Porous a/nc-Si:H films produced by HW-CVD as ethanol vapour detector and primary fuel cell

This work reports the use of undoped porous amorphous/nanocrystalline hydrogenated silicon (a/nc-Si:H) thin films produced by hot wire chemical vapour deposition (HW-CVD) as ethanol detector above 50 ppm and as a primary fuel cell where a power of 4 muW/cm(2) was obtained in structures of the type glass/ITO/i-a-nc-Si:H/Al. The porous silicon looks like a sponge constituted by grains and cluster of grains that determines the type of surface morphology and the behaviour of the structure under the presence of vapour moisture. Apart from that, the detector/device performances will also depend on the type of interlayer and interfaces with the metal contacts. The sponge like structure adsorbs the OH groups in uncompensated bonds, which behave as donor-like carriers, leading to an increase in the current flowing through the material, directly dependent on the ethanol vapour pressure. The corresponding role of the components of the microstructure on this detector was investigated by spectroscopic impedance. The response time of the current of the sensor and its recovery time are in the range of 10-50 s at room temperature. (C) 2004 Elsevier B.V. All rights reserved.