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Hydrogenated amorphous silicon has been prepared at a plasma excitation frequency in the very-high-frequency band at 70 MHz with the glow discharge technique at substrate temperatures between 280 and 50 °C. The structural properties have been studied using hydrogen evolution, elastic recoil detection analysis, and infrared spectroscopy. The films were further characterized by dark and photoconductivity and by photothermal deflection spectroscopy. With respect to films prepared at the conventional frequency of 13.56 MHz considerable differences concerning the electronic and structural properties are observed as the substrate temperature is decreased from 280 to 50 °C. Down to a substrate temperature of 150 °C the electronic film properties change only a little and the total hydrogen content cH and the degree of microstructure that can be directly correlated to cH increase only moderately. Below 150 °C the electronic properties deteriorate in the usual manner but still the total hydrogen content does not exceed 21 at. % even at a substrate temperature of 50 °C. It is argued that the influence of the higher excitation frequency on the plasma and on the growth kinetics plays a key role in this context by allowing a highly effective dissociation of the process gas with the maximum ion energies remaining at low levels. It is concluded that deposition processes at higher excitation frequencies can have important technological implications by allowing a decrease of the deposition temperature without losses in the material quality.

The formation and composition of room-temperature surface oxides on (1 10) orientated lnSb samples was studied with ESCA and AES. The oxides are composed of a mixture of In,03 and Sb205. It is shown that the Sb oxide is Sb2O5 and not Sb2O3, as has been previously generally assumed. Four surface-preparation techniques were compared: free etching, mechanical polishing, chemo-mechanical polishing and anodic oxidation. Chemo-mechanical polishing and free etching yield comparable oxide thicknesses of about 30 A. Mechanical polishing produces a 100 A thick disturbed oxide layer. Anodic oxidation allows a choice of the thickness but introduces a strong carbon contamination. The first monocell layer of natural oxide grows very fast, within 80 S a 15 A layer has formed. Thereafter the oxidation is diffusion controlled and much slower. From renormalisation curves it is concluded that the oxide mainly consists of In203 with some Sb205. The In oxide stays near the oxide/bulk interface and finally after some 25 days stops further oxidation, while the Sb oxide moves towards the oxide/air interface. In contrast to thermal oxides no Sb layer is found at the oxide/bulk interface.commercially Czochralski grown material (Cominco Ltd

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We have studied the inAuence of hydrogen on the structure of a-C:H films {produced by sputtering) by measuring the stress, hardness, and Raman spectrum as a function of the hydrogen concentration CH. Addition of hydrogen, on the one hand, reduces the stress and hardness, and on the other hand, reduces the intensity ratio {ID/I&) of the Raman D to G line. Discontinuous change of both stress and ID/IG, and a minimum of the 6-line full width at half maximum have been observed at CH=32. 5 at. %.Scanning-electron-microscopy analysis has been used to verify the stress transition. The role of hydrogen is discussed.