The integration of graphene (Gr) with nitride semiconductors is highly interesting for applications in high-power/high-frequency electronics and optoelectronics. In this work, we demonstrated the direct growth of Gr on Al0.5Ga0.5N/sapphire templates by propane (C3H8) chemical vapor deposition (CVD) at temperature of 1350°C. After optimization of the C3H8 flow rate, a uniform and conformal Gr coverage was achieved, which proved beneficial to prevent degradation of AlGaN morphology. X-ray photoemission spectroscopy (XPS) revealed Ga loss and partial oxidation of Al in the near-surface AlGaN region. Such chemical modification of a 2 nm thick AlGaN surface region was confirmed by cross-sectional scanning transmission electron microscopy (STEM) combined with electron energy loss spectroscopy (EELS), which also showed the presence of a bilayer of Gr with partial sp2/sp3 hybridization. Raman spectra indicated that the deposited Gr is nanocrystalline (with domain size 7 nm) and compressively strained. A Gr sheet resistance of 15.8 kOhm/sq was evaluated by four-point-probe measurements, consistently with the nanocrystalline nature of these films. Furthermore, nanoscale resolution current mapping by conductive atomic force microscopy (C-AFM) indicated local variations of the Gr carrier density at a mesoscopic scale, which can be ascribed to changes in the charge transfer from the substrate due to local oxidation of AlGaN or to the presence of Gr wrinkles.
Growth of mono-dispersed AlGaN nanowires of ternary wurtzite phase is reported using chemical vapour deposition technique in the vapour-liquid-solid process. The role of distribution of Au catalyst nanoparticles on the size and the shape of AlGaN nanowires are discussed. These variations in the morphology of the nanowires are understood invoking Ostwald ripening of Au catalyst nanoparticles at high temperature followed by the effect of single and multi-prong growth mechanism. Energy-filtered transmission electron microscopy is used as an evidence for the presence of Al in the as-prepared sampl…
Presently, the piezoelectric materials are finding tremendous applications in the micro-mechanical actuators, sensors and self-powered devices. In this context, the studies pertaining to piezoelectric properties of materials in the different size ranges are very important for the scientific community. The III-nitrides are exceptionally important, not only for optoelectronic but also for their piezoelectric applications. In the present study, we synthesized AlGaN via self catalytic vapor-solid mechanism by atmospheric pressure chemical vapor deposition technique on AlN base layer over intrinsic…
The polarized Raman spectroscopy is capable of giving confirmation regarding the crystalline phase as well as the crystallographic orientation of the sample. In this context, apart from crystallographic x-ray and electron diffraction tools, polarized Raman spectroscopy and corresponding spectral imaging can be a promising crystallographic tool for determining both crystalline phase and orientation. Sub-micron sized hexagonal AlGaN crystallites are grown by a simple atmospheric pressure chemical vapor deposition technique using the self catalytic vapor-solid process under N-rich condition. The …
The effect of Fe and Ni catalysts on the synthesis of carbon nanotubes (CNTs) using atmospheric pressure chemical vapor deposition (APCVD) was investigated. Field emission scanning electron microscopy (FESEM) analysis suggests that the samples grow through a tip growth mechanism. High-resolution transmission electron microscopy (HRTEM) measurements show multiwalled carbon nanotubes (MWCNTs) with bamboo structure for Ni catalyst while iron filled straight tubes were obtained with the Fe catalyst. The X-ray diffraction (XRD) pattern indicates that nanotubes are graphitic in nature and there is n…
Single-walled carbon nanotube (SWCNT) films are promising materials for transparent conductive films (TCFs) with potential applications in flexible displays, touch screens, solar cells and solid-state lighting1,2. However, further reductions in resistivity and in cost of SWCNT films are necessary for high quality TCF products3. Here, we report an improved floating catalyst chemical vapor deposition method to directly and continuously produce ultrathin and freestanding SWCNT films at the hundred meter-scale. Both carbon conversion efficiency and SWCNT TCF yield are increased by three orders of …
We studied the persistent photoconductivity (PPC) effect in AlGaN/AlN/GaN heterostructures with two different Al-compositions (x=0.15 and x=0.25). The two-dimensional electron gas formed at the AlN/GaN heterointerface was characterized by Shubnikov-de Haas and Hall measurements. Using optical illumination, we were able to increase the carrier density of the Al0.15Ga0.85N/AlN/GaN sample from 1.6x10^{12} cm^{-2} to 5.9x1012 cm^{-2}, while the electron mobility was enhanced from 9540 cm2/Vs to 21400 cm2/Vs at T = 1.6 K. The persistent photocurrent in both samples exhibited a strong dependence on …
The first vapor phase self-assembled heterocatalytic structure on surface is build from cobalt 5,10,15,20 tetrakis (4-aminophenyl)-21H, 23H-porphine through imide bonds. This heterogeneous catalyst possesses essential thermal and temporal stability along with catalytic activity in oxidation processes of organic substrates.
