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Vacuum vapor deposited thin films of a perylene dicarboximide derivative: microstructure versus deposition parameters
Classified abstracts 6836-6844 secondary ion mass spectrometry and X-ray diffraction studies on various films are presented. Hall mobility, resistivity and carrier concentration measurements are also presented. Growth of polycrystalline films (as determined by X-ray diffraction studies) on glass substrates at as low a temperature as 525°C were observed. Below this substrate temperature, films became amorphous. The grain size increased with the increase in the substrate temperature. The highest value of the Hall mobility measured was about 10 cm2 V ~ s -l. Both n-type and p-type films were obtained. N K Annamalal et al, Thin Solid Films, 155, 1988, 77-79. 20 6836. Vapor-deposited superconducting lanthanum sulfide films Films of lanthanum sulfide were prepared by vapor deposition of the separate constituents onto heated sapphire substrates. The technique can be used to produce films over the entire range of composition from La2S3, which is an insulator, to La3S4 which is a metal and a superconductor. This family of materials shows promise for use in three-terminal superconducting devices based on the metal field effect. D D Berkley et al, Thin Solid Films, 156, 1988, 271-275. 20 6837. On the properties of physically vapour-deposited Ti-AI-V-N coatings Wear-resistant coatings of the quaternary system Ti-AI-V-N exhibit superior wear properties when deposited onto cemented carbides. Previous investigations of multicomponent hard coatings have demonstrated their advantages compared with chemically vapour deposited films currently used on cutting tools. A number of wear tests on both carbide and high speed steel tools indicated that, for example, (Ti, A1)N and (Ti, Zr)N coatings possess superior wear resistance. The resistance of quaternary Ti-A1-V-N coatings is even higher than that of ternary hard compound films. Since coatings oftheTi-AI-V N system crystallize in an f.c.c. TiN structure, the alloying agents aluminium and vanadium have a significant influence on their physical and chemical properties. Microstructural, X-ray diffraction, microprobe and micrographic analyses confirm the importance of the aluminium and vanadium content of the multicompound hard coating. In addition, wear tests with coated tools show the effect of the alloying agents on the wear resistance of the coating. O Knotek et al, Thin Solid Films, 153, 1987, 83-90. 20 6838. Characteristics of titanium arc evaporation processes The characteristic photon and ion emissions from a titanium cathodic arc evaporator have been studied. The composition of the background gas in the vacuum vessel was found to influence the emissions strongly. High resolution optical spectroscopy revealed that the neutral titanium atoms had a lower velocity distribution than had the ionized particles. Ion energy analysis indicated that charge exchange processes dominate at high background pressures. External magnetic fields applied to the plasma stream were found to excite the vapour and to accelerate the ions. Internal fields applied to the cathode surface were found to increase the cathode spot velocity to a maximum of around 25 m s ~. Application of an external field resulted in deposited titanium films with a reduced microdroplet component whereas an internal field had no effect. The film quality further improved with the introduction of reactive gases such as oxygen and nitrogen. The properties of the deposited titanium, Tit2 and TiN films were examined as a function of the external field strength. P J Martin et al, Thin Solid Films, 153, 1987, 91 102. 20 6839. Uniform composition Te-Se film preparation from alloy sources The composition uniformity of vacuum-deposited Se-Te alloy films was studied. The dependence of the film composition profile in the depth direction on the deposition rate and the alloy source composition is investigated. Uniform composition alloy films can be obtained when the deposition rate is lower than 1.0 n m s -~ and when the selenium concentration of the alloy source is lower than 20 at%. The mechanism of uniform composition film formation is also discussed. R Chiba and N Funakoshi, Thin Solid Films, 157, 1988, 307-313. 20 6840. A study of the adhesion of vacuum-evaporated polyethylene films to niuminium The dependence of the adhesion of flash-evaporated polyethylene films to aluminium substrates on various preparation and post-preparation
conditions has been investigated. The influence of the metal surface, the source and substrate temperatures during evaporation, the thickness of the layers, and the effect of UV light illumination on the adhesion of the films is discussed. D Bekiarov et al, Thin Solid Films, 157, 1988, 43-48. 20 6841. Kinetics of growth coalescence of In/GaAs The nucleation and growth of In dusters on GaAs has been numerically modelled using a kinetic rate equation approach. The rate equations were solved using a propagator method which is more efficient than a finitedifference scheme, allowing large time steps during which clusters grow by many atoms. The rate of growth coalescence is calculated analytically. A Monte Carlo model of nucleation and growth is presented and shown to yield equivalent results to the propagator method. Both models are used to determine growth mechanisms and the diffusion rate of In atoms on GaAs, using the data of Savage and Lagally. The effect of changing the deposition rate or substrate temperature on the average island size is predicted, and shown to agree with the available data. J B Adams et al, J Vac Sci Technol, A6, 1988, 2029-2033. 20 6842. Vacuum vapor deposited thin films of a perylene dicarboximide derivative : microstructure versus deposition parameters The microscopic physical structure in thin films of vapor deposited, large heterocyclic organic molecules is strongly dependent on the deposition parameters. The scale of the microstructure can vary enormously compared to inorganic systems, strongly affecting the macroscopic properties. Multiple polymorphs frequently characterize these systems. We have extended our previous work with the perylene dicarboximides to include a phenethyl derivative. Films in the 300-1000 A thickness range, deposited on metal and transparent substrates at varying rates and substrate temperatures from - 1 6 5 to 155°C, with and without vacuum annealing, have been characterized by scanning electron microscopy, ultraviolet/visible, and infrared (IR) spectroscopies, and polarization modulation reflectivity changes. Evidence is presented for a critical substrate temperature between - 2 2 and -32°C. Also a polymorphic phase sensitivity to deposition substrate temperature and rate is demonstrated, consistent with an exothermic peak observed by differential scanning calorimetry of the vapor deposited material, and an annealing induced molecular reorientation observed by reflection absorption IR. M K Debe et ai, J Vac Sci Technol, A6, 1988, 1907-1911. 