Showing papers on "Evaporation (deposition) published in 2012"
TL;DR: A facile solution synthesis of stoichiometric Cu(2)ZnSnS(4) in size-controlled nanorod form (11 nm × 35 nm), which has a band gap of 1.43 eV and can be assembled into perpendicular aligned arrays by controlled evaporation from solution.
Abstract: The quaternary copper chalcogenide Cu2ZnSnS4 is an important emerging material for the development of low-cost and sustainable solar cells. Here we report a facile solution synthesis of stoichiometric Cu2ZnSnS4 in size-controlled nanorod form (11 nm × 35 nm). The monodisperse nanorods have a band gap of 1.43 eV and can be assembled into perpendicularly aligned arrays by controlled evaporation from solution.
380 citations
Patent•
05 Jan 2012
TL;DR: In this paper, a molecular beam epitaxy (MBE) is used to remove impurities existing around a raw material evaporation source cell without wasting raw material before the film deposition performed by a MBE.
Abstract: PROBLEM TO BE SOLVED: To provide: a film deposition apparatus which removes impurities existing around a raw material evaporation source cell without wasting a raw material before the film deposition performed by a molecular beam epitaxy (MBE), thereby achieving a desired high vacuum and thereby achieving highly reliable film deposition easily and surely; a film deposition method; and a method of manufacturing a compound semiconductor apparatus.SOLUTION: An MBE apparatus includes the raw material evaporation source cell 2, wherein the raw material evaporation source cell includes: a crucible 11 into which the raw material 10 is filled; a first heater 13 arranged to cover the crucible 11; a heat reflection plate 14 arranged to cover the first heater 13; and a second heater 15 arranged to cover the heat reflection plate. The MBE apparatus further includes a shroud 4 that partially surrounds the evaporation source cell 2, wherein the wall surface of the shroud can be cooled to the temperature of liquid nitrogen.
276 citations
TL;DR: A facile synthesis method of layered MoS(2) using a thermal evaporation technique, which requires modest conditions and is characterized using micro-Raman spectroscopy and atomic force microscope.
Abstract: Two dimensional molybdenum disulfide (MoS2) has recently become of interest to semiconductor and optic industries. However, the current methods for its synthesis require harsh environments that are not compatible with standard fabrication processes. We report on a facile synthesis method of layered MoS2 using a thermal evaporation technique, which requires modest conditions. In this process, a mixture of MoS2 and molybdenum dioxide (MoO2) is produced by evaporating sulfur powder and molybdenum trioxide (MoO3) nano-particles simultaneously. Further annealing in a sulfur-rich environment transforms majority of the excess MoO2 into layered MoS2. The deposited MoS2 is then mechanically exfoliated into minimum resolvable atomically thin layers, which are characterized using micro-Raman spectroscopy and atomic force microscopy. Furthermore Raman spectroscopy is employed to determine the effect of electrochemical lithium ion exposure on atomically thin layers of MoS2.
248 citations
TL;DR: Film synthesized with a 6% Mo, 2% W Bi VO4 films demonstrate the best PEC performance with photocurrent densities 10 times higher than for pure BiVO4 and greater than previously reported for Mo and W containing BiVO3.
Abstract: Porous, nanostructured BiVO4 films are incorporated with Mo and W by simultaneous evaporation of Bi, V, Mo, and W in vacuum followed by oxidation in air. Synthesis parameters such as the Bi : V : Mo : W atomic ratio and deposition angle are adjusted to optimize the films for photoelectrochemical (PEC) water oxidation. Films synthesized with a Bi : V : Mo : W atomic ratio of 46 : 46 : 6 : 2 (6% Mo, 2% W) demonstrate the best PEC performance with photocurrent densities 10 times higher than for pure BiVO4 and greater than previously reported for Mo and W containing BiVO4. The films consist of a directional, nanocolumnar layer beneath an irregular surface structure. Backside illumination utilizes light scattering off the irregular surface structure resulting in 30–45% higher photocurrent densities than for frontside illumination. To improve the kinetics for water oxidation Pt is photo-deposited onto the surface of the 6% Mo, 2% W BiVO4 films as an electrocatalyst. These films achieve quantum efficiencies of 37% at 1.1 V vs. RHE and 50% at 1.6 V vs. RHE for 450 nm light.
