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Revealing the Role of Gold in the Growth of Two-dimensional Molybdenum Disulfide by Surface Alloy Formation
摘要： Formation of Mo-Au surface alloy during Au-assisted chemical vapor deposition (CVD) of MoS2 was confirmed by a series of control experiments. We adapted a metalorganic chemical vapor deposition (MOCVD) system to conduct two-dimensional MoS2 growth in a controlled environment. Sequential injection of Mo and S precursors, which does not yield any MoS2 on a SiO2/Si, grows atomically thin MoS2 on Au, indicating formation of an alloy phase. Transmission electron microscopy of a cross-section of the specimen confirmed the confinement of the alloy phase near the surface only. These results show that the reaction intermediate is the surface alloy and that the role of Au in the Au-assisted CVD is formation of an atomically thin reservoir of Mo near the surface. This mechanism is clearly distinguished from that of MOCVD, which does not involve formation of any alloy phases.
关键词： Molybdenum Disulfide,Surface Alloy,Two-dimensional Material,Chemical vapor deposition,Metalorganic Chemical Vapor Deposition
更新于2025-09-23 15:21:01
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Applications of atomic layer deposition and chemical vapor deposition for perovskite solar cells
摘要： Metal halide perovskite solar cells (PSCs) have rapidly evolved over the past decade to become a photovoltaic technology on the cusp of commercialization. In the process, numerous fabrication strategies have been explored with the goal of simultaneously optimizing for device efficiency, stability, and scalability. Chemical vapor deposition (CVD) and atomic layer deposition (ALD) have proven to be effective tools for the fabrication of various components of PSCs. This review article examines the application of CVD and ALD for the deposition and modification of charge transport layers, passivation layers, absorber materials, encapsulants, and electrodes. It outlines the use of these vapor deposition techniques in state-of-the-art, multi-junction solar cell devices, and also contains a discussion of the stability of metal halide perovskite materials under CVD and ALD conditions based on in-situ characterization reported in literature. This article concludes with insights into future CVD and ALD research directions that could be undertaken to further aid the deployment of PSCs in emerging solar photovoltaic markets.
关键词： absorber materials,passivation layers,encapsulants,atomic layer deposition,charge transport layers,chemical vapor deposition,perovskite solar cells,electrodes
更新于2025-09-23 15:21:01
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Ultra-long high quality catalyst-free WO<sub>3</sub> nanowires for fabricating high-performance visible photodetectors
摘要： This work presents a study on the controlled growth of WO3 nanowires via chemical vapor deposition without catalyst, and their potential applications in visible photodetectors. The influence of growth conditions on the morphology of WO3 nanowires is studied in order to understand the growth mechanism of WO3 nanowires, and ultra-long (60 μm, the longest one ever reported) WO3 nanowires with a spindle shape are achieved by optimizing the growth conditions. The photoconductor detectors based on WO3 single nanowires present excellent device performance with a responsivity as high as 19 A/W at a bias of 0.1 V, a detectivity as high as 1.06 × 1011 Jones, and a response (rising and decay) time as short as 8 ms under the illumination of a 404 nm laser. These results indicate the great potential of WO3 nanowires for applications in fabricating high performance visible photodetectors.
关键词： visible light,high performance,photodetectors,chemical vapor deposition,WO3 nanowires
更新于2025-09-23 15:21:01
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High-performance and Flexible CsPbBr3UV-vis Photodetectors Fabricated via Chemical Vapor Deposition
摘要： Inorganic perovskite cesium lead halide (CsPbBr3) has attracted considerable attention because of its particularly excellent optoelectronics properties and high stability in humidity environments. Here, highly crystalline CsPbBr3 films with different morphologies and grain sizes were prepared via a one-step low pressure chemical vapor deposition (CVD). The structure-activity relationship between film microstructure and photodetectors (PDs) performance are investigated. The CsPbBr3 PD prepared at ~190 ℃ possess an excellent response in the UV-Vis region and exhibits a fast response time of 0.7 ms/1.0 ms. Under 405 nm laser irradiation, the PD has a high responsivity, detectivity, external quantum efficiency, and switch ratio of 3.49 A/W, 1.50×1013 Jones, 1075.4%, and 3.29×105, respectively. More importantly, the PD maintains 93% of original photocurrent when exposed to air for 28 days, which demonstrates excellent stability. At the same time, the CsPbBr3 films prepared via CVD are not dependent on the substrate, and the PDs exhibit similar performance on glass, SiO2/Si and polyimide (PI) substrates. The photocurrent of the flexible PD is maintained at 86% of the initial device performance parameters after 1000 bending cycles. These results indicate that the CsPbBr3 perovskite films prepared via CVD have great potential for application in high-performance, stable and flexible PDs.
