Gueorgui Kostov Gueorguiev

The self-induced formation of core-shell InAlN nanorods (NRs) is addressed at the mesoscopic scale by density functional theory (DFT)-resulting parameters to develop phase field modeling (PFM). Accounting for the structural, bonding, and electronic features of immiscible semiconductor systems at the nanometer scale, we advance DFT-based procedures for computation of the parameters necessary for PFM simulation runs, namely, interfacial energies and diffusion coefficients. The developed DFT procedures conform to experimental self-induced InAlN NRs' concerning phase-separation, core/shell interface, morphology, and composition. Finally, we infer the prospects for the transferability of the coupled DFT-PFM simulation approach to a wider range of nanostructured semiconductor materials.

The DFT-based approaches LDA-1/2, mBJ, and HSE06 are valuable tools for investigating the electronic and optical properties of core–shell InAlN nanorods. They can approximate the state-of-the-art methods GW and BSE with much lower computational cost.

Mono- and few-layer hexagonal AlN (h-AlN) has emerged as an alternative “beyond graphene” and “beyond h-BN” 2D material, especially in the context of its verification in ultra-high vacuum Scanning Tunneling Microscopy and Molecular-beam Epitaxy (MBE) experiments. However, graphitic-like AlN has only been recently obtained using a scalable and semiconductor-technology-related synthesis techniques, such as metal–organic chemical vapor deposition (MOCVD), which involves a hydrogen-rich environment. Motivated by these recent experimental findings, in the present work, we carried out ab initio calculations to investigate the hydrogenation of h-AlN monolayers in a variety of functionalization configurations. We also investigated the fluorination of h-AlN monolayers in different decoration configurations. We find that a remarkable span of bandgap variation in h-AlN, from metallic properties to nar-row-bandgap semiconductor, and to wide-bandgap semiconductor can be achieved by its hy-drogenation and fluorination. Exciting application prospects may also arise from the findings that H and F decoration of h-AlN can render some such configurations magnetic. We complemented this modelling picture by disclosing a viable experimental strategy for the fluorination of h-AlN.

An atomic resolution image of an intercalated structure at a graphene/SiC interface along the growth direction which is determined as a buckled GaN monolayer at the immediate interface with an underlying SiC substrate and ultrathin Ga₂O₃ on top.

Schematic illustration of precursors and reaction products of simulated MOCVD of Trimethyl-Indium on graphene.

Identification and synthesis of 2D topological insulators is particularly elusive. According to previous ab initio predictions 2D InBi (Indium Bismide) is a material exhibiting topological properties which are combined with a band gap suitable for practical applications. We employ ab initio molecular dynamics (AIMD) simulations to assess the thermal stability as well as the mechanical properties such as elastic modulus and stress–strain curves of 2D InBi. The obtained new knowledge adds further characteristics appealing to the feasibility of its synthesis and its potential applications. We find that pristine 2D InBi, H-InBi (hydrogenated 2D InBi) as well as 2D InBi heterostructures with graphene are all stable well above room temperature, being the calculated thermal stability for pristine 2D InBi 850 K and for H-InBi in the range above 500 K. The heterostructures of 2D InBi with graphene exhibit thermal stability exceeding 1000 K. In terms of mechanical properties, pristine 2D InBi exhibits similarities with another 2D material, stanene. The fracture stress for 2D InBi is estimated to be ∼3.3 GPa (∼3.6 GPa for stanene) while elastic modulus of 2D InBi reads ∼34 GPa (to compare with ∼23 GPa for stanene). Overall, the thermal stability, elastic, and fracture resistant properties of 2D InBi and its heterostructures with graphene appear as high enough to motivate future attempts directed to its synthesis and characterization.

The atomic structures of 2D InO and 2D In₂O₃ through first-principles calculations, that can support experimental verifications, are reported.