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Enhance near infrared performance of n-type vertically aligned MoS <sub/>2</sub> flakes photodetector with active p-type CZTS electrodes
摘要： Recently, MoS2 is extensively investigated as a potential 2D material to develop ultra-high responsive photodetector (PD) due to its direct band gap and high optical absorption. However, the development of broadband PD is impede due to the low light absorption of MoS2 in NIR region. Metal-semiconductor-metal (MSM) photodetector with conventional metal electrode is being used as base device structure for MoS2 PD owing its simple and cost-effective structure. However, passive metal electrodes limit light absorption and diminish the performance of photodetector. Herein, a broadband, self-powered photodetector is developed with enhanced NIR response by using n-type vertical MoS2 flakes and p-type Cu2ZnSnS4 (CZTS) active electrodes. Owing to high absorption of p-type CZTS electrode in NIR region along with MoS2 flakes in visible region and formation of p-n junction at CZTS-MoS2 flakes interface shows ultra-high responsivity of 49.31 A W?1 and external quantum efficiency of 7.6×103 (%) with enhanced performance in NIR and visible region in contrast to conventional and passive metal electrode. Moreover, proposed device showed very high detectivity 3.4×1013(2.4×1013) in NIR (visible) region. The responsivity with active CZTS based electrodes is increased upto 11-times in comparison to passive gold electrodes in NIR region at 1100 nm. Photodetetcor with p-type CZTS electrodes shows long term stability and reproducibility over more than 4000 h which clearly revealed advantage of using p-type CZTS electrode for MoS2 based next generation photodetector applications.
关键词： photodetector,CVD,self-powered,MoS2 edge-enriched,Cu–Zn–Sn–S electrode,broadband
更新于2025-09-23 15:19:57
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Epitaxial growth and electrical performance of graphene/3Ca??SiC films by laser CVD
摘要： High electrical conductivity graphene/epitaxial-3CeSiC (G/epi-3CeSiC) composite films have the potential to the applications such as micro-electro-mechanical systems, distributed Bragg reflectors, solar cells, and photocatalysis in harsh environments. In this study, G/epi-3CeSiC composite films were prepared through laser chemical vapor deposition (LCVD) using hexametyldisilane (HMDS) as a safe single precursor. The electrical conductivity (s) of the composite films reached 2.23 (cid:1) 104 S/m, which is 2.2 times of the highest s reported for G/epi-3CeSiC composite. The deposition rate (Rdep) of the composite film with the highest s is 8.2 times of that of the G/epi-3CeSiC with the highest s ever reported. s of the pure epitaxial 3CeSiC film is only 81.2 S/m, which is the lowest value reported to date of 3CeSiC prepared through CVD using HMDS as a single precursor. Elimination of carbon is beneficial for increasing the breakdown field intensity and decreasing the leakage current of heterojunction when epitaxial 3CeSiC is used as semiconductor material.
关键词： Electrical conductivity,Deposition rate,Laser CVD,Graphene/SiC film,Epitaxial
更新于2025-09-23 15:19:57
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Direct transfer of the CVD-grown graphene on copper foils on SiO2 substrate under supercritical CO2 assisted-cleaning technique
摘要： The transfer of CVD-grown graphene sheets onto arbitrary substrates is important for the development of practical applications. Unfortunately, designing a low cost and highly efficient graphene transfer technique to achieve defect-free graphene sheets with low contact resistance onto various substrates still remains a challenge. In this paper, a CVD grown monolayer graphene sheet was directly transferred on SiO2/Si substrate. We found that a combination of floating copper with graphene films on ammonium persulfate solution with an original method of supercritical CO2 fluid can effectively produce clean and dry samples without damaging the crystalline quality of graphene. This method does not require any polymeric material to be desposited on the graphene films at any stage. Samples are analyzed by optical microscopy, Raman spectroscopy, scanning electron microscopy and atomic force microscopy. This method is very promising for cleaning graphene samples for electronic device fabrication.
关键词： transfer technique,supercritical CO2,SiO2 substrate,graphene,CVD
更新于2025-09-23 15:19:57
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How to Grow Fully (100) Oriented SiC/Si/SiC/Si Multi-Stack
摘要： This paper reports on the successful elaboration of fully (100) oriented SiC/Si/SiC/Si multi-stack using chemical vapor deposition. Si(100) heteroepitaxy on 3C-SiC(100) is identified as the critical step which is solved by pulse insertion of precursors during cooling. It lead to the roughening of the 3C-SiC surface which in turn lead to the quasi-exclusive nucleation of (100) oriented islands at the expanse of (110) ones. Subsequent Si epitaxy on such modified surface allows growing fully (100) oriented Si layer, as confirmed by structural characterization of the layers. The 3C-SiC grown on top of such Si(100) layer is again of (100) orientation, forming thus a fully (100) oriented stack. Due to the high lattice mismatch, each interface of the stack is characterized by a high density of crystalline defects which are shown to recombine along with thickness. Antiphase domains present inside the 3C-SiC seed are shown to have no detrimental influence on the Si layer quality. Without the surface modification step, the Si layers grown on 3C-SiC are always polycrystalline with a mixture of (110) and (100) orientations.
