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Role of chamber pressure on crystallinity and composition of silicon films using silane and methane as precursors in hot-wire chemical vapour deposition technique
摘要： Hot-wire chemical vapour deposition is a versatile technique to deposit a-Si:H and nc-Si films at higher deposition rate (~5-10 ?/sec) as compared to Plasma enhanced chemical vapour deposition (1-2 ?/sec). We report the deposition of highly crystalline Si films at very high deposition rate (≥ 40?/sec) by adding methane to silane during thermal/catalytic decomposition. A series of films were deposited by varying the chamber pressure between 10-100 Pa at a substrate temperature of 300 °C and filament temperature 2000 °C. The hydrogen diluted silane (10% silane in hydrogen) and pure methane were used as precursors and gas flow rate ratio was kept constant at 10. Films prepared at lower pressure (≤ 20 Pa) were more crystalline and do not contain any trace of carbon atoms. Bandgap was found to increase from 1.24-1.63 eV when pressure was increased. It was observed that chamber pressure plays a key role in determining the crystallinity, disorder and composition of these films. Addition of methane to hydrogen diluted silane increased deposition rate and crystallinity of Si films at low pressure (≤ 20 Pa). Above 20 Pa pressure, carbon atoms signature was obtained. SiC films were obtained when pressure was > 100 Pa.
关键词： Deposition rate,Si films,Crystallinity,Hot-wire chemical vapour deposition
更新于2025-11-21 11:01:37
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Nano-Heteroepitaxy: An Investigation of SiGe Nano-Pillars Coalescence
摘要： In this paper, SiGe nano-pillars coalescence was investigated using industrial Reduced Pressure-Chemical Vapour Deposition integration scheme based on diblock copolymer patterning provided nanometer size templates for the selective epitaxy of SiGe 25% nano-pillars. In order to study merging, thicknesses ranging from 20 to 35 nm were grown and samples characterized by AFM, XRD, SSRM and TEM. The evolution in terms of grains shape, size and number was examined, with individual pillars merging into larger grains above 30 nm thickness. High degrees of macroscopic strain relaxation were obtained at the different stages of nano-pillars merging. Defects such as stacking faults and twins were identified as occurring at the early stages of nano-pillar coalescence.
关键词： SSRM,TEM,coalescence,AFM,SiGe nano-pillars,Reduced Pressure-Chemical Vapour Deposition,XRD
更新于2025-11-14 14:32:36
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Tailoring Shape and Crystallographic Phase of Copper Sulfide Nanostructures Using Novel Thiourea Complexes as Single Source Precursors
摘要： Copper sulfide thin films and nanoparticles have been prepared via aerosol assisted chemical vapour deposition and solvothermal hot injection routes, respectively. Both routes employed heterocyclic amine based benzoylthioureato-copper(II) complexes as single source precursors. Copper sulfide thin films of diverse morphologies ranging from cubic to snowy or irregular crystallites depending on the deposition temperature were observed. Powder X-ray diffraction studies of the as deposited thin films have indicated the formation of hexagonal and cubic phases of copper sulfide. In the case of the nanoparticles, Roxbyite (Cu1.75S) phase was obtained in dodecanethiol at temperatures of 150, 190 and 230 °C. However, a preferred growth of nanoparticles was observed in the presence of oleylamine whereas the roxbyite phase was obtained at temperatures of 150, 200 and 250 °C. Also transmission electron microscopy showed the formation of close to spherical, hexagonal nano-disk and rod shaped nanoparticles.
