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Growth Order-Dependent Strain Variations of Lateral Transition Metal Dichalcogenide Heterostructures
摘要： Understanding the heterojunction of a lateral heterostructured transition metal dichalcogenide (hTMD) is important to take advantage of the combined optoelectronic properties of individual TMDs for various applications but, however, is hampered by mingled effects from lattice mismatch and substrate interaction. Here, we systematically investigated the strain occurring at lateral hTMDs consisting of molybdenum disulfide (MoS2) and molybdenum diselenide (MoSe2) prepared by chemical vapor deposition. Comparison of homologous TMDs and hTMDs from controlled growth order revealed systematic change in photoluminescence behavior depending on substrate interaction and relative lattice mismatch. Near the heterojunction, a TMD with a larger lattice constant (a) exhibits photoluminescence (PL) red-shift, whereas a TMD with smaller a shows an opposite trend owing to lattice-induced strain. These effects are augmented in a subtractive or additive manner by tensile strain from the substrate interaction. Moreover, comparison of PLs revealed that the shell region grown from the core edges exhibits weak substrate interaction contrasted by that of a shell region independently grown on a shell. This study provides detailed understandings of the heterojunction at a lateral hTMD for various applications.
关键词： photoluminescence,lateral heterostructure,strain,transition metal dichalcogenides,chemical vapor deposition
更新于2025-09-23 15:23:52
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Chemical vapor deposition of graphene on refractory metals: The attempt of growth at much higher temperature
摘要： Large area graphene is usually grown by chemical vapor deposition on Cu or Ni catalysts at ～1000 °C. For most materials, high temperature leads to high quality. However, graphene growth at even higher temperatures is rarely reported. Therefore, here we systematically investigate the graphene deposition on refractory metals i.e. metals with extremely high melting points. The growth parameters and material characterizations are given in detail. On Ta which readily forms carbides during the carbon deposition, the growth mode is monolayer due to the chemical absorption of excess carbon in the bulk metal. On Re, there is no carbide formed (except in extreme conditions), which greatly simpli?es the scenario. Because of the relatively high carbon solubility in Re, the growth temperature has to be limited in order not to drift into the dominantly multilayer graphene regime caused by the carbon segregation. Graphene with reasonable quality has been achieved, although not as good as expected. For example, on Ta, the residual bonds between the graphene and substrate deteriorate the graphene crystalline quality. Despite the di?culties in refractory metal etching, the transfer technique of the graphene is also explored. This research contributes to the fundamental understanding of the graphene growth theory and technology on refractory metals.
关键词： Refractory metal,Graphene,Chemical vapor deposition,High temperature growth
更新于2025-09-23 15:23:52
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Raman analysis of strained graphene grown on dewetted cobalt
摘要： Graphene grows onto cobalt by means of diffusion of carbon atoms during the isothermal stage of exposure to hydrocarbon precursor, followed by precipitation during cooling. This method, largely applied with nickel catalyst, is known to produce continuous, but not uniform, layers with the concurrent presence of mono‐ and poly‐graphene areas. With the aid of Raman mapping of graphene still lying onto its catalyst, we are able to consider the possible origins for the observed distortions of the phonon modes with respect to the well‐known picture of the monolayer material. Optical effects, doping, the presence of multi‐layered islands, and strain are kept into account. It is shown that some isotropic observations can be interpreted in terms of the occurrence of strain with the uniaxial component superimposed at the metal discontinuities. Strain is proposed to originate from the difference between the thermal expansion coefficients of graphene and cobalt. The present paper shows that inhomogeneities in graphene grown onto catalysts with high C solubility are not always directly related to excess of precipitation. The observation of strain in as‐grown graphene opens the possibility of tailoring the electronic density of states via strain engineering directly during growth.
关键词： strain,graphene,micro‐Raman,cobalt,chemical vapor deposition
更新于2025-09-23 15:23:52
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Abrupt changes in the graphene on Ge(001) system at the onset of surface melting
摘要： By combining scanning probe microscopy with Raman and x-ray photoelectron spectroscopies, we investigate the evolution of CVD-grown graphene/Ge(001) as a function of the deposition temperature in close proximity to the Ge melting point, highlighting an abrupt change of the graphene’s quality, morphology, electronic properties and growth mode at 930 °C. We attribute this discontinuity to the incomplete surface melting of the Ge substrate and show how incomplete melting explains a variety of diverse and long-debated peculiar features of the graphene/Ge(001), including the characteristic nanostructuring of the Ge substrate induced by graphene overgrowth. We find that the quasi-liquid Ge layer formed close to 930 °C is fundamental to obtain high-quality graphene, while a temperature decrease of 10 degrees already results in a wrinkled and defective graphene film.
关键词： Chemical Vapor Deposition,Germanium,Scanning Tunneling Microscopy,Catalysis,Graphene
更新于2025-09-23 15:23:52
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Optical thickness identification of few-layer MoS <sub/>2</sub> deposited by chemical vapor deposition
摘要： The physical and optoelectronic properties of MoS2 are closely related to their thickness. Few-layer molybdenum disulfide (MoS2) has been intensively studied for its potential applications. In this work, monolayer and few-layer MoS2 nanosheets with large size and high crystallization quality were successfully prepared by chemical vapor deposition (CVD). Then, the layer number of CVD-grown MoS2 nanosheets were identified for the first time by extracting the R channel contrast of the optical image of the sample with ImageJ software. Compared with Raman spectra and PL spectra, this method can identify the layer number of CVD-grown MoS2 nanosheets efficiently and accurately, which provides a simple and feasible method for the study of the layer number of CVD-grown MoS2 nanosheets and can help us exploiting their applications in the future.
