Role of Surface Polarity in Self-Catalyzed Nucleation and Evolution of GaN Nanostructures

Abstract

Self-catalytic growth of GaN nanotips and nanoparticles, grown by chemical vapor deposition technique, are investigated. Three important parameters, comprised of incubation time, anisotropy of diffusion, and rate-limiting factors of Ga and N adatoms migration over polar and nonpolar surfaces, are found to play significant roles in determining the final morphology of these nanostructures. Nucleation of GaN nanotips takes place under Ga-rich conditions. As the reaction proceeds, the stochiometry changes occur as a result of a shift in Ga-rich to N-rich conditions on the surface. In all of these cases, the growth continues to be in vapor−solid mode. The conical shape of the nanotips is explained in terms of differential growth in the reduced surface diffusion of Ga under N-rich conditions on polar surfaces (0001) relative to nonpolar surfaces (101̅ 0). Nanoparticles are grown initially in N-rich conditions with significantly shorter incubation times. A mechanistic approach that expounds evolution of nanotips and nanoparticles is elucidated in details using crystallographic and electronic structural studies.

Pt-decorated GaN nanowires with significant improvement in H 2 gas-sensing performance at room temperature

“…5 presents the typical micro-Raman spectra of GaN NWs synthesized onto c-Al 2 O 3 substrate. The Raman peaks located at 534, 556, 577 and 731 cm −1 are attributed to A 1 (TO), E 1 (TO), E 2 (high), and A 1 (LO), respectively, which agrees with the Raman selection rules for wurtzite-type GaN structure [59][60][61].…”

“…Sahoo et al [59,62] explained well the appearance of these modes. When the dimension of nanomaterial are diminishing, the relaxation of q = 0 selection rule owing to the influence of finite size for nanostructured materials forms new phonon modes to generate modes that match to q ≠ 0 phonons.…”

“…, O − ) and H 2 gas molecules[13,50,63,64].The basic parameters limiting gas sensing characteristics of 1-D semiconducting nanostructures are mainly the surface-to-volume ratio and surface morphology[16,18,20,25,[55][56][57][58][59][60][61][62][63][64][65][66][67]. 1-D NWs usually have rough and zigzagged surface.…”

Polarized Raman and photoluminescence studies of a sub-micron sized hexagonal AlGaN crystallite for structural and optical properties

“…The intense and sharp peaks observed in the Raman spectra ensure the high quality of the crystal suitable for various optoelectronic applications. The growth process of AlGaN microcrystals follows purely the self‐catalytic vapor–solid mechanism . At the growth temperature (1100 °C), some AlN islands may form on the Al coated Si (100) (as discussed in x‐ray photoelectron spectroscopic (XPS) analysis [Fig.…”

Synthesis, microstructure, growth mechanism and photoluminescence of high quality [0001]-oriented InN nanowires and nanonecklaces

“…The accelerating voltage was set to 40 [25] , from the SEM (also in subsequent EDS and TEM), the heads or parts of InN nanomaterials in our experiments do not contain gold catalyst, indicating the vapor-solid (VS) growth mode [26] . The X-ray diffraction (XRD) data were obtained with a Philips X'Pert PRO diffractometere equipped with Cu-anode X-ray tube, Ni filter, and the focused optics is obtained with incident beam optics equipped with fixed divergence slit & anti-scatter slit module and hybrid monochromator, 4xGe220 Cu system, respectively.…”