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Depth profiles of au overlayers on ag films
Classified abstracts 1919-l
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Cr, Ti, Hf, Zr, Co, Ta, I’d, and Pt. The AI-Cr system was investigated in some detail using a conductance method and nuclear backscattering for reaction-rate measurements. The compounds CrAl, and Cr2AI,, were identified and their growth was found to be diffusion controlled. The temperature dependence of the rate constant for CrAl, obeyed an Arrhenius plot from 300” to 450°C with an activation energy of I .91 kO.1 eV. The Al-rich phases of the remaining transition metals were investigated; the compounds either exhibited a planar interface with parabolic growth kinetics or an irregular interface with nonparabolic growth. An empirical relationship involving the melting point and stability of the compounds was proposed to explain the different growth kinetics. J K Howard et al, J Var Sci Technol, 13 (I), 1976, 68-71. 30 1919. Effect of impurities on intrinsic stress in thin Ni films. (USA) Intrinsic stress has been investigated in thin nickel films, -1000 A thick, deposited at approximately 25 A/s in an UHV system equipped with a variable leak valve. The residual gas pressure d&ing depo&ion could be varied from IO-’ to 10e6 Pa. The cantilevered beam technique was used for measuring the film force per unit width as a function of film thickness. A new method, based on single slit diffraction, was developed for observing the substrate deflection. The stresses were tensile, and the average values decreased from 9.3 x IO9 dynes/cm” with 5.4 at % total impurities, to 4.2 x lo9 dynes/cm2 with 10.1 at % impurities. The film impurity concentrations, determined from AES depth-profile data, showed a correlation with the incremental stress as a function of film thickness. The major impurities were 0 and W from the evaporation filament, rather than the residual gasses, and film impurity content increased with filament outgassing time and power prior to evaporation. The films were examined with electron microscopy and were found to arain diameters. be polycrvstalline, with -100-500-8, P k Alexander and R W Hoffman, J pat Sci Technol, 13 (I), 1976, 96-98. 30 1920. Low-intrinsic-stress and good-adhesion alloy thin films. (USA) This paper illustrates that evaporated Ti-Cr alloy films have excellent adhesion on glass and also lower intrinsic stress. The intrinsic stress of this alloy film can be controlled by the alloy content, and the stress varies linearly with respect to Ti content in the film. The method of stress measurement, thin-film-composition determination, the critical thickness of the Ti-Cr film on glass, and the reason for low intrinsic stress are presented. H C Tong et al, J Vuc Sci Technol, 13 (I), 1976,99-101. 30 1921. Preparation and properties of adherent, transparent, conducting Rh 6hs. (USA) The optical and mechanical properties of thin rhodium films used as transparent electrodes can be altered and improved by the addition of a small partial pressure of oxygen and/or an applied substrate potential during evaporation. Transmission electron microscopy has been used to relate changes in morphology to the electrical, mechanical, and optical properties of thin Rh films of about 100 8, and also to the conditions of preparation. D M Hoffman and M D Coutts, J Vuc Sci Technol, 13 (I), 1976, 122-126. 30 1922. Optical properties of ultrathin Ag films. (USA) Reflection and transmission measurements from 1.8 to 4.4 eV have been made on evaporated Ag films with mass thicknesses less than 8 mn on fused silica substrates. The data were analyzed using approximative techniques. The results are discussed in terms of both the Maxwell-Garnett theory and the two-dimensional sphere model. Results indicate that the properties of specially heat-treated films are predicted very closely by the Maxwell-Ga.rnett theory. S L McCarthy, J Vuc Sci Technol, 13 (l), 1976,135-138. 30 1923. Growth and properties of vacuum deposited CulnSez thin 6hns. (VW The vacuum deposition of CuInCez thin films is reported. Asdeposited films are generally n-type due to selenide deficiencies. The temperature dependence of film mobility, conductivity, and carrier concentration are presented and indicate the dominance of the grain-boundary scatterihg mechanism. Mobilities of the range l-20 cmz/V s are reported for as-deposited films. Data are also 356
