143 (8 pages) | Cited 16 times

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The oxygen reactive ion etching characteristics of a silyl novolac polymer and an organic novolac polymer were investigated as a function of pressure, self‐bias voltage, power density, radio frequency (rf) frequency, and other system variables. For each etching condition, sheath thickness measurements were used as a diagnostic to estimate the flux and average bombardment energy of ions and the energetic neutral products of charge transfer collisions. The estimated flux allows the observed etching rate to be converted into a yield per bombarding particle. The trends for the etching rate as a function of pressure and other system variables were found to reflect a single trend for the yield as a function of the average bombardment energy. The yield of the organic novolac is proportional to the bombardment energy and is equal to 12 carbon atoms per 100 eV. The silicon atom yield of the organosilicon novolac is equal to the sputtering yield of SiO2 as predicted by the steady‐state model of organosilicon polymer etching. The selectivity in bilayer lithographic schemes (the ratio of the organic to organosilicon etching rates) increases as the bombardment energy decreases because the SiO2 sputtering yield is negligible for bombardment energies less than 50 eV.
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81.05.Lg Polymers and plastics; rubber; synthetic and natural fibers; organometallic and organic materials
81.65.-b Surface treatments
82.30.Fi Ion-molecule, ion-ion, and charge-transfer reactions

A multipurpose quadrupole mass spectrometer detector for surface kinetic and absolute surface coverage measurements

V. S. Smentkowski and J. T. Yates

J. Vac. Sci. Technol. A 7, 3325 (1989); http://dx.doi.org/10.1116/1.576144 (7 pages) | Cited 11 times

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A multipurpose mass spectrometer detector has been constructed for studies of adsorption and desorption from single‐crystal surfaces in an ultrahigh vacuum system. The detector may be used for studies of the kinetics of adsorption on single crystals using collimated and calibrated molecular‐beam dosers, as well as the direct measurement of the absolute sticking probability as a function of the absolute surface coverage. In addition, using a small sampling aperture for line‐of‐sight desorption procedures, it is possible to achieve high sensitivity for the detection of gaseous desorption products as well as condensible products. In the direct line‐of‐sight detection mode of operation, a desorbing free radical species has been detected. Normally, mass spectrometers used in ultrahigh vacuum systems are not able to be employed for the combination of purposes addressed by this instrument.
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07.75.+h Mass spectrometers
82.80.Ms Mass spectrometry (including SIMS, multiphoton ionization and resonance ionization mass spectrometry, MALDI)

A charged‐particle analyzer for radio‐frequency discharges

A. M. Smith, B. N. Beilby, and C. M. Horwitz

J. Vac. Sci. Technol. A 7, 3332 (1989); http://dx.doi.org/10.1116/1.576145 (5 pages) | Cited 10 times

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Ion and electron fluxes have been measured at the target electrode of an inverted radio‐frequency (rf) diode discharge. The retarding‐field analyzer uses a single suppressor electrode to select the charged particle polarity, and errors due to secondary particle generation have been minimized. The error sources in this apparatus are described, together with ways of avoiding them. This analyzer permits accurate determination of the directed particle flux with sampling aperture sizes ranging from 30 to 400 μm diameter. Examples of particle fluxes and energy distributions in both rf and direct current (dc) discharges are given, and it is shown that rf discharges have greater ion and electron fluxes at the target, and higher ion energies, than do comparable dc discharges.
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07.77.-n Atomic, molecular, and charged-particle sources and detectors
52.80.Pi High-frequency and RF discharges

Transmission characteristics of a cylindrical energy analyzer

J. H. Craig and W. G. Durrer

J. Vac. Sci. Technol. A 7, 3337 (1989); http://dx.doi.org/10.1116/1.576146 (4 pages) | Cited 8 times

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A ‘‘Bessel box’’ energy filter was constructed, adding design improvement features of increased length, a central grid, and a conical front end cap. The priorities of compactness, simplicity, and low cost were maintained relative to more complex models. Performance characteristics were determined in an ultrahigh vacuum system equipped for electron stimulated desorption work and thermal desorption experiments.
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07.75.+h Mass spectrometers