关键词： Aerosol assisted chemical vapour deposition,Nanoparticles,Heterocyclic thiourea,Copper sulfide,Thermolysis,Thin films
更新于2025-09-23 15:23:52
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Influence of experimental parameters on linear, nonlinear optical and ultrafast dynamics properties of In doped ZnO nanorods
摘要： In-doped ZnO (IZO) nanorods have been successfully synthesized by chemical vapour deposition method. The structure, morphology and linear optical properties of IZO nanorods have been characterized. The excitation intensity and temperature - dependent the photoluminescence of IZO nanorods were analyzed. The nonlinear optical absorption properties were studied by using the Z-scan technique with same wavelengths at different laser pulses and energies. IZO nanorods showed two-photon absorption (TPA) mechanism at 532 nm. In the low-energy pulse regime, IZO nanorods showed TPA induced ground state saturable absorption (SA). However, with increasing the energy pulse regime, an apparent TPA induced reverse-saturable absorption (RSA) was observed. The ultrafast dynamics properties of IZO nanorods were investigated by the pump-probe technique under different laser parameters. The femtosecond transient absorption spectra show that the few decades picosecond component has been assigned to the shallow donor mixed with donor bound recombination, and the slowed components represent the decay from donor–acceptor pair recombination.
关键词： Zinc oxide,Nonlinear optics properties,Photoluminescence,Chemical vapour deposition
更新于2025-09-23 15:23:52
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Photoluminescence of silicon vacancy centres as conceptual indicator for the condition of diamond protection coatings
摘要： Due to the outstanding properties polycrystalline diamond coatings are used for wear protection on tools and work pieces. Thereby adhesive and abrasive wear as well as spalling of the coating can lead to damage and downtimes of the working machines. By depositing silicon doped multilayer diamond coatings, an indication of the condition of the coatings could be achieved. In this study the behaviour and transmission of the zero-phonon line of silicon vacancy centres is investigated in doped multilayer diamond coatings. The in-situ silicon doped diamond coatings were synthesized in use of an atmospheric laser-based plasma chemical vapour deposition. Photoluminescence measurements were performed with an excitation area of 18 mm2 and a wavelength of 248 nm. While the photoluminescence of the doped layers conceptually proves suitability as an indicator for the condition of the coating, the undoped diamond layers in the coatings show a high transmissivity to the zero-phonon line for the used parameters.
关键词： Wear,Luminescent materials,Protective coating,Diamond films,Chemical vapour deposition
更新于2025-09-23 15:21:21
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Etching-controlled preparation of large-area fractal graphene by low-pressure CVD on polycrystalline Cu substrate
摘要： Fractal graphene can provide more active sites for electrocatalytic reactions due to its unique morphology. The preparation of large-area fractal graphene and the understanding of its morphology evolution are crucial to the improvement of catalytic performance. Chemical vapour deposition (CVD) technology is a unique method to obtain high quality fractal graphene. In this study, low-pressure CVD method was used to prepare fractal graphene on Cu substrate. Through the etching effect of hydrogen in the cooling process, the evolution process of graphene from compact to dentritic was realized and the fractal dimensions of graphene with different morphologies were calculated. It was found that the hydrogen etching reaction of graphene begins at the edges and moves towards the nucleation point gradually until the etching progress is completed. And continuous large-area fractal graphene films were obtained for the first time, which would find potential application in electrocatalysis and other fields.
关键词： Fractal graphene,Etching,Chemical vapour deposition
更新于2025-09-23 15:21:01
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p+ polycrystalline silicon growth via hot wire chemical vapour deposition for silicon solar cells
摘要： Hot wire chemical vapour deposition (HWCVD) is explored as a way of growing boron-doped silicon for photovoltaic devices. Deposition temperatures are measured using a custom-built monitoring system for two different filament configurations within the HWCVD tool. A refined fabrication process is presented, using an altered filament arrangement, that currently provides a maximum deposition temperature of 535 oC, for growing boron-doped silicon films via HWCVD, with the inclusion of a short post-deposition anneal at 800 oC for 2 minutes. Transmission electron microscopy reveals improvements in interfacial quality, as well as larger grains present after post-annealing treatments. In addition, re-crystallisation of as-deposited amorphous Si films under a short anneal is confirmed using Raman spectroscopy. The enhancements in morphology translate to a boost in current rectification based on our dark current-voltage measurements. This is further supported by secondary-ion mass spectrometry analysis, presenting p+ properties with uniform doping in the 1021 cm-3 region.
