AVS 45th International Symposium
    Selected Energy Epitaxy Topical Conference Wednesday Sessions
       Session SE-WeA

Paper SE-WeA9
Energetic Oxygen Atom Surface Passivation of Cd@sub 1-x@Zn@sub x@Te Radiation Detectors

Wednesday, November 4, 1998, 4:40 pm, Room 327

Session: Novel Sources for Selected Energy Growth
Presenter: M.A. Hoffbauer, Los Alamos National Laboratory
Authors: M.A. Hoffbauer, Los Alamos National Laboratory
S. Cook, Los Alamos National Laboratory
T. Prettyman, Los Alamos National Laboratory
J. Rennie, Los Alamos National Laboratory
J.C. Gregory, University of Alabama, Huntsville
M.A. George, University of Alabama, Huntsville
Correspondent: Click to Email
Recent investigations show considerable progress in developing large-volume Cd@sub 1-x@Zn@sub x@Te radiation detectors for room-temperature x-ray and gamma-ray spectroscopy and imaging where bulk material with high resistivity and uniform electrical properties is required.@footnote 1@ Surface effects can also play an important role in the performance of CdZnTe spectrometers, since dark current may be dominated by surface leakage in gridded or pixellated devices.@footnote 2@ A novel surface oxidation process has been developed for the treatment of CdZnTe using a source of energetic oxygen atoms to treat the surface held near ambient temperatures.@footnote 3@ Following the oxidation process the chemical composition and morphology of the surface were investigated using X-ray photoelectron spectroscopy and atomic force microscopy. No detectable unreacted Te substrate XPS feature is observed. The Te-oxide peak indicates that the oxidation process is complete, and that the suspected Te precipitates left on the surface following polishing and etching have been totally reacted to form a uniform Te-oxide layer >10 nm thick. AFM studies show a relatively uniform and smooth surface oxide layer. A significant reduction in surface leakage current and detector noise results in a 25% improvement in detector resolution measured at a gamma-ray energy of 662 keV. This new surface passivation method for high-quality, spectrometer-grade material increases the accuracy and sensitivity of measurements of radionuclides with complex gamma-ray spectra, including special nuclear material. When CdZnTe detectors with small spacing between electrodes become available, surface passivation will be even more critical in determining performance and energy resolution. @FootnoteText@ @footnote 1@K. B. Parnham, "Recent Progress in Cd@sub 1-x@Zn@sub x@Te Radiation Detectors," Nucl. Instr. Meth. Phys. Res., A377, 487(1996). @footnote 2@K.T.Chen, D.T. Shi, B. Granderson, M.A. George, W.E. Collins, A. Burger, and R.B. James, "Study of Oxidized Cadmium Zinc Telluride Surfaces," J. Vac. Sci. & Technol. A15, 850(1997). @footnote 3@M.A. Hoffbauer, J.C. Cross, and V.M. Bermudez, "Growth of Oxide Layers on Gallium Arsenide with a High Kinetic Energy Atomic Oxygen Beam", Appl. Phys. Lett., 2193(1990).