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halogen mixtures
Classified abstracts 3063-3071 of the self-scattering of the molecules moving within a molecular beam. By perturbing the zeroth-order solution of the Boltzmann equation with a B-G-K kinetic model for the gas upstream to the orifice, and performing a particle scattering calculation for molecules within a beam downstream to the orifice, such self-scattering collision cross sections can be determined from the experimental data of velocity distribution functions of molecules in a beam. Y S Lou, J ApplPhys, 48 (3), 1977, 1094-1097. 34 3063. Self-masking selective epitaxy by molecular-beam method. (USA) Using collimated Ga and As.* molecular beams from limited-source apertures, epitaxial GaAs layers were grown selectively by selfmasking on preferentially etched GaAs surfaces with a lateral accuracy of 0.1 t~m. From edge profile analysis, it is found that (1) the accuracy is limited by preferential growth of an obstruction layer, (2) the surface diffusion length of free Ga is dependent upon As., arrival rate, and furthermore (3) the length is less than 200 A in As-rich growth conditions, while in Ga-rieh conditions the length is 1900 A. (Japan) S Nagata and T Tanaka, J Appl Phys, 48 (3), 1977. 940-942. 34 3064. Spectrograph suitable for the mass and energy analysis of space plasmas over the energy range 0.1-10 keV. (USA) The design and performance of a small, high resolution ion massenergy spectrograph are described. By utilizing a second-order double-focusing field geometry, mass resolution sufficient to separate energetic space plasma ions such as C +, N +, and O + has been achieved. The instrument responds to ions over a wide range of parameters (0.1-10 keV, 1-200 amu) and has a sufficient sensitivity for rocket or satellite measurements of space plasma ion populations (geometric factor ~10-.,Eo cmZsr keV). Sample mass spectra are displayed to show the laboratory prototype's response to artificially generated beams containing a variety of energetic ions. Plans for future development are briefly discussed. T E Moore, Rer Sci hlstrum, 48 (3), 1977, 221-225. 34 3065. The formation of ions in noble-gas/halogen mixtures. (USA) We have studied positive and negative ions in Xe-CIz, Xe-Br2, and Ar-Br2 mixtures in a drift-tube mass spectrometer. By varying the partial pressure of the halogen gas, we have been able to identify several ion-molecule reaction channels, and have obtained estimates of reaction rate coefficients in the Xe-Br2 case. In no case did we observe stable noble-gas/halogen complexes to be formed. B A Huber and T M Miller, J Appl Phys, 48 (4), 1977, 1708-171 I.
35. PROCESSING OF MATERIALS 35 3066. The vacuum hot-pressing of germanium and silicon-germanium alloys. (GB) A vacuum hot-press suitable for operating at vacuums better than 0.1 N m -2 and at temperatures up to 1700 K is described. Its operating characteristics and the pressing cycles employed in the preparation of heavily doped germanium and silicon-germanium alloys are reported. Preliminary measurements of the electrical and thermal properties of the hot-pressed germanium indicate that a significant degradation in electrical properties accompanies the hotpressing method of preparation. R W Bunce and D M Rowe, JPhys D: Appl Phys, 10 (6), 1977, 941947. 35 3067. Technique for producing uniform charged drops of cryogenic liquids. (USA) We have investigated and developed a reliable method to produce uniformly charged liquid nitrogen drops. An apparatus has been built which is capable of producing and charging drops in the 200 t~ diameter range. Rayleigh's method of uniform droplet production, which consists of breaking up a smooth liquid jet into uniform drops by an acoustic wave, is used. The diameter of the drops is controlled by the inside diameter of the nozzle and the frequency of the acoustic wave. Charges injected into the jet through field emission or field ionization subsequently end up on the drops, thereby producing
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uniformly charged drops. The charge per drop is determined by the amount of charge injected into the jet and by the number of drops produced per second. The maximum charge which could be placed on a single drop without impairing its integrity was one-fifth of its Rayleigh limit. The method described here could be applied to other insulating cryogenic liquids such as liquid hydrogen. J P Woosley and R J Turnbull, Rer Sci Ins/rum, 48 (3), 1977, 254-260. 35 3068. Production and properties of homogeneously nucleated germanium particles. (USA) Germanium particles were produced by homogeneous nucleation from the metal vapour in a flowing stream of nitrogen at pressures of 0.13-2.6 kPa. Light scattering and light absorption measurements showed particle sizes of 15-300-nm radii while in the stream. Electron microscopy indicated that these particles can coagulate into much larger sizes on electron microscope grids. Electron and X-ray diffraction measurements did not show any crystalline structure in these particles. J Hecht et al, J Appl Phys, 48 (4). 1977, 1503-1508.
