Physical properties of nanostructures induced by irradiation in diamond

Abstract

We investigate the interaction of slow highly charged ions (SHCIs) with insulating type-Ib diamond (111) surfaces. Bismuth and Xenon SHCI beams produced using an Electron Beam Ion Trap (EBIT) and an Electron Cyclotron Resonance source (ECR) respectively, are accelerated onto type Ib diamond (111) surfaces with impact velocities up to 0.4 Bohr. SHCIs with charge states corresponding to potential energies between 4.5 keV and 110 keV are produced for this purpose. Atomic Force Microscopy analysis (AFM) of the diamond surfaces following SHCI impact reveals surface morphological modi cations characterized as nanoscale craters (nano-craters). To interpret the results from Tapping Mode AFM analysis of the irradiated diamond surfaces we discuss the interplay between kinetic and potential energy in nanocrater formation using empirical data together with Stopping and Range of Ions in Matter (SRIM) Monte Carlo Simulations. In the case of irradiation induced magnetic e ects in diamond, we investigate the magnetic properties of ultra-pure type-IIa diamond following irradiation with proton beams of 1-2 MeV energy. SQUID magnetometry of proton irradiated non-annealed diamond indicates formation of Curie type paramagnetism according to the Curie law. Raman and Photoluminescence spectroscopy measurements show that the primary structural features created by proton irradiation are the centers: GR1, ND1, TR12 and 3H. The Stopping and Range of Ions in Matter (SRIM) Monte Carlo simulations together with ii iii SQUID observations show a strong correlation between vacancy production, proton uence and the paramagnetic factor. At an average surface vacancy spacing of 1-1.6 nm and bulk (peak) vacancy spacing of 0.3-0.5 nm Curie paramagnetism is induced by formation of ND1 centres with an e ective magnetic moment eff (0.1-0.2) B. Post annealing SQUID analysis of proton irradiated diamond shows formation temperature independent magnetism with magnetic moment 6-7 emu superimposed to Curie-type paramagnetism. The response of ultra-pure type-IIa single crystal CVD diamond following 2.2 MeV proton micro-irradiation is further investigated using Atomic Force, Magnetic Force and Electrostatic Force Microscopy (AFM, MFM and EFM) under ambient conditions. Analysis of the phase shift signals using probe polarization dependent magnetization measurements and comparison of the MFM and EFM signals at zero electrical bias, show that measured force gradients originate from a radiation induced magnetic response in the micro-irradiated regions in diamond.