Tumilty, N.J.; (2010) Diamond based nanostructures for electronic applications. Doctoral thesis, UCL (University College London).
Abstract
Research in the area of CVD diamond thin films has increased significantly during the last decades to the point where single crystal diamond is now commercially available. The remarkable properties of diamond including its extreme hardness, low coefficient of friction, chemical inertness, high thermal conductivity, transparency and semiconducting properties make it attractive for a number of applications, among which electronic devices is one of the key areas. A detailed knowledge of electrical properties of diamond films is therefore critical. This thesis describes (1) a Hall effect study of highly boron-doped (111) diamond films (2) a Hall effect and impedance spectroscopic study of boron δ-doped diamond structures and (3) the synthesis of carbon nanotubes on single crystal diamond. Systematic investigations have been carried out on single crystal, boron-doped (111) diamond films. The influence of ultra pure gases, doping concentration and temperature on carrier transport are discussed in detail. A comprehensive study on boron δ-doped diamond films is also performed; Hall effect and impedance spectroscopy are used to evaluate these films, providing valuable insight into the complex carrier transport mechanisms occurring in these structures. The influence of temperature on carrier mobility and the free carrier density are discussed. This is allied with valuable information gained from impedance spectroscopy, where the presence of multiple semicircular responses (conduction pathways), modelled using a RC parallel circuit, yields data which leads to a greater understanding on the influence of the interface between the boron δ-doped layer and the surrounding intrinsic diamond layers. These semicircular responses are thus attributed to different crystalline regions in these structures, namely the boron δ -doped layer and the interfacial regions surrounding δ-layer. The influence of this interface region on the structures overall conductivity is discussed. Finally the synthesis of carbon nanotubes (CNTs) on single crystal diamond is reported for the first time. Scanning electron microscopy combined with Raman spectroscopy is used to understand the influence of temperature and differing growth gas mixtures on the yield and crystallinity of these as-grown CNTs.
