Bi-directional phase transition of Cu/6H-SiC(0 0 0 1) system discovered by positron beam study

Abstract

The slow positron beam facility at the University of Hong Kong has been used to study the Cu/6H-SiC(0 0 0 1) system. The S-E data show the presence of the Cu/SiC interface buried at a depth of 30 nm. Keeping the beam energy fixed and sweeping the sample temperature, sharp discontinuities are noted in the S-parameter at both ∼17 and ∼250 K. The S-parameter transitions, which are in opposite directions, are indicative of sharp free volume changes that come as a result of the sudden changes in the structure at the Cu/SiC interface accompanying some phase transition. Energy dispersive X-ray spectroscopy (EDXS) room temperature scans reveal the presence of O in addition to Cu, C, Si at the interface, and thus copper oxide phases should be considered in interpreting this new phenomenon. It is suggested that TEM investigation together with temperature dependent X-ray diffraction spectroscopy may be able to shed further light on the nature of this interesting bi-directional phase transition. © 2002 Elsevier Science B.V. All rights reserved.