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5111. Simulation of ion-beam etched pattern profiles
Classified abstracts 5107-5116 dependable in both levitation and recovery of the coated microspheres. The levitating gas flow does not appear to interfere with the deposition process, and the rotation of the microsphcre, which is produced by the gas flow. ensures that uniform coatings are obtained. Microradiography has shown the coatings to have a high degree of uniformity and the SEM reveals local surface finishes, under specific deposition conditions, of better than 250 A. Due to the excellent stability of the levitated microspheres, simultaneous deposition using multiple heads may be possible. J Varon and S Goldstein, Rer Sci hi.strum, 52 17), 19XI, 975 978. 31 5107. The properties of films prepared by the rf sputtering of PTFE and plasma polymerization of some freons. (GBI Fluorocarbon films were prepared by rf sputtering of PTFE at 6.65 Pa in glow discharges operated in the target emission alone and with argon or nitrogen added, A 75 mm dia target and an rf supply of 20 M H z with different power inputs between 100 and 500 W were used. Blank and aluminium-covered glass substrates were rested on grounded or biased supports above the target. The refractive index (NaD) and absorption of each film in the near u~ and uv regions of light were measured. Electrical properties like I V characteristics, dielectric constant and dielectric strength in the sandwich configuration AI film AI were also studied. In the second set of experiments the same properties of films prepared by plasma polymerization ofcertain freons (CF3CI, C F , C I , ) at a pressure of 15 Pa and higher were investigated at various flow rates and power inputs for comparison. (Czechoslovakial H Biederman, Vacuum, 31 17), 1981, 285 289. 31 5108. Magnetron sputtering of solar coatings inside tubes. (USA) A small post-cathode magnetron sputtering system using a moving magnet inside the cathode is described. Unusual features in the voltagecurrent characteristics of the device are discussed. The system is particularly useful for coating inside cylindrical substrates, especially glass tubes for solar energy collectors. (Australia) S J Walker and D R McKenzie, J I'acSci Teclmol, 19 13), 1981, 700 703 31 5109. Thick zone plate fabrication using reactive sputter etching. (USA) Reactive sputter etching has been used to produce patterns for thick micro-Fresnel zone plates. An integral aluminium mask was formed on 50 itm thick Mylar. and the exposed Mylar was etched in oxygen. Gold was then electroplated into the pattern to form a micro-Fresnel zone plate 40 itm thick. F Kalk and D Gloeker, J l'ac Sci Teclmol, 19 121, 1981. 170 172. 31 5110. Oxygen plasma etching of thick polymer layers. (USA) Reactive ion etching of thick ( > 100 Itm ) epoxy, polyester, and photoresist layers in oxygen was studied as a function of gas flow, gas pressure, gas purity and rf power density. Etch rates greater than 2500 A rain were obtained with low substrate temperatures. The etch was found to be extremely directional so that structures with aspect ratios as large as 30 to 1 were measured. Both the etch geometry and mask material appear to have some effect on this directionality. In addition the etch was found to smooth the etched surface so that surface finishes better than 200 A were possible. I S Goldslcin and F Kalk, J Vm Sci Teclmol, 19 13l, 1981, 743 747. 31 511 I. Simulation of ion-beam etched pattern profiles. ( USA ) Profiles of fine patterns formed by ion-beam etching were simulated with a three-dimensional model on the basis of redeposition effect. First, a revolution ellipsoid format was assumed to represent angular distribution ofsputtered atoms to simplify the simulation. Secondly, an experimentally obtained distribution was used. Consequently, the pattern width difference between mask and substrate decreases as the angular distribution changes from undercosine to overcosine. The pattern width difference, which shows a m a x i m u m value at the bottom of etched substrate patterns, is almost independent of pattern gap width. Pattern sidewalls become steeper with increasing gap width or with decreasing etched depth. These simulated pattern profiles are in good agreement with the experimental results. (Japan) H Tsuge et al, J I/ac Sci Technol. 19 (21, 1981, 221 224. 31 5112. Strains and photovoltaic response in Ta-sputtered Si metal-insulatorsemiconductor solar cells. ( USA ) Deformation by bending of Si or Si-SiO, wafers was achieved by sputter
deposition of tantalum films. Strains induced at Si-SiO, interface and in Ta films were investigated using a combination of X-ray diffraction, electron diffraction and transmission electron microscopy. Thin Ta film deposits had predominantly a fcc structure, while thicker films had the normal bcc structure with certain admixture of fce. Film strains generated by the coexistence of the polymorph structure were accommodated by formation of misfit dislocations at the film-Si substrate interface. The effect of the induced stress on the electronic parameters characterizing the SiSiO, interface was studied in the metal-oxide-semiconductor structure and for the effect on photovoltaic response a metal-insulatorsemiconductor solar cell configuration was used. Large changes with increasing stress were observed in the values of recombination time, capture cross section, diffusion length and in sharply decreased conversion efficiency, fill factor, open-circuit voltage and short-circuit current. B Lalevie et al, J Appl Phys, 52 17). 1981, 4808-4817.
