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High-performance long-wavelength InAs/GaSb superlattice detectors grown by MOCVD
摘要： We demonstrate high-performance long-wavelength InAs/GaSb superlattice (SL) infrared photodetectors based on an Al-free single heterojunction grown by metalorganic chemical vapor deposition (MOCVD). The device structure consists of a mid-wavelength InAs/GaSb SL p-n junction (PN) and a long-wavelength InAs/GaSb SL n-type absorber (n), so-called PNn design, to reduce the dark current. In addition, a shallow etch technique was employed by exposing only mid-wavelength materials during pixel isolation to suppress surface leakage currents. At 77 K and a bias voltage of -0.1 V, the device exhibited a 50% cut-off wavelength at 8.0 μm, a dark current density of 2.4×10-5 A/cm2, and a peak responsivity of 2.1 A/W. Temperature dependent dark current measurement indicated diffusion-limited behavior down to 75 K. The specific detectivity was estimated to be 7.3×1011 cm·Hz1/2/W, which is comparable with that of detectors grown by molecular beam epitaxy (MBE) at similar cut-off wavelengths.
关键词： InAs/GaSb type-II superlattices,metalorganic chemical vapor deposition,heterostructure,long-wavelength infrared
更新于2025-09-23 15:22:29
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Surface Planarization of Low-Temperature Flowable Silicon Oxide for Atomic Layer Deposition Al <sub/>2</sub> O <sub/>3</sub> Thin Film Encapsulation
摘要： In this research, a flowable chemical vapor deposition (FCVD) process was developed to planarize particle-scattered surfaces for thin film encapsulation by atomic layer deposition (ALD). Nanometer-thick ALD layers are known to have good barrier properties owing to the conformal deposition of the films and their high density, but those barrier properties are vulnerable to degradation because of surface particles on the substrates. In this study, FCVD silicon oxide layer was applied to particle-scattered surfaces as a planarization interlayer. Flowable silicon oxide thin films were deposited with tetrabutoxysilane and O2 in an inductively coupled plasmas reactor. The chemical bonding structure of the flowable silicon oxide was verified with Fourier transform infrared spectroscopy. To confirm the planarization effect, particles 2 μm in diameter were intentionally spread on the substrates by electrospray processing and nanometer-thick Al2O3 layers were deposited on top of the planarization interlayers. With the flowable silicon oxide interlayer and the same particle density on flexible substrates, the water vapor transmission rate was reduced to 1.2 × 10?3 g/(m2 · day) from 2.0 × 10?3 g/(m2 · day). The flowable silicon oxide layers are thus demonstrated to be effective interlayers to reduce the influence of particle contamination for ALD barrier films.
关键词： Thin Film Encapsulation,Planarization Effect,Flowable Chemical Vapor Deposition
更新于2025-09-23 15:22:29
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Control of 1-dimensionally structured tungsten oxide thin films by precursor feed rate modulation in flame vapor deposition
摘要： With the constant tungsten wire feed rate of 4 μm/s, the diameter of nanostructures increases with time and the multi-shell nanostructure and/or branched nanostructure eventually appears and grows. As the diameter and length of 1-D nanostructures increase with time, 1-D nanostructures are easily converted into multi-shell and/or branched nanostructures. The tungsten oxide vapor concentration and flame temperature also affect significantly this conversion of 1-D nanostructures. The increase of tungsten wire feed rate with time accelerated the appearance and growth of multi-shell and/or branched nanostructure, while the decrease of tungsten wire feed rate with time could help prepare the 1-D nanostructured WOX thin film without the growth of multi-shell and/or branched nanostructure. By the modulation of tungsten wire feed rate with time, the thin film thicker than 5μm with single shell nanotube structure could be prepared with almost no increase of nanotube diameter. For the preparation of longer 1-D nanostructured WOX thin film, it is found that the smooth decrease of wire feed rate with time, not the abrupt decrease of feed rate, is required in FVD process to prevent the multi-shell structure growth. We demonstrated that various attractive nanostructures can be prepared quickly by just changing precursor feed rate in FVD process for the first time. The results of this study can provide the basis for many practical applications of FVD process to fast fabrication of several interesting nanostructures.
