Showing papers on "Field electron emission published in 2006"
TL;DR: Current-voltage measurements of metal-molecule-metal junctions formed from pi-conjugated thiols exhibit an inflection point on a plot of ln(I/V(2)) vs 1/V, consistent with a change in transport mechanism from direct tunneling to field emission.
Abstract: Current-voltage measurements of metal-molecule-metal junctions formed from pi-conjugated thiols exhibit an inflection point on a plot of ln(I/V(2)) vs 1/V, consistent with a change in transport mechanism from direct tunneling to field emission. The transition voltage was found to scale linearly with the offset in energy between the Au Fermi level and the highest occupied molecular orbital as determined by ultraviolet photoelectron spectroscopy. Asymmetric voltage drops at the two metal-molecule interfaces cause the transition voltage to be dependent on bias polarity.
529 citations
TL;DR: This pulsed electron emitter, triggered by a femtosecond oscillator, could serve as an efficient source for time-resolved electron interferometry, for time -resolved nanometric imaging and for synchrotrons.
Abstract: We report a source of free electron pulses based on a field emission tip irradiated by a low-power femtosecond laser. The electron pulses are shorter than 70 fs and originate from a tip with an emission area diameter down to 2 nm. Depending on the operating regime we observe either photofield emission or optical field emission with up to 200 electrons per pulse at a repetition rate of 1 GHz. This pulsed electron emitter, triggered by a femtosecond oscillator, could serve as an efficient source for time-resolved electron interferometry, for time-resolved nanometric imaging and for synchrotrons.
412 citations
TL;DR: In this paper, the fabrication methods as well as optical and electrical characteristics of silicon carbide nanocrystals, nanowires, nanotubes, and nanosized films are reviewed.
319 citations
TL;DR: In this paper, a template-free thermal evaporation method was proposed for the growth of aligned ultralong ZnO nanobelts, yielding an average length of 3.3 mm and widths up to 6 lm.
Abstract: One-dimensional (1D) semiconducting nanoscale materials have attracted considerable attention because of their importance in understanding the fundamental properties of low dimensionality in materials as well as in nanodevice applications. Many methods, including vapor–liquid–solid (VLS), vapor–solid (VS), and solution-based, have been developed to synthesize 1D semiconducting nanoscale materials such as nanoscale wires, belts, rods, tubes, and needles. Usually, these methods require templates/catalysts and tedious operational procedures. Here, we demonstrate a new strategy for the growth of aligned ultralong ZnO nanobelts, yielding an average length of 3.3 mm and widths up to 6 lm, on metal substrates in a one-step process via molten-salt-assisted template-free thermal evaporation. These ultralong nanobelts show enhanced field emission. The electric field for an emission current density of 1 mA cm is 2.9 V lm, the lowest value ever reported for pure 1D ZnO nanostructures grown on flat surfaces, corresponding to a field-enhancement factor of about 1.4 × 10. This approach is simple, efficient, and inexpensive, which significantly facilitates device fabrication. By combining a general molten-salt process, which is usually used to prepare micrometer-scale ceramic powders (although it was also used for the synthesis of ZnO nanorods in a thermal evaporation process), we have designed a new approach, molten-salt-assisted thermal evaporation, and we demonstrate that this approach can produce aligned ultralong ZnO nanobelts over a large area. The key point of this new approach is the evaporation of Zn metal powder in a liquid environment of molten sodium chloride (NaCl) salt. A side-view camera photograph of the as-grown ZnO nanobelts on the Au substrate is shown in Figure 1a, indicating that the nanobelts can grow to several millimeters in length. Figure 1b shows a top-view optical microscopy photograph, demonstrating that the ZnO nanobelts are also transparent under an optical microscope. A higher-magnification optical microscopy image of the side-view is shown in Figure 1c, indicating nominal, though imperfect, alignment. Figure 2 shows field-emission scanning electron microscopy (SEM) images of the as-grown ZnO nanobelts under different magnifications. The low-magnification image shown in FigC O M M U N IC A IO N
280 citations
TL;DR: Most SWNTs imaged on millisecond time scales show steady emission, but a few fluctuate and suffer a reduction of intensity, and quantum efficiency is dramatically higher than that in previous reports.