This investigation deals with the effect of growth temperature on the growth behavior of Fe filled multiwalled carbon nanotubes (MWCNTs). Carbon nanotube (CNT) synthesis was carried out in a thermal chemical vapor deposition (CVD) reactor in the temperature range 650 to 950 1C using propane as the carbon source, Fe as the catalyst material, and Si as the catalyst support. Atomic force microscopy (AFM) analysis of the catalyst exhibits that at elevated temperature clusters of catalyst coalesce and form macroscopic islands. Field emission scanning electron microscopy (FESEM) results show that wi…
The exploration of new catalysts for the vapor-liquid-solid (VLS) synthesis of one-dimensional (1-D) materials promises to yield new morphologies and functionality. Here, we show, for the model ZnO system, that this possible using a semiconductor (Ge) catalyst. In particular, two unusual morphologies are described: twisted nanowires and twisted nanotubes, in addition to the usual straight nanowires. The twisted nanotubes show large hollow cores and surprisingly high twisting rates (up to 9o/μm), which cannot be easily explained through the Eshelby twist model. A combination of ex situ and in s…
In this study, the synthesis of multi-walled carbon nanotubes (MWCNTs) was carried out by chemical vapor deposition (CVD) using propane as the carbon source and Si as the catalyst support. The effect of CVD process variables such as temperature, choice of catalyst, etc on the growth behavior of nanotubes has been examined to understand the catalytic growth of CNTs. The transition metal catalysts, Fe and Ni, were used in both elemental metal form and in a metal complex form. In the case of elemental metal catalysts, the respective metals were deposited over the Si substrate using thermal evapor…
We report on a GaN/AlGaN quantum cascade detector operating in the terahertz spectral range. The device was grown by metal organic chemical vapor deposition on a c-sapphire substrate and relies on polar GaN/AlGaN step quantum wells. The active region thickness is in micrometer range. The structural, electrical and optical investigations attest of high structural quality of the synthetized nitride material. The detector exhibits a peak photocurrent at 5.7 THz (23.6 meV) with a responsivity of 0.1 mA/W at 10 K under surface normal irradiation through a 10 um period grating. The photocurrent pers…
Process of vapor pyrolytic deposition of carbon on nickel and cobalt-containing ordered mesoporous MCM-41 matrices at decomposition of acetylene have been investigated. Formation of nanotubes, nanowires and amorphous carbon particles depending pyrolysis conditions is observed.
The surface reconstruction of the Fe catalyst films due to high temperature processing in hydrogen prior to nanotube nucleation and its effect on the growth morphologies of partially filled carbon nanotubes (CNTs) synthesized using atmospheric pressure chemical vapor deposition (APCVD) of propane was investigated. Results show that pre-heating of the catalyst film deeply influences the particle size distribution, which governs the growth morphologies of the corresponding CNTs. The distribution of the catalyst particles over the Si substrate was analyzed before and after the heat treatment by a…
Uniform and large area synthesis of bulk insulating ultrathin films is an important subject toward applications of a surface of three dimensional topological insulators (3D-TIs) in various electronic devices. Here we report epitaxial growth of bulk insulating three dimensional topological insulator (3D-TI) Bi2-xSbxTe3-ySey (BSTS) ultrathin films, ranging from a few quintuple to several hundreds of layaers, on mica in a large-area (1 cm2) via catalyst free physical vapor deposition. These films can nondestructively be exfoliated using deionized water and transferred to various kinds of substrat…
To grow precisely aligned graphene on h-BN without metal catalyst is extremely important, which allows for intriguing physical properties and devices of graphene/h-BN hetero-structure to be studied in a controllable manner. In this report, such hetero-structures were fabricated and investigated by atomic resolution scanning probe microscopy. Moirre patterns are observed and the sensitivity of moirre interferometry proves that the graphene grains can align precisely with the underlying h-BN lattice within an error of less than 0.05 degree. The occurrence of moirre pattern clearly indicates that…
We present a transfer-free preparation method for graphene on hexagonal boron nitride (h-BN) crystals by chemical vapor deposition of graphene via a catalytic proximity effect, i.e. activated by a Cu catalyst close-by . We demonstrate the full coverage by monolayer graphene of half-millimeter-sized hexagonal boron nitride crystals exfoliated on a copper foil prior to growth. We demonstrate that the proximity of the copper catalyst ensures high yield with the growth rate estimated between of 2μm/min to 5μm/min . Optical and electron microscopies together with confocal micro-Raman mapping confir…
