All-Solution-Processed InGaO 3

We fabricated the crystallized InGaZnO thin films by sol-gel process and high-temperature annealing at 900°C. Prior to the deposition of the InGaZnO, ZnO buffer layers were also coated by sol-gel process, which was followed by thermal annealing. After the synthesis and annealing of the InGaZnO, the InGaZnO thin film on the ZnO buffer layer with preferred orientation showed periodic diffraction patterns in the X-ray diffraction, resulting in a superlattice structure. This film consisted of nanosized grains with two phases of InGaO3(ZnO)1 and InGaO3(ZnO)2 in InGaZnO polycrystal. On the other hand, the use of no ZnO buffer layer and randomly oriented ZnO buffer induced the absence of the InGaZnO crystal related patterns. This indicated that the ZnO buffer with high c-axis preferred orientation reduced the critical temperature for the crystallization of the layered InGaZnO. The InGaZnO thin films formed with nanosized grains of two-phase InGaO3(ZnO)m superlattice showed considerably low thermal conductivity (1.14 Wm−1 K−1 at 325 K) due to the phonon scattering from grain boundaries as well as interfaces in the superlattice grain

An Optimization of Composition Ratio among Triple-Filled Atoms in In

Bulk nanostructured materials are important as energy materials. Among thermoelectric materials, the skutterudite system of CoSb3 is a representative material of bulk nanostructured materials. Filling a skutterudite structure with atoms that have different localized frequencies (also known as triple filling) was reported to be effective for lowering thermal conductivity. Among studies representing superior power factors, In-filled skutterudite systems showed higher Seebeck coefficients. This study sought to optimize the composition ratio among the triple-filled atoms in an In0.3-x-yBaxCeyCo4Sb12 system. The composition dependence of the thermoelectric properties was investigated for specimens with different ratios among the three kinds of filler atoms in the In0.3-x-yBaxCeyCo4Sb12 system. In addition, the process variables were carefully optimized for filled skutterudite systems to obtain a maximum ZT value

Observation of oxide precipitates in InN nanostructures

We observed the formation of oxide precipitates (bcc-In(2)O(3)) in InN nanostructures formed during metal-organic chemical vapor deposition (MOCVD) and/or subsequent postgrowth procedures in H(2) ambient. It was found that InN is extremely unstable in H(2) ambient and the activation energy of N(2) desorption of InN is measured to be similar to 0.28 eV, which is one order of magnitude smaller than that of reported value of InN in vacuum. Instability of InN nanostructures under H(2) ambient together with residual oxidant in the reactor facilitates the formation of indium oxide precipitates in the nanostructure matrix during MOCVD or the oxidation of residual indium at the surface, resulting in indium oxide dots.open3

Photocatalytic behavior of Ba(Sb/Ta)2O6 perovskite for reduction of organic pollutants: Experimental and DFT correlation

We have synthesized closely packed hexagonal 2D plates and clustered nanoparticle morphologies of Ba(Sb/Ta)2O6 (BSTO) perovskite via the polymerizable complex method for photocatalytic dye degradation activities. The BSTO crystallized in a hexagonal structure. The presence of Ba2+, Sb5+, Ta5+, and O2− chemical states identified from XPS confirmed the formation of mixed Ba(Sb/Ta)2O6 phase accompanied with a minor amount of TaOx. Furthermore, BSTO showed excellent photocatalytic activity for the degradation of various organic dyes. The kinetic studies revealed 65.9%, 77.3%, 89.8%, and 84.2%, of Crystal Violet (CV), Methylene Blue (MB), Rhodamine blue (RhB), and Methylene Orange (MO), respectively, after irradiation of 180 min without using a cocatalyst. The formation of and OH−surface radicals, which are believed to facilitate the degradation of the dyes, are unveiled through first-principles Density Functional Theory (DFT) calculations and scavenging studies. Our results suggest that BSTO holds promise as an excellent photocatalyst with better degradation efficiency for various organic dyes

Oxide p-n Heterojunction of Cu2O/ZnO Nanowires and Their Photovoltaic Performance

Oxide p-n heterojunction devices consisting of p-Cu2O/n-ZnO nanowires were fabricated on ITO/glass substrates and their photovoltaic performances were investigated. The vertically arrayed ZnO nanowires were grown by metal organic chemical vapor deposition, which was followed by the electrodeposition of the p-type Cu2O layer. Prior to the fabrication of solar cells, the effect of bath pH on properties of the absorber layers was studied to determine the optimal condition of the Cu2O electrodeposition process. With the constant pH 11 solution, the Cu2O layer preferred the (111) orientation, which gave low electrical resistivity and high optical absorption. The Cu2O (pH 11)/ZnO nanowire-based solar cell exhibited a higher conversion efficiency of 0.27% than the planar structure solar cell (0.13%), because of the effective charge collection in the long wavelength region and because of the enhanced junction area

Tunable Electrical and Optical Properties in Composition Controlled Hf:ZnO Thin Films Grown by Atomic Layer Deposition

Hf:ZnO thin films doped with various Hf contents were prepared at 200°C by atomic layer deposition and assessed as transparent conductive oxides. Low Hf contents (≤6.7 at%) resulted in highly conductive polycrystalline thin films; high Hf contents reduced both crystallinity and conductivity due to the limited solubility of Hf in the ZnO matrix. The lowest electrical resistivity of 6 × 10 -4 Ω · cm and high electron density of 3 × 10 20 cm -3 were shown by the sample with 3.3 at% Hf. All the thin films showed ca. 80% transmittance in the visible region. The films' optical band-gaps increased from 3.29 to 3.56 eV with increasing Hf content up to 6.7 at%; further increases resulted in deviation from the Burstein-Moss effect and excess Hf incorporation induced two band edges due to phase separation, which was correlated with X-ray photoelectron spectroscopy and photoluminescence results. © 2012 The Electrochemical Society.

Morphological Evolution of Silver Nanoparticles and Its Effect on Metal-Induced Chemical Etching of Silicon

In this report, we have demonstrated the morphological evolution of the silver nanoparticles (AgNPs) by controlling the growth conditions and its effect on morphology of silicon (Si) during metalinduced electroless etching (MICE). Self-organized AgNPs with peculiarly shape were synthesized by an electroless plating method in a conventional aqueous hydrofluoric acid (HF) and silver nitrate (AgNO3) solution. AgNP nuclei were densely created on Si wafer surface, and they had a strong tendency to merge and form continuous metal films with increasing AgNO3 concentrations. Also, we have demonstrated that the fabrication of aligned Si nanowire (SiNW) arrays in large area of p-Si (111) substrates by MICE in a mixture of HF and hydrogen peroxide (H2O2) solution. We have found that the morphology of the initial AgNPs and oxidant concentration (H2O2) greatly influence on the shape of the SiNW etching profile. The morphological results showed that AgNP shapes were closely related to the etching direction of SiNWs, that is, the spherical AgNPs preferred to move vertical to the Si substrate, whereas non-spherical AgNPs changed their movement to the [100] directions. In addition, as the etching activity was increased at higher H2O 2 concentrations, AgNPs had a tendency to move from the original [111] direction to the energetically preferred [100] direction. Copyright © 2013 American Scientific Publishers.1