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1.
Single-wall carbon nanotubes (SWCNTs) were laterally grown on SiO2/Si substrates by means of an "all-laser" growth process. Our "all-laser" process stands out by its exclusive use of the same pulsed UV laser, first, to deposit the CoNi nanocatalyst and, second, to grow SWCNTs through the laser ablation of a pure graphite target. The "all-laser" grown SWCNTs generally self-assemble into bundles (5-15 nm-diam.) sprouting from the CoNi nanocatalyst and laterally bridging the 2 microm gap separating adjacent catalysed electrodes (in either "suspended" or "on-substrate" geometries). A comparative study of the oxidation resistance of both suspended and on-substrate SWCNTs was achieved. The "all-laser" grown SWCNTs were subjected to annealing under flowing oxygen at temperatures ranging from 200 to 1100 degrees C. Systematic scanning electron microscopy observations combined with micro-Raman analyses revealed that more than 20% of suspended nanotubes were still stable at temperatures as high as 900 degrees C under flowing O2 while the on-substrate counterpart were completely burnt out at this temperature. Accordingly, the activation energy, as deduced from the Arrhenius plot, of the suspended SWCNTs is found to be as high as approximately 180 kJ mol(-1) (approximately 9 times higher than that of the on-substrate ones). The high quality (almost defect-free) of the nanotubes synthesized by the "all-laser" approach, their protected tips into the embedded CoNi catalyst nanolayer together with their suspended geometry are thought to be responsible for their unprecedented ultra-high oxidation resistance. This opens up new prospects for the use of these suspended nanotubes into nanodevices that have to operate under highly oxidizing environments. 相似文献
2.
Plasma-sprayed MnZn ferrites with insulated fine grains and increased resistivity for high-frequency applications 总被引:1,自引:0,他引:1
Plasma-sprayed MnZn ferrite thick films are built up by splats, which consist of columnar grains with diameter /spl sim/200 nm and height /spl sim/1 /spl mu/m. The existence of the conductive wustite FeO in the as-sprayed films greatly reduces the dc resistivity. However, a useful structure can be developed in these ferrite films with fine equal-axis ferrite grains insulated by the high-resistivity hematite Fe/sub 2/O/sub 3/ because of the polygonization of the columnar grains and the oxidation of the wustite during an annealing process. The dc resistivity increases significantly after the annealing process, an effect ascribed to the growth of hematite Fe/sub 2/O/sub 3/ on the basis of impedance analysis. The magnetic properties of these ferrite films improve concurrently. The high-frequency response of the annealed plasma-sprayed MnZn ferrites shows a permeability of /spl sim/700 stabilized to above 10 MHz. The maximum Q factor at about 10 MHz increases from 5 to 20 as a result of the increase of the dc resistivity. 相似文献
3.
Chang-Ching Tu Yaw-Kuen Li Teng-Ming Chen Chung-Yu Wu 《Nanotechnology, IEEE Transactions on》2006,5(3):284-290
A newly developed four-layered photosensing nanodevice was fabricated by integrating nanoparticles (NPs) on a silicon substrate. Through ionic interaction, negatively charged Au NPs (/spl sim/15 nm) were assembled in alternate layers with positively charged CdSe NPs (/spl sim/5 nm) on the silicon oxide surface between the two Al electrodes. The silicon oxide surface after each step of the fabrication process was observed and evaluated by images obtained from the scanning electron microscope. By applying voltage biases across the electrodes, the currents were measured in the dark and under illumination using a 375-nm laser. It was found that a constant photocurrent increment can be obtained for different voltage biases, and the nanodevice structure with a longer length had less conductivity but a larger increment of photocurrent after illumination. In addition, the efficiency rate of photocurrent generation is much higher in comparison to that obtained from CdSe thin film. The fabrication process integrated a newly developed model of a diode-resistor array of semiconductor-metal junctions between CdSe and Au NPs (nano-Schottky-diode structures), which can successfully explain the measured results. While nanotechnology has unprecedented advantages over the traditional silicon electronics, its technology presents physical challenges. However, the success of the fabrication of the multilayered photosensing nanodevice directly on the silicon chip paves the way for further applications and research. 相似文献
4.
