Nanocrystalline diamond (NCD) films are being intensively researched for a variety of potential applications, such as optical windows, electrochemical electrodes, and electron emitting surfaces for field emission displays. In this study Zr, Ti, Cu, and Pt on intrinsic and lightly sulfur-doped (n -type) NCD films were electrically and photoelectrically characterized. Intrinsic and sulfur-doped NCD films were synthesized on 1 in. diameter quartz and silicon substrates by microwave plasma assisted chemical vapor deposition. All metals showed linear (Ohmic) current-voltage characteristics in the as-deposited state. The Schottky barrier heights (B) at the metal-film interface were investigated using x-ray and ultraviolet photoelectron spectroscopies. The undoped NCD films exhibited a negative electron affinity and a band gap of 5.0±0.4 eV. The B were calculated based on this band gap measurement and the consistent indication from Hall measurements that the films are n -type. The B values were calculated from shifts in the core-level (C1s) peaks immediately obtained before and after in situ, successive metal depositions. The B values for Zr, Ti, and Pt on undoped films were calculated to be 3.3, 3.2, and 3.7 eV, respectively. The S-doped films also showed increasing B with metal work functions: 3.0, 3.1, and 3.4 eV for Zr, Ti, and Pt, respectively. In general accordance with the barrier height trends, the specific contact resistivity (ρ c) values increased with the metal work functions for both undoped and S-doped films. For the undoped films ρ c increased from 3× 10-5 cm2 for Zr to 6.4× 10-3 cm2 for Pt. The ρ c values for the S-doped films were approximately two orders of magnitude lower than those for the undoped films: 3.5× 10-7 -4.5× 10-5 cm2 for Zr and Pt, respectively. The Hall-effect measurements indicated that the average sheet resistivity and carrier concentration values were 0.16 and 3.5× 1018 cm-3 for the undoped films and 0.15 cm and 4.9× 1019 cm-3 for the S-doped films.
ASJC Scopus subject areas
- Physics and Astronomy(all)