High resistivity ZnSe coated substrates for microstrip gas chambers

Microstrip gas chambers (MSGCs) require substrates with sheet resistance in the range of 10¹³-10¹⁶ ohms/square to eliminate polarization and surface charging effects between the electrodes. Thin films of II-VI semiconductors deposited on glass or plastic substrates are attractive for this application since bulk resistivity of these semiconductors vary in the range 10⁹-10 ¹² ohm-cm and films with good uniformity can be deposited over large-areas using inexpensive deposition techniques. In this paper, deposition, characterization, and fabrication of MSGCs using ZnSe thin films are reported for the first time. ZnSe thin films were deposited on glass and plastic substrates by thermal evaporation. Sheet resistance of ZnSe varied in the range of 10¹⁵ to 10¹⁶ ohms/square depending on the deposition conditions. A MSGC detector fabricated using a 0.5 μm thick ZnSe layer on glass substrate exhibited gas gain of 25000 and an energy resolution of about 16.7% FWHM at a gain of 1080 for a ⁵⁵Fe source