We present a feasible technology for batch assembly of carbon nanotube (CNT) devices by utilizing ac electrophoretic technique to manipulate multiwalled bundles on an Si/SiO/sub 2/ substrate. Based on this technique, CNTs were successfully and repeatably manipulated between microfabricated electrodes. By using this parallel assembly process, we have investigated the possibility of batch fabricating functional CNT devices when an ac electrical field is applied to an array of microelectrodes that are electrically connected together. Preliminary experimental results showed that over 70% of CNT functional devices can be assembled successfully using our technique, which is considered to be a good yield for nanodevices manufacturing. Besides, the devices were demonstrated to potentially serve as novel thermal sensors with low power consumption (/spl sim/microwatts) with electronic circuit response of approximately 100 kHz in constant current mode operation. In this paper, we will present the fabrication process of this feasible batch manufacturable method for functional CNT-based thermal sensors, which will dramatically reduce production costs and production time of nanosensing devices and potentially enable fully automated assembly of CNT-based devices. Experimental results from the thermal sensors fabricated by this batch process will also be discussed. 相似文献
5.
Christophe Brun Pierre‐Henri Elchinger Guillaume Nonglaton Cheikh Tidiane‐Diagne Raluca Tiron Aurélie Thuaire Didier Gasparutto Xavier Baillin 《Small (Weinheim an der Bergstrasse, Germany)》2017,13(33)
Metallic conductive nanowires (NWs) with DNA bundle core are achieved, thanks to an original process relying on double‐stranded DNA alignment and physical vapor deposition (PVD) metallization steps involving a silicon substrate. First, bundles of DNA are suspended with a repeatable process between 2 µm high parallel electrodes with separating gaps ranging from 800 nm to 2 µm. The process consists in the drop deposition of a DNA lambda‐phage solution on the electrodes followed by a naturally evaporation step. The deposition process is controlled by the DNA concentration within the buffer solution, the drop volume, and the electrode hydrophobicity. The suspended bundles are finally metallized with various thicknesses of titanium and gold by a PVD e‐beam evaporation process. The achieved NWs have a width ranging from a few nanometers up to 100 nm. The electrical behavior of the achieved 60 and 80 nm width metallic NWs is shown to be Ohmic and their intrinsic resistance is estimated according to different geometrical models of the NW section area. For the 80 nm width NWs, a resistance of about few ohms is established, opening exploration fields for applications in microelectronics. 相似文献
6.
Ahmed E. Awadallah Ateyya A. Aboul-Enein Mostafa A. Azab Yasser K. Abdel-Monem 《Fullerenes, Nanotubes and Carbon Nanostructures》2017,25(4):256-264
A series of mono-, bi- or tri-metallic Fe–Mo-Cu/MgO catalysts with the same metal loading of 6 wt% were prepared by impregnation method and used as catalysts for synthesis single-walled carbon nanotubes (SWCNTs) via methane decomposition. XRD, H2-TPR, and nitrogen physisorption techniques were used to characterize the freshly calcined catalysts, while HRTEM, Raman spectroscopy and TGA were employed to investigate the morphology and microstructure of the SWCNTs product. The obtained results indicated that the introduction of Mo or Cu in the Fe/MgO catalyst enhanced the catalytic growth activity. TEM images showed that both bundles and isolated SWCNTs were obtained over Mo containing catalysts, whereas only SWCNTs bundles were grown over the Fe-Cu/MgO catalyst. The obtained SWCNTs having a diameter of around 0.9–2.4 nm. Raman analysis illustrated that all promoted catalysts produced high quality of SWCNTs compared to the unpromoted Fe/MgO catalyst. 相似文献
7.
Pairs of electrodes with nanometer separation (nanogap) are achieved through an electromigration-induced break-junction (EIBJ) technique at room temperature. Lithographically defined gold (Au) wires are formed by e-beam evaporation over oxide-coated silicon substrates silanized with (3-Mercaptopropyl)trimethoxysilane (MPTMS) and then subjected to electromigration at room temperature to create a nanometer scale gap between the two newly formed Au electrodes. The MPTMS is an efficient adhesive monolayer between SiO/sub 2/ and Au. Although the Au wires are initially 2 /spl mu/m wide, gaps with length /spl sim/1 nm and width /spl sim/5 nm are observed after breaking and imaging through a field effect scanning electron microscope. This technique eliminates the presence of any residual metal interlink in the adhesion layer (chromium or titanium for Au deposition over SiO/sub 2/) after breaking the gold wire, and it is much easier to implement than the commonly used low-temperature EIBJ technique which needs to be executed at 4.2 K. Metal-molecule-metal structures with symmetrical metal-molecule contacts at both ends of the molecule are fabricated by forming a self-assembled monolayer of -dithiol molecules between the EIBJ-created Au electrodes with nanometer separation. Electrical conduction through single molecules of 1,4-Benzenedimethanethiol (XYL) is tested using the Au/XYL/Au structure with chemisorbed gold-sulfur coupling at both contacts. 相似文献
8.
