Nanostructuring and oxidation of diamond by two-photon ultraviolet surface excitation: An XPS and NEXAFS study

Abstract

We report C(1s) and O(1s) surface sensitive x-ray photoelectron spectroscopy (XPS) and C and O K-edge partial-electron yield near-edge x-ray absorption fine structure (NEXAFS) measurements for (100) and (110) oxidized diamond surfaces, etched by a laser two-photon ultraviolet (UV) desorption process. Etched regions of the (100) surface show increased oxygen coverage with a higher fraction of singly bonded termination species than unetched regions. Similar changes are observed for the (110) but with smaller magnitude. For both surfaces, no major change in sp 2 bonded carbon is observed. We show that the terminations observed for etched surfaces are consistent with the formation of oxidized {111} facets. For deeply etched samples, atomic force microscopy and scanning electron microscopy confirm the presence of {111}-like facets and reveals the development of nanoscale facetted ridges directed perpendicular to the etching beam polarization. An etching mechanism is proposed involving localized optical absorption by surface electronic states, with the probability for subsequent desorption events varying according to the relative directions of laser polarization and lattice orientation.

Spin coherence and depths of single nitrogen-vacancy centers created by ion implantation into diamond via screening masks

“…The C 1s peak at 285 eV arises primarily from sp 3 (in bulk), and the asymmetric shape indicates the presence of other bonds such as C-O, C=O (> 285 eV), and sp 2 (< 285 eV). 18,42 The O 1s peak at 532 eV has a broad linewidth, presumably composed of C-O-C, C-C-H, and C=O (< 532 eV). 18,42 Despite the limited spectral resolution, we can conclude that the chemical composition of the surface is essentially the same between the t = 0 and t = 0 areas.…”

Photochemical Etching of Carbonyl Groups from a Carbon Matrix: The (001) Diamond Surface

“…Recently, a novel 2-photon laser induced desorption (LID) phenomenon has been reported for diamond surfaces exposed to nanosecond ultraviolet (UV) pulses with incident fluence well below the threshold for laser ablation [1][2][3][4][5]. This "cool-etching" phenomenon appears to have a number of advantages over traditional ablative laser-machining (for which the minimum etch rates are around 10 nm/pulse); most notably, the LID process has no intensity threshold [3] and allows for carbon removal rates as low as 3×10 −9 nm/pulse for low incident fluence [6].…”

“…To date, a number of key features of LID have been characterized; in particular, the nonlinear nature of the underlying electronic excitation is evidenced by the dependence of the desorption rate on the intensity of the incident pulse [3,7]. The surface two-photon absorption cross-section -evaluated based on the LID etch ratesis close to 25-times higher than that of bulk diamond [4,8]; moreover, the threshold-free nature and observed dependence on the polarization of incident photons [4,5] points to a surface-specific multi-photon-excited desorption mechanism. Given that etching of the O-terminated diamond surface is quenched in vacuum [2], it seems likely that carbon removal involves laser induced carbon monoxide (CO) desorption.…”

“…Given that etching of the O-terminated diamond surface is quenched in vacuum [2], it seems likely that carbon removal involves laser induced carbon monoxide (CO) desorption. However, despite extensive characterization of the LID process and a number of proposed models for the mechanism [1][2][3][4][5], the process is poorly understood. Determination of the mechanism is made difficult, in contrast to ablation, by the short time and length scales upon which desorption occurs and which are especially challenging to access experimentally.…”

“…The {001} surface also supports a bridging (ether) termination; however, X-ray experiments have indicated a reduced number of carbonyl sites compared to bridging sites post etching, suggesting a preferential (or even exclusive) CO removal from carbonyl sites [5]. Moreover, post-etch diamond surfaces exhibit strong {111}-like faceting [5], indicating this surface is resistant to etching ; importantly, the {111} surface cannot support carbonyl groups, explaining the etch resistance of this surface. For these reasons, we focus on the carbonyl surface species for the present study.…”