Search

Beyond the predictions routinely achievable by first-principles calculations and using metal–organic chemical vapor deposition (MOCVD), we report a GaN monolayer in a buckled geometry obtained in confinement at the graphene/SiC interface. Conductive atomic force microscopy (C-AFM) was used to investigate vertical current injection across the graphene/SiC interface and to establish the uniformity of the intercalated regions. Scanning transmission electron microscopy (S/TEM) was used for atomic resolution imaging and spectroscopy along the growth direction. The experimentally obtained value of the buckling parameter, 1.01 ± 0.11 Å, adds to the existing knowledge of buckled GaN monolayers, which is based solely on predictive first-principles calculations. Our study reveals a discontinuity in the anticipated stacking sequence attributed to a few-layer graphitic-like GaN structure. Instead, we identify an atomic order suggestive of ultrathin gallium oxide Ga2O3, whose formation is apparently mediated by dissociative adsorption of oxygen onto the GaN monolayer. [ABSTRACT FROM AUTHOR]

2D SiN honeycomb monolayer structures predicted theoretically have been the focus of interest in materials science for a long time, most recently for their semiconducting and ferromagnetic properties. Herein, by investigating metal‐organic chemical vapor deposition processes and direct heat treatment of epitaxial graphene in ammonia flow, the possibility of realizing a certain periodic 2D structure via Si─N bonds under epitaxial graphene on SiC (0001) is reported. The result is of interest because it is compatible with semiconductor material deposition technologies and future use in nanoscience and nanotechnology. [ABSTRACT FROM AUTHOR]

The initial stages of metal organic chemical vapor deposition (MOCVD) of AlN on epitaxial graphene at temperatures in excess of 1200 °C have been rationalized. The use of epitaxial graphene, in conjunction with high deposition temperatures, can deliver on the realization of nanometer thin AlN whose material quality is characterized by the appearance of luminescent centers with narrow spectral emission at room temperature. It has been elaborated, based on our previous comprehensive ab initio molecular dynamics simulations, that the impact of graphene on AlN growth consists in the way it promotes dissociation of the trimethylaluminum, (CH3)3Al, precursor with subsequent formation of Al adatoms during the initial stages of the deposition process. The high deposition temperatures ensure adequate surface diffusion of the Al adatoms which is an essential factor in material quality enhancement. The role of graphene in intervening with the dissociation of another precursor, trimethylgallium, (CH3)3Ga, has accordingly been speculated by presenting a case of propagation of ultrathin GaN of semiconductor quality. A lower deposition temperature of 1100 °C in this case has better preserved the structural integrity of epitaxial graphene. Breakage and decomposition of the graphene layers has been deduced in the case of AlN deposition at temperatures in excess of 1200 °C. [ABSTRACT FROM AUTHOR]

Abstract We report the results of in-depth Raman study of quasi-free-standing monolayer graphene on the (0001) Si- face of 4H-SiC, which contains ~0.1–2·1011 cm−2 sp 3 defects that have been introduced by hydrogen intercalation. The nature of the intercalation-induced defects is elucidated and ascribed to the formation of the C-H bonds. At the higher intercalation temperature in the formed monolayer graphene the defect-related Raman scattering displays a great enhancement and new spectral features attributed to D ′ and D + D ′ modes appear. Comprehensive statistical analysis of the Raman data enabled us to estimate the homogeneity of the Raman scattering processes and to separate strain and doping effects. Analysis of the compressive strain and carrier density maps revealed that the intercalation temperature of 900 °C and intercalation time of 1 h are more favorable conditions for conversion of the buffer layer to uniformly relaxed and p -doped monolayer graphene in comparison to annealing at 1100 °C for 30 min. [ABSTRACT FROM AUTHOR]