Electronic structure & electrical properties of ultra-nanocrystalline diamond (UNCD) for multifunctional devices

Abstract

In this work, we have synthesized ultra-nano-crystalline diamond (UNCD) thin films with average thickness ∼200 nm on n-type mirror polished silicon (100) substrates using microwave plasma enhanced chemical vapour deposition (MW-PECVD) system. The synthesis was carried out in different gas (H2 - N2 - Ar - CH4) composition plasma atmospheres at 1200 W (2.45 GHz) and in the pressure of 120 Torr with plasma-temperature ∼475 °C. Surface morphology of all thin films were studied using high resolution scanning electron microscopy (HR -SEM) images. Raman spectroscopy was used for microstructural study and nanoindentation technique was used for the Hardness/Young’s modulus study; whereas X-ray absorption near edge structure (XANES), X-ray photoelectron (XPS) and ultraviolet photoemission spectroscopies (UV-PES) techniques were used to study electronic structure of UNCD thin films. Electrical measurements, current -voltage (I-V), were used to study the conductivity of the films. The hardness of the films is found to be ∼30 GPa, Young’s modulus to be ∼300 GPa and induced electron field emission, the turn on electric field, ETOE = 11 V/μm. The results, in general, show that the UNCD could be useful for different industrial semiconductor/optoelectronic devices and as flexible materials for thin film coating technology.