Dynamics of native oxide growth on CdTe and CdZnTe X-ray and gamma-ray detectors

Abstract

We studied the growth of the surface oxide layer on four different CdTe and CdZnTe X-ray and gamma-ray detector-grade samples using spectroscopic ellipsometry. We observed gradual oxidization of CdTe and CdZnTe after chemical etching in bromine solutions. From X-ray photoelectron spectroscopy measurements, we found that the oxide consists only of oxygen bound to tellurium. We applied a refined theoretical model of the surface layer to evaluate the spectroscopic ellipsometry measurements. In this way we studied the dynamics and growth rate of the oxide layer within a month after chemical etching of the samples. We observed two phases in the evolution of the oxide layer on all studied samples. A rapid growth was visible within five days after the chemical treatment followed by semi-saturation and a decrease in the growth rate after the first week. After one month all the samples showed an oxide layer about 3 nm thick. The oxide thickness was correlated with leakage current degradation with time after surface preparation.

Surface Planarization of CdZnTe Wafers: Effect of Slurry Formulation and CMP Processing Parameters on Surface Planarity

“…32,33 Also, the CZT surface undergoes surface oxidation very easily which leads to a change in the surface chemical composition. [34][35][36] It has been evidenced that inhomogeneous Zn atom distribution on the surface of CZT films (which is produced during the growth processevaporation of sources such as cadmium telluride and zinc telluride) revealed Bragg's splitting. Further, the splitting disappears when the surface becomes compositionally homogeneous.…”

Investigation of Deep Levels in CdZnTeSe Crystal and Their Effect on the Internal Electric Field of CdZnTeSe Gamma-Ray Detector

“…We fitted the experimental ellipsometry data by a theoretical model describing the CZTS/CZT materials. The CZTS/CZT materials were parametrized by a sum of Lorentz oscillators [20], [21]. The determined optical refractive index of CZTS bulk and CZT bulk is shown in figure 1.…”

Neutron Irradiation Effects on Boron Nitride-Based Ceramics for Use in X-ray Detection

“…Currently, the direct conversion of X-ray to electrical signal of commercial detectors is mainly based on amorphous selenium (α-Se) and cadmium zinc telluride (CZT). Other materials with high atomic numbers have also shown great potential for X-ray detection and imaging, such as CdTe, − lead oxide, polycrystalline HgI 2 , − and metal halide perovskites. − However, most of the current X-ray detection materials are still suffering from the poor stability, particularly under intense ionizing irradiation. It could be mainly due to the high attenuation coefficient of these dense materials with “heavy” atoms, and the incident high energy photons could be easily intercepted and have a great potential to generate large density of defects .…”