A low‐cost high performance low‐energy electron diffraction intensity measuring apparatus with video data acquisition rate

Zhi‐yuan Zhang, Jia‐ho Lu, and Si‐min Chai

J. Vac. Sci. Technol. A 7, 3341 (1989); http://dx.doi.org/10.1116/1.576147 (4 pages)

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In order to get the low‐energy electron diffraction (LEED) I–E curves of a time‐varying surface structure, we developed a well‐designed multichannel programmable data acquisition system. By using a 2 μs (ADC) chip and some other hardwares the video data acquisition rate is realized. Up to 20 beams could be acquired. The tracking of spots is accomplished by the computation of the spots’ position. The size of the sampling window is slectable in the range of (4×4) to (16×16) pixels according to the size of the spot. Considering the inertia of the camera tube and the LEED gun supply, a pause of one‐half to several tens of frames may be assigned after the control of energy is setup. In this paper, I–E curves of diffraction spots of Si (111)‐(7×7) structure, including that of individual fractional spots, are demonstrated. This system can also measure the intensity distribution pattern of diffraction, the spot intensity variation of time I–t curve, and may be used for reflection high‐energy electron diffraction (RHEED) as well.
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61.05.jh Low-energy electron diffraction (LEED) and reflection high-energy electron diffraction (RHEED)
07.05.Hd Data acquisition: hardware and software
07.05.Kf Data analysis: algorithms and implementation; data management
07.05.Rm Data presentation and visualization: algorithms and implementation

Multipole confined diffusion plasma produced by 13.56 MHz electrodeless source

R. W. Boswell, A. J. Perry, and M. Emami

J. Vac. Sci. Technol. A 7, 3345 (1989); http://dx.doi.org/10.1116/1.576148 (6 pages) | Cited 25 times

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An inductively coupled rf plasma source is shown to produce a large uniform diffusion plasma at low pressures in a reactor surrounded externally by small magnets arranged to produce cusp fields at the walls. Electron densities of >1011 cm−3 can be produced at pressures of <10−3 Torr argon with 800 W input power. With SF6 ion currents of 0.5 mA cm−2 uniform to ±1.5% over 15 cm diameter have been measured at 6×10−4 Torr and 400 W.
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81.15.Gh Chemical vapor deposition (including plasma-enhanced CVD, MOCVD, ALD, etc.)
81.65.-b Surface treatments
52.80.Pi High-frequency and RF discharges

Two‐point pressure method for measuring the outgassing rate

Nagamitsu Yoshimura and Haruo Hirano

J. Vac. Sci. Technol. A 7, 3351 (1989); http://dx.doi.org/10.1116/1.576149 (5 pages)

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The two‐point pressure method for measuring the outgassing rate of a solid material has been introduced, in which the pressures at two points in a pipe are measured. This method was applied to measuring the outgassing rates of two kinds of SUS304 plates, belt‐polished plates, and buff‐polished plates. The outgassing rates were measured under a pressure as low as that expected in the actual high‐vacuum system. Additionally, the one‐point pressure method has been introduced, whose validity was ascertained using measured pressures in the experimental setup. The outgassing rates for the same kinds of SUS304 plates were again measured by the conventional orifice method for comparison.
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07.30.Cy Vacuum pumps
06.30.-k Measurements common to several branches of physics and astronomy
81.90.+c Other topics in materials science (restricted to new topics in section 81)

