A comparative study of GaN and Ga2O3 nanocrystals obtained by hydrothermal and solid state phase reactions

There is actually a considerable interest in the preparation of nanoparticles on the basis of semiconductor and oxide materials due to the influence of nanoparticle dimensionality upon their optical, radiative, and magnetic properties. Particularly, optical properties of GaN nanostructures are interesting for applications in solid-state lightening. We report on monoclinic Ga2O3 nanoparticles preparation by two methods (hydrothermal growth and solid state phase reactions), and conversion of the obtained Ga2O3 nanoparticles into GaN nanocrystals by nitridation. Ga2O3 nanoparticles doped with Eu have been also produced. High purity Ga(NO3)3 9H2O and 1M NaOH chemicals from Sigma-Aldrich have been used for synthesis of Ga2O3 nanoparticles in the hydrothermal growth. The experimental procedure consists in dissolution of 2.5M of gallium nitrate in 50 ml of distilled water and adjustment of the solution pH to the value of 9 by means of the 1M NaOH solution under vigorous stirring. The suspension is introduced in a teflon autoclave with a steel shell to ensure a good sealing. The process lasts for 5 hours at the temperature of 220oC. The particle separation after autoclaving was performed by settling and filtering with a subsequent drying in an oven during 2 hours at 80oC. The obtained powder was studies by means of XRD spectroscopy which demonstrated the presence of a single Ga2O3 phase. Ga2O3 synthesis by solid state reactions has been performed with high purity Ga(NO3)3 9H2O and CH4N2O precursors from Sigma-Aldrich. The technological procedure consists in grinding together the precursors, introduction of the produced mixture in a porcelain crucible which is subsequently introduced in a furnace for calcinations through heating at 900oC for 4 hours. The obtained white powder was characterized by XRD spectroscopy which demonstrated the presence of a single Ga2O3 phase. GaN nanoparticles have been produced from Ga2O3 nanocrystals under flowing ammonia with a subsequent nitridation in a mixture of NH3 and H2 with flow rates of 0.35 and 2.5 l/min, respectively. The Ga2O3 powder was placed into a horizontal tube furnace with a quartz boat and heated at temperature of 900-950 oC during 90-150 min After annealing, the furnace was switched off, and cooling down occurred in a natural fashion. The diffraction peaks observed in the XRD pattern of the produced GaN powder can be indexed to a hexagonal wurtzite structure. The sizes of the produced high crystallinity GaN nanoparticles deduced from the XRD spectra according to Sherrer formula are around 28.6 nm. Apart from XRD characterization, the produced materials have been studied by means of scanning electron microscopy, EDX analysis, photoluminescence, Raman and FTIR spectroscopy. The results of these investigations are discussed in this report

Nanodimensional AlN layers grown on silicon in the system H2-HCl-Al-NH3

There were obtained nanodimensional AlN layers on Si by HVPE (Hydride Vapor Phase Epitaxy) method. SEM (Scanning Electron Microscopy) images of AlN layers, and cross-sections of AlN/Si structures are shown. The structure of surface layers was investigated by AFM (Atomic Force Microscopy) method at the stage of forming continuous layer. AlN grains nucleation on the surface of silicon occurs according to the three- dimensional (Folmer -Weber) mechanism. Granules represent a statistically dispersed ensemble of particles distributed on the substrate surface. Two mechanisms have been identified for estimating grains in the transition from the germination stage to the stage of continuous layer formation

Highly Porous and Ultra-Lightweight Aero-Ga2O3: Enhancement of Photocatalytic Activity by Noble Metals

A new type of photocatalyst is proposed on the basis of aero-β-Ga2O3, which is a material constructed from a network of interconnected tetrapods with arms in the form of microtubes with nanometric walls. The aero-Ga2O3 material is obtained by annealing of aero-GaN fabricated by epitaxial growth on ZnO microtetrapods. The hybrid structures composed of aero-Ga2O3 functionalized with Au or Pt nanodots were tested for the photocatalytic degradation of methylene blue dye under UV or visible light illumination. The functionalization of aero-Ga2O3 with noble metals results in the enhancement of the photocatalytic performances of bare material, reaching the performances inherent to ZnO while gaining the advantage of the increased chemical stability. The mechanisms of enhancement of the photocatalytic properties by activating aero-Ga2O3 with noble metals are discussed to elucidate their potential for environmental applications

Characterization of GaN thin films and Eu-doped GaN nanowires and nanoparticles produced on the basis of Ga2O3 nanomaterial

Due to advantageous properties such as wide bandgap, pronounced chemical and thermal stability, gallium nitride is currently considered as one of the most important semiconductor materials for practical applications. We present results of preparation of Eu doped GaN nanoparticles and nanowires by using Ga2O3 as source nanomaterial. Monoclinic Ga2O3 nanoparticles and nanowires have been prepared by hydrothermal growth with high purity Ga(NO3)3 9H2O and 1M precursors. The geometrical parameters of the nanomaterial were found to be determined by the duration of the hydrothermal process, Ga2O3 nanoparticles or nanowires being produced. The hydrothermal process lasts for 5 to 24 hours at the temperature of 220oC. The Ga2O3 nanomaterial is transformed unto GaN nanoparticles and nanowires by nitridation in a flow of NH3 and H2. The photoluminescence properties of Eu doped Ga2O3 and GaN nanomaterial were investigated under laser excitation. The photoluminescence proprieties of GaN films obtained by magnetron sputtering were compared with those of GaN nanowires and nanoparticles. The produced material was also investigated by means of XRD analysis, Raman scattering and Fourier transform infrared (FTIR) spectroscopy

Aero-TiO2 Prepared on the Basis of Networks of ZnO Tetrapods

In this paper, new aeromaterials are proposed on the basis of titania thin films deposited using atomic layer deposition (ALD) on a sacrificial network of ZnO microtetrapods. The technology consists of two technological steps applied after ALD, namely, thermal treatment at different temperatures and etching of the sacrificial template. Two procedures are applied for etching, one of which is wet etching in a citric acid aqua solution, while the other one is etching in a hydride vapor phase epitaxy (HVPE) system with HCl and hydrogen chemicals. The morphology, composition, and crystal structure of the produced aeromaterials are investigated depending on the temperature of annealing and the sequence of the technological steps. The performed photoluminescence analysis suggests that the developed aeromaterials are potential candidates for photocatalytic applications

Electromagnetic interference shielding in X-band with aero-GaN

Access full text - https://doi.org/10.1088/1361-6528/ab2023We investigate the electromagnetic shielding properties of an ultra-porous lightweight nanomaterial named aerogalnite (aero-GaN). Aero-GaN is made up of randomly arranged hollow GaN microtetrapods, which are obtained by direct growth using hydride vapor phase epitaxy of GaN on the sacrificial network of ZnO microtetrapods. A 2 mm thick aero-GaN sample exhibits electromagnetic shielding properties in the X-band similar to solid structures based on metal foams or carbon nanomaterials. Aero-GaN has a weight four to five orders of magnitude lower than the weight of metals

Behaviour of endothelial cells on surfaces functionalized by GaN nanoparticles

Only AbstractIn this work, we identify the mechanisms of interaction between GaN semiconductor compound nanoparticles and living endothelial cells. Cellular viability and uptaking of nanoparticles by cells as well as adhesion and proliferation of endothelial cells on surfaces functionalized by GaN nanoparticles have been investigated. Rather fast agglomeration of GaN nanoparticles around the endothelial cells was evidenced during incubation, the nanoparticles having not been released even in the cellular division process. The obtained results demonstrate good adhesion and proliferation of endothelial cells on surfaces functionalized by GaN nanoparticles