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Polycrystal Synthesis, Crystal Growth, Structure, and Optical Properties of AgGaGe <sub/><i> <i>n</i> </i> </sub> S <sub/> 2( <i> <i>n</i> </i> +1) </sub> ( <i>n</i> = 2, 3, 4, and 5) Single Crystals for Mid-IR Laser Applications
摘要： AgGaGenS2(n+1) crystal is a series of quaternary for mid-IR laser applications of nonlinear optical materials converting a 1.064 μm pump signal (Nd:YAG laser) to 4?11 μm laser output, but only AgGaGeS4 has attracted the most attention, remaining the other promising AgGaGenS2(n+1) crystal whose physicochemical properties can be modulated by n value. In this work, AgGaGenS2(n+1) (n = 2, 3, 4, and 5) polycrystals are synthesized by vapor transport and mechanical oscillation method with di?erent cooling processes. High-resolution X-ray di?raction analysis and re?nement have revealed that all the four compounds are crystallized in the noncentrosymmetric orthorhombic space group Fdd2, resulting in the excellent nonlinear optical property, and the distortion of tetrahedron with the variation of n value causes the discrepancy of physicochemical property. Besides, using the modi?ed Bridgman method, AgGaGenS2(n+1) single crystals with 15 mm diameter and 20?40 mm length have been grown. We have discussed the structure and composition of AgGaGenS2(n+1) by XPS spectra and analyzed the three kinds of vibration modes of tetrahedral clusters by the Raman spectra. The Hall measurement indicates that the AgGaGenS2(n+1) single crystals are p-type semiconductor, and the carrier concentration decreases with the increasing n value. All the transmittances of as-grown AgGaGenS2(n+1) samples exceeds 60% in the transparent range, especially the transmittance of AgGaGe2S6, is up to 70% at 1064 nm, and the band gap of as-grown crystal increases from 2.85 eV for AgGaGe2S6 to 2.92 eV for AgGaGe5S12. After a thermal annealing treatment, the absorptions at 2.9, 4, and 10 μm have been eliminated, and the band gap changed into the range of 2.89?2.96 eV.
关键词： Hall measurement,nonlinear optical materials,thermal annealing treatment,vapor transport,AgGaGenS2(n+1),Bridgman method,Raman spectra,mid-IR laser applications,XPS spectra,mechanical oscillation method
更新于2025-11-14 15:27:09
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Growth of vanadium dioxide nanostructures on graphene nanosheets
摘要： The metal oxide/graphene hybrid nanomaterials have been known as promising functional materials for advanced applications such as high capacitive electrode material of secondary batteries, and high sensitive material of high performance gas sensors. Here, morphology controlled vanadium dioxide (VO2) nanostructures were grown on Si wafer and exfoliated graphene by the vapor transport method using a horizontal furnace system. One-dimensional VO2 nanowires were grown on SiO2(300 nm)/Si substrate under 0.4 kPa condition. On the other hand, thick polycrystalline of VO2 platelets were grown on exfoliated graphene nanosheets under 0.4 kPa condition. In addition, polycrystalline VO2 platelets were only grown on exfoliated graphene nanosheets under 101 kPa (atmospheric pressure) condition. The growth of polycrystalline VO2 platelets on graphene nanosheets in atmospheric pressure condition is attributed to preferential growth on functional group of graphene surface such as carbonyl. The functional group is served as nucleation site of VO2 nanostructures.
关键词： Nanostructures,Hybrid Nanomaterials,Vapor Transport Method,Graphene,Vanadium Dioxide
更新于2025-09-23 15:23:52
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High infrared transmittance CdS single crystal grown by physical vapor transport
摘要： Φ55 × 15 mm2 CdS bulk single crystal with high infrared transmittance was grown by physical vapor transport. The single crystal has a consistent structure from top to bottom, which was confirmed by X-ray diffraction. The (002) full-width at half-maximum of the X-ray diffraction was measured to be 60.00 arcsec, indicating a good quality of the structure. Hall mobility, specific resistivity, and carrier concentration for the top and bottom of the crystal were observed as well. Transmittance for the CdS single crystal was measured to be higher than 70% from 2.5 to 4.5 μm, making the single crystal an important candidate for infrared window materials. Furthermore, the absorption mechanism of the CdS single crystal was analyzed.
