摘要:

This presentation is based upon that which was to be given by the Society President at the 25th National Symposium of the American Vacuum Society, 29 November 1978, in San Francisco, California. The talk to the Society by its President was an innovation of the 1979 Program Committee. The intention is that such a presentation be given each year at the awards acceptance plenary session along with those of the Welch and, when appropriate, Gaede–Langmuir awards. To be discussed are the recent highlights of Society activity, the direction the Society is taking, and an example of the multidisciplinary activities of Society members.

ISSN:0022-5355    

DOI:10.1116/1.570096

出版商:American Vacuum Society    

年代:1979

数据来源: AIP

摘要:

Molecular beam epitaxy (MBE) has emerged as a practical growth technique from surface studies of the interactions of thermal molecular beams with solid surfaces under UHV conditions. From this origin, a number of surface analytical techniques have been appliedinsituto assure that the desired conditions have been reached before and are being maintained during the crystal growth. The incorporation into the growth apparatus of surface diagnostic techniques, such as Auger electron spectroscopy (AES), reflection high energy electron diffraction (RHEED), and secondary ion mass spectroscopy (SIMS), is contributing important details on fundamental processes, which lead to the growth of high‐quality monocrystalline GaAs films by MBE. The formation of reconstructed surface structures on GaAs(100) as a function of growth parameters were observed during growth by RHEED. AES has been used, for example, to determine the relative Ga/As ratios for different reconstructed surface structures, to investigate the impurity contamination on substrate surfaces, and to study the surface segregation of Sn in MBE GaAs during doping. Finally, impurities incorporated during the growth of GaAs by MBE may be detected by SIMS immediately after growth and within the reaction chamber. The MBE technique has also enabled us to alter the surface composition in a well‐defined and reproducible manner and has been used to prepare flat, well‐ordered clean surfaces, which are essential for surface experiments. Experiments suitable in the MBE apparatus include low energy electron diffraction (LEED), low energy electron loss spectroscopy (LEELS), photoelectron spectroscopy (UPS and XPS), and Raman scattering.

ISSN:0022-5355    

DOI:10.1116/1.570097

出版商:American Vacuum Society    

年代:1979

数据来源: AIP

摘要:

Motivated by the stringent material requirements that low noise FET’s place upon underlying buffer layers, the electrical properties of unintentionally doped layers of GaAs grown by MBE have been investigated. A relatively shallow acceptor (0.027 eV) with a room temperature concentration of 2×1014cm−3is generally characteristic of undoped material presently grown by a number of laboratories involved in MBE. During experimental investigations, undesirable system configurations leading to higher background doping levels were identified. These configurations include BeO/Ta film substrate heaters (n?6×1016cm−3), fused quartz/Ta film substrate heaters (n?2×1015cm−3) and hot stainless steel fixtures illuminated by the Ga oven (p?1016cm−3).

ISSN:0022-5355    

DOI:10.1116/1.570098

出版商:American Vacuum Society    

年代:1979

数据来源: AIP

摘要:

A range of magnetron reactively sputtered metal carbide interference filters has been deposited onto sputtered copper on glass substrates and aged in vacuum at elevated temperature. These films show considerable promise as selective surfaces for incorporation in all glass vacuum insulated solar energy collectors. Surfaces produced by depositing homogeneous metal carbide films have solar absorptances α∠80% and emittances ε∠2.0% at 300 K. Solar absorptances above 90% and emittances 3.0%–4.0% at 300 K are obtained for multilayer metal carbide films fabricated by varying the reactive gas flow rate in steps during the deposition. Ageing experiments show that the reflectances of the multilayer films alter due to interdiffusion between the layers, resulting in a slow degradation of solar absorptance. Some diffusion coefficients for carbon in stainless steel and titanium films have been evaluated. Surfaces fabricated using chromium, molybdenum, and stainless steel carbides are superior to titanium carbide surfaces. Magnetron sputtering technology offers the possibility of more rapid and efficient deposition of these selective surfaces compared with the high pressure diode deposition technique utilized in previous work.

ISSN:0022-5355    

DOI:10.1116/1.570100

出版商:American Vacuum Society    

年代:1979

数据来源: AIP

摘要:

We give photoelectron spectroscopy results (hν?21.2 eV) on 1/4 and 1 Te monolayers deposited onto the (0001) Zn face. It is shown that a surface compound is formed whose density of states shows an increasing similarity to that of bulk amorphous ZnTe when the Te coverage increases. No ordered structures due to Te deposition have been detected with LEED.

