Diamond and Related Materials 11 (2002) 861–866 0925-9635/02/$ - see front matter  2002 Elsevier Science B.V. All rights reserved. PII: S0925-9635 Ž 01 . 00673-2 The oxidation of (100) textured diamond P. John *, N. Polwart , C.E. Troupe , J.I.B. Wilson a, a a,1 b Department of Chemistry, Heriot-Watt University, Edinburgh EH14 4AS, UK a Department of Physics, Heriot-Watt University, Edinburgh EH14 4AS, UK b Abstract The thermal oxidation of highly textured (100) chemical vapour deposited (CVD) diamond has been investigated using a combination of high resolution X-ray photoelectron spectroscopy. The diamond samples were oxidised in dry O in a vacuum 2 furnace at temperatures up to 800 8C. The kinetics of oxidation of well-defined crystal facets of (100) diamond have been studied using in-situ laser interferometry and thermogravimetric analysis. Concomitant scanning probe microscopic examination of individual facets after oxidation revealed negligible changes to the surface roughness. Oxygen containing functional groups such as ether (COC) and carbonyl ()C_O) have been observed using X-ray photoelectron spectroscopy at all the surface coverages investigated. Even at higher coverages the formation of higher oxidation states such as carboxylic acid groupings was negligible (-2.5%). Angle resolved X-ray photoelectron spectroscopy measurements have been used to discriminate between surface and sub-surface oxygen.  2002 Elsevier Science B.V. All rights reserved. Keywords: Thermal-oxidation; Surface; Photoelectron spectroscopy; Etching 1. Introduction Thermal oxidation provides a simple and convenient method to fine-tune the chemistry of diamond surfaces. Whilst the presence of oxygen on diamond surfaces alters the physical properties, such as electron emission, electrical conductivity and Schottky barrier heights w1x, an explanation of the influence of oxygen requires detailed knowledge of the chemical bonding environ- ment. The different geometries and electronic properties of the oxygen groupings that influence such properties are intimately related to the nature of the chemical bonding of oxygen to the surface. A key challenge is to control the nature and distribution of the oxygen on diamond surfaces and, thus, utilise fully the unique properties of diamond for physical and chemical sensors. Pioneering studies w2x of the role of oxygen on diamond were performed on diamond powders predom- inantly using Fourier transform infrared spectroscopy to ascertain the nature of the functional groups present on *Corresponding author. Tel.: q44-131-451-3247; fax: q44-131- 451-3180. E-mail address: p.john@hw.ac.uk (P. John). Present address: Omega Diagnostics Ltd, Omega House, Carse- 1 bridge Court, Winns Road, Alloa, Clackmannanshire, FK10 3LQ, UK. the surface. A variety of oxygen functional groups, such as ether, carbonyl, lactone, carboxylic acid and anhy- dride groupings, were identified w2x on thermally oxidi- sed diamond powders. Unambiguous identification of the various chemical structures is difficult because many planes, impurities and defects are exposed on the sur- faces of such materials. Studies of polycrystalline dia- mond films suffer from the same difficulties unless single crystal, homoepitaxial, heteroepitaxial w3x or high quality textured w4x films are employed. Further progress in understanding the surface chemistry of oxygenated diamond requires the study of oxygen chemisorption on well-defined crystallographic diamond planes. In this context, aligned CVD diamond films have been obtained with atomically smooth (100) planes which provide suitable substrates for these studies w5x. In the present work we describe the oxidation of (100) crystallographically textured CVD films by in- situ interferometry and thermogravimetric analysis (TGA) together with characterisation by X-ray photoe- lectron spectroscopy (XPS) and atomic force microsco- py (AFM). 2. Experimental Our microwave plasma enhanced chemical vapour deposition (MPECVD) system has previously been