1, The University of Texas at Dallas, Richardson, Texas, United States
3, Universidad Tecnológica de Panamá, Panamá, República de Panamá, Panama
4, The University of Texas at Dallas, Richardson, Texas, United States
The physics and applications of Ultrananocrystalline Diamond (UNCD) films are been investigated due to their unique combination of properties such as high wear resistance, highest hardness relative to any other film, lowest friction coefficient compared with metal and ceramic coatings, chemical inertness1 2, negative electron affinity, low work function, and the high electrical conductivity for boron doped and nitrogen incorporated diamond films. The combination of these properties make doped diamond films suitable for many applications like electrodes for water purification, thermionic and field emission devices, and high power electronic devices3 4 5 6 7. Boron doping of UNCD films during growth has the drawback of Boron contamination of the chamber where the film is grown, which can only be used for the growth of B-doped diamond films.
This presentation will focus on describing the results from research and development of a novel process for Boron doping large area UNCD films by thermal diffusion after growth, thus eliminating the problem of Boron contamination of the diamond film growth chamber. The research is focused on understanding the chemical, structural and electrical properties of the UNCD films before and after doping with Boron by thermal diffusion. The UNCD films were grown by Microwave Plasma Chemical Vapor Deposition (MPCVD) technique on a (1 0 0) Silicon substrate. Subsequently, a 200-nm thick Boron doped Polycrystalline Silicon film was grown on top of the UNCD film as a boron source and protective layer to avoid the C-based UNCD film being exposed, at the high temperature needed for Boron diffusion, to oxygen present in the oven where the Boron doping is produced, which would etch the UNCD film, during the process to induced diffusion of Boron atoms from the Silicon layer into the UNCD film. The diffusion process was carried in an atmospheric furnace at 800oC with a constant N2 flow of 4L/min (the furnace was expose to atmosphere during the process) for 1 hour. Once the diffusion process was over, the silicon layer was removed by CF4 RIE etching. The boron doped and as deposited films were characterized by Raman, XRD, XPS, 4-point probe and C-V analysis. Raman and XRD characterizations were done to confirm that there was no induced graphitization or damage in the films during the diffusion process, while XPS, 4-point probe and C-V characterizations were carried to confirm the boron doping and the change in electrical properties (sheet resistance, charge carrier concentration) during the diffusion process.