Galzerano G. Sani E. Toncelli A. Tonelli M. Svelto C. Laporta P. 《IEEE transactions on instrumentation and measurement》2006,55(1):128-131
The measurement of the frequency and intensity noise in a novel single-mode 2-/spl mu/m Tm-Ho:KYF laser is presented. The laser frequency noise is measured by exploiting the fringe side of the transmission of a Fabry-Pe/spl acute/rot interferometer. The measured power spectral density of the frequency noise is principally characterized by a random-walk noise contribution, which sets an emission linewidth of /spl sim/ 600 kHz for the 2-/spl mu/m radiation. The relative intensity noise (RIN) reaches the quantum limit of -155 dB/Hz for Fourier frequencies above 1 MHz and shows a maximum level of -90 dB/Hz at the relaxation-oscillation frequency of 20 kHz. 相似文献
9.
Zhao Z Jose G Fernandez TT Comyn TP Irannejad M Steenson P Harrington JP Ward M Bamiedakis N Penty RV White IH Jha A 《Nanotechnology》2012,23(22):225302
We propose an all-laser processing approach allowing controlled growth of organic-inorganic superlattice structures of rare-earth ion doped tellurium-oxide-based glass and optically transparent polydimethyl siloxane (PDMS) polymer; the purpose of which is to illustrate the structural and thermal compatibility of chemically dissimilar materials at the nanometer scale. Superlattice films with interlayer thicknesses as low as 2 nm were grown using pulsed laser deposition (PLD) at low temperatures (100?°C). Planar waveguides were successfully patterned by femtosecond-laser micro-machining for light propagation and efficient Er(3+)-ion amplified spontaneous emission (ASE). The proposed approach to achieve polymer-glass integration will allow the fabrication of efficient and durable polymer optical amplifiers and lossless photonic devices. The all-laser processing approach, discussed further in this paper, permits the growth of films of a multitude of chemically complex and dissimilar materials for a range of optical, thermal, mechanical and biological functions, which otherwise are impossible to integrate via conventional materials processing techniques. 相似文献
10.
For rectangular prisms of dimensions 2a/spl times/2b/spl times/2c with constant material susceptibility /spl chi/, we have calculated and tabulated the fluxmetric and magnetometric demagnetizing factors N/sub f/ and N/sub m/, defined along the 2c dimension as functions of c/(ab)/sup 1/2/(=1/spl sim/500), a/b(=1/spl sim/256), and /spl chi/(=0/spl sim/10/sup 9/). We introduce an interpolation technique for obtaining N/sub f,m/ with arbitrary values of c/(ab)/sup 1/2/, a/b, and /spl chi/. 相似文献
11.
12.
A monolithic CMOS microhotplate-based gas sensor system 总被引:2,自引:0,他引:2
Afridi M.Y. Suehle J.S. Zaghloul M.E. Berning D.W. Hefner A.R. Cavicchi R.E. Semancik S. Montgomery C.B. Taylor C.J. 《IEEE sensors journal》2002,2(6):644-655
A monolithic CMOS microhotplate-based conductance-type gas sensor system is described. A bulk micromachining technique is used to create suspended microhotplate structures that serve as sensing film platforms. The thermal properties of the microhotplates include a 1-ms thermal time constant and a 10/spl deg/C/mW thermal efficiency. The polysilicon used for the microhotplate heater exhibits a temperature coefficient of resistance of 1.067/spl times/10/sup -3///spl deg/C. Tin(IV) oxide and titanium(IV) oxide (SnO/sub 2/,TiO/sub 2/) sensing films are grown over postpatterned gold sensing electrodes on the microhotplate using low-pressure chemical vapor deposition (LPCVD). An array of microhotplate gas sensors with different sensing film properties is fabricated by using a different temperature for each microhotplate during the LPCVD film growth process. Interface circuits are designed and implemented monolithically with the array of microhotplate gas sensors. Bipolar transistors are found to be a good choice for the heater drivers, and MOSFET switches are suitable for addressing the sensing films. An on-chip operational amplifier improves the signal-to-noise ratio and produces a robust output signal. Isothermal responses demonstrate the ability of the sensors to detect different gas molecules over a wide range of concentrations including detection below 100 nanomoles/mole. 相似文献
13.
