Ž . Applied Surface Science 153 2000 240–244 www.elsevier.nlrlocaterapsusc Detection of As O arsenic oxide on GaAs surface by Raman 2 3 scattering Lucia G. Quagliano ) I.M.A.I.-C.N.R., Area della Ricerca di Roma, P.O. Box 10, Õia Salaria km 29.300-00016 Monterotondo Scalo, Rome, Italy Received 8 March 1999; accepted 26 August 1999 Abstract GaAs samples after wet chemical etching in nitric acid have been investigated for the first time by Raman spectroscopy. The GaAs surface prepared by this chemical etching results in a rough surface structure with an intrinsic chemically formed oxide film. The Raman scattering data suggest that the oxide layer is primarily composed of As O in the crystalline form of 2 3 arsenolite. This oxide film has been found to be subjected to a tensile stress. No experimental Raman observation of this kind of As O arsenic oxide on oxided GaAs surfaces has been reported yet. No trace of amorphous arsenic and of 2 3 elemental As has been detected. q 2000 Elsevier Science B.V. All rights reserved. The nature of III–V oxide thin film is of consid- erable importance in different technological areas such as preparation of wafers before epitaxy, encap- sulation, masks, passivation, etc. This has motivated studies on growth processes and on the properties of these films. Oxides can be grown either by dry processes or wet processes such as chemical and electrochemical oxidation. A large number of wet cleaning procedures have been developed to prepare semiconductor substrates for MBE growth and for device fabrication. The surface and interface mor- phology, oxide thickness, and atomic composition can vary greatly depending on the oxidation condi- tions. ) Tel.: q0039-6-9067-2214; fax: q0039-6-9067-2238. Ž E-mail address: quaglian@nserv.icmat.mlib.cnr.it L.G. . Quagliano III–V oxide thin films are generally studied using Ž . X-ray photoelectron spectroscopy XPS , secondary Ž . ion mass spectroscopy SIMS , electron-energy-loss Ž . spectroscopy EELS and ellipsometry. In the literature, only a few Raman studies deal- ing with these oxide films can be found. The Raman scattering data provide information concerning the structure, the crystallinity and the composition of the oxide layer. However, the previously reported Ra- man studies were devoted exclusively to the charac- terization of the oxide films formed on GaAs by thermal oxidation or by electrochemical anodization followed by thermal annealing. All these works have observed that in these conditions the oxides grown on GaAs surface are primarily composed of elemen- w x tal crystalline arsenic 1–4 . In the present paper, we report the first Raman study of oxides formed on GaAs surface after wet chemical etching. As a result, the composition and 0169-4332r00r$ - see front matter q 2000 Elsevier Science B.V. All rights reserved. Ž . PII: S0169-4332 99 00355-4