Influence of Nitridation on Structural and Photoluminescence Behaviour of CaZrO3:Eu3+ Nanophosphors

Ca1-xZrO3:xEu3+ (x = 0.05) phosphors have been prepared by using the low temperature solution combustion synthesis. The prepared nano phospors are well characterized by powder X-ray diffraction, scanning electron microscopy, Fourier infrared spectroscopy and transmission electron spectroscopy. PXRD results showed orthorhombic phase and SEM images showed porous agglomerated morphology. Influence of nitridation on structural and photoluminescence properties of the phosphor were investigated for wide range of nitridation time. The photoluminescence (PL) intensity was found to vary with nitridation with small shift in the photoluminescence emission peaks. The probable reasons for the variation of photoluminescence with nitridation are discussed.

Nanocrystalline Ga–Zn Oxynitride Materials: Minimized Defect Density for Improved Photocatalytic Activity?

We present an alternative synthesis strategy for developing nanocrystalline (Ga1−xZnx)(N1−xOx) semiconductors known to be very efficient photoabsorbers. In a first step we produce mixtures of highly crystalline β-Ga2O3 and wurtzite-type ZnO nanoparticles by chemical vapor synthesis. (Ga1−xZnx)(N1−xOx) nanoparticles of wurtzite structure are then formed by reaction of these precursor materials with ammonia. Microstructure as well as composition (zinc loss) changes with nitridation time: band gap energy, crystallite size and crystallinity increase, while defect density decreases with increasing nitridation time. Crystallite growth results in a corresponding decrease in specific surface area. In the UV regime photocatalytic activity for overall water splitting can be monitored for samples both before and after nitridation. We find a significantly lower photocatalytic activity in the nitrided samples, even though the crystallinity is significantly higher and the defect density is significantly lower after nitridation. Both properties should have led to a lower probability for charge carrier recombination, and, consequently, to a higher photocatalytic activity.

Influence of Nitridation Time on the Characteristics of GaN Films Deposited on Ni Metal Substrate by ECR-MOCVD

GaN films were deposited on metal Ni substrates using electron cyclotron resonance plasma-enhanced metal organic chemical vapour deposition system (ECR-PEMOCVD). The nitridation time dependent structural and morphological characteristics of GaN films were systematically investigated by reflection high energy electron diffraction (RHEED), X-ray diffraction (XRD), and scanning electron microscope (SEM) analysis. The results indicate that it is feasible to deposit GaN films on Ni metal substrate under the proper deposition procedures. The high quality GaN films with c-axis preferred orientation and dense and uniform microstructure are successfully obtained under the optimized nitridation time. The GaN/Ni structure has great potential for the improvement of short-wavelength optical devices with excellent heat dissipation.

Influence of the Nitridation Time after the Al Pre-Seeded Layer on the Properties of GaN Layer Grown on Si (1 1 1)

The epitaxial growth of Gallium Nitride (GaN) on 2 inch Si (1 1 1) substrates was investigated, and it was found that by inserting a surface nitridation layer prior to Aluminum Nitride (AlN) nucleation upon substrate, the discoid defects and cracks on the surface were suppressed. Furthermore, compared with the GaN epitaxial layer grown without nitridation, the one with a 30 sec. nitridation layer showed a twice brighter integrated photoluminescence (PL) spectra intensity and a (0 0 2) High-resolution X-ray diffraction (HRXRD) curve width of 13.6 arcminute. The crystalline quality of GaN epitaxial layer became worse when the nitridation time exceeded a critical value, and even more cracks appeared on the surface although no discoid defect appeared anymore.

EFFECT OF CAPPING LAYER ON InxGa1-xN QUANTUM DOTS GROWN USING NNAD METHOD BY MOCVD

In x Ga 1-x N quantum dots (QDs) were grown on GaN epitaxy using nitridation of nano-alloyed droplet (NNAD) method by metal-organic chemical vapor deposition (MOCVD) system. Before the In x Ga 1-x N QDs formation, In + Ga droplets were initially formed by the flow of TMI and TMG, which acts as a nucleation seed for the QDs growth. Density of the alloy droplets was increased with the increasing flow rate; however, droplet size was scarcely changed about 100–200 nm by flow rate. And In x Ga 1-x N QDs size can be easily changed by controlling the nitridation time or various factors. Also, the influence of GaN capping layer on the properties of In x Ga 1-x N QDs was discussed.