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

TL;DR

This study demonstrates that high-fluence MeV boron ion implantation at elevated temperatures creates highly conductive, sub-surface layers in diamond without graphitization, with potential for superconductivity and controlled doping.

Contribution

It introduces a method for producing highly conductive diamond layers via high-fluence MeV B-implantation at elevated temperatures, avoiding graphitization and enabling precise doping control.

Findings

High-fluence MeV B-implantation achieves 6 at.% doping density.

High-temperature annealing recovers diamond lattice structure.

Charge carrier densities approach the metal-insulator transition.

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 ion-implantation, 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.