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Reactive wetting of binary Sn Cr alloy on polycrystalline chemical vapour deposited diamond at relatively low temperatures
摘要： Synthetic diamond has excellent mechanical, thermal, and electrical properties, which makes it an ideal material in a wide range applications from abrasive grinding tools to modern electronic devices. Hence, understanding the wettability of metals on the synthetic diamond is of great importance for the development of diamond-related materials and devices. In this study, the wettability and spreading kinetics of binary SneCr alloy on chemical vapour deposed (CVD) polycrystalline diamond compacts were investigated using a sessile drop method. In situ observation of contact angle at elevating temperatures indicated trace addition of Cr dramatically improved the wettability of Sn on CVD diamond, and the SneCr alloy started to wet CVD diamond at approximately 750 °C. Isothermal spreading kinetic analysis revealed that the spreading of SneCr alloy on CVD diamond was controlled by the kinetics of chemical reaction at advancing triple line. Microstructure characterization indicated that the formation of nano-sized scallop-like Cr7C3 grains was responsible for the improved wettability of SneCr alloy on CVD diamond substrate. The wetting temperature was found to play a determinant role in the interfacial carbide formation, and hence the reactive wetting of SneCr alloy on CVD diamond at temperatures from 700 to 900 °C.
关键词： Reactive wetting,Interface reaction,Chromium carbides,CVD diamond
更新于2025-09-19 17:15:36
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European Microscopy Congress 2016: Proceedings || An in-situ Low Energy Argon Ion Source for Local Surface Modification
摘要： A new in-situ low energy ion source for surface modification of a sample surface has been designed. The source is based on the principle of low energy ion bombardment from a beam of ions such as Ar+, N+, or He+ can be used for a local modification of the sample surface. Typical energies are in the range 10 - 100 eV, covering the interaction types from chemical reaction to ion etching and to ion implantation. The source is based on the following principle: electrons from a filament are accelerated towards a grid by a potential difference between the filament and the grid. The electrons enter a gas-filled region between the grid and the sample, where they ionize the gas. The ions are then accelerated towards the sample by a potential difference between the grid and the sample. The source produces a static beam of ions with a selectable energy of 10-100 eV and a full width half maximum (FWHM) of 7.1 um. This corresponds to a central ion current density of 0.019 nA/um2 at 100 eV, which is very similar to the current density at 100 eV of a regular ICP source. In this way, the sample area that is affected by the low energy ions can be more or less defined by the applied bias voltage. The first application can be polishing the top surface of a TMD laminate produced by CVD, or improvement of and LPE surface prepared by ICP. An example of the interaction with the beam is shown in Figure 1, where a native oxide on Si has been removed in 25 seconds, using 100 eV Ar+ ions.
关键词： Ar+,surface modification,low energy ion source,chemical reaction,FWHM,native oxide removal,ion etching,ICP,current density,static beam,N+,ion bombardment,TMD,He+,LPE,ion implantation,in-situ,gas ionization,filament,grid,CVD
更新于2025-09-19 17:15:36
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Structure-dependent performance of single-walled carbon nanotube films in transparent and conductive applications
摘要： We investigate a complex relationship between structural parameters of single-walled carbon nanotubes (namely, mean length, diameter, and defectiveness) and optoelectrical properties (equivalent sheet resistance) of thin films composed of the nanotubes. We obtained a systematic dataset describing the influence of CO2 concentration and growth temperature. On the basis of the experimental results, we prove the high Raman peak ratio (IG/ID), length, and diameter of the nanotubes to decrease the equivalent sheet resistance of the nanotube-based film. The approach employed highlights the change in the nanotube growth mechanism at the temperature coinciding with the phase transition between α-Fe and γ-Fe catalyst phases. We believe this work to be of high interest for researchers working not only in the field of transparent and conductive films based on nanocarbons, but also for those who reveals the fundamentals of the nanotube growth mechanism.
