Microstrip gas chambers fabrication based on amorphous silicon and its carbon alloy

Thin (∼1000 Å) semiconducting films of hydrogenated amorphous 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 successfully controlled in the range of 10¹²-10¹⁶ Ω/□ 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. Gas gains of ∼2000 and energy resolution of 20% FWHM were achieved and the gain remained constant over a week of operation. Upon prolonged irradiation, the detector overcoated with a-Si:C:H aged more slowly by approximately an order of magnitude than the one without surface coating. A-Si:C:H film is an attractive alternative to ion-implanted or semiconducting glass due to the wide range of resistivities possible and the feasibility of making deposits over a large area at low cost.