Papers by Keyword: Vapor Deposition

Abstract: The perovskite solar cells (PSCs) with Al₂O₃ passivation layer were fabricated and characterized. The PSC have some advantages of easier and cheaper fabrication process than that of conventional Si solar cells, III-V compound semiconductor solar cells, and organic solar cells. The perovskite light harvester, CH₃NH₃PbI₃, was deposited by vapor deposition on [compact TiO₂ / F-doped tin oxide (FTO) / glass]. The advantage of vapor deposition over solution process is expected to be able to offer the thin film with smoother surface over larger area. Then, Al₂O₃ passivation layer was deposited by atomic layer deposition (ALD) on the CH₃NH₃PbI₃ light harvester. Al₂O₃ passivation layer was expected to prevent the CH₃NH₃PbI₃ light harvester from oxidation and improve the solar cell efficiency, and ALD has been one of the most effective methods to deposit Al₂O₃ thin film for last 25 years. The atomic layer deposited Al₂O₃ layer thickness was optimized from the solar cell characterization. The optimized power conversion efficiency (PCE) and Al₂O₃ thickness were ~8.0 % and ~10.0 nm, respectively.

Abstract: One-dimensional CdZnS nanostructures have been synthesized through the sublimation. Effect of high substrate temperature on morphology, structural and optical properties of these nanostructures has been studied. X-Ray diffraction peak intensity, lattice parameters, crystallite size decreased with an increase in substrate temperature. The morphology changed with the increase in the substrate temperature. Raman Spectroscopy confirmed the existence of constituent elements in CdZnS solid solution and an increase of Zn concentration with the rise in substrate temperature. The nanostructures exhibited strong photoluminescence emission in the green light region with a substrate temperature-dependent blue shift of 53 meV in emission energy. The Stoke’s shift energy raised from 45 meV to 302 meV as the substrate temperature increased from 510 °C to 550 °C. The stoichiometric deviancies, crystallite size, and quantum confinement effects resulted into an increase in the optical band gap from 2.4 eV to 2.71 eV. The results showed that CdZnS nanostructures could be potential candidates for nanostructure based optoelectronics and photovoltaic devices.

Abstract: Using wool fibers as template and Ce (NO₃)₃•6H₂O, PEG and NH_3·H₂O as precursors, micron-scale CeO₂ tubes composed of well-crystalline CeO₂ nanoparticles have been synthesized. Cerium oxide was first precipitated on the wool fibers by vapor deposition method, then the fibers were removed by a two-step calcination. The obtained products were characterized by scanning electron microscopy (SEM), thermogravimetric Analyzer (TGA), powder X-ray diffraction (XRD) and energy dispersive spectrometer (EDS). The results show that intact tubes with a diameter of 8~12μm have been successfully prepared.

Abstract: Dependence of the coating carbon layer configuration of cordierite monolith on reaction conditions in methane decomposition was investigated using N2 physisorption, SEM and TEM. The monolith surface area was increased after coating CNFs/CNTs. The microstructure of the coating layers in the coated monolith is dependent on the coating reaction conditions and the entanglement among CNFs/CNTs. High coating temperature and the presence of hydrogen in reaction gas for coating are advantageous to formation of CNTs. By comparison, coating layers of CNFs have better stability than that of CNTs in ultrasonic treatment.

Abstract: A vapor deposed LiFePO4/C composite cathode material was acquired through filled carbon to FePO4 precursor by vapor deposition. The results showed that the carbon could contact to LiFePO4 nanopaticle directly and uniformly and formed a conducting network. It showed a good discharge capacity retention at large discharge rate. It was 57.3% at 10C. It also showed an excellent capacity steady characteristic when cycling at 1C.

Abstract: Functionally graded material is a new kind of inhomogeneous material whose material properties change continuously with spatial positions. As a result of its excellent performance, it’s widely used in aerospace, nuclear engineering, biomedicine and some other fields that requirement of material is very strict. Classification based on different applications and research actuality are shown in this article.

Abstract: 25% Zinc doped Cadmium Telluride thin films were prepared using Stacked Elemental Layer method. The structural studies were conducted by the X-Ray technique and the results were compared with standard data which confirmed the presence of mixed phases (CdTe, ZnTe and CdZnTe) in the stack annealed at 425°C. Transmittance spectra depicted the effect of Zn on the optical properties of CdTe thin film. The calculated band gaps from the transmittance spectra were lie between 1.42 and 1.51eV. Scanning Electron Microscope images elucidated the influence of Zn on surface morphology and the grain growth for CdTe thin films.

Abstract: TiAlN coatings have been deposited by reactive magnetron sputtering from TiAl alloy target using a direct current (DC) power source. The crystal structure, chemical composition, surface morphology and hardness of TiAlN coatings which were prepared at various N2 flow rates have been systemically investigated. The results show a strong effect of N2 flow rates on the orientation, grain size and densification in TiAlN coatings. The TiAlN coating shows the highest hardness at a certain N2 flow rate when it has the most compact structure.

Abstract: A new nanostructure, (2D) nanopetal of SnO2, has been grown on single silicon substrates by Au-Ag alloying catalyst assisted carbothermal evaporation of SnO2. Field emission scanning electron microscopy (FESEM), x-ray diffraction (XRD) and Raman are employed to identify the morphology and structure of the synthesized productions. Room-temperature photoluminescence (PL) is used to characterize the luminescence of SnO2 nanostructure. Three new peaks at 356, 450 and 489 nm in the measured photoluminescence spectra are observed, implying that more luminescence centers exist in SnO2 nanopetals due to nanocrystals and defects. The growth of the SnO2 nanopetals is discussed on the basis of the self-catalyst mechanism.

Abstract: The present chapter deals with the difficult task of giving a brief survey of the synthetic routes employed to prepare materials with characteristic features on the nanometer scale. Definitions and general concepts regarding nanostructured and nanometer-sized materials are shortly tackled in the introductory part, which is followed by an overview of the most important approaches developed to synthesize such materials. No attempt is made to create a comprehensive and detailed synopsis of the experimental methods currently available. Rather, attention is focused on a selected number of general methodologies, the choice of which can be usually motivated by a mix of historical perspective, scientific significance and technological potential. So-called “top-down” approaches are discussed first, whereas the second part of the chapter is devoted to “bottom-up” ones. The former group includes mechanical processing, melt quenching, and de-vitrification methods. Sonochemistry, pulsed laser ablation, wet chemical synthesis, sol-gel processing, microwave processing, spray pyrolysis, flame synthesis, inert gas condensation, vapor deposition, and vapor-liquid-solid growth form instead the latter group.