ISSN:0022-5355    

DOI:10.1116/1.570101

出版商:American Vacuum Society    

年代:1979

数据来源: AIP

摘要:

Experimental results of sulfur line shape variations observed from various metal–sulfur compounds (Cu5FeS4, Cu2S, FeS) show that Auger fine structure analysis is able to separate chemical states of sulfur. Atomic sulfur presents a single Auger line at 149 eV whereas sulfur in the S2−oxidation state is characterized by a peak at 147 eV.

ISSN:0022-5355    

DOI:10.1116/1.570102

出版商:American Vacuum Society    

年代:1979

数据来源: AIP

摘要:

The binding of molecular benzene on clean (field‐evaporated) tungsten surfaces at 78 K has been investigated as a function of electric field strength using a new ramped field‐desorption technique. The resulting spectra, analogous to total pressure thermal desorption spectra (which do not mass analyze the desorbing species), show a physisorbed structure below 0.36 V/Å which increases continuously in area with increasing benzene coverage, a peak at 0.36 V/Å which grows until a saturation coverage is reached (and is thought to represent a physically adsorbed transition layer between chemisorbed and multiple layer physisorbed benzene at the surface), and a series of poorly resolved chemisorbed peaks (between ?0.38 and 1.13 V/Å) whose detailed shape depends on the local morphology of the surface region being examined. By recording the image of the desorbing species over the narrow field ranges which define these distinct features, the crystallographic behavior of the physisorbed and chemisorbed layers on the surface has been visually determined with angstrom resolution.

ISSN:0022-5355    

DOI:10.1116/1.570103

出版商:American Vacuum Society    

年代:1979

数据来源: AIP

摘要:

A high‐resistivity thin‐film resistor for Josephson logic devices has been experimentaly investigated. Resistivity measurements of Au1–xInxevaporated thin films demonstrate the existence of a resistivity maximum aroundx∠0.16 at liquid He temperature. A maximum resistivity of 0.14 μΩ m has been obtained, which is one order of magnitude higher than that of the previous AuIn2compound resistor. The temperature dependence and x‐ray diffraction experiments suggest that the resistivity maximum appears in the transition region from Au–In solid solution phase (x<0.16) to Au–In compound phase (x≳0.16). This means the resistivity maximum is mainly attributed to the contribution from impurity scattering in the Au–In solid solution.

ISSN:0022-5355    

DOI:10.1116/1.570104

出版商:American Vacuum Society    

年代:1979

数据来源: AIP

摘要:

It is known from previous work [R. W. Springer and D. S. Catlett, J. Vac. Sci. Technol. 15, 210 (1978)] that the residual gases can play a significant role in determining the resultant chemical purity of vacuum‐deposited films. The ability to alter the chemical composition and structure of a solid on a microdimensional scale can provide a means to tailor and control the mechanical properties of the material [see R. W. Springer and D. S. Catlett, Thin Solid Films 54, 197 (1978)]. Acetylene gas was admitted to the chamber over approximately two orders of magnitude of pressure during Ta deposition. Residual gas analysis was used to verify that a reaction between the Ta film and the gas occurred. Subsequent Auger analysis showed that the carbon in the films could be predicted using a simple pressure‐versus‐rate equation. The pulsed gas process (PGP) has been applied to the electron beam gun deposition of Ta. Tensile test specimens a few μm thick have been produced show fracture strengths varying from ∠ 170 to ∠860 mPa for pure to highly pulsed runs. The fracture strength loosely follows a Hall–Petch relation relating fracture strength to the time between pulses. Although diffusion of the carbon smoothes out the chemical period, it is thought that the remaining structure accounts for the strength enhancement.

ISSN:0022-5355    

DOI:10.1116/1.570105

出版商:American Vacuum Society    

年代:1979

数据来源: AIP

摘要:

A diagnostic technique is discussed and illustrated by experiment, which reveals sources of error in current integration dosimetry. The technique uses simple, specially prepared samples and an oscilloscope display of the measured current versus time.

ISSN:0022-5355    

DOI:10.1116/1.570106

出版商:American Vacuum Society    

年代:1979

数据来源: AIP