关键词： Selective area electron diffraction,Crystallisation,Emitter,Hot wire chemical vapour deposition,Silicon solar cells,Transmission electron microscopy
更新于2025-09-23 15:19:57
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Atomistic mechanisms of seeding promoter-controlled growth of molybdenum disulphide
摘要： Seeding promoters facilitate the nucleation and growth of transition metal dichalcogenides in chemical vapor deposition (CVD). However, sophisticated roles of seeding promoter remain unclear. Here, adopting triangular-shaped crystal violet (CV) consisting of nonpolar and polar parts as the seeding promoter, we study the role of seeding promoter for the growth of molybdenum disulfide (MoS2). We systematically control the geometrical configuration of CV on SiO2/Si substrate by changing the solvent polarity and find that it strongly affects the growth of monolayer or multilayer MoS2 domains via CVD. Monolayer MoS2 domains were predominantly grown on randomly lying-down CV configurations on SiO2/Si substrate, whereas multilayer MoS2 domains are synthesized at concentrated polar parts in CV micelle on the substrate. Density functional theory calculations reveal that the initial nucleation step for the MoS2 growth is the adsorption of S on CV and the most favourable S adsorption site is the polar part in CV. Furthermore, it is found that the polar CV part mediates the CV adsorption to SiO2 and additionally strengthened in the lying-down CV configuration. Enhancing the thermal stability as well as hindering the re-aggregation of CV at high temperature, the lying down CV configuration allows the predominant growth of monolayer MoS2.
关键词： seeding promoter,molybdenum disulphide,chemical vapour deposition,transition metal dichalcogenides
更新于2025-09-23 15:19:57
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Outstanding Photocurrent Density and IPCE of Liquida??State NiO Perovskitea??Sensitized Solar Cells
摘要： The efficiency and photocurrent density reported for a p-type sensitized solar cells up to now are still lagging behind that of the n-type counterparts, limiting the successful development of p-n tandem cells. To circumvent this issue, NiO thin film is fabricated by aerosol-assisted chemical vapour deposition (AACVD) technique and employed in p-type solar cells. A systematic study is conducted to comprehend the correlation between the NiO thickness and the power conversion efficiency (PCE) of liquid-state NiO-based sensitized solar cells. By carefully designing the cell components, this type of device demonstrates the highest photocurrent density (Jsc) exceeding 18 mA cm-2 when using iodine/triiodide as redox shuttle matching the one produced by TiO2 counterpart. This is accomplished by (1)using AACVD technique for one-step deposition of compact and mesoporous NiO electrodes, (2)optimizing the thickness of NiO layer through controlling the deposition time and (3)adopting methylammonium lead iodide (CH3NH3PbI3) as a light harvester prepared via a sequential deposition method.
关键词： aerosol-assisted chemical vapour deposition,photovoltaics,NiO,perovskite
更新于2025-09-23 15:19:57
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Interaction of Methane Concentration and Deposition Temperature in Atmospheric Laser Based CVD Diamond Deposition on Hard Metal
摘要： For laser-based plasma chemical vapour deposition (CVD) of diamond on hard metal at atmospheric pressure, without a vacuum chamber, the interaction between the deposition temperature and the methane concentration has to be understood to adjust the coating thickness, deposition duration, and medium diamond crystal size. The hypothesis of this study is that a wider range of methane concentrations could be used to deposit microcrystalline diamond coatings due to the increasing etching and deposition rates with rising deposition temperatures. The deposition of the CVD diamond coatings was carried out on K10 hard metal substrates. The process temperature and the methane concentration were varied from 650 to 1100°C and from 0.15% to 5.0%, respectively. The coatings were analysed by scanning electron and 3D laser-scanning confocal microscopy, energy dispersive X-ray and micro-Raman spectroscopy, as well as cryofracture-based microscopy analysis. The results showed that microcrystalline diamond coatings could be deposited in a wider range of methane concentrations when increasing the process temperature. The coating thickness saturates depending on the process temperature even though the methane concentration constantly increases. The coating thickness increases with an increasing deposition temperature until the cobalt diffusion hinders the deposition at the process temperature of 1100°C.
关键词： diamond film,chemical vapour deposition,hard metal,methane ratio,deposition temperature
更新于2025-09-19 17:13:59