Abstract: Single-walled carbon nanotubes (SWNTs) suspended in air over trenches are imaged using their intrinsic near-infrared (NIR) photoluminescence (1.0−1.6 μm). Far-field emission from extended suspended lengths (∼50 μm) is both spatially and spectrally resolved, and SWNTs are classified based on the spatial uniformity of their emission intensity and emission wavelength. In a few cases, emission assigned to different (n,m) species is observed along the same suspended segment. Most SWNTs imaged on millisecond time scales show steady emission, but a few fluctuate and suffer a reduction of intensity. The quantum efficiency is dramatically higher than that in previous reports and is estimated at 7%, a value that is precise but subject to corrections because of assumptions about absorption and coherence.
216 citations
TL;DR: In this article, the zinc oxide nanotube arrays were prepared by hydrothermal reaction in ammonia and zinc chloride solutions, and the field emission properties were tested and the turn-on field was extrapolated to be about 7.0V∕μm at a current density of 0.1μA∕cm2.
Abstract: Zinc oxide nanotube arrays were prepared by hydrothermal reaction in ammonia and zinc chloride solutions, and the field emission properties were tested. The turn-on field of the field emission was extrapolated to be about 7.0V∕μm at a current density of 0.1μA∕cm2. Meanwhile, the emission current densities reached 1mA∕cm2 at a bias field of 17.8V∕μm. The field enhancement factor β was estimated to be 910. The field emission of the zinc oxide nanotubes showed good stability. The variation of emission current density was less than 10% during a 24h test under a field of 15V∕μm.
209 citations
TL;DR: The electrical response of the ZnO nanonail arrays to different gases (CO, NO2, and H2S) indicated that there could be possible application as gas sensors for this material.
Abstract: One-dimensional ZnO nanostructure arrays such as nanowires, nanonails, and nanotrees, have been synthesized by oxygen assisted thermal evaporation of metallic zinc on a quartz substrate over a large area. Morphological evolution of ZnO nanostructures at different time scales and different positions of the substrates have been studied by electron microscopy. A self-catalyzed vapor-liquid-solid (VLS) process is believed to be responsible for the nucleation and subsequently a vapor-solid process is operative for further longitudinal growth. The photoluminescence spectrum showed a weak UV and a broad green emission peak at 3.25 and 2.49 eV, respectively. The latter was attributed to the presence of zinc interstitial defects. Electrical resistivity as a function of temperature showed activated mechanisms to be present. The electrical response of the ZnO nanonail arrays to different gases (CO, NO 2 , and H 2 S) indicated that there could be possible application as gas sensors for this material.
191 citations
TL;DR: In this paper, the growth of well-aligned AlN nanorods with hairy surfaces by a vapor-solid (VS) process was reported, which not only provide a new hierarchical nanostructure, but also serve as a promising candidate for field-emission (FE) applications of AlN materials.