Jeong SY Jeon SH Han GH An KH Bae DJ Lim SC Hwang HR Han CS Yun M Lee YH 《Journal of nanoscience and nanotechnology》2008,8(1):329-334
Individual single-walled carbon nanotubes (SWCNTs) were synthesized on the patterned water-soluble catalyst by thermal chemical vapor deposition. The individual SWCNTs were obtained by introducing polyvinylpyrrolidone (PVP) as a dispersant. The number of SWCNTs between two electrodes were approximately 1-2 with an average diameter of about 1.7 nm and a yield of forming electrodes of nearly 70%. The PVP played an important role in dispersing catalysts and suppressing the active sites to limit the number of SWCNTs during synthesis, which is a critical condition for fabrication of field effect transistors (FETs). The measured I-V characteristics of the over layer-deposited electrodes revealed a clear gating effect in large portion, in good agreement with Raman observations in several excitation energies. The patterning procedure, catalyst preparation, and growth condition for fabrication of the SWCNT-FET were further discussed. 相似文献
14.
Ying Tian Marina Y. Timmermans Samuli Kivistö Albert G. Nasibulin Zhen Zhu Hua Jiang Oleg G. Okhotnikov Esko I. Kauppinen 《Nano Research》2011,4(8):807-815
Single-walled carbon nanotubes (SWCNTs) with specific diameters are required for various applications particularly in electronics
and photonics, since the diameter is an essential characteristic determining their electronic and optical properties. In this
work, the selective growth of SWCNTs with a certain mean diameter is achieved by the addition of appropriate amounts of CO2 mixed with the carbon source (CO) into the aerosol (floating catalyst) chemical vapor deposition reactor. The noticeable
shift of the peaks in the absorption spectra reveals that the mean diameters of the as-deposited SWCNTs are efficiently altered
from 1.2 to 1.9 nm with increasing CO2 concentration. It is believed that CO2 acts as an etching agent and can selectively etch small diameter tubes due to their highly curved carbon surfaces. Polymer-free
as-deposited SWCNT films with the desired diameters are used as saturable absorbers after stamping onto a highly reflecting
Ag-mirror using a simple dry-transfer technique. Sub-picosecond mode-locked fiber laser operations at ∼1.56 μm and ∼2 μm are
demonstrated, showing improvements in the performance after the optimization of the SWCNT properties.
相似文献
15.
Inomata A. Taguchi J. Ajan A. Matsumoto K. Yamagishi W. 《IEEE transactions on magnetics》2005,41(2):636-641
Thermally assisted writing on high-coercivity synthetic ferrimagnetic media (SFM) was demonstrated using a conventional spin stand equipped with an optical head for commercial magnetooptical drives. The laser light (/spl lambda/ = 685 nm) was focused through a glass substrate onto a recording layer. The optical spot size was 1.1 /spl mu/m and a commercial magnetic head had a writer width of /spl sim/0.25 /spl mu/m. The recording properties were measured as a function of the writing current (I/sub w/) and the laser power (P/sub w/). For the thermally stable medium with H/sub c/ = 6 kOe, a laser irradiation with an optimum power significantly improved the overwrite performance and the signal-to-noise ratio (SNR) values. The SNR values were improved by optimizing P/sub w/ over a wide writing current range. The improvements with the assist were found in both the signal and the noise. The media with a large dynamic coercivity value or with thick magnetic layers clearly showed the advantages with thermal assist. 相似文献
16.
Abarra E.N. Gill P. Min Zheng Zhou J.N. Acharya B.R. Choe G. 《IEEE transactions on magnetics》2005,41(2):581-586
The effect of magnetic "preconditioning" on the recording performance of perpendicular media is investigated. Furthermore, the dependence of the magnetic write width (MWW) of shielded-pole heads (SPH) on soft-underlayer (SUL) type and thickness (t/sub SUL/) and the recording performance of perpendicular media with thin SULs are examined. The MWW dependence on SUL structure is influenced by the pole-to-trailing shield spacing. For a wide-gap (/spl sim/80 nm) SPH, thick single-layer, SULs are preferred. For a narrow-gap (/spl sim/50 nm) SPH, MWW is less sensitive to the SUL type. For both narrow and wide-gap SPH and for media with an antiferromagnetically-coupled SUL, MWW is reduced for t/sub SUL/<100 nm. Comparable performance is achieved relative to media with t/sub SUL//spl sim/150 nm. 相似文献
17.