关键词： CVD,3C-SiC,surface modification,multilayers,Si heteroepitaxy
更新于2025-09-19 17:15:36
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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
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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
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[SPIE Computer-Aided Diagnosis - Houston, United States (2018.2.10-2018.2.15)] Medical Imaging 2018: Computer-Aided Diagnosis - Convolutional neural networks for the detection of diseased hearts using CT images and left atrium patches
摘要： Cardiovascular disease is a leading cause of death in the United States. The identification of cardiac diseases on conventional three-dimensional (3D) CT can have many clinical applications. An automated method that can distinguish between healthy and diseased hearts could improve diagnostic speed and accuracy when the only modality available is conventional 3D CT. In this work, we proposed and implemented convolutional neural networks (CNNs) to identify diseased hearts on CT images. Six patients with healthy hearts and six with previous cardiovascular disease events received chest CT. After the left atrium for each heart was segmented, 2D and 3D patches were created. A subset of the patches were then used to train separate convolutional neural networks using leave-one-out cross-validation of patient pairs. The results of the two neural networks were compared, with 3D patches producing the higher testing accuracy. The full list of 3D patches from the left atrium was then classified using the optimal 3D CNN model, and the receiver operating curves (ROCs) were produced. The final average area under the curve (AUC) from the ROC curves was 0.840 ± 0.065 and the average accuracy was 78.9% ± 5.9%. This demonstrates that the CNN-based method is capable of distinguishing healthy hearts from those with previous cardiovascular disease.
关键词： Deep learning,Heart disease,Classification,Cardiovascular disease (CVD),Convolutional neural networks,Computer-aided diagnosis,3D Computed tomography
更新于2025-09-19 17:15:36
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Solution and on-surface synthesis of structurally defined graphene nanoribbons as a new family of semiconductors
摘要： Graphene nanoribbons (GNRs) are quasi-one-dimensional subunits of graphene and have open bandgaps in contrast to the zero-bandgap graphene. The high potential of GNRs as a new family of carbon-based semiconductors, e.g. for nanoelectronic and optoelectronic applications, has boosted the research attempts towards fabrication of GNRs. The predominant top-down methods such as lithographical patterning of graphene and unzipping of carbon nanotubes cannot prevent defect formation. In contrast, bottom-up chemical synthesis, starting from tailor-made molecular precursors, can achieve atomically precise GNRs. In this account, we summarize our recent research progress in the bottom-up synthesis of GNRs through three different methods, namely (1) in solution, (2) on-surface under ultrahigh vacuum (UHV) conditions, and (3) on-surface through chemical vapour deposition (CVD). The solution synthesis allows fabrication of long (>600 nm) and liquid-phase-processable GNRs that can also be functionalized at the edges. On the other hand, the on-surface synthesis under UHV enables formation of zigzag GNRs and in situ visualization of their chemical structures by atomic-resolution scanning probe microscopy. While the on-surface synthesis under UHV is typically costly and has limited scalability, the industrially viable CVD method can allow lower-cost production of large GNR films. We compare the three methods in terms of the affordable GNR structures and the resulting control of their electronic and optical properties together with post-processing for device integration. Further, we provide our views on future perspectives in the field of bottom-up GNRs.
关键词： semiconductors,CVD,on-surface synthesis,UHV,Graphene nanoribbons,optoelectronics,bottom-up synthesis,solution synthesis
更新于2025-09-19 17:15:36
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Fabrication of an Ultra-Thick-Oriented 3C-SiC Coating on the Inner Surface of a Graphite Tube by HHH-CVD
摘要： Cubic SiC (3C-SiC) is a promising material for nuclear industry applications due to its excellent properties. In this report, a highly oriented thick 3C-SiC coating with good crystallinity was prepared on the inner surface of a monolithic graphite tube via high-frequency induction-heated halide chemical vapor deposition (HHH-CVD) using SiCl4, CH4, and H2 as precursors. The texture coefficient (TC(hkl)), microstructure, and deposition rate along the tube axis was studied. 3C-SiC coating with a high (111) orientation and crystallinity was obtained. Along the tube axis, TC(111) was consistent with the temperature distribution. The surficial morphology of the 3C-SiC coating changed from pebble-like to hexangular facet and then to hemispherical. The deposition rate and coating thickness were 300 μm/h and 615 μm, respectively, which is sufficiently rapid and thick enough to obtain free-standing SiC tubes for nuclear reactors.
关键词： microstructure,orientation,3C-SiC coating,HHH-CVD
更新于2025-09-19 17:15:36
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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