Abstract: Aluminum nitride, an important member of the group III nitrides with the highest bandgap of about 6.2 eV, has excellent thermal conductivity, good electrical resistance, low dielectric loss, high piezoelectric response, and ideal thermal expansion, matching that of silicon. The interest in field-emission (FE) applications of AlN materials has grown because they exhibit a negative electron affinity. Exhibiting a negative electron affinity means that electrons excited into the conduction band can be freely emitted into vacuum. In addition, high-current emission at a relatively low field is most attractive for FE applications. As a result, significant effort is being devoted to reducing the tip size and increasing the density of the emitting sites by using hierarchical nanostructures. Therefore, the synthesis of AlN nanostructures, such as nanowires, nanotubes, nanocones, nanotips, hierarchical comb-like structures, and nanobelts, with controlled high-aspect-ratio shapes and sizes is an important topic worthy of exploration. The promise that one-dimensional (1D) nanostructures may dramatically improve the desired properties for many applications has stimulated great enthusiasm. For example, FE properties of various AlN nanostructures have been investigated. The turn-on fields of various 1D aluminum nitride nanostructures have been measured, such as nanowires (8.8 Vlm), nanocones (12 Vlm), nanotips (3.1–4.7 V lm), and hierarchical comb-like structures (2.45–3.76 Vlm). On the other hand, reports on the luminescence properties of AlN nanostructures are scarce. The AlN nanocones have been observed to have an emission band centered at 481 nm, referred to as a deeplevel or trap-level state. In the present study, we report the growth of well-aligned AlN nanorods with hairy surfaces by a vapor–solid (VS) process. The well-aligned AlN nanorods with hairy surfaces reported here not only provide a new hierarchical nanostructure, but also serve as a promising candidate for FE emitters because of their low electron affinity and the geometry of the multiple-nanotip surfaces. Compared with previous reports on hierarchal growth of AlN nanostructures, in this communication we report a higher density of smaller nanotips (∼ 3–15 nm) that were radially grown on the surfaces of AlN nanorods. Each nanotip may serve as an ultrasmall emitter. In addition, growing well-aligned AlN nanorods on Si substrates is amenable to current technology for the fabrication of Sibased microelectronics devices. The subsequent characterization of their cathodoluminescence (CL) reveals that these hierarchical AlN nanostructures possess an intense emission peak, further suggesting potential applications in optoelectronic nanodevices. The structure of the as-grown products has been determined by X-ray diffraction (XRD). As shown in Figure 1, all of the diffraction peaks in the XRD pattern can be identified; they correspond to a hexagonal wurtzite-structured AlN crys-
181 citations
TL;DR: In this paper, a CNT-based field emission x-ray source with high spatial and temporal resolution has been proposed, where modified asymmetric Einzel lenses for electron focusing and an elliptical shaped CNT cathode patterned by photolithography were obtained.
Abstract: Microcomputed tomography is now widely used for in vivo small animal imaging for cancer studies. Achieving high imaging quality of live objects requires the x-ray source to have both high spatial and temporal resolutions. Preliminary studies have shown that carbon nanotube (CNT) based field emission x-ray source has significant intrinsic advantages over the conventional thermionic x-ray tube including better temporal resolution and programmability. Here we report the design and characterization of a CNT based field emission x-ray source that also affords a high spatial resolution. The device uses modified asymmetric Einzel lenses for electron focusing and an elliptical shaped CNT cathode patterned by photolithography. Stable and small isotropic x-ray focal spot sizes were obtained.
179 citations
TL;DR: In this article, postthermal annealing in different ambience was conducted to optimize the field emission behavior of the ZnO nanorods, and the results showed that the field emissions of the nanorod are considerably improved after annaling in oxygen and getting worse when annealed in air or ammonia.
Abstract: To optimize the field emission behavior of the ZnO nanorods, postthermal annealing in different ambience was conducted. The field emission properties of the ZnO nanorods are considerably improved after annealing in oxygen and getting worse when annealing in air or ammonia. Photoluminescence and Raman spectroscopy were employed to elucidate the reason for such a significant improvement of the field emission when annealing in oxygen. Those detailed analyses suggested that oxygen annealing can reduce the oxygen vacancy concentration, improve the crystal quality, lower the work function, and increase the conductivity of the ZnO nanorods. Our work is important for applications of ZnO nanorods as a promising candidate in flat panel displays and high brightness electron sources.
176 citations
TL;DR: In this article, the authors reviewed the history of electron emission from a standpoint of the work function that determines the electron emission capability and of applications in the fields of scientific instruments and displays.