20 6843. A source replenishment device for vacuum deposition A device providing remotely controlled linear and intermittent rotational motion has been developed and applied to the task of adding successive pieces of source metal to the filament in a vacuum deposition apparatus. R. A. Hill, Vacuum, 37, 1987, 769-771. 20 6844. Deposition techniques for the preparation of thin film nuclear targets Of all the diverse physical, chemical and mechanical techniques used to make thin film nuclear targets, material deposition by vacuum evaporation is the most widely employed. This review commences with a brief description of the basic principles that regulate vacuum evaporation and the physical processes involved in thin film formation, followed by a description of the experimental methods used. The principal methods of heating the evaporant are detailed and the means of measuring and controlling the film thickness are elucidated. Types of thin film nuclear targets are considered and various film release agents are listed. Thin film nuclear target behaviour under ion bombardment is described and the dependence of nuclear experimental results upon target thickness and uniformity is outlined. Parameters such as thermal effects, radiation damage and sputtering of target material all influence the useful lifetime of thin nuclear targets. Target impurities can also have a serious effect upon experimental results; these effects are briefly considered. Special problems associated with preparing suitable targets for lifetime measurements are discussed. Carbon is used extensively as a target material and also for the manufacture of stripper-foils to change the polarity of the accelerated ions. The causes of stripper-foil thickening and breaking under heavy-ion bombardment are considered. A comparison is made between foils manufactured by a glow discharge process and those produced by vacuum sublimation. Consideration is given to the methods of carbon stripper-foil manufacture and to the characteristics of stripperfoils made by different techniques. Various methods to increase stripper973
conditions has been investigated. The influence of the metal surface, the source and substrate temperatures during evaporation, the thickness of the layers, and the effect of UV light illumination on the adhesion of the films is discussed. D Bekiarov et al, Thin Solid Films, 157, 1988, 43-48. 20 6841. Kinetics of growth coalescence of In/GaAs The nucleation and growth of In dusters on GaAs has been numerically modelled using a kinetic rate equation approach. The rate equations were solved using a propagator method which is more efficient than a finitedifference scheme, allowing large time steps during which clusters grow by many atoms. The rate of growth coalescence is calculated analytically. A Monte Carlo model of nucleation and growth is presented and shown to yield equivalent results to the propagator method. Both models are used to determine growth mechanisms and the diffusion rate of In atoms on GaAs, using the data of Savage and Lagally. The effect of changing the deposition rate or substrate temperature on the average island size is predicted, and shown to agree with the available data. J B Adams et al, J Vac Sci Technol, A6, 1988, 2029-2033. 20 6842. Vacuum vapor deposited thin films of a perylene dicarboximide derivative : microstructure versus deposition parameters The microscopic physical structure in thin films of vapor deposited, large heterocyclic organic molecules is strongly dependent on the deposition parameters. The scale of the microstructure can vary enormously compared to inorganic systems, strongly affecting the macroscopic properties. Multiple polymorphs frequently characterize these systems. We have extended our previous work with the perylene dicarboximides to include a phenethyl derivative. Films in the 300-1000 A thickness range, deposited on metal and transparent substrates at varying rates and substrate temperatures from - 1 6 5 to 155°C, with and without vacuum annealing, have been characterized by scanning electron microscopy, ultraviolet/visible, and infrared (IR) spectroscopies, and polarization modulation reflectivity changes. Evidence is presented for a critical substrate temperature between - 2 2 and -32°C. Also a polymorphic phase sensitivity to deposition substrate temperature and rate is demonstrated, consistent with an exothermic peak observed by differential scanning calorimetry of the vapor deposited material, and an annealing induced molecular reorientation observed by reflection absorption IR. M K Debe et ai, J Vac Sci Technol, A6, 1988, 1907-1911. 20 6843. A source replenishment device for vacuum deposition A device providing remotely controlled linear and intermittent rotational motion has been developed and applied to the task of adding successive pieces of source metal to the filament in a vacuum deposition apparatus. R. A. Hill, Vacuum, 37, 1987, 769-771. 20 6844. Deposition techniques for the preparation of thin film nuclear targets Of all the diverse physical, chemical and mechanical techniques used to make thin film nuclear targets, material deposition by vacuum evaporation is the most widely employed. This review commences with a brief description of the basic principles that regulate vacuum evaporation and the physical processes involved in thin film formation, followed by a description of the experimental methods used. The principal methods of heating the evaporant are detailed and the means of measuring and controlling the film thickness are elucidated. Types of thin film nuclear targets are considered and various film release agents are listed. Thin film nuclear target behaviour under ion bombardment is described and the dependence of nuclear experimental results upon target thickness and uniformity is outlined. Parameters such as thermal effects, radiation damage and sputtering of target material all influence the useful lifetime of thin nuclear targets. Target impurities can also have a serious effect upon experimental results; these effects are briefly considered. Special problems associated with preparing suitable targets for lifetime measurements are discussed. Carbon is used extensively as a target material and also for the manufacture of stripper-foils to change the polarity of the accelerated ions. The causes of stripper-foil thickening and breaking under heavy-ion bombardment are considered. A comparison is made between foils manufactured by a glow discharge process and those produced by vacuum sublimation. Consideration is given to the methods of carbon stripper-foil manufacture and to the characteristics of stripperfoils made by different techniques. Various methods to increase stripper973