关键词： nanostructure control,tungsten oxide thin film,precursor feed rate,preparation of 1-D nanostructure,flame vapor deposition
更新于2025-09-23 15:22:29
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Chemical Vapor Deposition for Nanotechnology || Atmospheric Pressure Chemical Vapor Deposition of Graphene
摘要： Recently, graphene has gained significant interest owing to its outstanding conductivity, mechanical strength, thermal stability, etc. Among various graphene synthesis methods, atmospheric pressure chemical vapor deposition (APCVD) is one of the best syntheses due to very low diffusivity coefficient and a critical step for graphene-based device fabrication. High-temperature APCVD processes for thin film productions are being recognized in many diversity technologies such as solid state electronic devices, in particular, high quality epitaxial semiconductor films for silicon bipolar and metal oxide semiconductor (MOS) transistors. Graphene-based devices exhibit high potential for applications in flexible electronics, optoelectronics, and energy harvesting. In this chapter, recent advances of APCVD-based graphene synthesis and their related applications will be addressed.
关键词： large-scale,atmospheric pressure chemical vapor deposition (APCVD),graphene,bilayer graphene (BLG),single-layer graphene (SLG),atmosphere pressure
更新于2025-09-23 15:22:29
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Conductive Fused Porphyrin Tapes on Sensitive Substrates by a Chemical Vapor Deposition Approach
摘要： Oxidative polymerization of nickel(II) 5,15-diphenyl porphyrin and nickel(II) 5,15-bis(di-3,5-tert-butylphenyl) porphyrin by an oxidative chemical vapor deposition (oCVD) approach yields multiply fused porphyrin oligomers in thin film form. The oCVD technique enables the formation, deposition and p-doping of conjugated poly(porphyrins) coatings in a single step without the use of solvents or post-treatments. The decisive reactions and side reactions during the oCVD process are evidenced by high-resolution mass spectrometry. Due to the highly conjugated structure of the fused porphyrin tapes the thin films exhibit an electrical conductivity of 3.6×10–2 S·cm–1 and strong absorption in the visible to near-infrared spectral region. The formation of smooth conjugated poly(porphyrins) thin films, even on sensitive substrates, is demonstrated by their successful deposition and patterning on glass, silicon and printer paper. The ability to form conductive poly(porphyrins) thin films could enable the design of a new category of optoelectronic devices using the oCVD approach.
关键词： Chemical Vapor Deposition,Polymerization,Oxidative Coupling,Porphyrins,Thin Films
更新于2025-09-23 15:22:29
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Design and Operation of an Optically-Accessible Modular Reactor for Diagnostics of Thermal Thin Film Deposition Processes
摘要： The design and operation of a simple, optically-accessible modular reactor for probing thermal thin film deposition processes, such as atomic layer deposition processes (ALD) and chemical vapor deposition (CVD), is described. This reactor has a nominal footprint of 225 cm2 and a mass of approximately 6.6 kg, making it small enough to conveniently function as a modular component of an optical train. The design is simple, making fabrication straightforward and relatively inexpensive. Reactor operation is characterized using two infrared absorption measurements to determine exhaust times for tetrakis(dimethylamino)titanium and water, proto-typical ALD precursors, in a pressure and flow regime commonly used for ALD.
关键词： ALD,atomic layer deposition,in situ,reactor,diagnostics,chemical vapor deposition,CVD,optical cell
更新于2025-09-23 15:21:21
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Crosslinked Organosilicon-Acrylate Copolymer Moisture Barrier Thin Film Fabricated by Initiated Chemical Vapor Deposition (iCVD)
摘要： Crosslinked organosilicon-acrylate copolymer thin film with desired chemical composition was successfully fabricated by a simply modified initiated chemical vapor deposition (iCVD) process. Unlike the conventional iCVD copolymerization process, in our novel process, comonomers were injected together as one gas phase into the polymerization chamber from miscible liquid comonomer mixture. 2,4,6,8-tetramethyl-2,4,6,8-tetravinylcyclotetrasiloxane (V4D4) and cyclohexyl methacrylate (CHMA) were used as the comonomers and tert-butyl peroxide was used as the initiator. From Fourier transform infrared (FTIR) spectra and solvent resistance test, we clearly confirmed that the crosslinked copolymer thin film with desired chemical composition could be obtained by controlling only the mixing ratio of liquid comonomers. It is expected that crosslinkable V4D4 organosilicon moiety provides hydrophobic moisture barrier property and CHMA acrylate moiety provides mechanical flexibility and better adhesion. We observed a certain level of moisture blocking capability of the copolymer thin film, implying potential application of the crosslinked organosilicon-acrylate copolymer thin film as flexible polymer buffer layer in organic/inorganic or metal oxide hybrid moisture barrier for flexible display or electronic devices.
