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Accession Number:
ADA106382
Title:
Deliberate Modification of the Behavior of n-Type Cadmium Telluride/Electrolyte Interfaces by Surface Etching: Removal of Fermi Level Pinning.
Descriptive Note:
Interim technical rept.,
Corporate Author:
MASSACHUSETTS INST OF TECH CAMBRIDGE DEPT OF CHEMISTRY
Report Date:
1981-09-02
Pagination or Media Count:
44.0
Abstract:
Single crystal, n-type CdTe E sub g 1.4 eV has been studied with respect to barrier height, E sub B, when contacting a liquid electrolyte solution containing a fast, one-electron, outer-sphere redox reagent. We approximate E sub B as equal to the photovoltage measured by cyclic voltammetry of various redox couples at illuminated n-CdTe vs. a reversible electrode. N-CdTe surfaces pretreated with an oxidizing etch give an E sub B of approximately 0.5 V or - 0.1 V in H2O0.1 M NaClO4 or CH3CN0.1 M n-Bu4NClO4 that is independent of the E sub 12 of the added redox couple. A reducing etch pretreatment gives an E sub B in either of the electrolyte solutions that depends on E sub 12 of the redox couple in a manner consistent with a nearly ideal semiconductor. The reduced CdTe exhibits an E sub B of up to 0.9 V for a redox couple having E sub 12 near 0.0V vs. SCE, whereas couples having E sub 12 negative of approx. -1.0 V vs. SCE give zero photovoltage. Auger and X-ray photoelectron spectroscopy of the reduced and oxidized surfaces are qualitatively different. The reduced surface exhibits signals for Cd and Te in relative intensities that are consistent with a close to stoichiometric 11 surface. The oxidized surface exhibits little or no detectable Cd signal and the Te signal is consistent with a thick overlayer of elemental Te.
Distribution Statement:
APPROVED FOR PUBLIC RELEASE