Abstract: The history of electron emission is reviewed from a standpoint of the work function that determines the electron emission capability and of applications in the fields of scientific instruments and displays. For years, in thermionic emission, a great deal of effort has been devoted to the search for low work function materials with high melting temperature, while reduction of the local change in time of the work function rather than the work function itself has been the main issue of field emission investigations. High brightness and long life are the central targets of emission material investigations for scientific instrument applications, while high current density and low power consumption are the guiding principles for display applications.In most of the present day industries, thermionic emission materials are exclusively used in such fields requiring high current and high reliability as cathode ray tubes, transmission and receiving tubes, x-ray sources and various electron beam machines. Field electron emission sources, however, since applied to high resolution electron microscopes in the 1970s have recently become dominant in research and development in the fields of scientific instruments as well as in the fields of various electron tubes and beam machines.The main issue in this report is to analyse the work function on the atomic scale and thereby to understand the fundamental physics behind the work function, the change in time of the local work function leading to field emission current fluctuation and the relationship between microscopic (on atomic scale) and macroscopic work functions.Our attempt is presented here, where the work function on the atomic scale is measured by utilizing a scanning tunnelling microscopy technique, and it is made clear how far the local work function extends its influence over neighbouring sites. As a result, a simple relationship is established between microscopic and macroscopic work functions.
TL;DR: Single-crystalline bamboo-like beta-SiC nanowires with hexagonal cross-sections were synthesized by thermal evaporation of mixed SiO+C+GaN powders in an Ar atmosphere to explore the growth and field-emission properties of the peculiar nanostructures.
Abstract: Single-crystalline bamboo-like β-SiC nanowires with hexagonal cross-sections were synthesized by thermal evaporation of mixed SiO+C+GaN powders in an Ar atmosphere. The as-synthesized nanowires were studied by x-ray diffraction, scanning electron microscopy and transmission electron microscopy. Studies found that the as-synthesized SiC nanowires are composed of hexagonal stems decorated with larger diameter knots along their whole length with the growth direction. The growth of bamboo-like SiC nanowires is governed by the vapour-liquid-solid mechanism. Field-emission properties of the peculiar nanostructures were also explored, showing a turn-on field of about 10.1 V μm-1.
TL;DR: The studies suggest that the growth of a multipod structure is governed by the screw dislocation propagation while the vapor-liquid-solid (VLS) mechanism is responsible for the formation of submicron wires and spheres.
Abstract: A simple method of vapor deposition for the shape selective synthesis of ZnO structures, namely, multipods, submicron wires, and spheres, has been successfully demonstrated. A plausible growth mechanism based on the studies of scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray diffraction (XRD), and X-ray photoelectron spectroscopy (XPS) is proposed. Our studies suggest that the growth of a multipod structure is governed by the screw dislocation propagation while the vapor-liquid-solid (VLS) mechanism is responsible for the formation of submicron wires and spheres. Moreover, the flow rate of the carrier gas plays a crucial role in governing the morphology. Further, these structures exhibit an enhanced field emission behavior. The nonlinearity in the Fowler-Nordheim (F-N) plot, a characteristic feature of electron emission from semiconductors, is explained by considering the contributions from both the conduction and the valence bands of ZnO.
TL;DR: In this paper, the field electron emission properties of boron and nitrogen doped carbon nanotubes (CNTs) grown in situ on tungsten (W) tips and silicon substrates have been studied.
Journal Article•
TL;DR: In this article, a selfconsistent analysis demonstrates that elastic electron scattering on collisions with atoms and ions plays a key role in formation of the electron energy distribution function and plasma-wall interaction.
Abstract: Recent analytical studies and particle-in-cell simulations suggested that the electron velocity distribution function in a Hall thruster plasma is non-Maxwellian and anisotropic. 1,2 The electron average kinetic energy in the direction parallel to walls is several times larger than the electron average kinetic energy in direction normal to the walls. Electrons are stratified into several groups depending on their origin (e.g., plasma discharge or thruster channel walls) and confinement (e.g., lost on the walls or trapped in the plasma). Practical analytical formulas are derived for wall fluxes, secondary electron fluxes, plasma parameters, and conductivity. The calculations based on analytical formulas agree well with the results of numerical simulations. The self-consistent analysis demonstrates that elastic electron scattering on collisions with atoms and ions plays a key role in formation of the electron energy distribution function and plasma-wall interaction. The fluxes of electrons from the plasma bulk are shown to be proportional to the rate of scattering to loss cone, thus collision frequency determines the wall potential and secondary electron fluxes. Secondary electron emission from the walls is shown to enhance the electron conductivity across the magnetic field, while having almost no effect on insulating properties of the near-wall sheaths. Such a self-consistent decoupling between secondary electron emission effects on electron energy losses and electron crossed-field transport is currently not captured by the existing fluid and hybrid models of the Hall thrusters.
