Quantum confinement effects in gallium nitride nanostructures:ab initioinvestigations

Abstract

Abstract. We present ab initio density functional investigations of the atomic and electronic structure of gallium nitride nanodots and nanowires. With increasing diameter, the average Ga-N bond length in the nanostructures increases, as does the relative stability (heat of formation), approaching the values for bulk GaN. As the diameter decreases, the band gap increases, with the variation of the nanodots greater than that of the nanowires, in qualitatively accordance with expectations based on simple geometrical quantum confinement considerations.

Correlation between band gap, dielectric constant, Young’s modulus and melting temperature of GaN nanocrystals and their size and shape dependences

“…(7) with λ = 1 according to the definition of the shape factor. As a comparison, available DFT simulations results 20 are also listed, which agree with the corresponding model predictions. As shown in Fig.…”

“…In Fig. 2a–c , the employed simulation results correspond to the nanowires with infinite length 17 18 19 20 21 22 23 . However, not only the diameter but also the length has an influence on how strong the size effect will be, when the length L of the nanowires is comparable to the diameter.…”

“…Although the nanocrystal has lattice contraction induced by the large surface-to-volume ratio, ab initio density functional investigations of the atomic structure of GaN nanocrystals with diameters ranging from 2.28 to 1.1 nm found that the contraction of Ga-N bond length at the surface is only 0.7–0.9% in comparison with the bulk 20 . Considering that the Y ( D ) depression reaches about 40% when the cross-sectional size of square nanowires is reduced to 1 nm 23 , we can concluded that the contribution of h ( D ) on Y ( D ) is negligible in this case as a first order approximation to simplify the derivations and calculations.…”

“…However, at the nanoscale, these parameters become tunable due to the size and shape dependences, and the change trends with size and shape are different from one another. Numerous computer simulations and experimental studies have found that the E g increase while the T m , Y and ε decrease with the decreasing size 15 16 17 18 19 20 21 22 23 . In order to understand these unusual properties of nanomaterials, a lot of theoretical models have also been proposed from various perspectives.…”

Strong Dependence of Structural and Electronic Properties of Rod-Shaped [RGaNH]3n (R = H, CH3) Oligomers on Terminal Groups

“…These structural changes are quantitatively similar to those obtained for contractions of surface Ga−N bond lengths in hydrogen saturated GaN nanorods with diameters up to 3.5 nm studied within DFT PBC approximation. 2,22 The expansion of intraring Ga−N bond lengths in closed nanorods near the Ga capped edge is ∼0.6% and near the N capped edge is ∼1.0% relative the bond lengths at the center of the rod. For open structures, the expansion is also length-dependent and up to 2% relative to the bond lengths at the center of the oligomer.…”