- 标题
- 摘要
- 关键词
- 实验方案
- 产品
-
Pulsed-grown graphene for flexible transparent conductors
摘要： In the race to find novel transparent conductors for next-generation optoelectronic devices, graphene is supposed to be one of the leading candidates, as it has the potential to satisfy all future requirements. However, the use of graphene as a truly transparent conductor remains a great challenge because its lowest sheet resistance demonstrated so far exceeds that of the commercially available indium tin oxide. The possible cause of low conductivity lies in its intrinsic growth process, which requires further exploration. In this work, I have approached this problem by controlling graphene nucleation during the chemical vapor deposition process as well as by adopting three distinct procedures, including bis(trifluoromethanesulfonyl)amide doping, post annealing, and flattening of graphene films. Additionally, van der Waals stacked graphene layers have been prepared to reduce the sheet resistance effectively. I have demonstrated an efficient and flexible transparent conductor with the extremely low sheet resistance of 40 Ω sq?1, high transparency (Tr ≈90%), and high mechanical flexibility, making it suitable for electrode materials in future optoelectronic devices.
关键词： doping,flexibility,chemical vapor deposition,graphene,transparent conductors,sheet resistance
更新于2025-09-19 17:15:36
-
Properties of Nitrogen/Silicon Doped Vertically Oriented Graphene Produced by ICP CVD Roll-to-Roll Technology
摘要： Simultaneous mass production of high quality vertically oriented graphene nanostructures and doping them by using an inductively coupled plasma chemical vapor deposition (ICP CVD) is a technological problem because little is understood about their growth mechanism over enlarged surfaces. We introduce a new method that combines the ICP CVD with roll-to-roll technology to enable the in-situ preparation of vertically oriented graphene by using propane as a precursor gas and nitrogen or silicon as dopants. This new technology enables preparation of vertically oriented graphene with distinct morphology and composition on a moving copper foil substrate at a lower cost. The technological parameters such as deposition time (1–30 min), gas partial pressure, composition of the gas mixture (propane, argon, nitrogen or silane), heating treatment (1–60 min) and temperature (350–500 ?C) were varied to reveal the nanostructure growth, the evolution of its morphology and heteroatom’s intercalation by nitrogen or silicon. Unique nanostructures were examined by FE-SEM microscopy, Raman spectroscopy and energy dispersive X-Ray scattering techniques. The undoped and nitrogen- or silicon-doped nanostructures can be prepared with the full area coverage of the copper substrate on industrially manufactured surface defects. Longer deposition time (30 min, 450 ?C) causes carbon amorphization and an increased fraction of sp3-hybridized carbon, leading to enlargement of vertically oriented carbonaceous nanostructures and growth of pillars.
关键词： vertically oriented graphene (VOG),Li-ion battery,roll-to-roll technology,inductively coupled plasma chemical vapor deposition (ICP CVD),supercapacitor
更新于2025-09-19 17:15:36
-
van der Waals Epitaxial Growth of Atomically Thin 2D Metals on Dangling-Bond-Free WSe <sub/>2</sub> and WS <sub/>2</sub>
摘要： 2D metals have attracted considerable recent attention for their special physical properties, such as charge density waves, magnetism, and superconductivity. However, despite some recent efforts, the synthesis of ultrathin 2D metals nanosheets down to monolayer thickness remains a significant challenge. Herein, by using atomically flat 2D WSe2 or WS2 as the growth substrate, the synthesis of atomically thin 2D metallic MTe2 (M = V, Nb, Ta) single crystals with the thickness down to the monolayer regime and the creation of atomically thin MTe2/WSe2 (WS2) vertical heterojunctions is reported. Comparison with the growth on the SiO2/Si substrate under the same conditions reveals that the utilization of the dangling-bond-free WSe2 or WS2 as the van der Waals epitaxy substrates is crucial for the successful realization of atomically thin MTe2 (M = V, Nb, Ta) nanosheets. It is further shown that the epitaxial grown 2D metals can function as van der Waals contacts for 2D semiconductors with little interface damage and improved electronic performance. This study defines a robust van der Waals epitaxy pathway to ultrathin 2D metals, which is essential for fundamental studies and potential technological applications of this new class of materials at the 2D limit.