prcscnted for films annealed in Ar atmospheres. Films annealed in Ar/H,Se can be madep-type with mobilities in the range l-8 cmZ/V s. Electron and x-ray dif?‘raction data are discussed. Grain size data, especially the consideration of the elfccts of substrate temperature, are included. Photoconductive decay times are reported for the films. L L Kazmerski et al, J Vat Sci Techjrol, 13 (I), 1976, 139-144. 30 1924. Metallurgical considerations with respect to electrodes and interconnection lines for Josephson tunneling circuits. (USA) A description is presented of the composition, structure, and thermal stability of the Pb-alloy films which were used in the process described by Greiner et a/ for fabricating experimental Josephson tunneling circuits. The films were used to form tunneling-junction electrodes, controls, and interconnection lines; they consisted of Pb with In and/ or Au additions. Both of the additions were used for the base electrodes, controls, and interconnection lines whereas only Au was added in the case of the counterelectrodes. Each contained an intermetallic compound, which was believed to cause some mechanical strengthening. The base electrodes, controls and interconnection lines contained, in addition, a Pb-In solid solution phase. Tunneling junctions and gates which were fabricated through use of the indicated types of Pb-alloy films displayed characteristics which were suitable for circuit operation. S K Lahiri, J Vat Sci Tcchrrol, 13 (I), 1976, 148-l 5 I. 30 1925. Size effects in catalysis by metal nuclei. (USA) A method has been developed for determining the minimum size for a nucleus of metal atoms to achieve catalytic properties. Submonolayer vacuum deposits of the metal in question are used for this purpose. The deposits consist of a distribution of atomic clusters of various sizes, depending upon the coverage. To be useful, the size distributions in the deposits must be known, and these are determined by special techniques using electron microscopy. The nuclei are then employed as catalysts for reduction-oxidation chemical reactions analogous to photographic physical-development processes. Minimum size is determined by comparison of data from counts of particles of the reaction product with the size-frequency calibration of the deposits. The significant changes in catalytic properties are found to occur in the size range of a few atoms. Attempts to relate these changes to the physical properties of the nuclei involve such approaches as XPS determination of the density of occupied states, spectroscopic investigation of the electronic transitions, and molecular orbital calculations of all of these properties. J F Hamilton, J Vat Sci Techno/. 13 (I), 1976, 3 19-324. 30 1926. Depth profiles of Au overlayers on Ag films. (USA) Depth profiles of gold overlayers deposited onto 600-A silver films have been obtained with ion-scattering spectrometry. The overlayers, 50, 200, 400, and 800 8, thick, were deposited at ~-10~~ Pa onto freshly deposited 600-A thick Ag films. Complete coverage of the Ag underlayer was not achieved with the 50-and 200-A Au layers. Detectable signals (0~0.001) of Ag could still be obtained even with a 400-A Au overlayer. After aging for six to seven months at room temperature, the depth profiles show evidence for some bulk diffusion at the interface and a considerably enhanced accumulation of silver ouer the gold. The latter is attributed to preferred diffusion paths for Ag “through” and/or on the Au overlayer; calculated values of the mean-square displacement for the several diffusion paths are compared for the dimensions of the film. A sputtering yield of 2.0 Au atoms per Ne ion was calculated for 1800-eV neon ions incident at 45” onto the Au films. A W Czanderna and R Summermatter, J Vuc Sci Techno/, 13 (l), 1976,384-387. 30 1927. Physical vapor deposition of thick Cr and its carbide and nitride films by hollow-cathode discharge. (USA) Approaches to a dry process of hard Cr plating to overcome industrial pollution problems should be extensively investigated for many possible applications. Deposition by using a hollow-cathode discharge (HCD) gun, however, is one of the potential solutions; HCD generates very high density plasma between the substrate and the evaporation source. The plasma also serves to produce compound chemical films when reactive gas is properly introduced during deposition. Ductile Cr films are obtained in a variety of substrate temperatures ranging from 20” to 670°C and an applied negative
