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The influence of electrode fabrication on induced X-ray photocurrents in CVD diamond radiation detectors

The main objective of this project was in to investigate the effect of different metal contacts on the electrical and dosimetric characteristics of semiconductor diamond in an attempt to develop a new type of x-ray dosimeter. This was achieved in a number steps, in the first part of the project the influence of the metal-diamond interfaces as well as the influence of annealing on the electrical and dosimetric characteristics of diamond based solid state radiation detectors was investigated. This allowed identification of the optimum metal contacts and conditions which maximize the detector performance as a dosimeter, in terms of time response, SNR, linearity, stability and reproducibility. For this purpose, three different samples (HPS-Pt, VS-Pt and HPS-Al/Pt) with different metal contacts were fabricated. 2In the second part of the project sensitivity mapping was performed on the sample designated VS-Pt. This sample was chosen due to its special features such as thin nitrogen lines and substrate area. Three different sources of focused x-ray beams were investigated in order to choose suitable conditions to obtain high resolution images of the nitrogen lines within the sample. Additionally the mapping sensitivity of HPS-Pt and HPS-Al/Pt was investigated to study the effect of certain parameters on the homogeneity of the current response and choose the suitable contact for synchrotron measurements. In the third part of this project three polycrystalline diamond x-ray dosimeters were fabricated. Two of which were fabricated by depositing carbon using a new deposition technique known as Pulsed Laser Deposition (PLD), the first with pure amorphous carbon (labelled Poly-C) and the second with amorphous carbon mixed with Nickel (labelled Poly-C/Ni). The third device was metalized by conventional sputtering of Platinum for comparison. The dosimetric characteristics and validity of the samples for potential use in radiation dosimetry was investigated in order to obtain a detector with a high SNR, fast time response, reproducible manner and a response that does not depend on the dose rate. In the fourth part of this project a single crystal CVD diamond x-ray dosimeter (SC-C/Ni) with a C/Ni contact was fabricated using Pulsed Laser Deposition in an attempt to remove the dose rate dependence in polycrystalline samples and a comparison drawn to the previous polycrystalline devices. Finally using alpha particle spectroscopy the electron and hole transport properties were separately investigated for samples SC-C/Ni, HPS-Pt, VS-Pt and HPS-Al/Pt, confirming the results of some of the previous measurements undertaken using x-rays.