Study On Cu/Ag Alloy Film Used For CdZnTe Detector Electrode

CdZnTe crystal has proved to be the most excellent material to detect X ray and gamma ray. CdZnTe probe can be widely used in many fields, such as security monitor, industrial flaw-detection, medical diagnosis and celestial body X ray telescope and so on. One of the most key technologies of CdZnTe detector is to make ohmic contact film electrode on CdZnTe crystal's surface. Evaporation technology have been used for the study, but the the cohesion of evaporated films are not very firm. Besides, electroless depositing films and sputtering films were reported in some paper for ohmic contact electrode on CdZnTe crystal. However optimized processing parameters of sputtering to get ohmic contact film have not been found by now. So the main aim of this paper is to optimize the sputtering parameters in order to establish groundwork for preparing CdZnTe detector, and the results are as follows:Using JGP560 magnetron sputtering machine, Cu/Ag films were deposited on CdZnTe crystal as the electrode films by RF magnetron sputtering and the influences of the main experiments parameters, such as sputtering power, gas flow, vacuum air pressure, and substrate temperature, on deposition rate and film's resistivity have been systematically studied.. The results show that the RF power is the most influencing factor on the deposition rate. Deposition rate increases linearly with the RF power increasing and isn't sensitive to the substrate's temperature, gas flow and vacuum pressure. The film's resistivity increases rapidly when the RF power is more than 70W and decreases rapidly when the substrate's temperature above 200°C. The film's resistivity is hardly influence by the gas flow and vacuum pressure.I-V curves of the (Cu/Ag)/CdZnTe/(Cu/Ag) systems film were measured with micro-current meter and the contact performance was estimated by it. The resultsshow that the contact performance of the film deposited under 100 W is better than that of the film deposited under 40W; The contact performance of the film deposited with the substrate temperature being 200°C is better than that of the film deposited with the substrates being 300°Cand 390°C.And it becomes better after the substrate surface polished and the contact performance is improved after annealed at suitable temperature and with suitable time. Infrared transmittance of the CdZnTe substrates were measured. The results show that heat treatment orheating at sputtering have no effect on CdZnTe substrates performance.