927
Cr, Ti, Hf, Zr, Co, Ta, I’d, and Pt. The AI-Cr system was investigated in some detail using a conductance method and nuclear backscattering for reaction-rate measurements. The compounds CrAl, and Cr2AI,, were identified and their growth was found to be diffusion controlled. The temperature dependence of the rate constant for CrAl, obeyed an Arrhenius plot from 300” to 450°C with an activation energy of I .91 kO.1 eV. The Al-rich phases of the remaining transition metals were investigated; the compounds either exhibited a planar interface with parabolic growth kinetics or an irregular interface with nonparabolic growth. An empirical relationship involving the melting point and stability of the compounds was proposed to explain the different growth kinetics. J K Howard et al, J Var Sci Technol, 13 (I), 1976, 68-71. 30 1919. Effect of impurities on intrinsic stress in thin Ni films. (USA) Intrinsic stress has been investigated in thin nickel films, -1000 A thick, deposited at approximately 25 A/s in an UHV system equipped with a variable leak valve. The residual gas pressure d&ing depo&ion could be varied from IO-’ to 10e6 Pa. The cantilevered beam technique was used for measuring the film force per unit width as a function of film thickness. A new method, based on single slit diffraction, was developed for observing the substrate deflection. The stresses were tensile, and the average values decreased from 9.3 x IO9 dynes/cm” with 5.4 at % total impurities, to 4.2 x lo9 dynes/cm2 with 10.1 at % impurities. The film impurity concentrations, determined from AES depth-profile data, showed a correlation with the incremental stress as a function of film thickness. The major impurities were 0 and W from the evaporation filament, rather than the residual gasses, and film impurity content increased with filament outgassing time and power prior to evaporation. The films were examined with electron microscopy and were found to arain diameters. be polycrvstalline, with -100-500-8, P k Alexander and R W Hoffman, J pat Sci Technol, 13 (I), 1976, 96-98. 30 1920. Low-intrinsic-stress and good-adhesion alloy thin films. (USA) This paper illustrates that evaporated Ti-Cr alloy films have excellent adhesion on glass and also lower intrinsic stress. The intrinsic stress of this alloy film can be controlled by the alloy content, and the stress varies linearly with respect to Ti content in the film. The method of stress measurement, thin-film-composition determination, the critical thickness of the Ti-Cr film on glass, and the reason for low intrinsic stress are presented. H C Tong et al, J Vuc Sci Technol, 13 (I), 1976,99-101. 30 1921. Preparation and properties of adherent, transparent, conducting Rh 6hs. (USA) The optical and mechanical properties of thin rhodium films used as transparent electrodes can be altered and improved by the addition of a small partial pressure of oxygen and/or an applied substrate potential during evaporation. Transmission electron microscopy has been used to relate changes in morphology to the electrical, mechanical, and optical properties of thin Rh films of about 100 8, and also to the conditions of preparation. D M Hoffman and M D Coutts, J Vuc Sci Technol, 13 (I), 1976, 122-126. 30 1922. Optical properties of ultrathin Ag films. (USA) Reflection and transmission measurements from 1.8 to 4.4 eV have been made on evaporated Ag films with mass thicknesses less than 8 mn on fused silica substrates. The data were analyzed using approximative techniques. The results are discussed in terms of both the Maxwell-Garnett theory and the two-dimensional sphere model. Results indicate that the properties of specially heat-treated films are predicted very closely by the Maxwell-Ga.rnett theory. S L McCarthy, J Vuc Sci Technol, 13 (l), 1976,135-138. 30 1923. Growth and properties of vacuum deposited CulnSez thin 6hns. (VW The vacuum deposition of CuInCez thin films is reported. Asdeposited films are generally n-type due to selenide deficiencies. The temperature dependence of film mobility, conductivity, and carrier concentration are presented and indicate the dominance of the grain-boundary scatterihg mechanism. Mobilities of the range l-20 cmz/V s are reported for as-deposited films. Data are also 356