217 citations
TL;DR: In this article, a SEM examination of the fracture surface of a slowly-dried cellulose film showed a surprisingly regular fan-like pattern which was shown to be characteristic of cross-sections of the left-handed helicoidal arrangement of nanocrystals, where the helicoidal axis was almost perpendicular to the film surfaces.
Abstract: The chiral nematic self-assembly of aqueous suspensions of cellulose nanocrystals is partially preserved on evaporation of water, but the ordering of the rod-like nanoparticles may become distorted by changes in volume, ionic strength and surface and convective forces during evaporation, thus affecting the morphology and optical properties of the dried film. Proposed applications for these solids with chiral nematic order require confirmation of their structure. A SEM examination of the fracture surface of a slowly-dried film showed a surprisingly regular fan-like pattern which is shown to be characteristic of cross-sections of the left-handed helicoidal arrangement of nanocrystals, where the helicoidal axis was almost perpendicular to the film surfaces. Superimposed on this pattern was what appeared to be a regular porosity, which is postulated to result from pull-out of the nanocrystals oriented orthogonal to the fracture surface.
192 citations
TL;DR: A novel growth technique that enables the direct deposition of graphene layers on SiO(2) with crystalline quality potentially comparable to graphene grown on Cu foils using chemical vapor deposition (CVD) rather than using Cu foil as substrates, which uses them to provide subliming Cu atoms in the CVD process.
Abstract: Direct deposition of high-quality graphene layers on insulating substrates such as SiO(2) paves the way toward the development of graphene-based high-speed electronics. Here, we describe a novel growth technique that enables the direct deposition of graphene layers on SiO(2) with crystalline quality potentially comparable to graphene grown on Cu foils using chemical vapor deposition (CVD). Rather than using Cu foils as substrates, our approach uses them to provide subliming Cu atoms in the CVD process. The prime feature of the proposed technique is remote catalyzation using floating Cu and H atoms for the decomposition of hydrocarbons. This allows for the direct graphitization of carbon radicals on oxide surfaces, forming isolated low-defect graphene layers without the need for postgrowth etching or evaporation of the metal catalyst. The defect density of the resulting graphene layers can be significantly reduced by tuning growth parameters such as the gas ratios, Cu surface areas, and substrate-to-Cu distance. Under optimized conditions, graphene layers with nondiscernible Raman D peaks can be obtained when predeposited graphite flakes are used as seeds for extended growth.
140 citations
26 Sep 2012-Metallurgical and Materials Transactions B-process Metallurgy and Materials Processing Science
TL;DR: In this paper, a novel mass transfer model for the removal of volatile impurities from silicon in vacuum induction refining is developed, and the boundary conditions for vacuum refining system are determined through thermodynamic and kinetic approaches.
Abstract: Metallurgical fundamentals for vacuum refining of molten silicon and the behavior of different impurities in this process are studied. A novel mass transfer model for the removal of volatile impurities from silicon in vacuum induction refining is developed. The boundary conditions for vacuum refining system—the equilibrium partial pressures of the dissolved elements and their actual partial pressures under vacuum—are determined through thermodynamic and kinetic approaches. It is indicated that the vacuum removal kinetics of the impurities is different, and it is controlled by one, two, or all the three subsequent reaction mechanisms—mass transfer in a melt boundary layer, chemical evaporation on the melt surface, and mass transfer in the gas phase. Vacuum refining experimental results of this study and literature data are used to study the model validation. The model provides reliable results and shows correlation with the experimental data for many volatile elements. Kinetics of phosphorus removal, which is an important impurity in the production of solar grade silicon, is properly predicted by the model, and it is observed that phosphorus elimination from silicon is significantly increased with increasing process temperature.
