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A model for diamond nucleation by energetic species (for example, bias-enhanced nucleation) is proposed. It involves spontaneous bulk nucleation of a diamond embryo cluster in a dense, amorphous carbon hydrogenated matrix; stabilization of the cluster by favorable boundary conditions of nucleation sites and hydrogen termination; and ion bombardment-induced growth through a preferential displacement mechanism. The model is substantiated by density functional tight-binding molecular dynamics simulations and an experimental study of the structure of bias-enhanced and ion beam-nucleated films. The model is also applicable to the nucleation of other materials by energetic species, such as cubic boron nitride.

COMMUNICATION (1 of 8)Diamond materials are central to an increasing range of advanced technological demonstrations, from high power electronics to nanoscale quantum bioimaging with unprecedented sensitivity. [1] However, the full exploitation of diamond for these applications is often limited by the uncontrolled nature of the diamond material surface, which suffers from Fermi-level pinning and hosts a significant density of electromagnetic noise sources. [2] These issues occur despite the oxide-free and air-stable nature of the diamond crystal surface, which should be an ideal candidate for functionalization and chemical engineering. In this work, a family of previously unidentified and near-ubiquitous primal surface defects, which are assigned to differently reconstructed surface vacancies, is revealed. The density of these defects is quantified with X-ray absorption spectroscopy, their energy structures are elucidated by ab initio calculations, and their effect on near-surface quantum Many advanced applications of diamond materials are now being limited by unknown surface defects, including in the fields of high power/ frequency electronics and quantum computing and quantum sensing. Of acute interest to diamond researchers worldwide is the loss of quantum coherence in near-surface nitrogen-vacancy (NV) centers and the generation of associated magnetic noise at the diamond surface. Here for the first time is presented the observation of a family of primal diamond surface defects, which is suggested as the leading cause of band-bending and Fermi-pinning phenomena in diamond devices. A combination of density functional theory and synchrotron-based X-ray absorption spectroscopy is used to show that these defects introduce low-lying electronic trap states. The effect of these states is modeled on band-bending into the diamond bulk and it is shown that the properties of the important NV defect centers are affected by these defects. Due to the paramount importance of near-surface NV center properties in a growing number of fields, the density of these defects is further quantified at the surface of a variety of differently-treated device surfaces, consistent with best-practice processing techniques in the literature. The identification and characterization of these defects has wide-ranging implications for diamond devices across many fields.

Oxygen adsorption on the Pd(111) surface has been studied at 100 and 300 K by temperature programmed desorption (TPD) and isotopic mixing experiments. At 100 K, the sticking coefficient is determined to be 1 up to the coverage of 0.3 O/Pd. The saturation coverage is 0.62 O/Pd, 27% of which dissociates during thermal desorption. Three molecular desorption processes are observed with the activation energy of 7.6, 9.1, and 12.3 kcal/mol, respectively. At 300 K, the sticking coefficient increases with coverage from ∼0.14 at zero coverage to 0.87 at θ≊0.05 O/Pd, then decreases to zero at a saturation coverage of 0.25 O/Pd. The desorption activation energy of 53 kcal/mol is calculated for the associative desorption process with a lateral repulsive interaction of 0.7 kcal/mol. Based on the isotopic mixing results and previous high resolution electron energy loss spectroscopy (HREELS) data, a more complete picture concerning adsorption, conversion, equilibration, desorption, and dissociation processes is suggested.