36. V A C U U M I N S T R U M E N T A T I O N FOR SURFACE STUDIES 36 3069. A high-resolution Auger photoelectron spectrometer using a concentric hemisphere with two sets of three-clement cylindrical electrostatic lenses. (G B) A detailed description is given of the construction of an electron spectrometer for studies of chemical phenomena on solid surfaces. Auger electron spectra, photoelectron spectra and electron loss spectra can be taken from the same sample and in the same vacuum. The conditions required to attain high resolution over a wide range of electron energy (from about 0 eV to more than 500 eV) with a small concentric hemisphere analyser are made clear. (Japan) H Nozoye et al, J Phys E: Scient Instrum, 10 (5), 1977, 496-501. 36 3070. Miniature plane mirror analyser suitable for angle-resolved photoelectron spectroscopy. (USA) A plane-parallel-plate electron energy analyser is described based on the second-order-focusing 30 ° injection geometry. The small size of the analyscr permits it to be attached to a commercial rotary feedthrough and to be used in angle-resolved photoemission studies. The analyscr is operated in a constant pass energy mode, and the electron energy spectrum is obtained by sweeping the voltage on a preretardation/aeceleration stage. A resolution function A E/E equal to ~ 6 % leads to a resolution of lower than 0.2 eV at sufficiently low pass energies. The performance is illustrated with results obtained using synehroton radiation in a system having two identical analysers. N V Smith et al, Rev Sci Instrum, 48 (4), 1977, 454-459. 36 3071. Design of an apparatus for low-energy ion scattering from solid surfaces. (GB) This paper presents the basic characteristics of an apparatus for experiments involving low-energy (0.1-5 keV) scattering of alkali ions from solid surfaces. To produce alkali ions, a thermionic ion source was used. The ion beam obtained passes through the magnetic sector (Rm = 10 era, ~,, = 90°), which operates in the stigmatic focusing regime. Due to the primary beam contamination effect, surface cleaning during the experiment was maintained by the deposition of a fresh film of the metal investigated. This was done by an effusion source with a maximum working temperature of 1300°C. The base pressure in the interaction chamber was 2.6 × 10 -7 Pa. The baekscattered ions were energy-analysed by the double cylinderical sector analyser (Ra = 5 cm, ~a = 90 °, E//~E~400), which was continually swung around the target in the angular interval 0 < 0 < 135 °. For monitoring surface cleanness during the experiment, we used an Auger spectrometer consisting of the cylindrical energy analyser (Rs = 5 cm, ~s = 90 °) and electron gun (Ema~ = 3 keV). Finally, some results of the measured energy spectra of Na + ions backscattered from an Ag surface are presented. (Yugoslavia) I Terzic et al, JPhys E: Scient Instrum, 10 (4), 1977, 420-423.
