AVS 46th International Symposium
    Applied Surface Science Division Monday Sessions
       Session AS2-MoA

Paper AS2-MoA1
Determination by XPS of the Reactions Taking Place at the Semiconductor/'Heteropolyanion Solution' Interface

Monday, October 25, 1999, 2:00 pm, Room 6A

Session: Applied Surface Science for Microelectronics
Presenter: C. Debiemme-Chouvy, CNRS - France
Authors: A. Quennoy, CNRS - France
A. Rothschild, CNRS - France
A. Etcheberry, CNRS - France
C. Debiemme-Chouvy, CNRS - France
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When semiconductors (SC) are immersed in a solution containing oxydizing species they could undergo an oxidation/dissolution process. Therefore their surface chemical composition can evolve. The knowledge of the SC surface composition after the treatment allow sometimes to determine the reactions which had taken place at the SC/solution interface. In this communication, an example will be shown. The heteropolyanions (HPA) based on oxometallate compounds can undergo multiple one- or two-electron reduction of the metallic atoms. @footnote 1@ Thus depending on their oxidizing power they could oxidize SC. We studied the behavior in acidic solution of two HPA species with a Keggin structure H@sub 4@SiW@sub 12@O@sub 40@ (SiW@sub 12@) and H@sub 4@SiMo@sub 12@O@sub 40@ (SiMo@sub 12@) toward GaAs. The XPS analyses shown that after immersion in the HPA solution a deposit is formed on the GaAs surface. For immersion longer than one hour the substrate is no more detected. The deposit obtained in the presence of SiW@sub 12@ is composed of WO@sub 3@.@footnote 2@ Concerning SiMo@sub 12@, the HPA structure seems conserved in the deposit. Moreover the peak fitting of the Mo3p XPS spectrum indicates that some Mo atoms have remained at the oxidation state (VI) and that others have reached the oxidation state V. Otherwise, whatever the HPA studied As atoms are present in the deposit. They are at an oxidation state higher than that of As atoms inside the substrate. All these results indicate that in the presence of SiW@sub 12@ or SiMo@sub 12@ GaAs is oxidized while the HPA species are reduced. The conclusions obtained just on the basis of the XPS analyses were confirmed by electrochemical studies and profilometry. @FootnoteText@ @footnote 1@ M.T. Pope, Heteropoly and Isopoly Oxometalates, Springer, Heidelberg, 1983. @footnote 2@ A. Rothschild, C. Debiemme-Chouvy, A. Etcheberry, Applied Surface science 135 (1998) 65.