关键词： physical vapor transport,X-ray diffraction,semiconducting materials,single crystal growth
更新于2025-09-23 15:23:52
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Electrochemical Polishing of Two-Dimensional Materials
摘要： Two-dimensional (2D) layered materials demonstrate their exquisite properties such as high temperature superconductivity, superlubricity, charge density wave, piezotronics, flextronics, straintronics, spintronics, valleytronics, and optoelectronics, mostly, at the monolayer limit. Following initial breakthroughs based on micromechanically exfoliated 2D monolayers, significant progress has been made in recent years towards the bottom-up synthesis of large-area monolayer 2D materials such as MoS2 and WS2 using physical vapor deposition (PVD) and chemical vapor deposition (CVD) techniques in order to facilitate their transition into commercial technologies. However, the nucleation and subsequent growth of the secondary, tertiary, and greater numbers of vertical layers poses a significant challenge not only towards the realization of uniform monolayers, but also to maintain their consistent electronic and optoelectronic properties which change abruptly when transitioning from the monolayer to multilayer form. Chemical or physical techniques which can remove the unwarranted top layers without compromising the material quality will have tremendous consequence towards the development of atomically flat, large-area, uniform monolayers of 2D materials. Here, we report a simple, elegant, and self-limiting electrochemical polishing technique which can thin down any arbitrary thickness of 2D material, irrespective of whether these are obtained using powder vapor transport (PVT) or mechanical exfoliation, into their corresponding monolayer form at room temperature within a few seconds without compromising their atomistic integrity. The effectiveness of this electrochemical polishing technique is inherent to 2D transition metal dichalcogenides (TMDCs) owing to the stability of their basal planes, enhanced edge reactivity, and stronger-than-van der Waals (vdW) interaction with the substrate. Our study also reveals that 2D monolayers are chemically more robust and corrosion resistant compared to their bulk counterparts in similar oxidative environments which enables electrochemical polishing of such materials down to a monolayer.
关键词： physical vapor transport,MoS2,WS2,monolayer,corrosion,two-dimensional (2D) materials,electrochemical polishing,electro-ablation
更新于2025-09-23 15:21:21
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Controllable orientations for Sb <sub/>2</sub> S <sub/>3</sub> solar cells by vertical VTD method
摘要： Antimony sulfide (Sb2S3) is a promising photoelectric material because of its wide bandgap approximately 1.7 eV for next-generation solar cells, high optical absorption coefficient, and its green and earth-abundant constituents. Different to traditional cubic structure photovoltaic materials, Sb2S3 holds one-dimensional crystal structure and its thin film with [hk1] preferred orientation shows one-order-higher carrier transport mobility. However, all the reported Sb2S3 films exhibited [hk0] preferred orientation on CdS-based superstrate device structure up to now. Thus, it is indispensable to study the controllable-orientations Sb2S3 film deposition and the relationship between the orientation and performances. In this paper, we develop a vertical vapor transport deposition (V-VTD) method, which can tune the preferred orientation of Sb2S3 thin film from [hk0] to [hk1] by reaction recipe monitoring. Combining the experiment results, a reasonable deposition/reevaporation competing model is suggested to explain above orientation conversion mechanism. The device efficiency increases from less than 2% to about 4% with the orientation of Sb2S3 film changing from [hk0] to [hk1]. By fine regulating the technique of deposition, the device with [hk1] orientation has better crystallinity, lower interface recombination, and higher built-in voltage comparing with the [hk0] one. Finally, a champion power conversion efficiency (PCE) of 4.5% has been achieved, and the VOC of 730 mV is the top value among the Sb2S3 solar cells. The present versatile orientation tuning strategy could overcome the bottleneck of strong anisotropic materials and show high potential for noncubic material deposition and related optoelectronic device performance enhancement.
关键词： vertical vapor transport deposition,solar cell,controllable orientations,Sb2S3,orientation conversion mechanism
更新于2025-09-23 15:21:01
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Epitaxial CdTe Thin Films on Mica by Vapor Transport Deposition for Flexible Solar Cells
摘要： Most high-quality CdTe thin films are epitaxially grown on single-crystalline substrates through chemical bondings by either molecular beam epitaxy or metalorganic chemical vapor deposition. The epitaxial CdTe films are rarely applied in electronic or optoelectronic devices because of the rigid single-crystalline substrate. We present high-quality CdTe films epitaxially grown on mica by vapor transport deposition process through weak interface interactions. The full-width-at-half-maximum (FWHM) of X-ray diffraction rocking curve of CdTe(111) and the FWHM of azimuthal in-plane angular dispersion of CdTe(111) were 0.23° and 0.36°, respectively. The weak interaction at the interface enables a transfer of the epitaxial film from mica onto other flexible substrates for applications. The epitaxial CdTe film was separated from the mica substrate by the surface tension of water during immersion, and then transferred onto a flexible SU-8 photoresist substrate for the fabrication of CdTe solar cells. We successfully fabricated the flexible all-epitaxial, epi-CdS/epi-CdTe solar cells with a power conversion efficiency of 9.59%, which showed low interface defects and high diode quality compared to the poly-CdS/epi-CdTe solar cells.
