Investigation of defects in diamond implanted with N-O molecular ions

Abstract

The incorporation of shallow n-type dopants in diamond is one of the major challenges for its electronic applications. n-Type behavior in diamond has been observed for substitutional phosphorus and nitrogen, with activation energies of approximately 0.62 eV and 1.7 eV respectively. Both nitrogen and phosphorus are deep lying substitutional impurity states in diamond. It has been theoretically demonstrated that the substitution of the N-O molecule into the diamond lattice forms a stable defect in the band gap and in the negatively charged state induces a shallow defect below the conduction band edge which may lead to n-type conductivity. In this project, surface characterization and optical spectroscopy were carried out to investigate the nature and behavior of the defects induced by the implantation of N-O ions into type IIa Chemical Vapor Deposition (CVD) diamond samples. Photoluminescence peaks attributed to N-O complexes were observed at 293.3 nm, 297.3 nm, 305.9 nm, 309.8 nm, 314.4 nm for the sample which was implanted with N-O molecular ions and annealed at 600 C. The mechanism of electronic transitions leading to emission of photoluminescence of these peaks is proposed. In addition, a peak at 533 nm was observed on the cathodoluminescence spectrum of the same sample and was tentatively attributed to a radiative recombination of a shallow n-type defect and a deep lying p-type defect in the middle of the band gap, associated to vacancy-related states. The results presented extends the knowledge on defects leading to shallow n-type dopants in diamond. We believe that this thesis creates a paradigm for future studies on the search for alternative suitable shallow dopants, which is the sine qua non for potential application of diamond-based electronic devices