112 citations
TL;DR: In this article, clean evaporation under ultra-high vacuum conditions of two spin crossover materials, yielding either microcrystallites or homogeneous thin films, was reported, showing that thermal and light-induced spin crossover properties are preserved.
Abstract: We report clean evaporation under ultra-high vacuum conditions of two spin crossover materials, yielding either microcrystallites or homogeneous thin films. Magnetic and photomagnetic studies show that thermal and light-induced spin crossover properties are preserved. Preliminary STM imaging of sub-monolayers indicates that the deposited molecules remain intact on the surface.
105 citations
TL;DR: In this article, the authors synthesize ultra-long, ultra-dense, and free-standing VO2 micro/nanowires using a simple vapor transport method, which is achieved by enhancing the VO2 nucleation and growth rates using rough-surface quartz as the substrate and V2O5 powder as the evaporation source.
Abstract: Recently, it was discovered that single-crystalline VO2 nanostructures exhibit unique, single-domain metal-insulator phase transition. They enable a wide range of device applications as well as discoveries of oxide physics beyond those can be achieved with VO2 bulk or thin films. Previous syntheses of these nanostructures are limited in density, aspect ratio, single-crystallinity, or by substrate clamping. Here we break these limitations and synthesize ultra-long, ultra-dense, and free-standing VO2 micro/nanowires using a simple vapor transport method. These are achieved by enhancing the VO2 nucleation and growth rates using rough-surface quartz as the substrate and V2O5 powder as the evaporation source.
103 citations
TL;DR: In this paper, the authors compared the oxidation behavior of the uncoated ferritic Fe-22Cr steel Sanergy HT with an 640 nm Co-coated version of the same material, and showed that despite the fact that the Co coating is very thin, it effectively blocks Cr evaporation for at least 3000 h.
90 citations
TL;DR: In this article, two types of NiO-Li2CO3 nanocomposite electrodes have been prepared for the electrochemical decomposition studies, and the results showed that the NiO phase does not change significantly after charging process and may act as catalyst for the Li 2CO3 decomposition.
TL;DR: In this article, a nanocolumnar Ta3N5 photoanodes (band gap of ∼2.0 eV) were synthesized via a two-step process: first, tantalum metal was evaporation in a vacuum chamber in a low pressure oxygen ambient followed by heating in an ammonia gas flow to convert Ta2O5 into orthorhombic Ta3n5.
Abstract: Nanostructured Ta3N5 photoanodes (band gap of ∼2.0 eV) were synthesized via a two-step process: first, nanocolumnar Ta2O5 films were deposited by evaporation of tantalum metal in a vacuum chamber in a low pressure oxygen ambient followed by heating in an ammonia gas flow to convert Ta2O5 into orthorhombic Ta3N5. Under Xe lamp irradiation (∼73 mW/cm2), a 100 nm nanoporous Ta3N5 electrode achieved an anodic photocurrent of ∼1.4 mA/cm2 at +0.5 V versus Ag/AgCl in 1 M KOH solution. By comparison, a dense film achieved ∼0.4 mA/cm2 clearly illustrating the importance of nanostructuring for improving the performance of Ta3N5 photoanodes. However, Ta3N5 films suffered from inherent self-oxidation under light illumination, and application of a cobalt cocatalyst layer was found to improve the stability as well as photocatalytic activity of the Ta3N5 films.
TL;DR: In this paper, a 9.15% efficient kesterite co-evaporation process is described and several techniques for identifying phases in these films with resolution adequate to discern changes that are important to device performance.
