Surface and optical analysis of SiC x films prepared by RF-RMS technique A. Mahmood a , S. Muhl b , R. Machorro c, * , A. Lousa d , J. Esteve d , J. Heiras c a Applied Physics Division, PINSTECH, P.O. Nilore, Islamabad, Pakistan b Instituto de Investigaciones en Materiales, UNAM, Apdo. Postal 670-360, D.F., 045110, Me ´xico c Centro de Ciencias de la Materia Condensada-UNAM, Apdo. Postal 2681, Ensenada, B.C., 22800, Me ´xico d Departament de Fı ´sica Aplicada i O ` ptica, Universitat de Barcelona, Avda. Diagonal 647, E-08028 Barcelona, Catalunya, Spain Received 23 September 2004; accepted 6 July 2005 Available online 15 August 2005 Abstract Silicon Carbide thin films have been prepared by RF reactive magnetron sputtering of a silicon target in a mixture of Ar and CH 4 . Surface analysis was performed by X-ray photoelectron spectroscopy (XPS) to examine the elemental bonding at the surface and in bulk of the material. Optical analysis was carried out by ellipsometry to study the optical constants (n and k ) and band gap of the films. Transmission and scanning electron microscopy, FTIR and X-ray diffraction, were employed to supplement our results. The near surface of SiC exposed to atmosphere was primarily composed of SiO 2 along with amorphous carbon while the bulk of the material was SiC. At higher plasma power and lower CH 4 concentration, the graphitic phase in the surface decreases and the refractive index increases while surface oxide layer remains present. D 2005 Elsevier B.V. All rights reserved Keywords: Silicon carbide; Thin films; XPS; Ellipsometry; Surface analysis; Optical properties 1. Introduction Silicon carbide, SiC x is an important material for the semiconductor industry both in crystalline [1,2] as well as in amorphous form [3,4]. Crystalline silicon carbide is a large band gap semiconductor (> 2 eV) with high thermal stability (melting point ¨ 2800 -C), good mechanical properties, large thermal conductivity (¨3.9 W/cm per -C), high electric break down field (¨4  10 6 V/cm) and a saturation drift velocity of approximately 2  10 7 cm/s [5,6]. Such properties make crystalline SiC a very attractive candidate for high temperature and high power applications in the electronic industry [7,8]. Amorphous silicon carbide (a- Si 1x C x ) is a wide band gap semiconductor and is potentially useful for a variety of applications including solar selective coatings. Unfortunately, the high melting point and the diversity of crystal structures adopted by SiC make difficult to prepare good quality single crystal or polycrystalline samples. SiC thin films have been prepared by high temperature chemical vapour deposition but this technique produces unintention- ally doped films with high concentration of lattice defects. Several methods involving lower temperature processing, such as thermal and laser recrystallization [9,10], plasma and hot-filament enhanced chemical vapor deposition [11,12], low pressure chemical vapor deposition [13], gas source molecular beam epitaxy [14] and UHV reactive DC magnetron sputtering [15,16], have been attempted to overcome these difficulties. However, the present know- ledge concerning the relation between physical properties and preparation processes of different forms of silicon carbide is very limited. The purpose of this work is the study of the surface oxygen content in SiC thin films prepared by RF reactive magnetron sputtering (RF-RMS) in order to establish the dependence of optical properties on chemical composition and structure on deposition parameters. Our results suggest that SiC is a wide band gap semiconductor whose native oxide is suitable to be used as a MOS insulator in electronic devices. 0925-9635/$ - see front matter D 2005 Elsevier B.V. All rights reserved doi:10.1016/j.diamond.2005.07.006 * Corresponding author. E-mail address: roberto@ccmc.unam.mx (R. Machorro). Diamond & Related Materials 15 (2006) 71 – 79 www.elsevier.com/locate/diamond