A continuous CO2 vapor-fed electrochemical cell prototype that performs CO2R with high faradaic efficiency for desired carbon products for up to 72 hours of operation is presented. The cell design facilitates a flow through configuration, capitalizing on gas diffusion electrode (GDE) and membrane electrode architecture (MEA) without requiring a catholyte. We demonstrate stable performance and design adaptability by incorporating various CO2R catalysts and membranes into the cell, investigating lifetime performance and selectivity under established experimental conditions. With an Ag foil and P…
The nucleation of carbon caps on small nickel clusters is studied using a tight binding model coupled to grand canonical Monte Carlo simulations. It takes place in a well defined carbon chemical potential range, when a critical concentration of surface carbon atoms is reached. The solubility of carbon in the outermost Ni layers, that depends on the initial, crystalline or disordered, state of the catalyst and on the thermodynamic conditions, is therefore a key quantity to control the nucleation.
We report a process to fabricate carbon nanotubes (CNT) by chemical vapor deposition at predetermined location. This process was enabled by patterning catalyst nanoparticles directly on silicon substrates with nanometer-scale precision using Dip Pen Nanolithography(R) (DPN(R)). A multi-pen writing method was employed to increase the patterning rate. The development of new molecular inks for the deposition of the precursor catalyst resulted in a high yield of isolated carbon nanotubes, ideal for subsequent device fabrication. Here, we demonstrate the advantages of the new method for producing h…
Structures of iron and cobalt bimetallic clusters for optimized chemical vapor deposition growth of single-walled carbon nanotubes
The University of Tokyo（东京大学）；Center for Multidimensional Carbon Materials (CMCM), Institute for Basic Science (IBS)（基础科学研究院多维碳材料中心）；Dalian University of Technology（大连理工大学）；University of Antwerp（安特卫普大学）
The molecular dynamics method, based on an empirical potential energy surface, was used to study the effect of catalyst particle size on the growth mechanism and structure of single-walled carbon nanotubes (SWNTs). The temperature for nanotube nucleation (800-1100 K), which occurs on the surface of the cluster, is similar to that used in catalyst chemical vapor deposition experiments, and the growth mechanism, which is described within the vapor-liquid-solid model, is the same for all cluster sizes studied here (iron clusters containing between 10 and 200 atoms were simulated). Large catalyst …
This report introduces the electromagnetic absorption of the catalyst as a novel knob in optimizing chemical vapor deposition of graphene. A chromium film initially deposited at one side of a catalyst copper foil absorbs radiative thermal energy several times higher than the plain copper foil and migrates to the other side of the foil in the form of microscale grains. The process involves local melting of the copper which together with the increased operation temperature, improves the crystalline quality of growing graphene. Local melting of copper replaces the otherwise-necessary annealing pr…
In most envisioned applications, full utilization of a graphene-carbon nanotube (CNT) construct requires maintaining the integrity of the graphene layer during the CNT growth step. In this work, we exhibit an approach towards controlled CNT growth atop graphene substrates where the reaction equilibrium between source hydrocarbon decomposition and carbon saturation into and precipitation from the catalyst nanoparticles shifts towards CNT growth rather than graphene consumption. By utilizing C2H4 feedstock, we demonstrate that the low temperature growth permissible with this gas suppresses undes…
GaN/SiO2 core/shell nanowires are grown by cobalt phthalocyanine catalyst assisted vapor-liquid-solid route, in which Si wafer coated with a mixture of gallium and indium is used as the source for Ga and Si and ammonia is used as the precursor for nitrogen and hydrogen. Gallium in the presence of indium and hydrogen, which results from the dissociation of ammonia, forms Si-Ga-In alloy at the growth temperature around 910 degree Celsius. This alloy acts as the source of Si, Ga and In. A detailed study using a variety of characterization tools reveals that these wires, which are several tens of …