关键词： van der Waals epitaxy,field-effect transistors,2D materials,chemical vapor deposition,transition metal dichalcogenides
更新于2025-09-19 17:15:36
-
Low pressure chemical vapor deposition of In <sub/>2</sub> O <sub/>3</sub> films on off-axis c-sapphire substrates
摘要： Heteroepitaxial In2O3 films were grown on transparent c-sapphire substrates with 0°, 3.5°, 6° and 8° off-axis angles via low pressure chemical vapor deposition (LPCVD). Metallic solid indium and oxygen gas were used as the precursors. X-ray diffraction (XRD) spectroscopy and cross-sectional scanning transmission electron microscopy (STEM) were used to study the effects of substrate off-axis on the crystalline quality of the as-grown films. The XRD 2θ-ω spectra confirmed the growth of body centered cubic bixbyite In2O3 films with (111) out-of-plane orientation. STEM images revealed the suppressed dislocation density in the films grown on substrates with off-axis angles. The crystal structure was further confirmed by Raman spectroscopy. Fifteen peaks corresponding to bcc-In2O3 Raman modes were observed at room temperature (RT). XRD ω-rocking curves, XRD Φ-scan profiles and STEM images indicate improved crystalline quality in films grown on substrates with, particularly, 3.5° and 6° off-cut angles. Growth rates in a wide range of ~ 0.5 - 30 μm/hr were achieved. RT photoluminescence peak at ~2.15 eV is attributed to the deep level defect transitions. RT photoluminescence excitation peak at ~3.38 eV corresponds to the optical bandgap of bcc-In2O3. RT electron Hall mobilities of ~ 88 - 116 cm2/V.s were measured with background carrier concentrations of ~ 6 - 9x1017 cm-3.
关键词： low pressure chemical vapor deposition,Indium oxide,off-axis substrate,c-sapphire
更新于2025-09-19 17:15:36
-
Nonlinear Optical Properties of CdS Semiconductor nanowires
摘要： In this work, we report on the nonlinear optical properties in single Cadmium sulfide nanowires (CdS NWs). The high qulity growth of CdS semiconductor nanowires were synthesized by chemical vapor deposition (CVD) method. The as-obtained products were characterized by X-ray diffraction (XRD) , Scanning electron microscopy (SEM), and the energy dispersive X-ray spectrom (EDS) was used to determine the specific elemental distribution and show purity of the CdS semiconductor nanowires . The excitation of femtosecond laser(800 nm, 50 fs, 80 MHz) was used to study the nonlinear optical properties of CdS nanowires, such as the Second Harmonic Generation(SHG) and optical waveguide effect. CdS NW has a second harmonic generation with a blue emission bands at a wavelength of 400 nm . Finally, based on the dark field image of the CCD taken and combined with the spectrum, it is proved that CdS NW has an optical waveguide effect.
关键词： Cadmium sulfide (CdS),Waveguide,nanowires (NWs),Second- Harmonic Generation (SHG),Chemical Vapor Deposition (CVD)
更新于2025-09-19 17:15:36
-
Influence of trimethylaluminum predoses on the growth morphology, film-substrate interface, and microstructure of MOCVD-grown AlN on (111)Si
摘要： Aluminum nitride (AlN) was deposited on (111) silicon by metalorganic chemical vapor deposition after varied trimethylaluminum predoses. Growth morphologies, film-substrate interfaces, and film microstructures were examined using scanning electron microscopy, atomic force microscopy, X-ray diffraction, and transmission electron microscopy. In samples grown with predoses, lateral growth was observed over faceted "patches" formed during the predose. Three-dimensional growth was observed to seed from small islands on the surface of these patches and eventually overgrow them. The three-dimensional growth mode was similar to that observed when AlN was grown without a predose, resulting in similar morphologies in all films, regardless of predose, after the islands coalesced. The AlN-silicon interface was found to be predominantly amorphous when no predose was used. However, narrow regions were observed over which the film was in atomic registry with the substrate. This indicates AlN nucleates in epitaxy with the substrate and amorphous silicon nitride forms between nucleation sites due to ammonia exposure. Films grown with predoses had structurally abrupt interfaces, suggesting aluminum within the observed patch features inhibits the reaction between ammonia and silicon at the onset of growth. A structure distinct from both wurtzite AlN and diamond cubic silicon was observed at the substrate interface in films grown with a predose, consistent with either zinc blende AlN or a strained Si/Al alloy. A mosaic microstructure was observed in all films, grown with or without predoses, which consisted of sub-boundaries formed by clusters of threading dislocations. Threading dislocations, separated by hundreds of nanometers, were found to be tilted along common directions, providing evidence for a dislocation bending mechanism possibly enhanced by the predose.
