Substrate temperature influence on boron carbide coatings grown by the PLD technique

Abstract

Boron carbide films were synthesized by laser ablation technique, using a target of B4C with 99.9% of purity, varying the substrate temperature between room temperature and 650°C, in order to produce the hexagonal phase (h-BC). Films were grown on (111)-silicon wafers in an ultra high vacuum system with a base pressure in the order of 10−7Pa. For the films' growth, an atmosphere of (CH4) at a pressure of 2.5Pa was used. During the process, the substrate temperature was varied in order to identify the influence of this parameter on the coatings' structure, composition and morphology. XRD analysis did not present peaks of BC, possibly because of the amorphous character of the film that has different phases. Films were characterized by several techniques as in situ Auger electron spectroscopy (AES), X-ray photoelectron spectroscopy (XPS) and ex situ electron diffraction. Results present a concentration of 50at.% for the sample grown to 650°C. Electron diffraction showed an interplanar spacing (d(002)=0.334nm) and also other hkl reflections have been identified. Lattice parameters calculated from the interplanar spacing a=0.585nm and c=1.2nm obtained for the sample grown at 650°C are similar to those reports for hexagonal boron carbide.