Hydrogen retention and nitrogen distribution in delta-doped diamond films

Abstract

Nitrogen delta-doped diamond layers can be fabricated by exposing diamond substrates to radio frequency (RF) N2 plasma, followed by growth of a diamond capping layer. A recent report shows that preferential retention of hydrogen occurs within the volume where the nitrogen atoms are localized. Here we investigate the distribution and source of hydrogen in the delta layer as well as the influence of the grain boundaries on nitrogen distribution. Delta-doped diamond layers are fabricated onto polycrystalline diamond thin films having different grain boundary densities and roughness. The capping layer was grown using D2 by replacing H2 in the gas mixture to investigate the source of hydrogen in the delta layer. In-situ X-ray photoelectron spectroscopy was used to study the chemical states of nitrogen present on the RF N2 plasma treated diamond surfaces. Time-of-flight - secondary ion mass spectrometer was used to measure the nitrogen and hydrogen concentrations. The concentration of nitrogen is of the order of 1019 cm−3 in nitrogen delta-doped layers and the width of the delta layers is up to ∼33 nm. Our study shows that the source of hydrogen is the capping layer deposition process and the grain boundary density has no significant influence on the nitrogen retention in the delta layer.