关键词： photodetector,chemical vapor deposition,stability,CsPbBr3,flexible
更新于2025-09-23 15:21:01
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Low temperature platinum chemical vapor deposition on functionalized self-assembled monolayers
摘要： The reaction pathways of Pt CVD using (COD)PtMe2 – xClx (x = 0, 1, 2) have been investigated on functionalized self-assembled monolayers (SAMs) as models for organic substrates. Residual gas analysis for (COD)PtMe2 and (COD)PtMeCl is consistent with the loss of methyl radicals as the initial step in deposition, while for (COD)PtCl2, the first step is the loss of a chlorine radical. It is further shown using x-ray photoelectron spectroscopy and time-of-flight secondary ion mass spectrometry that the deposition process leads to chemical damage of the SAM layer and little Pt deposition. Using this understanding, it is demonstrated that the Pt CVD rate can be controlled using a radical trap. In the presence of 1,4-cyclohexadiene, a well-known alkyl radical trap, Pt deposition was increased by 5× to 10×, creating a room-temperature effective Pt CVD process.
关键词： time-of-flight secondary ion mass spectrometry,x-ray photoelectron spectroscopy,Pt CVD,chemical vapor deposition,self-assembled monolayers,radical trap
更新于2025-09-23 15:21:01
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Pure Anatase Phase Titanium Dioxide Films Prepared by Mist Chemical Vapor Deposition
摘要： In this research, pure anatase phase titanium dioxide thin films were successfully fabricated for the first time using the mist chemical vapor deposition method, and optional values for deposition temperature and concentration of titanium tetraisopropoxide were established. It was found that the crystallinity of the titanium dioxide film was significantly improved by increasing the deposition temperature. The best crystallinity of titanium dioxide film was obtained at 400 ?C. It was confirmed that pure anatase phase titanium dioxide films could be obtained using different concentrations of titanium tetraisopropoxide. The lower concentration of titanium tetraisopropoxide produced better crystallinity in the resultant titanium dioxide film. The morphologies of the titanium dioxide thin films were also significantly influenced by the concentration of titanium tetraisopropoxide in the precursor solution.
关键词： titanium dioxide,anatase,thin films,mist chemical vapor deposition,growth control
更新于2025-09-23 15:21:01
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A Bean-Like Formation of Germanium Nanoparticles Inside CNTs by the Subsequent Operation of Colloidal Synthesis and Catalytic Chemical Vapor Deposition Methods
摘要： The first attempts of implanting Ge nanoparticles (Ge NPs) inside iron filled CNTs (IF-CNTs) by a subsequent use of the bench top colloidal synthesis and chemical vapor deposition (CVD) approach is shown. Ge NPs are colloidally synthesized (with a 3.8 ± 0.6 nm in size) before the deposition. The hybrid Ge NPs/IF-CNTs structure and morphology are characterized using high-resolution transmission electron microscopy, scanning electron microscopy, selective area electron diffraction, and X-ray diffraction studies. After the deposition, Ge NPs appear to be grown in size and to be sprinkled almost homogeneously into the IF-CNTs similar to a bean-like deposition. CNTs diameter is also identified to be enlarged drastically when using Ge NPs as a catalyst in CVD compared to the CNTs formation without Ge NPs. In addition, micro-length rectangular Ge μPs are also found outside the nanotube core. Rietveld analysis shows the presence of γ-Fe (Fm-3m), ferromagnetic α-Fe (Im-3m), Fe3C, Ge (Fd-3m), and multiwall CNTs. The results indicate that Ge NPs and IF-CNTs demonstrate cocatalytic activity in increasing the respective sizes, which are dramatically larger than those obtained by the conventional approaches.
