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Comparison of ZnO Films Grown on before- and after-vapor Transport Equilibration (VTE) LiAlO2 Substrates by Pulsed Laser Deposition (PLD)
Comparison of ZnO Films Grown on before- and after-vapor Transport Equilibration (VTE) LiAlO2 Substrates by Pulsed Laser Deposition (PLD)

Jun ZOU,Shengming ZHOU,Jun XU,

材料科学技术学报 , 2006,
Abstract: About Ф45 mm LiAlO2 single crystal was grown by Czochralski (Cz) technique. However, the full-width at half-maximum (FWHM) value was high to 116.9 arcsec. After three vapor transport equilibration (VTE) processes,we can obtain high-quality LiAlO2 slice with the FWHM value of 44.2 arcsec. ZnO films were fabricated on as-grown slices and after-VTE ones by pulsed laser deposition (PLD). It was found that ZnO films on the two slices have similar crystallinity, optical transmittance and optical band gap at room temperature. These results not only show that LAO substrate is suitable for ZnO growth, but also prove that the crystal quality of LAO substrate slightly affects the structural and optical properties of ZnO film.
On the Growth and Microstructure of Carbon Nanotubes Grown by Thermal Chemical Vapor Deposition  [cached]
Handuja Sangeeta,Srivastava P,Vankar VD
Nanoscale Research Letters , 2010,
Abstract: Carbon nanotubes (CNTs) were deposited on various substrates namely untreated silicon and quartz, Fe-deposited silicon and quartz, HF-treated silicon, silicon nitride-deposited silicon, copper foil, and stainless steel mesh using thermal chemical vapor deposition technique. The optimum parameters for the growth and the microstructure of the synthesized CNTs on these substrates are described. The results show that the growth of CNTs is strongly influenced by the substrate used. Vertically aligned multi-walled CNTs were found on quartz, Fe-deposited silicon and quartz, untreated silicon, and on silicon nitride-deposited silicon substrates. On the other hand, spaghetti-type growth was observed on stainless steel mesh, and no CNT growth was observed on HF-treated silicon and copper. Silicon nitride-deposited silicon substrate proved to be a promising substrate for long vertically aligned CNTs of length 110–130 μm. We present a possible growth mechanism for vertically aligned and spaghetti-type growth of CNTs based on these results.
Luminescence and Structure of ZnO Grown by Physical Vapor Deposition  [PDF]
R. García-Gutiérrez,M. Barboza-Flores,D. Berman-Mendoza,R. Rangel-Segura,O. E. Contreras-López
Advances in Materials Science and Engineering , 2012, DOI: 10.1155/2012/872597
Abstract: Nanostructured ZnO was deposited on different substrates (Si, SiO2, and Au/SiO2) by an enhanced physical vapor deposition technique that presents excellent luminescent properties. This technique consists in a horizontal quartz tube reactor that uses ultra-high purity Zn and UHP oxygen as precursors. The morphology and structure of ZnO grown in this work were studied by electron microscopy and X-ray diffraction. The XRD patterns revealed the highly crystalline phase of wurtzite polycrystalline structure, with a preferred (1011) growth direction. Room temperature cathodoluminescence studies revealed two features in the luminescence properties of the ZnO obtained by this technique, first a high-intensity narrow peak centered at 390?nm (~3.2?eV) corresponding to a near band-to-band emission, and secondly, a broad peak centered around 517?nm (2.4?eV), the typical green-yellow luminescence, related to an unintentionally doped ZnO. 1. Introduction Zinc oxide (ZnO) has been an object of growing attention in the last decade due to its potential applications in electronics and optoelectronics. ZnO is a wideband gap semiconductor with a hexagonal crystalline structure (wurtzite type) showing a direct band gap of ~3.3?eV. As a direct wide band gap semiconductor material, ZnO has attracted much attention towards applications, such as UV photodetectors, solar cells, light emitting diodes and laser diodes [1, 2]. Several techniques have been adopted to synthesize ZnO nanostructures such as metalorganic chemical vapor deposition (MOCVD) [3], microwave plasma deposition [4], hydrothermal synthesis [5–7], electrochemical deposition [8–11], and ultrasonic spray pyrolysis [12]. Nevertheless, physical vapor deposition (PVD) technique is an easy, reproducible, low-cost method that can be scaled up and used for the production of wide range of nanostructures such as nanowires, nanobelts, nanohelixes, nanorings, and nanoneedles [13–16]. In this work, nanostructured ZnO has been grown on different substrates (Si, SiO2, and Au/SiO2) by physical vapor deposition technique; the nanostructures obtained were sheets and plaques. 