Field emission property of ZnO nanowires prepared by ultrasonic spray pyrolysis

The field emission property of cold cathode emitters utilizing the ZnO nanowires with various conditions prepared by ultrasonic spray pyrolysis technique was discussed. It is found that the emission current was enhanced in the emitters having higher aspect ratio as well as smaller sheet resistance. Applying of post-annealing process, utilization of additional Mo back electrode in the cathode, and coating of Moon the ZnO nanowires resulted in the improvement of the emission current and lowering the threshold voltage. A threshold voltage of about 5.5 V/mu m to obtain 1.0 mu A/cm(2) was achieved in the sample prepared at the growth temperatures varying continuously from 250 degrees C to 300 degrees C. (C) 2015 Elsevier Ltd. All rights reserved.ArticleSUPERLATTICES AND MICROSTRUCTURES. 84:144-153 (2015)journal articl

Position-selective growth of ZnO nanowires by ultrasonic spray pyrolysis

Position-selective growth of ZnO nanowires was realized by utilizing a patterned soda-lime glass layer. The soda-lime glass layer contributes as the origin of nucleation sites for the growth of nanowires in economically viable ultrasonic spray pyrolysis technique. The formation of nanowires took place with good reproducibility at relatively low substrate temperatures of 250-400 degrees C when the soda-lime glass matrix was present at the surface of substrates, and such a nitrate compound as nitric acid or nitrate salt was mixed in the precursor solutions. Based on this technique, the position-selective growth and density-controlled growth of ZnO nanowires can be performed on various types of substrate. The presence of a CaO compound in the glass matrix was revealed as an important condition to grow the nanowires. (C) 2009 Elsevier B.V. All rights reserved.ArticleJOURNAL OF CRYSTAL GROWTH. 311(20):4499-4504 (2009)journal articl

Synthesis of optical quality ZnO nanowires utilizing ultrasonic spray pyrolysis

ZnO nanowires were grown by an ultrasonic spray pyrolysis technique. The aspect ratio and size of the wire were dependent mainly on the pH value of a precursor solution and the growth temperature. By high-resolution transmission electron microscopic analysis and photoluminescence measurements, it was confirmed that the nanowires are monocrystalline with good optical quality.ArticleJOURNAL OF MATERIALS SCIENCE-MATERIALS IN ELECTRONICS. 20:341-345 (2009)journal articl

Synthesis of a cuprite thin film by oxidation of a Cu metal precursor utilizing ultrasonically generated water vapor

A Cu2O thin film of cuprite crystal structure was fabricated via a decomposition reaction of water vapor generated by ultrasonic vibration. The thin film, which was grown on a soda-lime glass substrate at 530 degrees C, exhibited a prominent (111) preferred orientation with an optical bandgap of about 2.1 eV and resistivity of 2.81 x 10(4) Omega cm. Generation of H-2 gas during the reaction process contributed to suppressing the growth of impurity tenorite phase. In a conventional process of thermal oxidation, the formation of the cuprite phase was always accompanied by that of the tenorite phase due to an excess oxygen exposure near the surface of the films.ArticleTHIN SOLID FILMS. 556:211-215 (2014)journal articl

Cu2ZnSn(SxSe1-x)4 Thin-Film Solar Cells Utilizing Simultaneous Reaction of a Metallic Precursor with Elemental Sulfur and Selenium Vapor Sources

A Cu2ZnSn(SxSe1-x)(4) (CZTSSe) solid alloy was prepared by reacting a metallic precursor with sulfur and selenium in a closed tube simultaneously. It was confirmed that the CZTSSe alloy could be synthesized over the whole compositional range and its lattice transformation was in good agreement with Vegard's law. The crystal grain size and electrical conductivity were enhanced when the selenium content was increased. In a CdS/CZTSSe heterojunction solar cell, the photovoltaic efficiency was improved due to the enhancement of the short-circuit current in accordance with the narrowing of the optical bandgap of the CZTSSe absorber. (c) 2012 The Japan Society of Applied PhysicsArticleAPPLIED PHYSICS EXPRESS. 5(8): 81201 (2012)journal articl

A Cadmium-Free Cu2ZnSnS4/ZnO Hetrojunction Solar Cell Prepared by Practicable Processes

A cadmium-free Cu2ZnSnS4/ZnO hetrojunction solar cell with conversion efficiency of 4.29% has been obtained. The Cu2ZnSnS4 absorber film was formed utilizing sulfurization of laminated metallic precursors, and the ZnO buffer layer was then deposited on it by ultrasonic spray pyrolysis. In comparison with a conventional Cu2ZnSnS4/CdS hetrojunction solar cell, the open circuit voltage as well as the relative quantum efficiency at the short-wavelength regions was increased. The in-plane homogeneity of p-n junction was improved by depositing the ZnO layer on Cu2ZnSnS4 film via ultrasonic spray pyrolysis. (C) 2011 The Japan Society of Applied PhysicsArticleJAPANESE JOURNAL OF APPLIED PHYSICS. 50(3): 032301 (2011)journal articl

Influence of Ge composition in the Cu2Sn1-xGexS3 thin-film photovoltaic absorber prepared by sulfurization of laminated metallic precursor

Cu2Sn1-xGexS3 thin-film absorbers are prepared by sulfurization of laminated precursors. The crystal grain size is enhanced under higher growth temperature and/or sulfur pressure. By the XRD and Raman analyses, the crystal alloy is considered to be composed of majority monoclinic phase with minority secondary phase such as Cu-2(Sn1-xGex)(3)S-7 throughout the whole Ge/(Ge+Sn) composition range. The optical band gap is observed to be varied between 0.94 eV and 1.30 eV in relation with the Ge contents. A photovoltaic conversion efficiency of about 2% is obtained in the sample utilizing Cu2Sn0.6Ge0.4S3 absorber. (C) 2015 Elsevier B.V. All rights reserved.ArticleSOLAR ENERGY MATERIALS AND SOLAR CELLS. 140:312-319 (2015)journal articl