关键词： moisture barrier property,copolymer thin film,initiated chemical vapor deposition (iCVD),cyclohexyl methacrylate (CHMA),2,4,6,8-tetramethyl-2,4,6,8-tetravinylcyclotetrasiloxane (V4D4)
更新于2025-09-23 15:21:21
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Selective Transfer of Rotationally Commensurate MoS <sub/>2</sub> from an Epitaxially Grown van der Waals Heterostructure
摘要： Large-scale synthesis of high quality two-dimensional (2D) semiconductors are critical for their incorporation in emerging electronic and optoelectronic technologies. In particular, chemical vapor deposition (CVD) of transition metal dichalcogenides (TMDs) via van der Waals epitaxy on epitaxial graphene (EG) leads to rotationally commensurate TMDs in contrast to randomly aligned TMDs grown on amorphous oxide substrates. However, the interlayer coupling between TMDs and EG hinders the investigation and utilization of the intrinsic electronic properties of the resulting TMDs, thus requiring their isolation from the EG growth substrate. To address this issue, we report here a technique for selectively transferring monolayer molybdenum disulfide (MoS2) from CVD-grown MoS2-EG van der Waals heterojunctions using copper (Cu) adhesion layers. The choice of Cu as the adhesion layer is motivated by density functional theory calculations that predict the preferential binding of monolayer MoS2 to Cu in contrast to graphene. Atomic force microscopy and optical spectroscopy confirm the large-scale transfer of rotationally commensurate MoS2 onto SiO2/Si substrates without cracks, wrinkles, or residues. Furthermore, the transferred MoS2 shows high performance in field-effect transistors with mobilities up to 30 cm2/Vs and on/off ratios up to 106 at room temperature. This transfer technique can likely be generalized to other TMDs and related 2D materials grown on EG, thus offering a broad range of benefits in nanoelectronic, optoelectronic, and photonic applications.
关键词： molybdenum disulfide,van der Waals epitaxy,two-dimensional semiconductors,field-effect transistors,copper adhesion layers,transition metal dichalcogenides,chemical vapor deposition
更新于2025-09-23 15:21:21
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Transparent Conductive Materials (Materials, Synthesis, Characterization, Applications) || Graphene
摘要： Graphene regards to a monolayer of carbon atoms arranged in a ?at two-dimensional (2D) honeycomb lattice. It belongs to the family of carbon nanostructures that have won two Nobel Prizes and have been the focus of intensive research and development in the past few decades with well-known members including zero-dimensional (0D) fullerenes (or bucky-balls), one-dimensional (1D) carbon nanotubes, and three-dimensional (3D) graphite as illustrated in Figure 3.2.1. Since its discovery in 2004, graphene has attracted enormous interest due to its superior physical properties including high charge carrier mobility, optical transparency, ?exibility, and chemical stability. The intrinsic graphene has a zero energy bandgap, Eg, which has prevented it to be used in a similar way to the conventional semiconductors of well-de?ned Eg. However, the low charge carrier density and high charge mobility in graphene imply that graphene can be an excellent transparent conductor (TC) with both high electrical conductivity and optical transparency. Therefore, graphene makes an excellent alternative to transparent conducting oxides (TCOs) demanded for a large variety of photonic and optoelectronic applications including ?exible displays, light-emitting devices, detectors, touch screens, transistors, electromechanical resonators, ultracapacitors, and photovoltaics (PVs).
关键词： Photovoltaics,Optoelectronics,Graphene,Transparent Conductors,Chemical Vapor Deposition
更新于2025-09-23 15:21:21
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Effect of low-energy ion impact on the structure of hexagonal boron nitride films studied in surface-wave plasma
摘要： A high‐density surface‐wave plasma source is used to deposit hexagonal boron nitride (hBN) films in a gas mixture of He, H2, N2, Ar, and BF3 under a high ion flux condition using low‐energy ion irradiation. The ion energy is controlled between around zero and 100 eV by applying a negative or positive bias voltage to a substrate, while the ion flux is increased by locating a substrate upstream in the diffusive plasma. For ion energies above ～37 eV, the structure of the films depends upon ion energy more than substrate temperature, typical of subplantation processes. As a result, the structural order and crystallinity of sp2‐bonded phase in the films characterized by Fourier transform infrared spectroscopy and X‐ray diffraction are increased with decreasing ion energy, while the mass density of the films characterized by X‐ray reflectivity is retained relatively high with a slight dependence upon ion energy.
关键词： surface‐wave plasma,Fourier transform infrared spectroscopy (FTIR),chemical vapor deposition (CVD),hexagonal boron nitride (hBN),X‐ray diffraction (XRD),X‐ray reflectivity (XRR)
更新于2025-09-23 15:21:21