The examination of microstructure of tensile specimens of pultruded 60% V
f carbon fibre-reinforced epoxide of up to 6 mm unreduced diameter shows that transverse cracking precedes the tensile failure of groups of fibres. In material whose strength is 2 GN m–2, the process can commence in waisted specimens at stresses as low as 1 GN m–2; in those of unreduced section it was not detected below 1.5 GN m–2. This failure initiation stage can be associated with the decrease in the slope of the load-extension curve. With increasing load the inter-tow cracks were observed to grow and some surface fibre bundles detached. It is suggested that misaligned fibres in these surface bundles were straightened out and contributed to the load-carrying capacity of the rod. Only following detachment of numerous bundles (for the specimens with unreduced section) or growth of interlaminar cracks into the specimen shoulders (for those with a reduced gauge diameter) did tensile failure of fibre bundles lead to catastrophic fracture. It is to this last propagation stage that statistical models of failure of bundles at different cross-sections should refer. 相似文献
18.
Esfandyarpour B. Mohajerzadeh S. Khodadadi A.A. Robertson M.D. 《IEEE sensors journal》2004,4(4):449-454
Ultrahigh-sensitivity SnO/sub 2/-CuO sensors were fabricated on Si(100) substrates for detection of low concentrations of hydrogen sulfide. The sensing material was spin coated over platinum electrodes with a thickness of 300 nm applying a sol-gel process. The SnO/sub 2/-based sensors doped with copper oxide were prepared by adding various amounts of Cu(NO/sub 3/)/sub 2/.3H/sub 2/O to a sol suspension. Conductivity measurements of the sensors annealed at different temperatures have been carried out in dry air and in the presence of 100 ppb to 10-ppm H/sub 2/S. The nanocrystalline SnO/sub 2/-CuO thin films showed excellent sensing characteristics upon exposure to low concentrations of H/sub 2/S below 1 ppm. The 5% CuO-doped sensor having an average grain size of 20 nm exhibits a high sensitivity of 2.15/spl times/10/sup 6/ (R/sub a//R/sub g/) for 10-ppm H/sub 2/S at a temperature of 85/spl deg/C. By raising the operating temperature to 170/spl deg/C, a high sensitivity of /spl sim/10/sup 5/ is measured and response and recovery times drop to less than 2 min and 15 s, respectively. Selectivity of the sensing material was studied toward various concentrations of CO, CH/sub 4/, H/sub 2/, and ethanol. SEM, XRD, and TEM analyses were used to investigate surface morphology and crystallinity of SnO/sub 2/ films. 相似文献
19.
Lili Zhang Dong‐Ming Sun Peng‐Xiang Hou Chang Liu Tianyuan Liu Jianfeng Wen Nujiang Tang Jian Luan Chao Shi Jin‐Cheng Li Hong‐Tao Cong Hui‐Ming Cheng 《Advanced materials (Deerfield Beach, Fla.)》2017,29(32)
A major obstacle for the use of single‐wall carbon nanotubes (SWCNTs) in electronic devices is their mixture of different types of electrical conductivity that strongly depends on their helical structure. The existence of metal impurities as a residue of a metallic growth catalyst may also lower the performance of SWCNT‐based devices. Here, it is shown that by using silicon oxide (SiOx) nanoparticles as a catalyst, metal‐free semiconducting and metallic SWCNTs can be selectively synthesized by the chemical vapor deposition of ethanol. It is found that control over the nanoparticle size and the content of oxygen in the SiOx catalyst plays a key role in the selective growth of SWCNTs. Furthermore, by using the as‐grown semiconducting and metallic SWCNTs as the channel material and source/drain electrodes, respectively, all‐SWCNT thin‐film transistors are fabricated to demonstrate the remarkable potential of these SWCNTs for electronic devices. 相似文献
20.
A biosensor for bacterial detection was developed based on microelectromechanical systems, heterobifunctional crosslinkers and immobilized antibodies. The sensor detected the change in impedance caused by the presence of bacteria immobilized on interdigitated gold electrodes and was fabricated from (100) silicon with a 2-/spl mu/m layer of thermal oxide as an insulating layer. The sensor active area is 9.6 mm/sup 2/ and consists of two interdigital gold electrode arrays measuring 0.8 /spl times/ 6 mm. Escherichia coli specific antibodies were immobilized to the oxide between the electrodes to create a biological sensing surface. The impedance across the interdigital electrodes was measured after immersing the biosensor in solution. Bacteria cells present in the sample solution attached to the antibodies and became tethered to the electrode array, thereby causing a change in measured impedance. The biosensor was able to discriminate between different cellular concentrations from 10/sup 5/ to 10/sup 7/ CFU/mL in pure culture. The sample testing process, including data acquisition, required 5 min. The design, fabrication, and testing of the biosensor is discussed along with the implications of these findings toward further biosensor development. 相似文献