Abstract: Kesterite thin films [(i.e., Cu2ZnSn(S,Se)4 and related alloys] have been the subject of recent interest for use as an absorber layer for thin film photovoltaics due to their high absorption coefficient (>104 cm−1), their similarity to successful chalcopyrites (like CuInxGa1−xSe2) in structure, and their earth-abundance. The process window for growing a single-phase kesterite film is narrow. In this work, we have documented, for our 9.15%-efficient kesterite co-evaporation process, (1) how appearance of certain undesirable phases are controlled via choice of processing conditions, (2) several techniques for identification of phases in these films with resolution adequate to discern changes that are important to device performance, and (3) reference measurements for those performing such phase identification. Data from x-ray diffraction, x-ray fluorescence, Raman scattering, scanning electron microscopy, energy dispersive spectroscopy, and current-voltage characterization are presented.
TL;DR: This all-gas-phase approach permits controlled deposition of dense, functional nanocrystal films suitable for application in electronic devices.
Abstract: We present an all-gas-phase approach for the fabrication of nanocrystal-based light-emitting devices. In a single reactor, silicon nanocrystals are synthesized, surface-functionalized, and deposited onto substrates precoated with a transparent electrode. Devices are completed by evaporation of a top metal electrode. The devices exhibit electroluminescence centered at a wavelength of λ = 836 nm with a peak external quantum efficiency exceeding 0.02%. This all-gas-phase approach permits controlled deposition of dense, functional nanocrystal films suitable for application in electronic devices.
TL;DR: It is argued that this type of evolution is associated with the formation of a transition region that propagates ahead of the drying front, in this region the gradient of osmotic pressure balances the drag force exerted on the particles by capillary flow toward the liquid-solid front.
Abstract: We present the results from a small-angle X-ray scattering (SAXS) study of lateral drying in thin films. The films, initially 10 μm thick, are cast by dip-coating a mica sheet in an aqueous silica dispersion (particle radius 8 nm, volume fraction ϕs = 0.14). During evaporation, a drying front sweeps across the film. An X-ray beam is focused on a selected spot of the film, and SAXS patterns are recorded at regular time intervals. As the film evaporates, SAXS spectra measure the ordering of particles, their volume fraction, the film thickness, and the water content, and a video camera images the solid regions of the film, recognized through their scattering of light. We find that the colloidal dispersion is first concentrated to ϕs = 0.3, where the silica particles begin to jam under the effect of their repulsive interactions. Then the particles aggregate until they form a cohesive wet solid at ϕs = 0.68 ± 0.02. Further evaporation from the wet solid leads to evacuation of water from pores of the film but l...
TL;DR: In this paper, the formation mechanism of the cubic mesoporous carbon, FDU-16, synthesized by evaporation-induced self-assembly (EISA) was investigated at the molecular level by electron paramagnetic resonance (EPR) spectroscopic techniques.
Abstract: The formation mechanism of the cubic mesoporous carbon, FDU-16, synthesized by evaporation-induced self-assembly (EISA) was investigated at the molecular level by electron paramagnetic resonance (EPR) spectroscopic techniques. This material is synthesized using F127 pluronic block copolymer [poly(ethylene oxide)–poly(propylene oxide)–poly(ethylene oxide) (PEO106-PPO70-PEO106)] as a structure-directing agent (template) and phenolic resol as a carbon precursor. Using two spin probes derived from pluronics with PEO and PPO chains of different lengths that are designed to sense different regions of the system, we followed the evaporation and thermopolymerization stages of the synthesis in situ. To make such studies possible, we have used a polyurethane foam support, placed in the EPR tube, which allows for the efficient solvent evaporation as required for EISA. We focused on the evolution of the dynamics of the template and its interactions with the resol during the reaction. We observed that during the evapo...
TL;DR: In this article, a model was used to quantify the impact of buffer gas on the energy and the incidence angle distributions of the deposited W and Se atoms, depending on the efficiency of the preferential sputtering of Se atoms.
TL;DR: In this paper, a poly-(3-hexylthiophene) (P3HT)/[6,6]-phenyl-C61-butyric-acid-methyl-ester (PCBM) bilayer structure has been realized by single step matrix-assisted pulsed laser evaporation (ss-MAPLE) technique using the same solvent for both the polymers under vacuum conditions.
