Electric field mapping by Pockels effect and I(V) characteristic of CdTe nuclear detectors by different Pt contact deposition

Abstract

In this work, we present the optimized principal methods of surface cleaning and treatment for CdTe nuclear detectors, namely: powder lapping, polishing and chemical etching mainly by Br- Methanol. We have studied the electric field mapping by Pockels effect technique. We made a comparison between the three main methods of Pt contact deposition: molecular beam epitaxy, cathode sputtering and the electroless (autocatalytic) methods in term of I(V) characteristic and electric field mapping. The two first method show: i) quite high uniform electric field, ii) the characteristic I(V) is non-uniform, iii) the detection suffer from the polarization effect. The I (V) characteristic shows that the contact is not ohmic. It is in the reversible I ∼ Vn with n varying from 0.643 to 1.651. The optimized contact deposit by electroless technique seems to be the more suitable one for detection with 2.10−8 A current at 200 V, a quite high uniform electric field up to 7 kV/cm, an absence of polarization effect and a spectrometric quality of nuclear detection.