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35. PROCESSING OF MATERIALS 35 3066. The vacuum hot-pressing of germanium and silicon-germanium alloys. (GB) A vacuum hot-press suitable for operating at vacuums better than 0.1 N m -2 and at temperatures up to 1700 K is described. Its operating characteristics and the pressing cycles employed in the preparation of heavily doped germanium and silicon-germanium alloys are reported. Preliminary measurements of the electrical and thermal properties of the hot-pressed germanium indicate that a significant degradation in electrical properties accompanies the hotpressing method of preparation. R W Bunce and D M Rowe, JPhys D: Appl Phys, 10 (6), 1977, 941947. 35 3067. Technique for producing uniform charged drops of cryogenic liquids. (USA) We have investigated and developed a reliable method to produce uniformly charged liquid nitrogen drops. An apparatus has been built which is capable of producing and charging drops in the 200 t~ diameter range. Rayleigh's method of uniform droplet production, which consists of breaking up a smooth liquid jet into uniform drops by an acoustic wave, is used. The diameter of the drops is controlled by the inside diameter of the nozzle and the frequency of the acoustic wave. Charges injected into the jet through field emission or field ionization subsequently end up on the drops, thereby producing
658
uniformly charged drops. The charge per drop is determined by the amount of charge injected into the jet and by the number of drops produced per second. The maximum charge which could be placed on a single drop without impairing its integrity was one-fifth of its Rayleigh limit. The method described here could be applied to other insulating cryogenic liquids such as liquid hydrogen. J P Woosley and R J Turnbull, Rer Sci Ins/rum, 48 (3), 1977, 254-260. 35 3068. Production and properties of homogeneously nucleated germanium particles. (USA) Germanium particles were produced by homogeneous nucleation from the metal vapour in a flowing stream of nitrogen at pressures of 0.13-2.6 kPa. Light scattering and light absorption measurements showed particle sizes of 15-300-nm radii while in the stream. Electron microscopy indicated that these particles can coagulate into much larger sizes on electron microscope grids. Electron and X-ray diffraction measurements did not show any crystalline structure in these particles. J Hecht et al, J Appl Phys, 48 (4). 1977, 1503-1508.
36. V A C U U M I N S T R U M E N T A T I O N FOR SURFACE STUDIES 36 3069. A high-resolution Auger photoelectron spectrometer using a concentric hemisphere with two sets of three-clement cylindrical electrostatic lenses. (G B) A detailed description is given of the construction of an electron spectrometer for studies of chemical phenomena on solid surfaces. Auger electron spectra, photoelectron spectra and electron loss spectra can be taken from the same sample and in the same vacuum. The conditions required to attain high resolution over a wide range of electron energy (from about 0 eV to more than 500 eV) with a small concentric hemisphere analyser are made clear. (Japan) H Nozoye et al, J Phys E: Scient Instrum, 10 (5), 1977, 496-501. 36 3070. Miniature plane mirror analyser suitable for angle-resolved photoelectron spectroscopy. (USA) A plane-parallel-plate electron energy analyser is described based on the second-order-focusing 30 ° injection geometry. The small size of the analyscr permits it to be attached to a commercial rotary feedthrough and to be used in angle-resolved photoemission studies. The analyscr is operated in a constant pass energy mode, and the electron energy spectrum is obtained by sweeping the voltage on a preretardation/aeceleration stage. A resolution function A E/E equal to ~ 6 % leads to a resolution of lower than 0.2 eV at sufficiently low pass energies. The performance is illustrated with results obtained using synehroton radiation in a system having two identical analysers. N V Smith et al, Rev Sci Instrum, 48 (4), 1977, 454-459. 36 3071. Design of an apparatus for low-energy ion scattering from solid surfaces. (GB) This paper presents the basic characteristics of an apparatus for experiments involving low-energy (0.1-5 keV) scattering of alkali ions from solid surfaces. To produce alkali ions, a thermionic ion source was used. The ion beam obtained passes through the magnetic sector (Rm = 10 era, ~,, = 90°), which operates in the stigmatic focusing regime. Due to the primary beam contamination effect, surface cleaning during the experiment was maintained by the deposition of a fresh film of the metal investigated. This was done by an effusion source with a maximum working temperature of 1300°C. The base pressure in the interaction chamber was 2.6 × 10 -7 Pa. The baekscattered ions were energy-analysed by the double cylinderical sector analyser (Ra = 5 cm, ~a = 90 °, E//~E~400), which was continually swung around the target in the angular interval 0 < 0 < 135 °. For monitoring surface cleanness during the experiment, we used an Auger spectrometer consisting of the cylindrical energy analyser (Rs = 5 cm, ~s = 90 °) and electron gun (Ema~ = 3 keV). Finally, some results of the measured energy spectra of Na + ions backscattered from an Ag surface are presented. (Yugoslavia) I Terzic et al, JPhys E: Scient Instrum, 10 (4), 1977, 420-423.
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