A theoretical approach to the energetic stability and geometry of hydrogen and oxygen terminated diamond (100) surfaces
- PDF / 686,324 Bytes
- 7 Pages / 612 x 792 pts (letter) Page_size
- 15 Downloads / 181 Views
0890-Y08-19.1
A theoretical approach to the energetic stability and geometry of hydrogen and oxygen terminated diamond (100) surfaces
D. Petrini* and K. Larsson Department of Materials Chemistry, Angstrom Laboratory, Uppsala University Box 538, SE-751 21 Uppsala, Sweden [email protected] ABSTRACT The thermodynamic stability of diamond (100) surfaces as a function of degree of hydrogen and oxygen-related termination coverage has been theoretically studied using DFT techniques. The results show that an exchange of the hydrogen atoms with hydroxyl groups is disfavored, whereas a corresponding exchange with oxygen atoms (in the ketone or ether position) is energetically preferred. The adsorption of up to about 50 % oxygen coverage (ether position) is, however, largely disfavored compared to a fully hydrogen-terminated surface. However, this oxygen termination will be energetically improved as the coverage increases above the 50 % level. The adsorption energy per terminating species (at 100% surface coverage) is -4.13 eV, -4.30 eV, -5.95 eV and 6.21 eV for H, OH, O(ketone) and O(ether) species, respectively.
INTRODUCTION The properties of diamond surfaces (e.g., high thermal conductivity, large breakdown voltage, high electron and hole mobility, as well as chemically inertness) have an evident potential for interesting new applications. The surface carbon atoms are terminated, and some specific terminating species show pronounced effects on the various surface properties. Some properties (e.g., electron affinity (EA)1-3, wetting capabilities4 and optical characteristics5) will change whether the diamond surface is hydrogen or oxygen terminated. The dipole moment of diamond surfaces change with the replacement of hydrogen by oxygen as a surface terminator. Using this effect, diamond surfaces sensors have been made capable of detecting, for example, dopamine6, pH7, halogen ions8 and potassium9. The influence of surface polarization on the sensing capabilities of diamond sensors is essential. Small transistors, down to ~10 nm, have been fabricated using local oxidation by means of lithographic techniques.10 Three of the most common oxygen related terminating species shown to exist on a diamond surface are oxygen in ketone and ether positions, as well as a hydroxyl group.11-13 The electronic and geometrical properties of non-terminated and hydrogen-terminated diamond surfaces have earlier been thoroughly studied.1, 14, 15 However, oxygen-containing terminating species have not been as carefully investigated, and a more deep knowledge of oxygen-terminated diamond surfaces is vital. The purpose of this study is to theoretically examine the change in energetic and geometrical properties of diamond surfaces due to various degrees of hydrogen and oxygen-related surface coverage, using DFT techniques under periodic boundary conditions. The adsorption systems
0890-Y08-19.2
considered are the following two-component systems; i) non-terminated/H, ii) H/OH, and iii) H/O. The oxygen-terminating species include oxygen in t
Data Loading...
