دانلود رایگان مقاله ژرمانیوم نیترید و فیلم نیتریت سطح غیرفعال آشکارسازهای پرتو ژرمانیوم

Abstract

This work reports a detailed investigation of the properties of germanium nitride and oxynitride films to be applied as passivation layers to Ge radiation detectors. All the samples were deposited at room temperature by reactive RF magnetron sputtering. A strong correlation was found between the deposition parameters, such as deposition rate, substrate bias and atmosphere composition, and the oxygen and nitrogen content in the film matrix. We found that all the films were very poorly crystallized, consisting of very small Ge nitride and oxynitride nanocrystallites, and electrically insulating, with the resistivity changing from three to six orders of magnitude as a function of temperature. A preliminary test of these films as passivation layers was successfully performed by depositing a germanium nitride film on the intrinsic surface of a high-purity germanium (HPGe) diode and measuring the improved performance, in terms of leakage current, with respect to a reference passivated diode. All these interesting results allow us to envisage the application of this coating technology to the surface passivation of germanium-based radiation detectors.

4. Conclusions

In view of the application to the surface passivation of germanium-based radiation detectors, we produced and investigated in detail the physical properties of germanium nitride and oxynitride films, deposited at room temperature by reactive RF magnetron sputtering. We found that the film composition was strongly affected by the deposition rate, ultimate pressure and deposition atmosphere composition. At low deposition rates germanium oxynitride films were obtained. At increasing deposition rate and decreasing ultimate pressure, the oxygen incorporation in the film drastically decreased and germanium nitride coatings were deposited. In this case, the films were over-stoichiometric in N when pure N2 was used as deposition gas, but became stoichiometric when Ar/N2 gas mixtures were used. The film stoichiometry was strongly affected by an applied dc substrate bias, going from over-stoichiometry in nitrogen at low biases down to under-stoichiometry at increasing bias. In biased films, the oxygen content was always below the RBS detection threshold. Allthe films were very poorly crystallized and resulted to be highly insulating at room temperature, their resistivity being strictly related to the film composition and deposition parameters.