Jiwen Zhao

Diamond Deposition on Graphite in Hydrogen Microwave Plasma

Hydrogen plasma etching of graphite generates radicals that can be used for diamond synthesis by chemical vapor deposition (CVD). We studied the etching of polycrystalline graphite by a hydrogen microwave plasma, growth of diamond particles of the non-seeded graphite substrates, and characterized the diamond morphology, grain size distribution, growth rate, and phase purity. The graphite substrates served simultaneously as a carbon source, this being the specific feature of the process. A disorder of the graphite surface structure reduces as the result of the etching as revealed with Raman spectroscopy. The diamond growth rate of 3 – 5 μm/h was achieved, the quality of the produced diamond grains improving with growth time due to inherently nonstationary graphite etching process. Received on 29-12-2017 Accepted on 05-03-2018 Published on 16-08-2018

Impact of UV spot position on forward and reverse photocurrent symmetry in a gold-diamond-gold detector

A UV detector based on a planar quadrant electrode structure with a 100-μm isolating cross-gap deposited on chemical vapor deposition diamond was fabricated. An asymmetrical behavior was observed for the amplitude of photocurrent when in forward and reverse bias. A linear relationship between the sum of the photocurrents at biases U and −U, and the light spot position was also observed. The aim of this study is to clarify the mechanism underlying this asymmetrical behavior and exhibit its potential application based on this behavior. A mechanism involving lowering of the contact barrier height between gold and i-diamond by carrier generation upon UV illumination was adopted to account for the photocurrent behavior and confirmed when an opposite asymmetrical photocurrent behavior was observed in other samples. In addition, position-sensitive detection performance, based on this asymmetrical photocurrent behavior, was preliminarily studied. The results exhibited the potential for application as a position-sensitive detector.