Two-hole “desorption” mechanism of interstitial-vacancy pair generation visualized by avalanche-like color-center yield in synthetic diamond under ultrashort-pulse laser exposure

Abstract

A model sectorial synthetic Ib-diamond plate with a minor concentration of substitutional atomic nitrogen C-centers was exposed in its bulk by tightly focused 0.2-ps, 525-nm laser pulses, coming at 80-MHz repetition rate and nJ-level variable pulse energies. Structural conversion into NV- and other carbon vacancy/interstitial-related centers was observed by infrared, optical and 3D confocal photoluminescence (PL) microspectroscopy, exhibiting in the optical range the ultra-broad (UV-near-IR) and smooth (structureless) absorption/photoluminescence spectra. PL intensity measured at the selected 480 and 530-nm wavelengths demonstrates its third power of the corresponding pulse energy dependences (∝E3) and avalanche-like dynamics as a function of laser exposure. Our analysis of electron-hole plasma photoexcitation and related generation of non-thermalized Auger carriers as a function of laser pulse energy (∝E1/2 and ∝E3/2, respectively) indicates that the known two-hole Auger-induced surface desorption mechanism could be anticipated in bulk diamond for interstitial-vacancy Frenkel pair generation, which rate could be evaluated via structural conversion rate for C-centers. At higher pulse energies tremendous interstitial-vacancy Frenkel pair generation rates could result not only in structural conversion of impurity-based color centers, but also in ultrafast “non-thermal” structural disordering in diamond.