D. E. Aspnes1, Hans Arwin1
1Bell Communications Research, Inc., Murray Hill, New Jersey 07974
Tóm tắt
Chemical oxidation and etching reactions are studied using the real-time analytic capabilities of spectroscopic ellipsometry to avoid ambiguities arising from air exposure or delays between processing and measurement. We show that bromine–methanol treatments leave the surfaces of these materials covered with an optically identifiable Te layer about 7 Å thick. Previous XPS measurements indicating TeO2 as a reaction by-product of Br exposure can be understood as an artifact of air oxidation and the inability to resolve the 3d core-level signal of metallic surface Te from that of semiconductor substrate Te. The Te layer can be removed from the Hg-containing compounds by oxidizing and stripping freshly polished samples with HNO3 or by reducing them with NaBH4. The Te layer cannot be completely removed in this way from CdTe. Chemical oxidations of these materials with H2O2 solutions of different pH values show that the oxide on CdTe is a single stoichiometric compound, probably the tellurite CdTeO3, while that formed on HgTe is a physical mixture of TeO2 and probably HgTeO3. The H2O2-grown oxides can be removed with HCl, but a Te residue remains. No evidence is found for chemically induced bulk damage in any of the compounds studied.
