Surface stability and electronic structure of hydrogen- and fluorine-terminated diamond surfaces: A first principles inv

  • PDF / 918,892 Bytes
  • 10 Pages / 584.957 x 782.986 pts Page_size
  • 42 Downloads / 232 Views

DOWNLOAD

REPORT


Surface stability and electronic structure of hydrogen- and fluorine-terminated diamond surfaces: A first principles investigation Fatih G. Sena) Department of Mechanical, Automotive and Materials Engineering, University of Windsor, Windsor, Ontario N9B 3P4, Canada

Yue Qi Materials and Processes Laboratory, General Motors R&D Center, Warren, Michigan 48090-9055

Ahmet T. Alpas Department of Mechanical, Automotive and Materials Engineering, University of Windsor, Windsor, Ontario N9B 3P4, Canada (Received 17 February 2009; accepted 20 April 2009)

The effects of fluorine termination on the stability and bonding structure of diamond (111) surfaces were studied using first principles calculations and compared with hydrogen termination by creating mixed F- and H-containing diamond surfaces. Surface F atoms, similar to H, formed sp3-type bonding with C atoms, which resulted in a stable 1  1 configuration. The surface phase diagram built showed that the F-terminated surface was more stable in a larger phase space than H termination, because of the formation of strong ionic C–F bonds and the development of attractive forces between large F atoms, resulting in close packing of F atoms. Hence, the F-terminated diamond surface was more chemically inert. A large repulsive force was required to bring two F-terminated surfaces together, because of the negative charge on F atoms, resulting in reduced adhesion tendency between two F-terminated diamond surfaces compared with H-terminated surfaces.

I. INTRODUCTION

Diamond is known to be the hardest and stiffest material, chemically inert, and has the highest thermal conductivity at room temperature. Because of this remarkable set of properties, synthetic diamond films, such as diamond-like carbon (DLC), nanocrystallinediamond (ND), and amorphous carbon (a-C), have found a wide range of applications. Some examples include hard and wear-resistant tool coatings, biomedical applications, micro- and nanoelectromechanical systems (MEMS/NEMS), optical windows, magnetic data storage, and electrodes for electrochemical processes.1 DLC films are produced by either physical vapor deposia)

Address all correspondence to this author. e-mail: [email protected] This paper was selected as an Outstanding Symposium Paper for the 2008 MRS Fall Meeting, Symposium W Proceedings, Vol. 1130E. To maintain JMR’s rigorous, unbiased peer review standards, the JMR Principal Editor and reviewers were not made aware of the paper’s designation as Outstanding Symposium Paper. DOI: 10.1557/JMR.2009.0309 J. Mater. Res., Vol. 24, No. 8, Aug 2009

http://journals.cambridge.org

Downloaded: 19 Feb 2015

tion (PVD) or chemical vapor deposition (CVD) methods, and their physical and chemical properties depend primarily on the sp3/sp2 bonding ratio of carbon atoms and their hydrogen content.2 The tribological properties of DLC films show diverse characteristics depending on environmental conditions.3,4 The presence of dangling carbon bonds plays an important role in controlling the friction characteristics. The passiva

Data Loading...