Amorphous silicon sensors: from photo to chemical detection

This paper reports the performances of metal/insulator/semiconductor devices, simultaneously sensitive to hydrogen and to the visible region of the spectrum. The sensors used in this work are based on glass/Cr/a-SiH(n(+))/a-Si:H(i)/SiOx/Pd structures, where the amorphous silicon was deposited by conventional r.f. techniques and the oxide grown thermally tin air) or chemically tin hydrogen peroxide). The proposed sensors present a response of similar to 3 orders of magnitude change in the saturation current when in the presence of 400 ppm of hydrogen and an open circuit voltage that decreases in the presence of hydrogen, with a maximum spectral response at 500 nm. These sensors were also compared with equivalent crystalline silicon devices whose oxides were prepared exactly in the same conditions as the ones used for the a-Si:H devices. (C) 1998 Elsevier Science B.V. All rights reserved.