Abstract: A poly-(3-hexylthiophene) (P3HT)/[6,6]-phenyl-C61-butyric-acid-methyl-ester (PCBM) bilayer structure has been realized by single step matrix-assisted pulsed laser evaporation (ss-MAPLE) technique using the same solvent for both the polymers under vacuum conditions. Our ss-MAPLE procedure allows the fabrication of polymeric multilayer device stacks, which are very difficult to realize with the conventional solvent assisted deposition methods. A proof of concept bilayer P3HT/PCBM solar cell based on ss-MAPLE deposition has been realized and characterized. This demonstration qualifies ss-MAPLE as a general and alternative technique for the implementation of polymeric materials in hetero-structure device technology.
TL;DR: In this article, high conducting aluminum-doped ZnO (30,nm)/Ag (5,15,nm) multilayer thin films were deposited on glass substrate by rf magnetron sputtering and e-beam evaporation.
TL;DR: In this article, a polycrystalline thin films of Cu2ZnSnS4 (CZTS) were produced by sulfurizing the precursors in a sulfur atmosphere at a temperature of 550 °C for 3 h for 3H Fabricated CZTS thin films were characterized by X-ray diffraction, energy dispersive Xray spectroscopy, ultraviolet-visible-near infrared spectrophotometry, the Hall effect system, and 3D optical microscopy.
Abstract: Sn/Cu/ZnS precursor were deposited by evaporation on soda lime glass at room temperature, and then polycrystalline thin films of Cu2ZnSnS4 (CZTS) were produced by sulfurizing the precursors in a sulfur atmosphere at a temperature of 550 °C for 3 h Fabricated CZTS thin films were characterized by X-ray diffraction, energy dispersive X-ray spectroscopy, ultraviolet-visible-near infrared spectrophotometry, the Hall effect system, and 3D optical microscopy. The experimental results show that, when the ratios of [Cu]/([Zn] + [Sn]) and [Zn]/[Sn] in the CZTS are 0.83 and 1.15, the CZTS thin films possess an absorption coefficient of larger than 4.0 × 104 cm−1 in the energy range 1.5–3.5 eV, and a direct band gap of about 1.47 eV. The carrier concentration, resistivity and mobility of the CZTS film are 6.98 × 1016 cm−3, 6.96 Ωcm, and 12.9 cm2/(Vs), respectively and the conduction type is p-type. Therefore, the CZTS thin films are suitable for absorption layers of solar cells.
TL;DR: The influence of film deposition conditions during vacuum co-evaporation, including the flux ratio and partial pressure of hydrogen, on the structural and photoelectrochemical properties of copper gallium selenide (CGSe) films was examined in this article.
Abstract: The influence of film deposition conditions during vacuum co-evaporation, including the flux ratio and the partial pressure of hydrogen, on the structural and photoelectrochemical properties of copper gallium selenide (CGSe) films was examined. The flux ratio between Se and the other metals strongly affected both surface morphology and crystallite size. After ZnS modification, CGSe films grown at flux ratios (JSe/JCu+Ga) of 3 to 5 had the highest energy conversion efficiency under AM 1.5G irradiation. In addition, introducing hydrogen during the growth of CGSe films induced the selective growth of the (112) plane and an increase in the grain size. ZnS-modified photocathodes using CGSe with an increased grain size due to hydrogen introduction had high solar energy conversion efficiencies because of their improved structural properties.
Patent•
21 Nov 2012
TL;DR: In this article, a method for preparing a graphene membrane is described, where carbon atoms are released from a solid carbon source by a method such as heat treatment, heat evaporation, sputtering, electron beam deposition, laser deposition or plasma deposition.
