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Seminar: "Chemical vapour deposition of diamond" (Lecture)

Date
Monday 25 June 2018Add to my calendar
Time
from 16:00
Location
HG00.304
Speaker
prof. Mike Ashfold (Univ.Bristol, UK)
Description


Mike AshfoldDiamond is now synthesised by chemical vapour deposition (CVD) methods. Most commercial diamond CVD employs microwave (MW) activated C/H (typically CH4/H2) gas mixtures. Many previous studies have sought to explore and optimise radical formation in such activated gas mixtures, and the ways in which these radicals add to and are accommodated on the growing diamond surface. Our activities in this area have used a three-pronged approach involving:

  1. i) electronic spectroscopy methods (cavity ring down absorption and optical emission spectroscopies) to determine the spatial distributions of selected species (g. H atoms, CH and C2 radicals) as functions of process variables like the source gas mixing ratio, flow rate, total pressure and applied MW power,

  1. ii) complementary 2-dimensional modelling of the plasma chemistry and composition with the aims of rationalising the spatial resolved experimental column density data and predicting the concentrations of other key gas phase species (g. CH3 radicals, which are now generally considered to be the dominant growth species) that are not amenable to spectroscopic detection, as functions of process conditions, and

iii) quantum mechanical (QM) and QM-molecular mechanics calculations of the energetics of the elementary steps by which a radical species adds to, migrates on and eventually accommodates on a growing diamond surface.

This presentation will begin by summarising the various ways of forming diamond, some of the ways by which the as-grown material is characterised, and some of the spectacular properties of diamond and applications that follow. The major part of the presentation will describe our current understanding of diamond CVD from traditional C/H gas mixtures, and results of more recent studies designed to explore the potential benefits of adding trace quantities of boron and nitrogen to the C/H process gas mixture.

Contact
dr. Joost Bakker, dr. Gilles de Wijs