TL;DR: In this article, the authors describe the plasma enhanced chemical vapor deposition growth of vertically aligned carbon nanotubes and how well controlled arrays of such structures can be grown, and how high current densities of ∼1A∕cm2, under direct current and 1.5GHz direct modulation, can be obtained from CNT cathodes.
Abstract: Most long-range telecommunication systems are based upon microwave links. The transmitters use microwave amplifiers which in the very near future will be required to work at up to 30–100GHz with output power in the region of a few tens of watts. Carbon nanotubes (CNTs), which exhibit extraordinary field emission properties because of their high electrical conductivity, ideal high aspect ratio whisker-like shape for geometrical field enhancement, and remarkable thermal stability, can be used as the emitter in such applications. This article will describe the plasma enhanced chemical vapor deposition growth of vertically aligned carbon nanotubes, and how well controlled arrays of such structures can be grown. We will also describe how high current densities of ∼1A∕cm2, under direct current and 1.5GHz direct modulation, can be obtained from CNT cathodes. These CNT cold cathodes offer considerable weight and size savings over conventional hot cathodes used in microwave applications (e.g., SATCOM, radar).
TL;DR: In order to improve the field emission properties of screen-printed carbon nanotube films, ZnO nanostructures were deposited on multiwall carbon nanotsubes (MWNTs) using vapor phase transport method as mentioned in this paper.
Abstract: In order to improve the field emission properties of screen-printed carbon nanotube films, ZnO nanostructures were deposited on multiwall carbon nanotubes (MWNTs) using vapor phase transport method. Based on the combined effect of geometrical structure of MWNT/ZnO, a low turn-on field of ∼0.7V∕μm at current density of 0.1μA∕cm2, a low threshold field of ∼2.3V∕μm at current density of 1mA∕cm2, a high field enhancement factor of 8.2×103, and a homogeneous emission image with emission spot density of ∼105cm−2 were obtained from ZnO nanomultipods grown on MNWT film.
TL;DR: In this paper, a room temperature stable electride was realized by thermally annealing an insulating 12CaO·7Al2O3 (C12A7) single crystal in a calcium metal vapor.
Abstract: A room temperature (RT) stable electride was realized by thermally annealing an insulating 12CaO·7Al2O3 (C12A7) single crystal in a calcium metal vapor. Here we report a simple and direct method for synthesizing polycrystalline C12A7 electride (C12A7:e-); the solidification of a “melt” in a reducing atmosphere and the crystallization of a “glass” with an oxygen-deficient composition in a vacuum. The carbon-related anion (C22-) presumably serves as the template for the formation of the C12A7 phase in the solidification process and may be spontaneously released from the lattice during the cooling process, leaving mobile electrons in the lattice. Also the C22- ions accommodated in the glass may play a significant role in the formation of C12A7:e- during the crystallization. The polycrystalline C12A7:e- exhibits an electrical conductivity up to 5 S·cm-1 at 300 K, which corresponds to an electron concentration of ∼3 × 1019 cm-3 and a nearly equal mobility of ∼0.1 cm2·V-1·s-1 to that of the single crystalline C...
TL;DR: In this article, the authors reported a similar method to fabricate solid-state nanopores using the electron source of a conventional field-emission scanning electron microscope (FESEM) instead.
