Optical and electronic properties of sub-surface conducting layers in diamond created by MeV B-implantation at elevated temperatures

Abstract

Boron implantation with in-situ dynamic annealing is used to produce highly conductive sub-surface layers in type IIa (100) diamond plates for the search of a superconducting phase transition. Here we demonstrate that high-fluence MeV ionimplantation, at elevated temperatures avoids graphitization and can be used to achieve doping densities of 6 at.%. In order to quantify the diamond crystal damage associated with implantation Raman spectroscopy was performed, demonstrating high temperature annealing recovers the lattice. Additionally, low-temperature electronic transport measurements show evidence of charge carrier densities close to the metal-insulator-transition. After electronic characterization, secondary ion mass spectrometry was performed to map out the ion profile of the implanted plates. The analysis shows close agreement with the simulated ion-profile assuming scaling factors that take into account an average change in diamond density due to device fabrication. Finally, the data show that boron diffusion is negligible during the high temperature annealing process. a)

Micro-Raman spectroscopy of near-surface damage in diamond irradiated with 9-MeV boron ions

“…Higher annealing temperatures may be required for a full recovery of the lattice. Implantation at elevated temperatures [8] could also help to reduce damage.…”

“…Focused ion-beam irradiation, in particular, enables selective doping in a well-controlled way. The implantation of high energy ions in the MeV range allows for the fabrication of buried doped layers and also graphite electrodes [6][7][8]. Graphitization has been reported to occur after high temperature annealing for irradiations where the lattice damage is above a threshold of 10 22 vacancies/cm 3 [9].…”

“…Graphitization has been reported to occur after high temperature annealing for irradiations where the lattice damage is above a threshold of 10 22 vacancies/cm 3 [9]. Nonetheless, when the implantation layer is buried, graphitization seems to be prevented in part by the large internal pressure in the surrounding bulk crystal [10][11][12] and, additionally, by high temperature implantation [8]. In that way damage thresholds close to 10 23 vacancies/cm 3 have been reached [10,12].…”

“…In this work we study the damage in the diamond lattice caused by boron ion irradiation and its healing after high temperature annealing, with ion energies as high as 9-MeV and fluences up to 4.42 × 10 16 ions/cm 3 . We have used Raman and photoluminescence spectroscopy, which are very sensitive to the lattice damage and quite complementary [8,[10][11][12][13][14][15]. We focus specifically on the damage of the near-surface layers, well separated from the deep boron implantation layer.…”

Effect of Nitrogen Impurities on the Raman Line Width in Diamond, Revisited

“…Raman scattering spectroscopy has proven to be an effective and powerful technique to characterize diamond and diamond-related materials synthesized under different conditions [1][2][3][4][5][6][7][8][9][10]. The first-order Raman scattering spectrum of diamond is one of the simplest of its kind and consists of a single narrow line at around 1332 cm −1 .…”