Surface transfer doping of hydrogen-terminated diamond has been achieved utilising V₂O₅ as a surface electron accepting material. Contact between the oxide and diamond surface promotes the transfer of electrons from the diamond into the V₂O₅ as revealed by the synchrotron-based high resolution photoemission spectroscopy. Electrical characterization by Hall measurement performed before and after V₂O₅ deposition shows an increase in hole carrier concentration in the diamond from 3.0 × 10¹² to 1.8 × 10¹³cm⁻² at room temperature. High temperature Hall measurements performed up to 300 °C in atmosphere reveal greatly enhanced thermal stability of the hole channel produced using V₂O₅ in comparison with an air-induced surface conduction channel. Transfer doping of hydrogen-terminated diamond using high electron affinity oxides such as V₂O₅ is a promising approach for achieving thermally stable, high performance diamond based devices in comparison with air-induced surface transfer doping.

Recently, solid state photovoltaic Schottky diodes, able to detect ionizing radiation, in particular, x-ray and ultraviolet radiation, have been developed at the University of Rome “Tor Vergata.” We report on a physical and electrical properties analysis of the device and a detailed study of its detection capabilities as determined by its electrical properties. The design of the device is based on a metal/nominally intrinsic/p-type diamond layered structure obtained by microwave plasma chemical vapor deposition of homoepitaxial single crystal diamond followed by thermal evaporation of a metallic contact. The device can operate in an unbiased mode by using the built-in potential arising from the electrode-diamond junction. We compare the expected response of the device to photons of various energies calculated through Monte Carlo simulation with experimental data collected in a well controlled experimental setup i.e., monochromatic high flux x-ray beams from 6 to 20 keV, available at the Diamond Light Source synchrotron in Harwell (U.K.).

We report on a comparative study of transfer doping of hydrogenated single crystal diamond surface by insulators featured by high electron affinity, such as Nb₂O₅, WO₃, V₂O₅, and MoO₃. The low electron affinity Al₂O₃ was also investigated for comparison. Hole transport properties were evaluated in the passivated hydrogenated diamond films by Hall effect measurements, and were compared to un-passivated diamond films (air-induced doping). A drastic improvement was observed in passivated samples in terms of conductivity, stability with time, and resistance to high temperatures. The efficiency of the investigated insulators, as electron accepting materials in hydrogenated diamond surface, is consistent with their electronic structure. These surface acceptor materials generate a higher hole sheet concentration, up to 6.5 × 10¹³ cm⁻², and a lower sheet resistance, down to 2.6 kΩ/sq, in comparison to the atmosphere-induced values of about 1 × 10¹³ cm⁻² and 10 kΩ/sq, respectively. On the other hand, hole mobilities were reduced by using high electron affinity insulator dopants. Hole mobility as a function of hole concentration in a hydrogenated diamond layer was also investigated, showing a well-defined monotonically decreasing trend.

Recently, a compact solid-state neutron detector capable of simultaneously detecting thermal and fast neutrons was proposed [M. Marinelli et al., Appl. Phys. Lett. 89, 143509 (2006)]. Its design is based on a $p$ -type/intrinsic/metal layered structure obtained by Microwave Plasma Chemical Vapor Deposition (CVD) of homoepitaxial diamond followed by thermal evaporation of an Al contact and a ${}^6\text{L}\text{iF}$ converting layer. Fast neutrons are directly detected in the CVD diamond bulk, since they have enough energy to produce the ${}^{12}\text{C}\left(n,\alpha \right){}^9\text{B}\text{e}$ reaction in diamond. Thermal neutrons are instead converted into charged particles in the ${}^6\text{L}\text{iF}$ layer through the ${}^6\text{L}\text{i}\left(n,\alpha \right)T$ nuclear reaction. These charged particles are then detected in the diamond layer. The thickness of the ${}^6\text{L}\text{iF}$ converting layer and the CVD diamond sensing layer affect the counting efficiency and energy resolution of the detector both for low- (thermal) and high-energy neutrons. An analysis is carried out on the dynamics of the ${}^6\text{L}\text{i}\left(n,\alpha \right)T$ and the ${}^{12}\text{C}\left(n,\alpha \right){}^9\text{B}\text{e}$ reactions products, and the distribution of the energy released inside the sensitive layer is calculated. The detector counting efficiency and energy resolution were accordingly derived as a function of the thickness of the ${}^6\text{L}\text{iF}$ and CVD diamond layers, both for thermal and fast neutrons, thus allowing us to choose the optimum detector design for any particular application. Comparison with experimental results is also reported.