2. Experimental Procedure The schematic setup for the physical vapor deposition of ZnO is shown in Figure 1. The reactor consists of a quartz tube heated in a three-zone horizontal furnace. A boat with UHP Zn is placed at the first zone of the quart tube, and a boat that holds the substrates (silicon wafer, fused silica disk and a gold-covered fused silica disk) is placed in zone 2. Figure 1: Experimental setup to grow ZnO by physical vapor deposition in a
Synthetic Graphene Grown by Chemical Vapor Deposition on Copper Foils  [PDF]
Ting Fung Chung,Tian Shen,Helin Cao,Luis A. Jauregui,Wei Wu,Qingkai Yu,David Newell,Yong P. Chen
Physics , 2013, DOI: 10.1142/S0217979213410026
Abstract: The discovery of graphene, a single layer of covalently bonded carbon atoms, has attracted intense interests. Initial studies using mechanically exfoliated graphene unveiled its remarkable electronic, mechanical and thermal properties. There has been a growing need and rapid development in large-area deposition of graphene film and its applications. Chemical vapour deposition on copper has emerged as one of the most promising methods in obtaining large-scale graphene films with quality comparable to exfoliated graphene. In this chapter, we review the synthesis and characterizations of graphene grown on copper foil substrates by atmospheric pressure chemical vapour deposition. We also discuss potential applications of such large scale synthetic graphene.
Direct dry transfer of chemical vapor deposition graphene to polymeric substrates  [PDF]
Guilhermino J. M. Fechine,Inigo Martin-Fernandez,George Yiapanis,Ricardo V. Bof de Oliveira,Xiao Hu,Irene Yarovsky,Antonio H. Castro Neto,Barbaros Ozyilmaz
Physics , 2014,
Abstract: We demonstrate the direct dry transfer of large area Chemical Vapor Deposition graphene to several polymers (low density polyethylene, high density polyethylene, polystyrene, polylactide acid and poly(vinylidenefluoride-co-trifluoroethylene) by means of only moderate heat and pressure, and the later mechanical peeling of the original graphene substrate. Simulations of the graphene-polymer interactions, rheological tests and graphene transfer at various experimental conditions show that controlling the graphene-polymer interface is the key to controlling graphene transfer. Raman spectroscopy and Optical Microscopy were used to identify and quantify graphene transferred to the polymer substrates. The results showed that the amount of graphene transferred to the polymer, from no-graphene to full graphene transfers, can be achieved by fine tuning the transfer conditions. As a result of the direct dry transfer technique, the graphene-polymer adhesion being stronger than graphene to Si/SiO2 wafer.
ZnO Nanowires Synthesized by Vapor Phase Transport Deposition on Transparent Oxide Substrates  [cached]
Yu Dongshan,Trad Tarek,McLeskey James,Craciun Valentin
Nanoscale Research Letters , 2010,
Abstract: Zinc oxide nanowires have been synthesized without using metal catalyst seed layers on fluorine-doped tin oxide (FTO) substrates by a modified vapor phase transport deposition process using a double-tube reactor. The unique reactor configuration creates a Zn-rich vapor environment that facilitates formation and growth of zinc oxide nanoparticles and wires (20–80 nm in diameter, up to 6 μm in length, density <40 nm apart) at substrate temperatures down to 300°C. Electron microscopy and other characterization techniques show nanowires with distinct morphologies when grown under different conditions. The effect of reaction parameters including reaction time, temperature, and carrier gas flow rate on the size, morphology, crystalline structure, and density of ZnO nanowires has been investigated. The nanowires grown by this method have a diameter, length, and density appropriate for use in fabricating hybrid polymer/metal oxide nanostructure solar cells. For example, it is preferable to have nanowires no more than 40 nm apart to minimize exciton recombination in polymer solar cells.