The growth of graphene on copper by atmospheric pressure chemical vapor deposition in a system free of pumping equipment is investigated. The emphasis is put on the necessity of hydrogen presence during graphene synthesis and cooling. In the absence of hydrogen during the growth step or cooling at slow rate, weak carbon coverage, consisting mostly of oxidized and amorphous carbon, is obtained on the copper catalyst. The oxidation originates from the inevitable occurrence of residual oxidizing impurities in the reactor's atmosphere. Graphene with appreciable coverage can be grown within the vac…
Synthesis of monolayer MoS2 is essential for fulfilling the potential of MoS2 in catalysis, optoelectronics and valleytronics, etc. Herein, we report for the first time the scalable growth of high quality, domain size tunable (edge length from ~ 200 nm to 50 μm), strictly monolayer MoS2 on commercially available Au foils, via a low pressure chemical vapor deposition method. The nanosized triangular MoS2 flakes on Au foils was proved to be an excellent electrocatalyst for hydrogen evolution reaction (HER), featured by a rather low Tafel slope (61 mV/decade) and a supreme exchange current densit…
Nanobelts, nanoribbons and other quasi-one-dimensional nanostructures formed from layered, so-called, van der Waals semiconductors have garnered much attention due to their high-performance, tunable optoelectronic properties. For layered alloys made from the gallium monochalcogenides GaS, GaSe, and GaTe, near-continuous tuning of the energy bandgap across the full composition range has been achieved in GaSe1-xSx and GaSe1-xTex alloys. Gold-catalyzed vapor-liquid-solid (VLS) growth of these alloys yields predominantly nanobelts, nanoribbons and other nanostructures for which the fast crystal gr…
We report the growth of single-crystalline Bi2Se3 nanoribbons with lengths up to several millimeters via a catalyst-free physical vapor deposition method. Scanning transmission electron microscopy analysis reveals that the nanoribbons grow along the (1120) direction. We obtain a detailed characterization of the electronic structure of the Bi2Se3 nanoribbons from measurements of Shubnikov-de Haas (SdH) quantum oscillations. Angular dependent magneto-transport measurements reveal a dominant two-dimensional contribution originating from surface states and weak contribution from the bulk states. T…
Growth of GaN nanowires are carried out via metal initiated vapor-liquid-solid mechanism, with Au as the catalyst. In chemical vapour deposition technique, GaN nanowires are usually grown at high temperatures in the range of 900-1100 ^oC because of low vapor pressure of Ga below 900 ^oC. In the present study, we have grown the GaN nanowires at a temperature, as low as 700 ^oC. Role of indium in the reduction of growth temperature is discussed in the ambit of Raoult's law. Indium is used to increase the vapor pressure of the Ga sufficiently to evaporate even at low temperature initiating the gr…
Ultrathin InAs nanowires (NW) with one-dimensional (1D) sub-band structure are promising materials for advanced quantum-electronic devices, where dimensions in the sub-30 nm diameter limit together with post-CMOS integration scenarios on Si are much desired. Here, we demonstrate two site-selective synthesis methods that achieve epitaxial, high aspect ratio InAs NWs on Si with ultrathin diameters below 20 nm. The first approach exploits direct vapor-solid growth to tune the NW diameter by interwire spacing, mask opening size and growth time. The second scheme explores a unique reverse-reaction …
The direct growth of high-quality, large single-crystalline domains of graphene on a dielectric substrate is of vital importance for applications in electronics and optoelectronics. Traditionally, graphene domains grown on dielectrics are typically only ~1 nm with a growth rate of ~1 nm/min or less, the main reason is the lack of a catalyst. Here we show that silane, serving as a gaseous catalyst, is able to boost the graphene growth rate to ~1 um/min, thereby promoting graphene domains up to 20 um in size to be synthesized via chemical vapor deposition on hexagonal boron nitride. Hall measure…
The synthesis of Ni filled multiwalled carbon nanotubes was performed by atmospheric pressure chemical vapor deposition with propane on Si at 850 C using a simple mixture of Ni(salen), and a conventional photoresist. Analysis of the carbon nanotubes using scanning electron microscopy together with high resolution transmission electron microscopy show that the nanotubes have grown by a tip growth mechanism and exhibit a multi walled structure with partial Ni filling. The high quality of the Ni filled nanotubes is evidenced by Raman spectroscopy. The magnetic properties of Ni filled nanotubes we…