关键词： aerosol CVD,nanotube growth mechanism,optoelectronic properties,transparent conductive films,single-walled carbon nanotubes
更新于2025-09-19 17:13:59
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Analysis of infrared spectra with narrow band absorption by a graphene/square-ring structure
摘要： A graphene covered on square-ring structure is designed and fabricated to achieve narrow band absorption of three peaks in the infrared band. The absorption rates of graphene/square-ring structures calculated by simulation are 90.49%, 65.67% and 20.38%, respectively, and the experimentally measured absorption rates are 82.12 %, 53.13 %, and 16.58 %, respectively. Comparing the absorption rate of simulation calculation with experimental measurement, as well as the reasons for the differences are presented. The dynamic control characteristics of the graphene device are not observed with this structure in the experiment, which is different from the simulation. We analyzed the reason for this distinction and proposed three solutions based on the experimental design. The research results of this paper provide an important reference to the design and preparation of graphene devices.
关键词： infrared spectroscopy,absorption,graphene,CVD
更新于2025-09-19 17:13:59
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[IEEE 2019 IEEE 5th International Conference for Convergence in Technology (I2CT) - Bombay, India (2019.3.29-2019.3.31)] 2019 IEEE 5th International Conference for Convergence in Technology (I2CT) - Growth of Different Microstructure of MoS <sub/>2</sub> through Controlled Processing Parameters of Chemical Vapor Deposition Method
摘要： The anisotropic bonding in layered materials crystallize to form different structure such as smooth films, nanotubes, and fullerene-like nanoparticles. Here, the growth of different microstructure of MoS2 via chemical vapor deposition (CVD) method through controlled processing parameters is reported. Scanning electron microscopy and Raman spectroscopy ascertained the MoS2 on insulating substrate (SiO2/Si). It was observed that poor sulfur environment and slow vapor flow were unable to induce complete transition from MoO3-x to MoS2 and formed intermediate MoO2.The MoS2 and MoO2/MoS2 heterostructure were synthesized via single step. In addition, by adjustment of heating rate with temperature of centre zone and vapor flow, flower like structure of MoS2 was achieved.
关键词： Sulfurization,CVD,MoS2,Layered materials,2D materials
更新于2025-09-19 17:13:59
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High-performance hydrogen evolution of MoSe2-Mo2C seamless heterojunction enabled by efficient charge transfer
摘要： A novel heterojunction consisted of Mo2C and MoSe2 is synthesized through CVD as high-performance electrocatalyst for HER in both acidic and basic media. The enhanced conductivity and the large surface area of as-prepared Mo2C/MoSe2 contribute to the efficient HER. Further DFT calculations can prove that in the interface region of Mo2C and MoSe2, there are MIGS which could benefit the fast charge transfer, boosting the hydrogen evolution.
关键词： DFT calculations,HER,Mo2C,heterojunction,CVD,MoSe2,electrocatalyst,MIGS
更新于2025-09-19 17:13:59
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Showerhead-Assisted Chemical Vapor Deposition of Perovskite Films for Solar Cell Application
摘要： In the last years, perovskite solar cells have attracted great interest in photovoltaic (PV) research due to their possibility to become a highly efficient and low-cost alternative to silicon solar cells. Cells based on the widely used Pb-containing perovskites have reached power conversion efficiencies (PCE) of more than 20 %. One of the major hurdles for the rapid commercialization of perovskite photovoltaics is the lack of deposition tools and processes for large areas. Chemical vapor deposition (CVD) is an appealing technique because it is scalable and furthermore features superior process control and reproducibility in depositing high-purity films. In this work, we present a novel showerhead-based CVD tool to fabricate perovskite films by simultaneous delivery of precursors from the gas phase. We highlight the control of the perovskite film composition and properties by adjusting the individual precursor deposition rates. Providing the optimal supply of precursors results in stoichiometric perovskite films without any detectable residues.