Abstract: The invention discloses a method for preparing a graphene membrane Carbon atoms are released from a solid carbon source by a method such as heat treatment, heat evaporation, sputtering, electron beam deposition, laser deposition or plasma deposition to form the graphene membrane on a catalytic layer or a substrate, wherein the solid carbon source is graphite, amorphous carbon, diamond, fullereneor carbon nano tubes In the method for preparing the graphene membrane, the solid carbon source is used, the method is simple; and the prepared graphene membrane is easy to control in terms of thickness, structure and size, has excellent photoelectric characteristics and is suitable for preparing high-performance photoelectronic devices on a large scale
TL;DR: In this paper, the gas sensing characteristics of Fe-doped (10 at.%) tungsten oxide thin films of various thicknesses (100-500 nm) prepared by electron beam evaporation were investigated.
Abstract: This study reports on the gas sensing characteristics of Fe-doped (10 at.%) tungsten oxide thin films of various thicknesses (100–500 nm) prepared by electron beam evaporation. The performance of these films in sensing four gases (H2, NH3, NO2 and N2O) in the concentration range 2–10,000 ppm at operating temperatures of 150–280 °C has been investigated. The results are compared with the sensing performance of a pure WO3 film of thickness 300 nm produced by the same method. Doping of the tungsten oxide film with 10 at.% Fe significantly increases the base conductance of the pure film but decreases the gas sensing response. The maximum response measured in this experiment, represented by the relative change in resistance when exposed to a gas, was ΔR/R = 375. This was the response amplitude measured in the presence of 5 ppm NO2 at an operating temperature of 250 °C using a 400 nm thick WO3:Fe film. This value is slightly lower than the corresponding result obtained using the pure WO3 film (ΔR/R = 450). However it was noted that the WO3:Fe sensor is highly selective to NO2, exhibiting a much higher response to NO2 compared to the other gases. The high performance of the sensors to NO2 was attributed to the small grain size and high porosity of the films, which was obtained through e-beam evaporation and post-deposition heat treatment of the films at 300 °C for 1 h in air.
TL;DR: In this paper, secondary ion mass spectrometry, X-ray diffraction and scanning electron microscopy were used to investigate the development over time of compositional gradients in Cu(In,Ga)Se2 thin films grown in th
Abstract: We use secondary-ion mass spectrometry, X-ray diffraction and scanning electron microscopy to investigate the development over time of compositional gradients in Cu(In,Ga)Se2 thin films grown in th
TL;DR: In this paper, the authors analyzed the NMR relaxation times (T2, T1) behavior of polyvinyl alcohol in real-time by means of low-field nuclear magnetic resonance (NMR) methods.
Abstract: The film formation of poly(vinyl alcohol) of different molecular weights from concentrated solution has been observed in real time by means of low-field nuclear magnetic resonance (NMR) methods. The drying of films was followed with a depth resolution of 50 μm up to the formation of the final film of typically 300 μm thickness, and the molecular mobility was determined with spatial resolution by analyzing the NMR relaxation times (T2, T1) behavior. A gradient in the molecular dynamics was observed from T1 data during evaporation process up to an intermediate time when the film shrinkage rate decreases significantly; T2 indicates dynamical heterogeneity as well, persisting up to complete removal of water. The relaxation times suggest an increase of local molecular order which is more pronounced toward the air/film interface. Wide-angle X-ray diffraction confirms the formation of an ordered region at this interface with a crystallinity higher—depending on molecular weight—than at the bottom side of the film.
TL;DR: In this article, phase separation of co-evaporated zinc phthalocyanine (ZnPc) and fullerene (C60) for efficient organic photovoltaic cells was demonstrated.
Abstract: We demonstrate phase separation of co-evaporated zinc phthalocyanine (ZnPc) and fullerene (C60) for efficient organic photovoltaic cells. With introducing a poly(3,4-ethylenedioxythiophene):poly(styrene sulfonate) film and a crystalline copper iodide film on indium tin oxide, 20-nm-thick ZnPc film adopts a lying-down crystalline geometry with grain sizes of about 50 nm. This surface distributed with strong interaction areas and weak interaction areas enables the selective growth of ZnPc and C60 molecules during following co-evaporation, which not only results in a phase separation but also improve the crystalline growth of C60. This blend film greatly enhances the efficiencies in photocurrent generation and carrier transport, resulting in a high power conversion efficiency of 4.56% under 1 sun.