33. N U C L E O N I C S 33
5113. Slopping power measurements in the 20 150 keV region using thick target backscattering: tH and "*He on carbon, silicon and gold. (USA) Stopping powers for 20 150 keV hydrogen and helium ions in carbon (graphite). silicon and gold were determined using thick target backscattering. Present results (which have an estimated probable error of less than 5".) are in good agreement with other measurements performed on 'bulk" type targets, indicating that the technique is a viable method for performing absolute stopping power measurements in the intermediate and low-energy regions. However, present results are consistently higher than those reported from thin-film measurements, suggesting that possible allotropic and/or density phenomena arc present in evaporated films which effect stopping power measurements at intermediate and low ion energies. J D Pearce and R R Hart, ./ Appl Phys, 52 (8), 1981, 5056--5065. 33 5114. A Fabry Perot interferometer for plasma diagnostics. (GB) A Fabry Perot interferometer for the measurement of tokamak plasma electron cyclotron emission is described. The interferometcr operates in either a static or a scanning mode. In the static mode the resolving power is typically 30 and the time resolution (limited by the detector bandwidth) typically 1 t*s. In the scanning mode, the emission in narrow regions of the spectrum--usually the second harmonic of the electron cyclotron frequency typically covering the range 120 to 170 G H z ~ a n be measured in 2,5 ms with a resolving power > 25. Results obtained on the DITE tokamak are presented. B Walker el al, J Phys E: Sci hzstrzml. 14 17), 1981, 832-837. 33 5115. Impurity studies in fusion devices using laser-fluorescence spectroscopy. (USA) Resonance fluorescence excitation of neutral atoms using tunable radiation from dye lasers offers a number of unique advantages for impurity studies in fusion devices. Using this technique, it is possible to perform local time-resolved measurements of the densities and velocity distributions of metallic impurities in fusion devices without disturbing the plasma. Velocities are measured by monitoring the fluorescence intensity while tuning narrow bandwidth laser radiation through the Doppler-broadened absorption spectrum of the transition. The knowledge of the velocity distribution of neutral impurities is particularly useful for the determination of impurity introduction mechanisms. The laser fluorescence technique will be described in terms of its application to metallic impurities in fusion devices and related laboratory experiments. Particular attention will be given to recent results from the ISX-B tokamak using pulsed dye lasers where detection sensitivities for neutral Fe 10~' atoms c m - s with a velocity resolution of 600 m/s (0.1 eV) have been achieved. W R Husinsky, J I/ac Sci Teclmol. 18 (3), 1981, 1054 1061. 33
5116. Transition from diffusion-convection to sheath-convection of a cold Langmuir probe in a moving compressible plasma. (GB) The behaviour of the ion current to a negatively biased probe in a highpressure, flowing plasma for the situation where the current cannot be considered to be solely dominated by either diffusion or convection is discussed. The transition has been investigated before; here, however, the cooling induced reduction in the local ion mobility and the distortion of the hydrodynamic flow pattern close to the probe are also taken into account. These problems arise inherently because in virtually every 447
deposition of tantalum films. Strains induced at Si-SiO, interface and in Ta films were investigated using a combination of X-ray diffraction, electron diffraction and transmission electron microscopy. Thin Ta film deposits had predominantly a fcc structure, while thicker films had the normal bcc structure with certain admixture of fce. Film strains generated by the coexistence of the polymorph structure were accommodated by formation of misfit dislocations at the film-Si substrate interface. The effect of the induced stress on the electronic parameters characterizing the SiSiO, interface was studied in the metal-oxide-semiconductor structure and for the effect on photovoltaic response a metal-insulatorsemiconductor solar cell configuration was used. Large changes with increasing stress were observed in the values of recombination time, capture cross section, diffusion length and in sharply decreased conversion efficiency, fill factor, open-circuit voltage and short-circuit current. B Lalevie et al, J Appl Phys, 52 17). 1981, 4808-4817.
