Abstract
Growth, diverse properties, and possible applications of ultrananocrystalline diamond (UNCD) films are investigated in this research work. Initially, possibility of improving the electron field emission (EFE) property of the films by using ion implantation process is investigated. We have found that high dose N ion implantation could improve the EFE properties, which is possibly due to the doping effect of N into the grain boundaries of UNCD and charge transfer-doping mechanism. Furthermore, multi-energy N ion implantation (MENII) processes are designed to implant dopant species uniformly in the films to improve further the EFE properties. The MENII process carried out at an elevated temperature tremendously improved the EFE properties. We believe that this new technique can be applied to implant species into materials in a controlled manner to improve their properties. The field emitting pyramidal shape UNCD tips were fabricated by novel process, in which the UNCD was used as the emission site on highly N-doped (20%) NCD tips. Emitters with tip size of 2 □m showed high EFE properties as compared to tips with larger sizes. Moreover, the EFE property of tips is improved using the high dose N ion implantation process. Alternatively, field emitting silicon nanostructures (SiNS) were fabricated and the emission is enhanced by the growth of UNCD. However, a modified pre-seeding (UND) process had to be developed to create nucleation sites on the tips by without deteriorating their properties. We found that, sub-2 nm UNCD grains are grown on the nanotips, which improved the emission properties tremendously. We expect that, the UND process can be used effectively for creating nucleation sites on other nanostructures to grow diamond films. The transmittance study of thin UNCD films on transparent quartz substrate has shown to possess very high transmittance in comparison with other larger grain diamonds (NCD or MCD) of similar thickness. We have analyzed the possibility of utilizing ion implantation for controlled modification on the optical properties of the films. In addition, UNCD films were fabricated on YZ-cut LiNbO3 substrates by using a modified growth process, which is designated as LPP process. The as grown UNCD film has shown to possess room temperature conductivity and high EFE properties. Insulating UNCD films on these substrates were fabricated using interlayer of either Si or SiO2, which was applied to study the surface acoustic wave (SAW) characteristics.