Ballistic transport in graphene grown by chemical vapor deposition  [PDF]
V. E. Calado,Shou-En Zhu,S. Goswami,Q. Xu,K. Watanabe,T. Taniguchi,G. C. A. M. Janssen,L. M. K. Vandersypen
Physics , 2014, DOI: 10.1063/1.4861627
Abstract: In this letter we report the observation of ballistic transport on micron length scales in graphene synthesised by chemical vapour deposition (CVD). Transport measurements were done on Hall bar geometries in a liquid He cryostat. Using non-local measurements we show that electrons can be ballistically directed by a magnetic field (transverse magnetic focussing) over length scales of ~\mu m. Comparison with atomic force microscope measurements suggests a correlation between the absence of wrinkles and the presence of ballistic transport in CVD graphene.
Carbon Replicas of Porous Concrete Obtained by Chemical Vapor Deposition—Some Aspects of the Synthesis Mechanism  [PDF]
Olaf Klepel, Nina Danneberg, Matthias Suckow, Marcel Erlitz
Materials Sciences and Applications (MSA) , 2017, DOI: 10.4236/msa.2017.88043
Abstract: In this contribution, the template assisted synthesis of porous carbons by chemical vapor deposition in porous concrete templates has been described for the first time. Porous concrete made templates can be obtained in almost any geometrical shape and are therefore attractive templates to prepare porous carbon monoliths. The carbon deposition process in porous concrete follows a three-stage-course consisting in an initial period, a period of fast carbon deposition and a period of slow carbon deposition. The carbon growth within the template pores occurs obviously plug-like from the inner to the outer sphere. Any continuous covering of the template pore walls by carbon could not be observed. In difference to porous concrete, the carbon deposition in silica gel is strongly accompanied by mass transfer limitations. For porous concrete, such strong effect has not been observed obviously due to its hierarchical pore system. The template materials have been loaded with carbon by chemical vapor deposition in a flow reactor. The process of the template pore filling has been characterized by the time dependence of the template mass gain. The materials have been characterized by means of X-ray tomography and nitrogen adsorption at 77 K, respectively.
Revealing the grain structure of graphene grown by chemical vapor deposition  [PDF]
Péter Nemes - Incze,Kwon Jae Yoo,Levente Tapasztó,Gergely Dobrik,János Lábár,Zsolt E. Horváth,Chanyong Hwang,László Péter Biró
Physics , 2011, DOI: 10.1063/1.3610941
Abstract: The physical processes occurring in the presence of disorder: point defects, grain boundaries, etc. may have detrimental effects on the electronic properties of graphene. Here we present an approach to reveal the grain structure of graphene by the selective oxidation of defects and subsequent atomic force microscopy analysis. This technique offers a quick and easy alternative to different electron microscopy and diffraction methods and may be used to give quick feedback on the quality of graphene samples grown by chemical vapor deposition.
Suitability of carbon nanotubes grown by chemical vapor deposition for electrical devices  [PDF]
B. Babic,J. Furer,M. Iqbal,C. Schonenberger
Physics , 2004, DOI: 10.1063/1.1812153
Abstract: Using carbon nanotubes (CNTs) produced by chemical vapor deposition, we have explored different strategies for the preparation of carbon nanotube devices suited for electrical and mechanical measurements. Though the target device is a single small diameter CNT, there is compelling evidence for bundling, both for CNTs grown over structured slits and on rigid supports. Whereas the bundling is substantial in the former case, individual single-wall CNTs (SWNTs) can be found in the latter. Our evidence stems from mechanical and electrical measurements on contacted tubes. Furthermore, we report on the fabrication of low-ohmic contacts to SWNTs. We compare Au, Ti and Pd contacts and find that Pd yields the best results.
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