Band offsets of metal oxide contacts on TlBr radiation detectors

Metal oxides are investigated as an alternative to metal contacts on thallium bromide (TlBr) radiation detectors. X-ray photoelectron spectroscopy studies of SnO2/TlBr and ITO/TlBr devices indicate that a type-II staggered heterojunction forms between TlBr and metal oxides upon contacting. By using the Kraut method of valence band offset (VBO) determination, the VBOs of SnO2/TlBr and ITO/TlBr heterojunctions are determined to be 1.05 & PLUSMN; 0.17 and 0.70 & PLUSMN; 0.17 eV, respectively. The corresponding conduction band offsets are then found to be 0.13 & PLUSMN; 0.17 and 0.45 & PLUSMN; 0.17 eV, respectively. The I-V response of symmetric In/SnO2/TlBr and In/ITO/TlBr planar devices is almost Ohmic with a leakage current of less than 2.5 nA at 100 V.