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1321. LEED, Auger spectroscopy, and contact potential studies of copper-gold alloy single crystal surfaces
Classified abstracts
1311-I 322
33 1311. Photocathodes for use in an electron image projector. (USA) In this paper factors influencing the choice of photocathode for an image projector are discussed. First of all, a description is given of the principles of operation of an image projector. It is shown that ionic insulators are likely to be the best materials, and the most likely ones are considered. Of these, cesium iodide is the best. In the last section a table is given comparing the observed properties of cesium iodide to those of palladium which has been used up to this time. (GB) J P Scott, J Appl Z’hys, 46 (2), 1975, 661-664. 33 1312. An electron spectrometer for surface studies. (Germany) Recent measurements of the mean free path for inelastic scattering of low energy electrons in solids have indicated the surface sensitivity of photoelectron spectroscopy. The present paper describes an ultrahigh vacuum system which makes possible XPS, UPS, LEED and other surface measurements in one system. Examples of its application are given for the chemisorption system tungsten (I lO)/oxygen. A M Bradshaw
and D Menzel,
Vakuum-Tech,
1313. Measurements of photoelectric (111) surfaces. (Germany)
24 (I), 1975, 15-20.
yield of pure and Ag-covered
33 Si
The photoelectric yield of pure and Ag-covered silicon-surfaces has been measured. It was possible to separate direct and indirect transitions by an evaluation of the measurements with Ballantyne’s theory. The ionization energy < has been determined from the low frequency limit for indirect transitions. The experimental yields could be interpreted from the bulk band structure in the case of pure Si. This was not possible, when the Si was covered by an ordered adsorption layer of Ag. Von H Beckermann et al, Vukuum-Tech, 24 (I), 1975, 12-14 (in Gfrman). 1314. Some applications spectral region. (USA)
of GM counters
in the vacuum
33 ultraviolet
The applicability of GM and proportional counters naturally extends into the vacuum ultraviolet (vuv) spectral region. A simple modification to this detector enables GM counters to be used to measure very small cross section variations or to be used as high efficiency detectors over a narrow spectral range with excellent second order discrimination.
valuable tool in the self-consistent interpretation measurements on an insulating specimen. B Kramer et al, J Vat Sci Tech&,
34. HIGH
ALTITUDE
AND
of photovoltagc
12 (3). 1975, 7 I 3P720.
SPACE
TECHNOLOGY
34 1318. Helical channel multiplier package design for space instrumentation. (USA)
A design for packaging helical channel multipliers with large input cones is discussed. This design utilizes silicon rubber to bond the channel multiplier into its housing and also provides magnetic shielding up to 150 G. Detector modules built from this design have been qualified to fly on the Apollo-Soyuz Test Project over the temperature range from ---35 to +8O”C and with up to 100 g of vibrational loading. These detectors have also been operated successfully under vacuum in their appropriate instruments. H H Hoshiko, Rev Sci Instrum, 46 (3), 1975, 33 I-332. 34 1319. Monte Carlo simulation of energy deposition by low-energy electrons in molecular hydrogen. (USA)
A set of detailed atomic cross sections has been used to obtain the spatial deposition of energy by l-20 eV electrons in molecular hydrogen by a Monte Carlo simulation of the actual trajectories. The energy deposition curve (energy per distance traversed) is quite peaked in the forward direction about the entry point for electrons with energies above the threshold of the electronic states, but the peak decreases and broadens noticeably as the electron energy decreases below 10 eV (threshold for the h3&+ state). The curve also assumes a very symmetrical shape for energies below 10 eV, indicating the increasing importance of elastic collisions in determining the shape of the curve, although not the mode of energy deposition. M G Heaps et al, J Appl Phys, 46 (4), 1975, 1798-l 803. 1320. Pressure, surfaces? (GB)
what does it mean in vacuum
chambers
34 with cryo-
A space simulation chamber is designed to test the thermal control and the temoeratures which arise inside a satellite. The cold block of space is simulated at 80 K. The size of the thus arising change in temperature distribution is calculated and taken into consideration in the temperature prediction for orbit. (Germany) P Kleber, Vucuun?, 25 (25), 1975, 191-196.