关键词： ferromagnetism,germanium,nanoparticles,colloidal,chemical vapor deposition,CNTs
更新于2025-09-23 15:21:01
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Controlled growth of InGaN quantum dots on photoelectrochemically etched InGaN quantum dot templates
摘要： Controlled growth of InGaN quantum dots (QDs) using photoelectrochemically (PEC) etched InGaN QD templates is demonstrated. The InGaN QDs are grown by a self-assembly (SA) method using metal-organic chemical vapor deposition on templates consisting of planar GaN and PEC etched InGaN QDs for comparison. The InGaN QD templates are formed using quantum-size-controlled PEC etching of planar InGaN layers on GaN, which produces controlled QD radiuses with a statistical mean (μ) of 17.3 nm and standard deviation (σ) of 6.2 nm, and densities of 1.2 × 1010 cm?2. The PEC etched QDs are capped with an AlGaN interlayer and GaN barrier layer to recover a planar surface morphology for subsequent SA growth of QDs. The PEC QD templates behave as seeds via localize strain near the PEC QDs which provide improved control of the SA QD growth. The SA grown QDs on PEC QD templates are smaller and have controlled radiuses with μ = 21.7 nm and σ = 11.7 nm compared to the SA QDs on planar GaN templates with radiuses of μ = 37.8 nm and σ = 17.8 nm. Additionally, the dot densities of the SA QDs on PEC QD templates are ~3 times higher and more closely match the underlying densities of the template (8.1 × 109 cm?2). Multiple quantum dots (MQDs) are also grown on both templates that consist of 4 periods of SA QDs and AlGaN/GaN interlayer/barrier layers. The MQDs grown on PEC QD templates better retain their planarized smooth surfaces after barrier layer growth, and exhibit ~3 times stronger PL intensity at room temperature compared to MQDs grown on planar GaN.
关键词： Metalorganic chemical vapor deposition,Nitrides,Quantum dots,Light emitting diodes,Atomic force microscopy,Photoelectrochemical etching
更新于2025-09-23 15:21:01
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Epitaxial Growth of Monolayer MoS <sub/>2</sub> on SrTiO <sub/>3</sub> Single Crystal Substrates for Applications in Nanoelectronics
摘要： Monolayer molybdenum disulfide (MoS2) crystals grown on amorphous substrates such as SiO2 are randomly oriented. However, when MoS2 is grown on crystalline substrates, the crystal shapes and orientations are also influenced by their epitaxial interaction with the substrate. In this paper we present the results from chemical vapor deposition growth of MoS2 on three different terminations of single crystal strontium titanate (SrTiO3) substrates. On SrTiO3(111) the monolayer MoS2 crystals form equilateral triangles with two main orientations, in which they align their <21?1?0>-type directions (i.e., the sulfur-terminated edge directions) with the <11?0>-type directions on SrTiO3. This arrangement allows near perfect coincidence epitaxy between seven MoS2 unit cells and four SrTiO3 unit cells. On SrTiO3(110) the MoS2 crystals tend to align their edges with both <11?0> and <11?2?> directions on SrTiO3 as these both provide favorable coincidence lattice registry. This distorts the crystal shapes and introduces an additional strain detectable by photoluminescence. When triangular MoS2 crystals are grown on SrTiO3(001), they again show a preference to align their edges with the <11?0> directions on SrTiO3. Our observations can be explained if the interfacial van der Waals (vdW) bonding between MoS2 monolayers and SrTiO3 is greatest when the maximum commensuration between the lattices is achieved. Therefore, a key finding of this paper is that the vdW interaction between MoS2 and SrTiO3 substrates determines the supported crystal shapes and orientations by the epitaxial relations. Controlled crystal orientations make the growth of large sheets of MoS2 possible when there are multiple nucleation sites. This minimizes the number of grain boundaries and optimizes electronic properties of the material, e.g., charge mobility, which is crucial for the application of monolayer MoS2 in next-generation nanoelectronic devices.
关键词： Raman spectroscopy,van der Waals epitaxy,scanning tunneling microscopy,SrTiO3,2D materials,chemical vapor deposition,MoS2,photoluminescence spectroscopy
更新于2025-09-23 15:21:01
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Low-temperature growth of n<sup>++</sup>-GaN by metalorganic chemical vapor deposition to achieve low-resistivity tunnel junctions on blue light emitting diodes
摘要： We report on low-resistivity GaN tunnel junctions (TJ) on blue light-emitting diodes (LEDs). Si-doped n++-GaN layers are grown by metalorganic chemical vapor deposition directly on LED epiwafers. Low growth temperature (< 800 °C) was used to hinder Mg-passivation by hydrogen in the p++-GaN top surface. This allows achieving low-resistivity TJs without the need for post-growth Mg activation. TJs are further improved by inserting a 5 nm thick In0.15Ga0.85N interlayer (IL) within the GaN TJ thanks to piezoelectric polarization induced band bending. Eventually, the impact of InGaN IL on the internal quantum efficiency of blue LEDs is discussed.
关键词： metalorganic chemical vapor deposition,GaN tunnel junctions,blue light-emitting diodes
更新于2025-09-23 15:21:01