Monolayers of transition metal dichalcogenides (TMDCs) are atomically thin direct-gap semiconductors with potential applications in nanoelectronics, optoelectronics, and electrochemical sensing. Recent theoretical and experimental efforts suggest that they are ideal systems for exploiting the valley degrees of freedom of Bloch electrons. For example, Dirac valley polarization has been demonstrated in mechanically exfoliated monolayer MoS2 samples by polarization-resolved photoluminescence, although polarization has rarely been seen at room temperature. Here we report a new method for synthesiz…
Nominally undoped silicon nanowires (NW) were grown by catalytic chemical vapor deposition. The growth process was optimized to control the NWs diameters by using different Au catalyst thicknesses on amorphous SiO2, Si3N4, or crystalline-Si substrates. For SiO2 substrates an Ar plasma treatment was used to homogenize the catalyst coalescence, and thus the NWs diameter. Furthermore, planar field effect transistors (FETs) were fabricated by implementing 10 to 30 nm thin nominally undoped Si-NWs as the active region. Various silicides were investigated as Schottky-barrier source and drain contact…
Careful research on different materials reveals that the material properties are mostly affected by the size of it. Material size down to nanometer scale exhibits some remarkable properties, resulting in unique physical and chemical characteristics. In todays world of nanotechnology, carbon nanotubes (CNTs) have become a high priority material because of their exclusive structure, novel characteristics with enormous potential in many technological applications. Till date chemical vapor deposition (CVD) is the preferred and widely used technique among different CNT growth methods, because of it…
Graphene and carbon nanotubes (CNTs) share the same atomic structure of hexagonal carbon lattice. Yet, their synthesis differs in many aspects, including the shape and size of the catalyst. Here, we demonstrate a floating-catalyst chemical vapor deposition (FCCVD) technique for substrate-free, single-step growth of CNT-graphene heterostructures (CNT-G-H) using ethylene as a carbon source. The formation of CNT-G-H is directly evidenced by lattice-resolved (scanning) transmission electron microscopy (STEM) and electron diffraction experiments, corroborated by atomic force microscopy (AFM). Our e…
Local effects of multiple electrostatic gates placed beneath carbon nanotubes grown by chemical vapor deposition (CVD) are reported. Single-walled carbon nanotubes were grown by CVD from Fe catalyst islands across thin Mo "finger gates" (150 x 10nm). Prior to tube growth, several finger gates were patterned lithogrpahically and subsequently coated with a patterned high-k dielectric using low-temperature atomic layer deposition. Transport measurements demonstrate that local finger gates have a distinct effect from a global backgate.
A significant advance toward achieving practical applications of graphene as a two-dimensional material in nanoelectronics would be provided by successful synthesis of both n-type and p-type doped graphene. However reliable doping and a thorough understanding of carrier transport in the presence of charged impurities governed by ionized donors or acceptors in the graphene lattice are still lacking. Here we report experimental realization of few-layer nitrogen-doped (N-doped) graphene sheets by chemical vapor deposition of organic molecule 1, 3, 5-triazine on Cu metal catalyst. By reducing the …
Si- and C-Induced Modifications in Vapor-Solid-Grown InGaAs Nanowires: From Crystal Structure to Carrier Dynamics
Walter Schottky Institute, TUM School of Natural Sciences, Technical University of Munich（沃尔特·肖特基研究所，慕尼黑工业大学自然科学学院）；Institute of Physics and Astronomy, Technical University Berlin（柏林工业大学物理与天文研究所）
We report catalyst-free direct synthesis of vertical graphene nanosheets (VGNs) on SiO2/Si and quartz substrates using microwave electron cyclotron resonance - plasma enhanced chemical vapor deposition. The evolution of VGNs is studied systematically at different growth stages. Raman analysis as a function of growth time reveals that two different disorder-induced competing mechanisms contributing to the defect band intensity. The VGNs grown on SiO2/Si substrates predominantly consists of both vacancy-like and hopping defects. On the other hand, the VGNs grown on quartz substrates contain main…
The integration of two-dimensional (2D) materials with functional non-2D materials such as metal oxides is of key importance for many applications, but underlying mechanisms for such non-2D/2D interfacing remain largely elusive at the atomic scale. To address this, we here investigate the nucleation stage in atomic layer deposition (ALD) of the important metal oxide HfO2 on chemical vapor deposited graphene using atomically resolved and element specific scanning transmission electron microscopy (STEM). To avoid any deleterious influence of polymer residues from pre-ALD graphene transfers we em…