33. N U C L E O N I C S 33
5113. Slopping power measurements in the 20 150 keV region using thick target backscattering: tH and "*He on carbon, silicon and gold. (USA) Stopping powers for 20 150 keV hydrogen and helium ions in carbon (graphite). silicon and gold were determined using thick target backscattering. Present results (which have an estimated probable error of less than 5".) are in good agreement with other measurements performed on 'bulk" type targets, indicating that the technique is a viable method for performing absolute stopping power measurements in the intermediate and low-energy regions. However, present results are consistently higher than those reported from thin-film measurements, suggesting that possible allotropic and/or density phenomena arc present in evaporated films which effect stopping power measurements at intermediate and low ion energies. J D Pearce and R R Hart, ./ Appl Phys, 52 (8), 1981, 5056--5065. 33 5114. A Fabry Perot interferometer for plasma diagnostics. (GB) A Fabry Perot interferometer for the measurement of tokamak plasma electron cyclotron emission is described. The interferometcr operates in either a static or a scanning mode. In the static mode the resolving power is typically 30 and the time resolution (limited by the detector bandwidth) typically 1 t*s. In the scanning mode, the emission in narrow regions of the spectrum--usually the second harmonic of the electron cyclotron frequency typically covering the range 120 to 170 G H z ~ a n be measured in 2,5 ms with a resolving power > 25. Results obtained on the DITE tokamak are presented. B Walker el al, J Phys E: Sci hzstrzml. 14 17), 1981, 832-837. 33 5115. Impurity studies in fusion devices using laser-fluorescence spectroscopy. (USA) Resonance fluorescence excitation of neutral atoms using tunable radiation from dye lasers offers a number of unique advantages for impurity studies in fusion devices. Using this technique, it is possible to perform local time-resolved measurements of the densities and velocity distributions of metallic impurities in fusion devices without disturbing the plasma. Velocities are measured by monitoring the fluorescence intensity while tuning narrow bandwidth laser radiation through the Doppler-broadened absorption spectrum of the transition. The knowledge of the velocity distribution of neutral impurities is particularly useful for the determination of impurity introduction mechanisms. The laser fluorescence technique will be described in terms of its application to metallic impurities in fusion devices and related laboratory experiments. Particular attention will be given to recent results from the ISX-B tokamak using pulsed dye lasers where detection sensitivities for neutral Fe 10~' atoms c m - s with a velocity resolution of 600 m/s (0.1 eV) have been achieved. W R Husinsky, J I/ac Sci Teclmol. 18 (3), 1981, 1054 1061. 33
5116. Transition from diffusion-convection to sheath-convection of a cold Langmuir probe in a moving compressible plasma. (GB) The behaviour of the ion current to a negatively biased probe in a highpressure, flowing plasma for the situation where the current cannot be considered to be solely dominated by either diffusion or convection is discussed. The transition has been investigated before; here, however, the cooling induced reduction in the local ion mobility and the distortion of the hydrodynamic flow pattern close to the probe are also taken into account. These problems arise inherently because in virtually every 447