D L Ederer and P Dhez, Rev Sci Znstrum, 46 (2), 1975, 144-146. 33 1315. Intense atomic-hydrogen A new design for a hydrogen
beam source. (USA)
atom beam source is described. A long tube is used as the source and is heated by radiation from a heater loop. Dissociation fractions of more than 80% are achieved at oven temperatures of 2500 K, with beam number densities exceeding lOLo atoms/cm3. (GB) H Koschmieder and V Raible, Ret Sci Instrum, 46 (5), 1975, 536-537. 33 1316. Electron excitation in noble gases. (Canada) Calculations for cross sections for some states of Ne excited by electron impact have been carried out. A parametrization of total and differential cross section in the Born-Ochkur approximation has been proposed. Using this parametrization and appropriate wave functions for the states involved in the collision processes, differential and total cross sections have been calculated. The results have shown that this parametrization is very convenient to study this type of problem. (Brasil) H G P Lins de Barros and H S Brandi, Can J Phys, 53 (7), 1975, 689699. 33 1317. Comparison of photovoltic and photoconductive effects in insulating CdS crystals. (USA) Photovoltage measurements with insulating CdS crystals capacitively coupled to the external circuit have been performed at room temperature in 1 atm oxygen and 10m8 torr vacuum, and at 100 K at IO-’ torr vacuum, and have been interpreted self consistently with photoconductivity measurements. It was found that the Dember voltage is about 0.06 V at room temperature and 0.02 V at 100 K, that the oxygen chemisorption-induced surface barrier is at least 0.15 eV at room temperature, and that photoconductivity measurements are a 460
METALLURGY, INORGANIC ANALYTICAL CHEMISTRY
37.
CHEMISTRY, 37
1321. LEED, copper-gold
Auger spectroscopy, and contact alloy single crystal surfaces. (USA)
potential
studies
of
The (IOO), (111) and (110) surfaces of copper-gold alloy single crystals (Cu, Cu3Au, CuAu, AU&J, Au) have been studied. Results are presented for (i) the variation of relative Auger peak strengths with bulk composition, (ii) the variation of work function with orientation and bulk composition, and (iii) the occurrence of surface ordering. The average work function Q increases as the bulk Au concentration increases from Cu to Au3Cu, with the orientation dependence in accord with the expected variation of surface dipole with ‘atomic roughness’, i.e., @(I I I) _, @(lOO) _ @(I IO); the surfaces of Au do not follow this simple rule. LEED indicates that Au(lOO), Au(llO), Au,Cu(I IO) and CuAu(ll0) surfaces have complex structures. Observed differences in the kinetics of ordering of the Cu3Au (100) and (11 I ) surfaces are discussed. H C Potter and J M Blakely, J Vat Sri Technol,
12 (2), 1975, 635
642. 1322. Switching (USA)
regulator
emission
control
circuit
for ion sources.
An electron emission control circuit of the switching regulator type operating at 100 kHz has been developed which maintains a constant emission current within 0.1 “/, for a cathode power demand variation of approximately lOO’%. The power output stage has an efficiency of 67 %, and the overall efficiency is 45 % when driving a thoria-coated iridium cathode having a nominal resistance at operating temperature of 2.5 (1. Under optimum conditions, the bus power demand is 1.75 W. The circuit is useful in controlling the electron emission current of
1311-I 322
33 1311. Photocathodes for use in an electron image projector. (USA) In this paper factors influencing the choice of photocathode for an image projector are discussed. First of all, a description is given of the principles of operation of an image projector. It is shown that ionic insulators are likely to be the best materials, and the most likely ones are considered. Of these, cesium iodide is the best. In the last section a table is given comparing the observed properties of cesium iodide to those of palladium which has been used up to this time. (GB) J P Scott, J Appl Z’hys, 46 (2), 1975, 661-664. 33 1312. An electron spectrometer for surface studies. (Germany) Recent measurements of the mean free path for inelastic scattering of low energy electrons in solids have indicated the surface sensitivity of photoelectron spectroscopy. The present paper describes an ultrahigh vacuum system which makes possible XPS, UPS, LEED and other surface measurements in one system. Examples of its application are given for the chemisorption system tungsten (I lO)/oxygen. A M Bradshaw
and D Menzel,
Vakuum-Tech,
1313. Measurements of photoelectric (111) surfaces. (Germany)
24 (I), 1975, 15-20.
yield of pure and Ag-covered
33 Si
The photoelectric yield of pure and Ag-covered silicon-surfaces has been measured. It was possible to separate direct and indirect transitions by an evaluation of the measurements with Ballantyne’s theory. The ionization energy < has been determined from the low frequency limit for indirect transitions. The experimental yields could be interpreted from the bulk band structure in the case of pure Si. This was not possible, when the Si was covered by an ordered adsorption layer of Ag. Von H Beckermann et al, Vukuum-Tech, 24 (I), 1975, 12-14 (in Gfrman). 1314. Some applications spectral region. (USA)
of GM counters
in the vacuum
33 ultraviolet
The applicability of GM and proportional counters naturally extends into the vacuum ultraviolet (vuv) spectral region. A simple modification to this detector enables GM counters to be used to measure very small cross section variations or to be used as high efficiency detectors over a narrow spectral range with excellent second order discrimination.
valuable tool in the self-consistent interpretation measurements on an insulating specimen. B Kramer et al, J Vat Sci Tech&,
34. HIGH
ALTITUDE
AND
of photovoltagc
12 (3). 1975, 7 I 3P720.