Vertically-aligned carbon nanotube (CNT) "forest" microstructures fabricated by chemical vapor deposition (CVD) using patterned catalyst films typically have a low CNT density per unit area. As a result, CNT forests have poor bulk properties and are too fragile for integration with microfabrication processing. We introduce a new self-directed capillary densification method where a liquid is controllably condensed onto and evaporated from CNT forests. Compared to prior approaches, where the substrate with CNTs is immersed in a liquid, our condensation approach gives significantly more uniform s…
High-quality nitrogen-doped graphene on nickel is prepared by exploiting both the catalytic properties of nickel and the solubility of nitrogen atoms into its bulk. Following the standard chemical vapor deposition procedure, a previously nitrogen-doped nickel substrate is exposed to carbon-containing precursors so that nitrogen atoms, segregating to the surface, remain trapped in the growing graphene network. Morphological and chemical characterization by scanning tunneling microscopy and X-ray photoelectron spectroscopy demonstrates that the process yields a flat, wide, continuous nitrogen-do…
We present electronic transport measurements of GaAs nanowires grown by catalyst-free metal-organic chemical vapor deposition. Despite the nanowires being doped with a relatively high concentration of substitutional impurities, we find them inordinately resistive. By measuring sufficiently high aspect-ratio nanowires individually in situ, we decouple the role of the contacts and show that this semi-insulating electrical behavior is the result of trap-mediated carrier transport. We observe Poole-Frenkel transport that crosses over to phonon-assisted tunneling at higher fields, with a tunneling …
Single electron transistors (SETs) made from single wall carbon nanotubes (SWCNTs) are promising for quantum electronic devices operating with ultra-low power consumption and allow fundamental studies of electron transport. We report on SETs made by registered in-plane growth utilizing tailored nanoscale catalyst patterns and chemical vapor deposition. Metallic SWCNTs have been removed by an electrical burn-in technique and the common gate hysteresis was removed using PMMA and baking, leading to field effect transistors with large on/off ratios up to 10^5. Further segmentation into 200 nm shor…
We analyze the optical, chemical, and electrical properties of chemical vapor deposition (CVD) grown hexagonal boron nitride (h-BN) using the precursor ammonia-borane ($H_3N-BH_3$) as a function of $Ar/H_2$ background pressure ($P_{TOT}$). Films grown at $P_{TOT}$ less than 2.0 Torr are uniform in thickness, highly crystalline, and consist solely of h-BN. At larger $P_{TOT}$, with constant precursor flow, the growth rate increases, but the resulting h-BN is more amorphous, disordered, and $sp^3$ bonded. We attribute these changes in h-BN grown at high pressure to incomplete thermolysis of the …
Boosting the sensitivity of solid-state gas sensors by incorporating nanostructured materials as the active sensing element can be complicated by interfacial effects. Interfaces at nanoparticles, grains, or contacts may result in non-linear current-voltage response, high electrical resistance, and ultimately, electric noise that limits the sensor read-out. Here we report the possibility to prepare nominally one atom thin, electrically continuous metals, by straightforward physical vapor deposition on the carbon zero-layer grown epitaxially on silicon carbide. With platinum as the metal, its el…
Producing and manipulating graphene on fab-compatible scale, while maintaining its remarkable carrier mobility, is key to finalize its technological application. We show that a large-scale approach (chemical vapor deposition on Cu followed by polymer-mediated semi-dry transfer) yields single-layer graphene crystals fully comparable, in terms of electronic transport, to micro-mechanically exfoliated flakes. hBN is used to encapsulate the graphene crystals $-$ without taking part to their detachment from the growth catalyst $-$ and study their intrinsic properties in field-effect devices. At roo…
Demonstration of Si-doped Al-rich thin regrown Al(Ga)N films on AlN on sapphire templates with $\gt10^{15}/cm^3$ free carrier concentration using close-coupled showerhead MOCVD reactor
Fibres of ultralong and aligned carbon nanotubes (CNT) have axial properties above reference engineering materials, proving to be exceptional materials for application in structural composites, energy storage and other devices. For CNT fibres produced by direct spinning from floating catalyst chemical vapor deposition (FCCVD), a scaled-up method, the challenge is to simultaneously achieve high process conversion and high-performance properties. This work presents a parametric study of the CNT fibre spinning process by establishing the relation between synthesis conditions, molecular compositio…