关键词： Defects,Crystal morphology,Metalorganic chemical vapor deposition,Semiconducting aluminum compounds,Nucleation,Nitrides
更新于2025-09-19 17:15:36
-
Quick and Practical Cleaning Process for Silicon Carbide Epitaxial Reactor
摘要： In order to develop a quick and practical cleaning process for the silicon carbide chemical vapor deposition reactor, a pyrolytic carbon-coated susceptor was used. A 30-μm-thick silicon carbide film was formed on the susceptor; the film was cleaned by chlorine trifluoride gas at 460 oC for 15 min. The remained fluorine was removed by the annealing at 900 oC in ambient hydrogen. The pyrolytic carbon surface did not suffer from any damage, because the pyrolytic carbon film surface morphology after the cleaning process was the same that before the silicon carbide film deposition.
关键词： epitaxial reactor cleaning,Chemical vapor deposition,chlorine trifluoride gas
更新于2025-09-19 17:15:36
-
Single Crystal Diamond Deposited by Dual Radio-Frequency Plasma Jet CVD with High Growth Rate
摘要： Single crystal diamonds were deposited on high pressure high temperature (HPHT) substrate with high growth rate, up to 18.5 μm/h, by using dual radio-frequency inductive coupled plasma jet. The methane ?ux was found to in?uence the growth rate of single crystal diamond. The reason for this might be ascribed to the electron temperature increase, raising the ?ux of methane, based on the plasma diagnosis results by optical emission spectra (OES). The results of Raman spectroscopy and the X-ray rocking-curve indicated that as-deposited diamonds are of good quality.
关键词： growth rate,single crystal diamond,methane ?ux,dual radio frequency,chemical vapor deposition (CVD),inductive coupled plasma jet
更新于2025-09-19 17:15:36
-
Two-dimensional (PEA) <sub/>2</sub> PbBr <sub/>4</sub> perovskite single crystals for a high performance UV-detector
摘要： Two-dimensional (2D) metallic transition metal dichalcogenides (MTMDCs), the complement of 2D semiconducting TMDCs, have attracted extensive attentions in recent years because of their versatile properties such as superconductivity, charge density wave, and magnetism. To promote the investigations of their fantastic properties and broad applications, the preparation of large-area, high-quality, and thickness-tunable 2D MTMDCs has become a very urgent topic and great efforts have been made. This topical review therefore focuses on the introduction of the recent achievements for the controllable syntheses of 2D MTMDCs (VS2, VSe2, TaS2, TaSe2, NbS2, NbSe2, etc.). To begin with, some earlier developed routes such as chemical vapor transport, mechanical/chemical exfoliation, as well as molecular beam epitaxy methods are briefly introduced. Secondly, the scalable chemical vapor deposition methods involved with two sorts of metal-based feedstocks, including transition metal chlorides and transition metal oxidations mixed with alkali halides, are discussed separately. Finally, challenges for the syntheses of high-quality 2D MTMDCs are discussed and the future research directions in the related fields are proposed.
关键词： metallic transition metal dichalcogenides,synthesis,chemical vapor deposition,two dimensional
更新于2025-09-19 17:15:36
-
GaN grown by metalorganic vapor phase epitaxy
摘要： We report on residual impurities in semi-polar (3031) and (2021) GaN homo-epitaxial layer grown by metal-organic chemical vapor deposition. The (3031) and (2021) GaN layer showed atomically smooth surface and clear steps toward [0001] and [000-1], respectively. The residual impurity concentrations of oxygen and carbon were below the detection limit of secondary-ion mass spectroscopy. Low-temperature photoluminescence revealed that (2021) GaN layer consisted free excitons and Si donor bound excitons, along with two-electron satellite lines and longitudinal optical (LO) phonon coupling transitions. The results indicate semi-polar (3031) and (2021) GaN epitaxial layers are promising candidates in obtaining a high quality GaN drift layer for vertical GaN devices.
关键词： B2. Semiconducting III-V materials,A3. Metalorganic chemical vapor deposition,B1. Nitrides,A1. Crystal structure,A1. Impurities
更新于2025-09-19 17:15:36