Maximum hole concentration for Hydrogen-terminated diamond surfaces with various surface orientations obtained by exposure to highly concentrated NO2

Abstract

NO2 exposure drastically increases the hole concentration on the surface of hydrogen (H)-terminated diamond. When the NO2 gas concentration is higher than 300ppm, the saturated hole sheet concentration ps stays the same. Therefore, the ps value is regarded as the high limit of the concentration of holes on H-terminated diamond surface, ps,max. In this work, we compared ps,max, mobility μ, and sheet resistance Rs for (100), (110), and (111) H-terminated surfaces of chemical-vapor-deposited single-crystal diamond. On (110), (111), (100) surfaces, the ps,max values are 1.717×1014 and 1.512×1014cm−2, and 0.981×1014, respectively. This result supports the first-principle calculations: the hole concentration depends on the energy difference between the valence band maximum and the unoccupied orbitals of adsorbent NO2 molecules. We have achieved Rs of 719.3 Ω/sq (ps=1.456×1014cm−2 and μ=59.6 cm2 V−1s−1), the lowest reported so far, on (111) surfaces under 20,000-ppm NO2 atmosphere.