prcscnted for films annealed in Ar atmospheres. Films annealed in Ar/H,Se can be madep-type with mobilities in the range l-8 cmZ/V s. Electron and x-ray dif?‘raction data are discussed. Grain size data, especially the consideration of the elfccts of substrate temperature, are included. Photoconductive decay times are reported for the films. L L Kazmerski et al, J Vat Sci Techjrol, 13 (I), 1976, 139-144. 30 1924. Metallurgical considerations with respect to electrodes and interconnection lines for Josephson tunneling circuits. (USA) A description is presented of the composition, structure, and thermal stability of the Pb-alloy films which were used in the process described by Greiner et a/ for fabricating experimental Josephson tunneling circuits. The films were used to form tunneling-junction electrodes, controls, and interconnection lines; they consisted of Pb with In and/ or Au additions. Both of the additions were used for the base electrodes, controls, and interconnection lines whereas only Au was added in the case of the counterelectrodes. Each contained an intermetallic compound, which was believed to cause some mechanical strengthening. The base electrodes, controls and interconnection lines contained, in addition, a Pb-In solid solution phase. Tunneling junctions and gates which were fabricated through use of the indicated types of Pb-alloy films displayed characteristics which were suitable for circuit operation. S K Lahiri, J Vat Sci Tcchrrol, 13 (I), 1976, 148-l 5 I. 30 1925. Size effects in catalysis by metal nuclei. (USA) A method has been developed for determining the minimum size for a nucleus of metal atoms to achieve catalytic properties. Submonolayer vacuum deposits of the metal in question are used for this purpose. The deposits consist of a distribution of atomic clusters of various sizes, depending upon the coverage. To be useful, the size distributions in the deposits must be known, and these are determined by special techniques using electron microscopy. The nuclei are then employed as catalysts for reduction-oxidation chemical reactions analogous to photographic physical-development processes. Minimum size is determined by comparison of data from counts of particles of the reaction product with the size-frequency calibration of the deposits. The significant changes in catalytic properties are found to occur in the size range of a few atoms. Attempts to relate these changes to the physical properties of the nuclei involve such approaches as XPS determination of the density of occupied states, spectroscopic investigation of the electronic transitions, and molecular orbital calculations of all of these properties. J F Hamilton, J Vat Sci Techno/. 13 (I), 1976, 3 19-324. 30 1926. Depth profiles of Au overlayers on Ag films. (USA) Depth profiles of gold overlayers deposited onto 600-A silver films have been obtained with ion-scattering spectrometry. The overlayers, 50, 200, 400, and 800 8, thick, were deposited at ~-10~~ Pa onto freshly deposited 600-A thick Ag films. Complete coverage of the Ag underlayer was not achieved with the 50-and 200-A Au layers. Detectable signals (0~0.001) of Ag could still be obtained even with a 400-A Au overlayer. After aging for six to seven months at room temperature, the depth profiles show evidence for some bulk diffusion at the interface and a considerably enhanced accumulation of silver ouer the gold. The latter is attributed to preferred diffusion paths for Ag “through” and/or on the Au overlayer; calculated values of the mean-square displacement for the several diffusion paths are compared for the dimensions of the film. A sputtering yield of 2.0 Au atoms per Ne ion was calculated for 1800-eV neon ions incident at 45” onto the Au films. A W Czanderna and R Summermatter, J Vuc Sci Techno/, 13 (l), 1976,384-387. 30 1927. Physical vapor deposition of thick Cr and its carbide and nitride films by hollow-cathode discharge. (USA) Approaches to a dry process of hard Cr plating to overcome industrial pollution problems should be extensively investigated for many possible applications. Deposition by using a hollow-cathode discharge (HCD) gun, however, is one of the potential solutions; HCD generates very high density plasma between the substrate and the evaporation source. The plasma also serves to produce compound chemical films when reactive gas is properly introduced during deposition. Ductile Cr films are obtained in a variety of substrate temperatures ranging from 20” to 670°C and an applied negative