Looi, Hui Jin; (2000) Hydrogen doped thin film diamond: Properties and application for electronic devices. Doctoral thesis (Ph.D.), University College London (United Kingdom).

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Abstract

The face centered cubic allotrope of carbon, diamond, is a semiconducting material which possesses a valuable combination of extreme properties such as super-hardness, highest thermal conductivity, chemical hardness, radiation hardness, wide bandgap and others. Advances in chemical vapour deposition (CVD) technology have lead to diamond becoming available in previously unattainable forms for example over large areas and with controllable purity. This has generated much research interest towards developing the knowledge and processing technology that would be necessary to fully exploit these extreme properties. Electronic devices fabricated on oxidised boron doped polycrystalline CVD diamond (PCD) displayed very poor and inconsistent characteristic. As a result, many electronic applications of polycrystalline diamond films were confined to ultra-violet (UV) and other forms of device which relied on the high intrinsic resistivity on undoped diamond films. If commercially accessible PCD films are to advance in areas which involve sophisticated electronic applications or to compete with existing semiconductors, the need for a more reliable and fully ionised dopant is paramount. This thesis describes a unique dopant discovered within the growth surface of PCD films. This dopant is related to hydrogen which arises during the growth of diamond films. The aim of this study is to characterise and identify possible applications for this form of dopant. The mechanism for carrier generation remains unknown and based on the experimental results in this work, a model is proposed. The Hall measurements conducted on this conductive layer revealed a p-type nature with promising properties for electronic device application. A more detailed study based on electrical and surface science methods was carried out to identify the stability and operating conditions for this dopant. The properties of metal-semiconductor contacts on these surfaces were investigated. The fundamental knowledge is essential for exploring more advanced electronic devices such as the field effect transistors (FETs). Diamond is the only material suitable for detecting UV in the 220nm wavelength without any appreciable visible response. The prospect of introducing a doped layer based on Schottky mode for UV detection is important as it allows monolithic integration with other electronic devices.

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