SPACE
TECHNOLOGY
34 1318. Helical channel multiplier package design for space instrumentation. (USA)
A design for packaging helical channel multipliers with large input cones is discussed. This design utilizes silicon rubber to bond the channel multiplier into its housing and also provides magnetic shielding up to 150 G. Detector modules built from this design have been qualified to fly on the Apollo-Soyuz Test Project over the temperature range from ---35 to +8O”C and with up to 100 g of vibrational loading. These detectors have also been operated successfully under vacuum in their appropriate instruments. H H Hoshiko, Rev Sci Instrum, 46 (3), 1975, 33 I-332. 34 1319. Monte Carlo simulation of energy deposition by low-energy electrons in molecular hydrogen. (USA)
A set of detailed atomic cross sections has been used to obtain the spatial deposition of energy by l-20 eV electrons in molecular hydrogen by a Monte Carlo simulation of the actual trajectories. The energy deposition curve (energy per distance traversed) is quite peaked in the forward direction about the entry point for electrons with energies above the threshold of the electronic states, but the peak decreases and broadens noticeably as the electron energy decreases below 10 eV (threshold for the h3&+ state). The curve also assumes a very symmetrical shape for energies below 10 eV, indicating the increasing importance of elastic collisions in determining the shape of the curve, although not the mode of energy deposition. M G Heaps et al, J Appl Phys, 46 (4), 1975, 1798-l 803. 1320. Pressure, surfaces? (GB)
what does it mean in vacuum
chambers
34 with cryo-
A space simulation chamber is designed to test the thermal control and the temoeratures which arise inside a satellite. The cold block of space is simulated at 80 K. The size of the thus arising change in temperature distribution is calculated and taken into consideration in the temperature prediction for orbit. (Germany) P Kleber, Vucuun?, 25 (25), 1975, 191-196.
D L Ederer and P Dhez, Rev Sci Znstrum, 46 (2), 1975, 144-146. 33 1315. Intense atomic-hydrogen A new design for a hydrogen
beam source. (USA)
atom beam source is described. A long tube is used as the source and is heated by radiation from a heater loop. Dissociation fractions of more than 80% are achieved at oven temperatures of 2500 K, with beam number densities exceeding lOLo atoms/cm3. (GB) H Koschmieder and V Raible, Ret Sci Instrum, 46 (5), 1975, 536-537. 33 1316. Electron excitation in noble gases. (Canada) Calculations for cross sections for some states of Ne excited by electron impact have been carried out. A parametrization of total and differential cross section in the Born-Ochkur approximation has been proposed. Using this parametrization and appropriate wave functions for the states involved in the collision processes, differential and total cross sections have been calculated. The results have shown that this parametrization is very convenient to study this type of problem. (Brasil) H G P Lins de Barros and H S Brandi, Can J Phys, 53 (7), 1975, 689699. 33 1317. Comparison of photovoltic and photoconductive effects in insulating CdS crystals. (USA) Photovoltage measurements with insulating CdS crystals capacitively coupled to the external circuit have been performed at room temperature in 1 atm oxygen and 10m8 torr vacuum, and at 100 K at IO-’ torr vacuum, and have been interpreted self consistently with photoconductivity measurements. It was found that the Dember voltage is about 0.06 V at room temperature and 0.02 V at 100 K, that the oxygen chemisorption-induced surface barrier is at least 0.15 eV at room temperature, and that photoconductivity measurements are a 460
METALLURGY, INORGANIC ANALYTICAL CHEMISTRY
37.
CHEMISTRY, 37
1321. LEED, copper-gold
Auger spectroscopy, and contact alloy single crystal surfaces. (USA)
potential
studies
of
The (IOO), (111) and (110) surfaces of copper-gold alloy single crystals (Cu, Cu3Au, CuAu, AU&J, Au) have been studied. Results are presented for (i) the variation of relative Auger peak strengths with bulk composition, (ii) the variation of work function with orientation and bulk composition, and (iii) the occurrence of surface ordering. The average work function Q increases as the bulk Au concentration increases from Cu to Au3Cu, with the orientation dependence in accord with the expected variation of surface dipole with ‘atomic roughness’, i.e., @(I I I) _, @(lOO) _ @(I IO); the surfaces of Au do not follow this simple rule. LEED indicates that Au(lOO), Au(llO), Au,Cu(I IO) and CuAu(ll0) surfaces have complex structures. Observed differences in the kinetics of ordering of the Cu3Au (100) and (11 I ) surfaces are discussed. H C Potter and J M Blakely, J Vat Sri Technol,
12 (2), 1975, 635
642. 1322. Switching (USA)
regulator
emission
control
circuit
for ion sources.
An electron emission control circuit of the switching regulator type operating at 100 kHz has been developed which maintains a constant emission current within 0.1 “/, for a cathode power demand variation of approximately lOO’%. The power output stage has an efficiency of 67 %, and the overall efficiency is 45 % when driving a thoria-coated iridium cathode having a nominal resistance at operating temperature of 2.5 (1. Under optimum conditions, the bus power demand is 1.75 W. The circuit is useful in controlling the electron emission current of