Preferable orientation of turbostratic BN basal planes from an x-ray absorption study
- PDF / 164,646 Bytes
- 6 Pages / 612 x 792 pts (letter) Page_size
- 92 Downloads / 149 Views
C.Y. Chan, W.J. Zhang,a) I. Bello, and S.T. Lee Center of Super-Diamond and Advanced Films (COSDAF) and Department of Physics and Materials Science, City University of Hong Kong, Hong Kong SAR, People’s Republic of China
F. Heigl and A. Jürgenen Canadian Synchrotron Radiation Facility (CSRF) at the Synchrotron Radiation Center, University of Wisconsin–Madison, Madison, Wisconsin 53589-3097
H. Hofsäss II. Institute of Physics, University of Göttingen, D-37077 Göttingen, Germany (Received 15 August 2005; accepted 19 September 2005)
Two cubic boron nitride (c-BN) thin films (thickness, 80 nm), which were grown on silicon by mass-selected ion beam deposition and thin diamond film-coated silicon by magnetron sputtering technique respectively, were investigated by x-ray absorption near-edge spectroscopy (XANES) at the B K-edge. The angular dependences of the XANES recorded in fluorescence yield (FY) were used to show that the preferable orientation of the sp2-bonded turbostratic BN (t-BN) basal planes at the interfacial layers between the top c-BN film and Si substrate is normal or nearly normal to the substrate, which is consistent with previous transmission electron microscope analysis. The angular dependence was also used to show that the film deposited on diamond-coated Si has a higher relative amount of ordered t-BN at its film-substrate interface than the film on Si substrate. This work that shows a technique to determine the thin film structure, especially the interfacial structure between the thin films and their substrates x-ray absorption fine structure is a powerful mode.
I. INTRODUCTION
Cubic boron nitride (c-BN) films have been prepared by a number of ion-assisted physical vapor deposition (PVD) and plasma-enhanced chemical vapor deposition (PECVD) techniques. Some common features in the synthesis of c-BN and diamond have been explored due to the striking similarities in their structures. For instance, a nucleation process is necessitated for the depositions of both diamond and c-BN films on hetero-substrates. Unlike diamond, however, c-BN cannot nucleate directly on a silicon surface. Cross-sectional transmission electron microscopic (TEM) analyses indicate a layered structure in a sequence of amorphous BN (a-BN), turbostratic BN (t-BN), and then c-BN on silicon substrates.1,2 Obviously, the interfacial a-BN/t-BN layers are precursors for the
a)
Address all correspondence to these authors. e-mail: [email protected] e-mail: [email protected] DOI: 10.1557/JMR.2006.0005
c-BN nucleation and therefore important for the understanding of the nucleation behavior and initial evolution of c-BN crystallites. Additionally, both TEM images1,2 and x-ray photoelectron spectroscopy (XPS)3 reveal that there is a very thin (several atomic layers) hexagonal BN (h-BN) layer at the topmost surface. Transmission electron energy loss spectroscopy (EELS)4,5 at some local spots demonstrates that both the a-BN and t-BN layer at the interface between c-BN films and their substrate are sp2-bonded, while the c-BN layer is in cubic
Data Loading...