The molecular drag gauge as a calibration standard

Sharrill Dittmann, Bernd E. Lindenau, and C. R. Tilford

J. Vac. Sci. Technol. A 7, 3356 (1989); http://dx.doi.org/10.1116/1.576150 (5 pages) | Cited 9 times

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The National Institute of Standards and Technology has used molecular drag gauges for six years as transfer standards in the high‐vacuum range, 1×10−4 to 1×10−1 Pa. We report on the experience gained with these gauges and, in particular, on their long‐ and short‐term calibration stability, on factors affecting accuracy, on the predictability of the effective accommodation coefficient, and on factors affecting the stability of the offset correction.
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07.30.Hd Vacuum testing methods; leak detectors
06.20.F- Units and standards

Analysis of pumping down process

K. Kanazawa

J. Vac. Sci. Technol. A 7, 3361 (1989); http://dx.doi.org/10.1116/1.576151 (10 pages) | Cited 3 times

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A pumping down process is analyzed considering desorption and adsorption of gas molecules. Starting from a set of equations which describes the surface kinetics of adsorption and desorption and the evacuation of gas phase molecules, a quasi‐steady‐state condition is defined. Under this condition, if the temperature is constant, the total outgassing rate from the surface is approximately equal to the pumping rate of gas phase molecules out of the system. But with temperature variation the total outgassing rate is considerably different from the pumping rate and the difference contributes to the change of pressure. Under the same condition a single equation which contains an adsorption isotherm explicitly and describes the pressure variation during pumping down including the baking process is obtained. The solution of this equation is defined as a quasi‐steady solution. An actual pumping down curve (of water vapor) for an all‐metal system including the baking process can be fitted up to just before cool down by the quasi‐steady solution with the Freundlich isotherm. With the Temkin isotherm the quasi‐steady solution gives a t−1 variation of pressure. As the application of the quasi‐steady‐state condition for the vacuum system with thermal desorption, it is shown that the Temkin isotherm plays a special role in the consideration of a heterogeneous surface system and in the calculation of a pressure distribution.
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68.03.Fg Evaporation and condensation of liquids
68.43.Mn Adsorption kinetics

Temperature dependence of contact resistance in noble metal/high‐Tc superconductor systems

C.‐L. Huang, G. Sh. Gildenblat, and S. J. Fonash

J. Vac. Sci. Technol. A 7, 3371 (1989); http://dx.doi.org/10.1116/1.576152 (2 pages) | Cited 3 times

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A combination of three‐ and four‐terminal measurements was used to study the temperature dependence of the contact resistance of Au/YBa2Cu3O7−y and Ag/YBa2Cu3O7−y contacts. Both as‐deposited and oxygen annealed contacts were investigated. It is shown that not only the magnitude of the contact resistance but its temperature dependence above and below the transition point are strongly affected by the annealing process.
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74.70.-b Superconducting materials other than cuprates
73.40.Cg Contact resistance, contact potential

A solid‐state ultrahigh vacuum compatible source of molecular iodine

Andrew Mowbray and Robert G. Jones

J. Vac. Sci. Technol. A 7, 3373 (1989); http://dx.doi.org/10.1116/1.576345 (2 pages) | Cited 1 time

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The construction and operation of an ultrahigh vacuum compatible source of molecular iodine vapor is described. The iodine is generated by the solid‐state electrolysis of AgI doped 5% by weight with CdI2.
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07.77.-n Atomic, molecular, and charged-particle sources and detectors
37.20.+j Atomic and molecular beam sources and techniques
82.47.-a Applied electrochemistry

A laser drilled aperture for use in an ultrahigh vacuum gas doser

Patrick L. Hagans, Benjamin M. DeKoven, and Joseph L. Womack

J. Vac. Sci. Technol. A 7, 3375 (1989); http://dx.doi.org/10.1116/1.576346 (3 pages) | Cited 1 time

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Abstract Unavailable
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07.30.Kf Vacuum chambers, auxiliary apparatus, and materials

Vacuum limits of an economical, O‐ring sealed, versatile motion feedthrough

Martin P. Stockli

J. Vac. Sci. Technol. A 7, 3377 (1989); http://dx.doi.org/10.1116/1.576347 (4 pages)

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Abstract Unavailable
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07.30.Cy Vacuum pumps
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