关键词： epitaxy,van der Waals,vapor transport deposition,CdTe,flexible photovoltaics
更新于2025-09-23 15:19:57
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Quasi-Vertically-Orientated Antimony Sulfide Inorganic Thin-Film Solar Cells Achieved by Vapor Transport Deposition
摘要： The one-dimensional photovoltaic absorber material Sb2S3 requires crystal orientation engineering to enable efficient carrier transport. In this work, we adopted a vapor transport deposition (VTD) method to fabricate vertically aligned Sb2S3 on a CdS buffer layer. Our work shows that such a preferential vertical orientation arises from the sulfur deficit of the CdS surface which creates a beneficial bonding environment between exposed Cd2+ dangling bonds and S atoms in the Sb2S3 molecules. The CdS/VTD-Sb2S3 interface recombination is suppressed by such properly aligned ribbons at the interface. Compared with typical [120]-oriented Sb2S3 films deposited on CdS by rapid thermal evaporation (RTE) method, the VTD-Sb2S3 thin film is highly [211]- and [121]- oriented and the performance of the solar cell is increased considerably. Without using any hole transportation layer, a conversion efficiency of 4.73% is achieved with device structure of ITO/CdS/Sb2S3/Au. This work provides a potential way to acquire vertical aligned thin films on different buffer layers.
关键词： inorganic device,Sb2S3 solar cell,Vapor transport deposition,thin film,vertical growth
更新于2025-09-23 15:19:57
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Renewable and Sustainable Composites || Methodologies for Achieving 1D ZnO Nanostructures Potential for Solar Cells
摘要： One-dimensional (1D) nanostructures are generally used to describe large aspect ratio rods, wires, belts, and tubes. The 1D ZnO nanostructures have become the focus of research owing to its unique physical and technological significance in fabricating nanoscale devices. When the radial dimension of the 1D ZnO nanostructures decreases to some lengths (e.g., the light wavelength, the mean of the free path of the phonon, Bohr radius, etc.), the effect of the quantum mechanics is definitely crucial. With the large surface-to-volume ratio and the confinement of two dimensions, 1D ZnO nanostructures possess the captivating electronic, magnetic, and optical properties. Furthermore, 1D ZnO nanostructure’s large aspect ratio, an ideal candidate for the energy transport material, can conduct the quantum particles (photons, phonons, electrons) to improve the relevant technique applications. To date, many methods have been developed to synthesize 1D ZnO nanostructures. Therefore, methodologies for achieving 1D ZnO nanostructures are expressed, and the relevant potential application for solar cells are also present to highlight the attractive property of 1D ZnO nanostructures.
关键词： hydrothermal,nanostructures,one dimensional,ZnO,solar cell,chemical vapor transport and condensation (CVTC),vapor-liquid-solid (VLS),electrochemical,metal-organic chemical vapor deposition (MOCVD),chemical vapor deposition (CVD)
更新于2025-09-11 14:15:04
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Synthesis of graphene/black phosphorus hybrid with highly stable P-C bond towards the enhancement of photocatalytic activity
摘要： Black phosphorus (BP), a superior two-dimensional (2D) semiconductor, has attracted much attention due to its unique properties. The graphene (GR)-BP hybrid was synthesized through one pot chemical vapor transport (CVT) approach. The characterization results indicated that P atom was successfully incorporated into GR by the formation of P-C bond. Remarkably, the newly-synthesized GR-BP represented high photocatalytic activity towards 2-chlorophenol (2-CP) degradation, due to the high efficiency of charge separation and transformation caused by the direct band gap of BP and carrier mobility of GR. The removal efficiency for 2-CP reached up to 87.08% within visible light irradiation for 180 min (l > 420 nm). The degradation rate of GR-BP hybrid for 2-CP was approximately 7.29-fold than that of BP within 30 min. In addition, the little increasing of the peak for P-O bond in GR-BP hybrid was observed after being exposed in air for 15 days, meant that the stability of BP was significantly enhanced. It was caused by the decreasing of the oxidation sites in BP due to the formation of P-C bond in hybrid. In brief, our synthetic method for GR-BP not only provides a novel route for the improvement of the stability of BP, but also constitutes an insight into the promising practical application of BP in the photocatalysis field.
关键词： P-C bond,Photocatalytic,Chemical vapor transport,Graphene,Black phosphorus
更新于2025-09-09 09:28:46