关键词： Thickness identification,chemical vapor deposition,MoS2,optical microscopy,Raman spectroscopy
更新于2025-09-23 15:23:52
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Black Diatom Colloids toward Efficient Photothermal Converters for Solar-to-Steam Generation
摘要： Steam generation from solar power using converters has attracted significant research attention in recent years as an alternative form of energy conversion from solar energy. Rationally designed photothermal converters are essential to increase the efficiency of steam generation. Here we propose a novel colloidal type of photothermal converter based on a frustule skeleton, which is a naturally designed colloid containing through-pore structures. Several coating processes were used to provide broadband absorption, magnetic, and water-floating properties without deteriorating pore structures, through vapor deposition polymerization of polypyrrole, weak base treatment, and additional vapor deposition polymerization of polystyrene. The prepared colloidal photothermal converter showed superior efficiency for steam generation under sun-light irradiation.
关键词： Solar-to-steam generation,surface treatment,diatom,chemical vapor deposition,broadband absorption
更新于2025-09-23 15:23:52
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Growth of Highly (110) Oriented Diamond Film by Microwave Plasma Chemical Vapor Deposition
摘要： In this study, we propose a simple and effective approach to enhance (110) orientation in diamond films grown on (100) Si substrates by microwave plasma chemical vapor deposition. It is found that the crystalline structure of diamond films strongly rely on the time and CH4 concentration in the nucleation stage. Nucleation for more than 30 mins would promote the (110) oriented growth of diamond films. Under the same growth condition, when the CH4 concentration is less than 7% (≤7%) in the nucleation stage, the diamond films exhibit randomly oriented structure; once the value exceeds 7%, the deposited films are strongly (110) oriented. It could be verified by experiments that the formation of (110) orientation in diamond films are related to the high nucleation density and high fraction of diamond-like carbon existing in nucleation samples.
关键词： diamond,orientation,chemical vapor deposition
更新于2025-09-23 15:23:52
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Fabrication and Investigation of Two-Component Film of 2,5-Diphenyloxazole and Octafluoronaphthalene Exhibiting Tunable Blue/Bluish Violet Fluorescence Based on Low Vacuum Physical Vapor Deposition Method
摘要： Organic luminescent materials play an important role in the fields of light-emitting diodes and fluorescent imaging. Moreover, new synthetic approaches towards π-conjugated molecular systems with high fluorescence quantum efficiency are highly desired. Herein, different 2,5-diphenyloxazole-octafluoronaphthalene (DPO-OFN) films with tunable fluorescence have been prepared by Low Vacuum Physical Vapor Deposition (LVPVD) method. DPO-OFN films showed some changed properties, such as molecular vibration and fluorescence. All films exhibited blue/bluish violet fluorescence and showed blueshift, in comparison with pristine DPO. This work introduced a new method to fabricate two-component molecular materials with tunable blue/bluish violet luminescence properties and provided a new perspective to prepare organic luminescent film materials, layer film materials, cocrystal materials, and cocrystal film materials. Importantly, these materials have potential applications in the fields of next generation of photofunctional materials.
关键词： blue/bluish violet luminescence,organic luminescent materials,tunable fluorescence,two-component film,low vacuum physical vapor deposition
更新于2025-09-23 15:22:29
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Synthesis of Tungsten Oxide Nanowires onto ITO Glass Using T-CVD
摘要： Tungsten oxide is an n-type semiconductor with interesting physical and chemical properties that make it suitable for various technological applications. Tungsten oxide nanowires were synthesized not only at low temperature but also without the use of any catalysts. The tungsten oxide nanowires were synthesized at 550 °C with tungsten layers onto the ITO glass using thermal chemical vapor deposition (T-CVD). The SEM image shows that the tungsten oxide nanowires are effectively grown with the 200 nm tungsten film. The Raman spectra shoulder at ~690 cm-1 proves the synthesized of tungsten oxide nanowires.
关键词： ITO glass,thermal chemical vapor deposition,Tungsten oxide nanowires
更新于2025-09-23 15:22:29
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Heteroepitaxial growth of thick <i>α</i> -Ga <sub/>2</sub> O <sub/>3</sub> film on sapphire (0001) by MIST-CVD technique
摘要： The 8 μm thick single-crystalline α-Ga2O3 epilayers have been heteroepitaxially grown on sapphire (0001) substrates via mist chemical vapor deposition technique. High resolution X-ray diffraction measurements show that the full-widths-at-half-maximum (FWHM) of rocking curves for the (0006) and (10-14) planes are 0.024° and 0.24°, and the corresponding densities of screw and edge dislocations are 2.24 × 106 and 1.63 × 109 cm?2, respectively, indicative of high single crystallinity. The out-of-plane and in-plane epitaxial relationships are [0001] α-Ga2O3//[0001] α-Al2O3 and [11-20] α-Ga2O3//[11-20] α-Al2O3, respectively. The lateral domain size is in micron scale and the indirect bandgap is determined as 5.03 eV by transmittance spectra. Raman measurement indicates that the lattice-mismatch induced compressive residual strain cannot be ruled out despite the large thickness of the α-Ga2O3 epilayer. The achieved high quality α-Ga2O3 may provide an alternative material platform for developing high performance power devices and solar-blind photodetectors.
关键词： chemical vapor deposition,ultra-wide bandgap semiconductor,gallium oxide,epitaxy
更新于2025-09-23 15:22:29