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Title: Nanoscale investigations of the crystal structure and surface electronic properties of polycrystalline boron-doped diamond films
Author: Lay, Joshua Henry
ISNI:       0000 0004 5366 7087
Awarding Body: University of Bristol
Current Institution: University of Bristol
Date of Award: 2014
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Existing as much more than just a gemstone or refractory material, boron-doped diamond is a semiconductor with enormous potential as an electronic material. Diamond will form the basis of future high-power electronic devices, radiation-hard electronics and radiation detectors. It is also a highly effective electron emitter and a unique, biocompatible material for biomedical devices. Still, many questions remain surrounding the versatile, easy to grow polycrystalline form of boron-doped diamond. What is the surface atomic structure of these films after growth? How uniform is the boron-induced conductivity? How and why does the work function vary across the films? All of these properties affect how diamond electronic devices can be designed, fabricated and used. In this thesis we investigate nanoscale variation in properties across the surfaces of a number of differently grown boron-doped diamond films under ultra-high vacuum and evaluate the potential impact of the changes in these properties to surface electronic applications of diamond. Kelvin probe force microscopy results demonstrate significant variation in work function across the diamond surface, with a step change in work function of 0.8 eV measured between hydrogen and oxygen surface terminations, and variations across a single diamond surface are calculated to correspond to a 310% change in dopant concentration . The effect of this dopant variation is demonstrated by conductive atomic force microscopy studies in which entire crystallites exhibit insulating behaviour, with significant variation in conduction also observed across the surface. Finally, scanning tunneling microscopy studies of the diamond surface demonstrate that nanoscale roughness on large microcrystals is caused by the existence of a layer of nanocrystalline diamond at the surface. These nanocrystals persist throughout the growth process and exhibit many different surface reconstructions. The implications of all of these discoveries are discussed, with possibilities and suggestions for further work given also.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available