TL;DR: In this article, a Ni + CrAlYSiN composite coating was prepared on a Ni-based superalloy K417 by vacuum arc evaporation, mainly consisting of nanocrystalline gamma-Ni, fcc-AlN and fcc -CrN.
TL;DR: Comparing Pd/Fe(3)O(4) samples created via Pd evaporation under UHV conditions and those resulting from the solution deposition of Pd-hydroxo complexes reveals that changes in the interfacial functionalization of such samples reveals the facile decomposition of the Pd complexes deposited from the liquid phase.
Abstract: Using single-crystalline Fe3O4(111) films grown over Pt(111) in UHV as a model-support, we have characterized the nucleation behaviour and chemical properties of Pd particles grown over the film using different deposition techniques with scanning tunnelling microscopy and X-ray photoelectron spectroscopy. Comparison of Pd/Fe3O4 samples created via Pd evaporation under UHV conditions and those resulting from the solution deposition of Pd-hydroxo complexes reveals that changes in the interfacial functionalization of such samples (i.e. roughening and hydroxylation) govern the differences in Pd nucleation behavior observed over pristine oxides relative to those exposed to alkaline solutions. Furthermore, it appears that other differences in the nature of the Pd precursor state (i.e. gas-phase Pd in UHV vs. [Pd(OH)2]n aqueous complexes) play a negligible role in Pd nucleation and growth behaviour at elevated temperatures in UHV, suggesting facile decomposition of the Pd complexes deposited from the liquid phase. Applying temperature programmed desorption and infrared spectroscopy to probe the CO chemisorption properties of such samples after reduction in different reagents (CO, H2) shows the formation of bimetallic PdFe alloys following reduction in H2, but monometallic Pd particles after CO reduction.
TL;DR: Youse et al. as discussed by the authors investigated the effects of thermal evaporation set-up conditions and substrate temperature on the morphological and optical properties of ZnO nano/microstructures.
Abstract: By Ramin Yousefi,* Farid Jamali-Sheini, and Ali Khorsand ZakZnO nano/microstructures are grown on Si(111) substrates using two types of thermal evaporation set-up The effects ofthermal evaporation set-up conditions and substrate temperature on the morphological and optical properties of ZnO nano/microstructuresareinvestigatedTubeswitheitherone-endopenandoneendsealed(OOE),orbothendsopen(TOE)areusedas the objects that could change the conditions in a thermal evaporation set-up Observations show that, under similar sourceand substrate temperatures, such changes result in different shapes and sizes of ZnO structures Room temperaturephotoluminescence (PL) and Raman spectroscopy (RS) studies demonstrate that the ZnO structures grown in the OOEtube have better crystalline quality and optical properties than those grown in the TOE tube In fact, the results show that themorphology and crystalline qualities of the products can be controlled by the set-up conditionsKeywords: Photoluminescence, Raman spectroscopy, Substrate temperature, Thermal evaporation set-up,ZnO nanostructures
TL;DR: In this paper, the epitaxial growth of Bi2Se3 thin films on (0001) Al2O3 substrates by hybrid physical-chemical vapor deposition (HPCVD) is reported.
Abstract: We report the epitaxial growth of Bi2Se3 thin films on (0001) Al2O3 substrates by hybrid physical-chemical vapor deposition (HPCVD). The HPCVD technique combines the thermal decomposition of trimethylbismuth with the thermal evaporation of Se and leads to a high Se partial pressure in the growth ambient. The Bi2Se3 films are highly c-axis oriented on sapphire but contain planar defects including stacking faults and twin boundaries. Variable-temperature Hall-effect measurements demonstrate a carrier concentration of 5.8 × 1018 cm−3 and a mobility of 900 cm2/Vs at 4.2 K. These results demonstrate the potential of HPCVD for producing high quality Bi2Se3 films for topological insulator studies.