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1445265 
Journal Article 
An XPS study of bromine in methanol etching and hydrogen peroxide passivation treatments for cadmium zinc telluride radiation detectors 
Babar, S; Sellin, PJ; Watts, JF; Baker, MA 
2013 
Yes 
Applied Surface Science
ISSN: 0169-4332 
264 
681-686 
WOS:000312004800105 
The performance of single crystal CdZnTe radiation detectors
is dependent on both the bulk and the surface properties of the material. After single crystal
fabrication and mechanical polishing, modification of the surface to remove damage and reduce the
surface leakage current is generally achieved through chemical etching followed by a passivation
treatment. In this work, CdZnTe single crystals have been chemically etched using a bromine in
methanol (BM) treatment. The BM concentrations employed were 0.2 and 2.0 (v/v) % and exposure
times varied between 5 and 120 s. Angle resolved XPS and sputter depth profiling has been
employed to characterize the surfaces for the different exposure conditions. A Te rich surface
layer was formed for all exposures and the layer thickness was found to be independent of
exposure time. The enriched Te layer thickness was accurately determined by calibrating the
sputter rate against a CdTe layer of known thickness. For BM concentrations of 0.2 (v/v) % and 2
(v/v) %, the Te layer thickness was determined to be 1.3 +/- 0.2 and 1.8 +/- 0.2 nm,
respectively. The BM etched surfaces have subsequently been passivated in a 30 wt.% H2O2 solution
employing exposure time of 15 s. The oxide layer thickness has been calculated using two standard
XPS methodologies, based on the Beer-Lambert expression. The TeO2 thickness calculated from ARXPS
data are slightly higher than the thickness obtained by the simplified Beer-Lambert expression.
For BM exposures of 30-120 s followed by a passivation treatment of 30 wt. % H2O2 solution
employing an exposure time 15 s, the ARXPS method gave an average TeO2 thickness value of 1.20 nm
and the simplified Beer-Lambert expression gave an average thickness value of 0.99 nm. (C) 2012
Elsevier B.V. All rights reserved. 
Cadmium zinc telluride; CZT; XPS; Passivation; Oxide thickness 
• Methanol (Non-Cancer)
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