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The hydrogenated amorphous silicon nitride thin films are deposited by DC magnetron sputtering in argon, molecular hydrogen and nitrogen plasma mixture. The films are deposited at 150 °C and at 130 W sputtering power with wide range of nitrogen mole fraction. The plasma is characterized by the target voltage measurement. The samples are characterized by the optical transmission measurements and the physicochemical structure is studied by the FTIR absorption spectroscopy. When the nitrogen mole fraction increases from 0.075 to 0.24 the target voltage decrease from 413 to 325 V and increases suddenly to 450 V when nitrogen mole fraction increases to 0.69. The decrease of target voltage may be due to the transition from metallic to reactive sputtering process and its increase can be explained by the implantation of reactive ions in the target. Sputtering rate and refractive index decrease respectively from 8.33 to 1.73 Å/sec and from 2.52 to 1.68 with nitrogen mole fraction. The value of refractive index at critical nitrogen mole fraction is about 1.8. When the nitrogen mole fraction increases the frequency related to Si‐H band, on FTIR spectrum, shift from 2097 cm‐1 to reach 2209 cm‐1 at the critical nitrogen mole fraction. Thereafter it varies sharply to 2190 cm‐1 and remains constant. A sudden change is observed on the sputtering rate, on the intensity of the band attributed to the stretching vibration of N‐H and Si‐H bonds. From these results we believe that the stoichiometric composition is reached at the critical nitrogen mole fraction and beyond this the deposited films are rich of nitrogen and hydrogen. This is consistent with the explanation given of the variation of the target voltage. (© 2014 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)

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The Photoelectrical properties of hydrogenated amorphous silicon thin films (a-Si:H) deposited on porous silicon (PSi) were investigated. Porous Si layers were formed by electrochemical etching of p+-type crystalline Si in a hydrofluoric solution, whereas a-Si:H films were deposited in a partially hydrogenated atmosphere using the DC-Magnetron sputtering method. Samples with a-Si:H films deposited at different H2 flow rates and with PSi layers of different porosities and thicknesses were characterized. The Dark and under illumination I-V characteristics as well as the photocurrent response of these samples, were recorded on Al/a-Si:H/PSi/Si structures using both sandwich and planar configurations. These measurements were compared to that obtained with a-Si:H directly in contact with c-Si substrate. The results of our investigation demonstrate that the PSi layer characteristics strongly affect the photoelectrical properties of a-Si:H thin films and their influence depends on the electrical properties of these films.