关键词： precursor deposition rates,stoichiometric perovskite films,showerhead-based CVD,chemical vapor deposition,perovskite solar cells
更新于2025-09-19 17:13:59
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Transition from Hopping to Band-like Transport in Weakly-coupled Multilayer MoS2 Field Effect Transistors
摘要： In this article, multilayer MoS2 manufactured from multiple-transfer process of chemical vapor deposition (CVD) grown monolayer MoS2 is studied. Due to the lattice mismatch and larger distance between adjacent MoS2 layers, the interlayer-interaction is weakened and the band structure transition from direct to indirect as well as band-gap shrinkage effect in multilayer is suppressed, as indicated by Raman and photoluminescence (PL) spectra. These structural differences from that of the exfoliated MoS2 make stacked MoS2 layers a better configuration for fabricating high-performance MoS2 FET. Here, back-gate MoS2 field effect transistors (FETs) with different number of layers were fabricated. As the number of layers increases from 1 to 3, the devices’ mobility and on/off ratio show an enhancement from 2 to 62cm2/s·V and 106 to 108, respectively. Metal to insulator transition (MIT) phenomena is also observed in bilayer MoS2 FET. A distributed resistance based model is proposed to study the conductivity of weak-coupled MoS2 layers. Combining the resistance model with temperature dependence characteristics, it is demonstrated that the electron mobility in monolayer MoS2 is limited by hopping transport mechanism, whereas the electron in bilayer can be excited to band-like transport mode due to the immunity of the influence from the charge traps at substrate, which explain the enhancement of mobility and MIT phenomena. This study is universally valid for other two dimensional (2D) materials, paving a way to fabricate high performance nano-electronics for integrated circuits.
关键词： CVD,MoS2,multilayer,metal-to-insulator transition,FET
更新于2025-09-19 17:13:59
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CVD controlled growth of large-scale WS <sub/>2</sub> monolayers
摘要： Monolayer tungsten disulfide (WS2) with a direct band gap of ca. 2.0 eV and stable properties has been a hotspot in two-dimensional (2D) nanoelectronics and optoelectronics. However, it remains challenging to successfully prepare monolayer WS2. In this paper, we report the chemical vapor deposition (CVD) growth behavior of hexagonal WS2 monolayers by using WS2 powders and sodium triosulfate (Na2S2O3) as precursors. We observed the Na2S2O3 has a significant effect on the WS2 triangular and leaf-like shapes. In addition, based on proposed S-termination and W-termination theory, the growth mechanisms for different shapes of WS2 were discussed.
关键词： monolayer,WS2,CVD,growth mechanism,Na2S2O3
更新于2025-09-16 10:30:52
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Single-walled carbon nanotube growth at low temperature by alcohol gas source method using Co catalyst: enhancement effects of Al<sub>2</sub>O<sub>3</sub> buffer layer on carbon nanotube yield
摘要： Using an alcohol gas source chemical vapor deposition method, we attempted to grow single-walled carbon nanotube (SWCNT) growth using Co catalysts on Al2O3 buffer layers. Reducing the growth temperature decreased the optimal ethanol pressure to obtain the highest SWCNT yield. By optimizing the ethanol pressure, we succeeded in growing SWCNTs at 400oC. Irrespective of the growth temperature, SWCNT yields from Co catalysts on Al2O3 buffer layers were higher than those on SiO2/Si substrates, but the enhancing effects of Al2O3 buffer layers on SWCNT yield were reduced below 500oC. Taking into account both in-plane X-ray diffraction results and decrease of catalyst aggregation in the low temperature region, we concluded that the density of Co particles suitable for SWCNT growth increased on SiO2 surface at low temperature, resulting in the reduction of difference in SWCNT yield at low temperature between Al2O3 buffer layers and SiO2/Si substrates.
关键词： catalyst,CVD,low-temperature growth,single-walled carbon nanotube,Co
更新于2025-09-16 10:30:52