MICROSTRIP GAS-CHAMBERS FABRICATION BASED ON AMORPHOUS-SILICON AND ITS CARBON ALLOY

Thin (similar to 1000 Angstrom) semiconducting films of hydrogenated a morphous silicon (a-Si:H) and its carbon alloy (a-Si:C:H) were applied to microstrip gas chambers in order to control gain instabilities due to charges in or on the substrate. The surface resistivity has been s uccessfully controlled in the range of 10(12) similar to 10(16) Omega/ square by changing the relative amount of the carbon content and boron doping level. The light sensitivity, which is defined as the ratio of light-to-dark conductivity, was reduced to nearly unity by doping. Ga s gains of similar to 2000 and energy resolution of 20% FWHM were achi eved and the gain remained constant over a week of operation. Upon pro longed irradiation, the detector overcoated with a-Si:C:H aged more sl owly by approximately an order of magnitude than the one without surfa ce coating. A-SI:C:H film is an attractive alternative to ion-implante d or semiconducting glass due to the wide range of resistivities possi ble and the feasibility of making deposits over a large area at low co st.