Abstract: The fabrication of solid-state nanopores using the electron beam of a transmission electron microscope (TEM) has been reported in the past. Here, we report a similar method to fabricate solid-state nanopores using the electron source of a conventional field-emission scanning electron microscope (FESEM) instead. Micromachining was used to create initial pore diameters between 50nm and 200nm, and controlled pore shrinking to sub 10nm diameters was performed subsequently during in situ processing in the FESEM. Noticeably, different shrinking behavior was observed when using irradiation from the electron source of the FESEM than the TEM. Unlike previous reports of TEM mediated pore shrinkage, the mechanism of pore shrinkage when using the FESEM could be a result of surface defects generated by radiolysis and subsequent motion of silicon atoms to the pore periphery.
TL;DR: The experimental results indicated that the field emission characteristics of the devices fitted well to the Fowler-Nordheim model of emission.
Abstract: Polypyrrole nanowires have been electrosynthesized by direct oxidation of 0.1 mol l(-1) pyrrole in a medium of 75% isopropyl alcohol + 20% boron trifluoride diethyl etherate + 5% poly (ethylene glycol) (by volume) using porous alumina membranes as the templates. The as-prepared nanowires had a smooth surface and uniform diameter and were arranged in an orderly manner in a high density. The conductivity of a single nanowire was measured by the four-electrode technique to be 23.4 S cm(-1) at room temperature. The field emission devices based on the nanowire array were fabricated and their operations were explored. The experimental results indicated that the field emission characteristics of the devices fitted well to the Fowler-Nordheim model of emission. The turn-on electric field was only 1.2 V microm(-1) and the current density reached 200 microA cm(-2) at 2.6 V microm(-1).
TL;DR: In this paper, multiwalled carbon nanotubes (CNTs) were coated, using atomic layer deposition, with a thin layer of ZnO and subsequently annealed.
Abstract: Multiwalled carbon nanotubes (CNTs) were coated, using atomic layer deposition, with a thin layer of ZnO and subsequently annealed. Studies of the morphologies of the ZnO-coated CNTs revealed no significant change in the internal structures (multiwalled graphite sheets) and the diameters of the CNTs, but the ZnO appeared to form bead-shaped single crystalline particles attaching to the surface of the nanotubes. The electron field-emission properties of the ZnO-coated CNTs were dramatically improved over both uncoated CNTs and ZnO nanowires. It is reasoned that numerous ZnO “nanobeads” on the surface of the nanotubes serve as additional emission sites, in addition to the tips of CNTs, and result in the enhancement of electron field emission.
TL;DR: In this paper, thin multiwalled carbon nanotube (t-MWCNTs)-based field emitters are made by use of a spray method, where the number of tube walls is between 2 and 6, with the corresponding outer diameters between 3 and 6nm.
TL;DR: In this article, an individual multiwalled carbon nanotube, driven by a customer-built piezomanipulator, was measured in a transmission electron microscope and a linear dependence of field enhancement factor β on the distance d between the nanotubes tip and its counteranode was found.
Abstract: Field emission of an individual multiwalled carbon nanotube, driven by a customer-built piezomanipulator, was measured in a transmission electron microscope. The measurement geometry and the nanotube structure were imaged in situ. A linear dependence of field enhancement factor β on the distance d between the nanotube tip and its counteranode is found. The enhanced field emission mechanism is studied by a tip-flat emission model. The results indicate that the radius of emission apex r is an important factor in field emission with a relationship of β∝r−1∕2, while the tube length has little influence on β.
TL;DR: In this paper, the authors used the solvothermal process to grow ZnO nanorod arrays at low temperature on conducting substrate, which is extremely important for making efficient electrical contacts in various applications based on nanorods.
Abstract: The solvothermal process was employed to grow ZnO nanorods at low temperature on conducting substrate, which is extremely important for making efficient electrical contacts in various applications based on ZnO nanorods. Efforts were made to find the ideal growth parameters for better alignment of the ZnO nanorods with a view to tailor their luminescent properties. The ZnO nanorod arrays were characterized by scanning electron microscopy (SEM), transmission electron microscopy (TEM), energy dispersive analysis of x-rays (EDAX) and x-ray diffraction study. The ZnO nanorod arrays were found to have excellent UV emission properties at room temperature. Aligned ZnO nanorod arrays exhibit good field emission properties, revealing their applicability as cathode materials for field emission based devices.
TL;DR: In this paper, a variety of one-dimensional micro-and nanostructures of zinc oxide (ZnO) were self-assembled on amorphous carbons using thermal chemical vapor transport and condensation without any metal catalysts.
Abstract: A variety of one-dimensional (1D) micro- and nanostructures of zinc oxide (ZnO) were self-assembled on amorphous carbons using thermal chemical vapor transport and condensation without any metal catalysts. The low turn-on electronic field and the higher current density were achieved on these 1D ZnO micro- and nanostructural emitters. It was found that the geometry of the micro- and nanostructural emitters plays a crucial role in the field emission of ZnO.
TL;DR: In this article, the authors have characterized field emission properties of freestanding, 1nm thick graphene layers, called carbon nanosheets (CNSs), which were grown perpendicular to the growth surface using a radio-frequency plasma-enhanced chemical vapor deposition technique.
Abstract: The authors have characterized field emission properties of freestanding, 1nm thick graphene layers, called carbon nanosheets (CNSs), which were grown perpendicular to the growth surface using a radio-frequency plasma-enhanced chemical vapor deposition technique. The CNSs are metallic impurity-free and have uniform height distribution (standard deviation of 200h at 1.3mA emission current level. Over this time, no degradation has been observed, the variability of the individual I-V curves is small among 7216 voltage cycles, and the standard deviation at the maximum current was no more than 2.3%. A nanosheet-based backgated triode emission device has been developed to take advantage of the nanosheet field emission performance. Prototype devices have confirmed triode operation and stable electron emission.
TL;DR: In this paper, the fabrication of different architectures of carbon nanotubes on conducting substrates via contact transfer of nanotube using low temperature solders is demonstrated, where both negative and positive patterns can be obtained by changing the printing parameters.
Abstract: The authors demonstrate the fabrication of different architectures of carbon nanotubes on conducting substrates via contact transfer of nanotubes using low temperature solders. Lithographically patterned multiwalled carbon nanotube arrays grown on silica substrates by chemical vapor deposition methods are transferred onto solder coated substrates. Both negative and positive patterns can be obtained by changing the printing parameters. Good wetting and electrical contacts are confirmed by measuring their field emission properties. This method can be used to construct nanotube structures of different shapes and dimensions over large areas on substrates of choice and could be a feasible process to integrate nanotubes into various devices.
TL;DR: In this paper, a conductive TiO2 nanotube array was grown on metal Ti substrates by hydrothermal reaction and subsequent postannealing in vacuum, and the nanotubes were vertically grown and adhered well to the substrates.
Abstract: Conductive TiO2 nanotube arrays were grown on metal Ti substrates by hydrothermal reaction and subsequent postannealing in vacuum. The nanotubes were vertically grown and adhered well to the substrates. The crystal structure of the postannealed TiO2 nanotubes was identified to be oxygen-defective anatase. The nanotube arrays exhibited efficient electron field emission even at room temperature with rather low turn-on fields ∼280V per electrode distance of 100μm. The emission current density exceeded 0.15mA∕cm2 at an extraction voltage of 800V. The emission current was reproducible and stable in the lower voltage (<800V) region.
TL;DR: In this paper, four hierarchical ZnO nanostructures, including nanosleeve-fishes, radial nanowire arrays, nanocombs and nanoflowers, have been successfully fabricated through thermal chemical vapour deposition by adjusting the source temperature and the gas flow rate.
Abstract: Four different hierarchical ZnO nanostructures, including nanosleeve-fishes, radial nanowire arrays, nanocombs and nanoflowers, have been successfully fabricated through thermal chemical vapour deposition by adjusting the source temperature and the gas flow rate. Field emission measurements of these nanostructures showed a high emission current density and a low turn-on field of 1.3, 1.9, 2.5 and 3.4 V μm−1 in sequence, which is comparable to that of one-dimensional ZnO nanostructures and carbon nanotubes. The good performance for field emission makes the hierarchical ZnO nanostructures promising candidates for further applications in field emission microelectronic devices.