Online ISSN
1750-0443
Micro & Nano Letters
Volume 4, Issue 1, March 2009
Volumes & issues:
Volume 4, Issue 1
March 2009
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- Author(s): Q. Li ; S. Xue ; Z. Li ; J. Gong ; D. Zhu
- Source: Micro & Nano Letters, Volume 4, Issue 1, p. 1 –4
- DOI: 10.1049/mnl:20080036
- Type: Article
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Carbon nanofibres (CNFs) have been fabricated by oblique ion sputtering diamond films at room temperature. Scanning electron microscopy shows that the ordered carbon protrusions with a size of ∼1 µm are formed after 1 h ion irradiation and CNFs on the protrusions with a density of 1−2×108/cm2, diameter of ∼40 nm and length of 1−4 µm are achieved after 2 h ion sputtering. Raman spectra indicates that the amorphous or defect content increases with the duration of irradiation. The investigation of field emission shows that the turn-on field is 1.8 V/µm and the threshold field is 4.6 V/µm. - Author(s): T. Prodromakis and C. Papavassiliou
- Source: Micro & Nano Letters, Volume 4, Issue 1, p. 5 –8
- DOI: 10.1049/mnl:20080049
- Type: Article
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Surface texturing techniques that are applied in laminar structures to extend the supported Maxwell–Wagner polarisation are described. The roughness of the semiconductor surface is increased, resulting in a subdivision of the large Si–SiO2 interfaces to a multitude of small interfaces. Measured results demonstrate that this surface texturing has a direct effect on the relaxation of the Maxwell–Wagner polarisation and, in particular, at the interfacial to atomic polarisation transition. - Author(s): C. Liu ; D. Zhang ; H. Zhang ; J.Z. Jiang
- Source: Micro & Nano Letters, Volume 4, Issue 1, p. 9 –15
- DOI: 10.1049/mnl:20080044
- Type: Article
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The dynamic characteristics of micro-optothermal (OT) expansion and novel OT microactuators are theoretically analysed using a heat transient model and finite element modelling thermal simulation. Three different-shaped microactuators are machined by an excimer laser micromachining system using a single layer material; first with a single OT expansion arm; second with a bi-direction microactuator (BDMA); and third with a bi-direction microswitch (BDMS). A red laser diode (650 nm) with a maximum power output of 30 mW and an adjustable frequency of 0–20 Hz is used as an irradiation light source. The experimental results show that the maximum response frequency of the OT microactuators can be at least 15 Hz, and the deflections of the BDMA (about 13 µm at 10 mW, 2 Hz) and the BDMS (about 10 µm at 8 mW, 2 Hz) are significantly magnified compared with the OT expansion (1.32 µm at 10 mW, 2 Hz) of the single arm, proving the feasibility of the enlarged bi-direction deflection/vibration of the microactuators. The expansion and deflection amplitude of the microactuators decrease as the laser frequency increases, and the experimental data and curves greatly agree with the theoretical predictions. The new method of OT microactuators can be widely applied in the fields where simple structure, easy fabrication, large displacement and wireless controlling are required. - Author(s): A. Seyedi ; A.A. Pavel ; A.K. Sharma ; N.E. Islam
- Source: Micro & Nano Letters, Volume 4, Issue 1, p. 16 –21
- DOI: 10.1049/mnl:20080046
- Type: Article
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The design and analysis of a silicon nanowire inverter with a wrap-around-gate nMOS is presented and its performance is compared with that of a conventional inverter. The analysis shows that the nano-channel structure design can improve carrier mobility by suppressing the transverse component of the electric field. This results in an enhancement in the current drive of the nMOS, and contributes to lowering power consumption and the switching delay. Simulated power consumption and rise time of the proposed design was found to be about 20 µW and 0.5 ns, respectively, compared with 2.5 mW and 1.5 ns achievable with conventional planar MOSFETs. Investigation of the gate length shows that a nMOS with shorter gates have an improved switching response compared with long channel devices. - Author(s): S. Ssenyange ; R. Du ; M.T. McDermott
- Source: Micro & Nano Letters, Volume 4, Issue 1, p. 22 –26
- DOI: 10.1049/mnl:20080047
- Type: Article
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New methods to pattern and etch a variety of materials are proving to be extremely important owing to the broad impact of microfabrication technology on chemistry and biology. A method, for etching graphitic carbon materials that opens pathways for the creation of arrays of carbon structures, has been developed. The method involves standard photolithographic pattern transfers to a thin carbon film and anodisation of the exposed carbon substrate in basic electrolytes. Structures of various shapes can be fabricated that range in size from tens of microns to submicrons. Arrays of these structures can be fabricated over areas encompassing hundreds of microns with low failure rates. The shape, size and distance between array objects are easily controlled by the fabrication procedure. Scanning electron microscopy is used to visualise the various structures fabricated. The authors show that this technology is useful for the fabrication of microelectrode arrays. - Author(s): Y. Yu ; A. Cimeno ; Y.C. Lan ; J. Rybczynski ; D.Z. Wang ; T. Paudel ; Z.F. Ren ; D.J. Wagner ; M.Q. Qiu ; T.C. Chiles ; D. Cai
- Source: Micro & Nano Letters, Volume 4, Issue 1, p. 27 –33
- DOI: 10.1049/mnl:20080054
- Type: Article
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Patterned carbon nanotube arrays (PCNTAs) with reduced density and length were developed with polystyrene sphere masked catalyst dots followed by the plasma enhanced chemical vapour deposition method. The nanotubes were then uniformly coated with electropolymerised polypyrrole (PPy). The coating thickness was conformally adjustable. Gold nanoparticles (AuNP) together with glucose oxidase (Gox) were doped into the PPy film on the nanotubes to develop a high-performance PCNTA glucose sensor. The sensitivity of the sensor was improved by the co-existence of Gox and AuNP on the carbon nanotube. Moreover, in contrast to previous reported PCNTA glucose sensors, the design herein utilised the entire surface of nanotubes as active sensing areas in order to maximise the faradic currents. This research outlines a practical avenue to fabricate high-performance PCNTA sensor chips with multiple molecules and functional nano-architectures. - Author(s): X. Zheng ; Z. Jin ; Y. Wang ; X. Zhang ; S. Hu ; L. Xu
- Source: Micro & Nano Letters, Volume 4, Issue 1, p. 34 –38
- DOI: 10.1049/mnl:20080052
- Type: Article
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An introduction of a bulk micromachined frame gyroscope and the efforts made to lower the footing effect during deep reactive ion etching (DRIE) is featured. The gyroscope is driven into oscillation electrostatically and senses rate signal by the varying overlapped area of the electrodes, which eliminates the nonlinear behaviour of sensing the varying gap. Damping factors for the driving and sensing modes are low due to the slide-film damping, resulting in high quality factors in the atmosphere. A large proofmass can be made by DRIE, which also ensures a large pull-in voltage. The footing effect during fabrication has been greatly reduced by the improved process flow, which also increases the proof mass by 50%. Thus device quality and yield rate are both improved. Functional results of an improved prototype are given. - Author(s): Y.L. Wang ; L.Z. Chu ; Y.L. Li ; G.S. Fu
- Source: Micro & Nano Letters, Volume 4, Issue 1, p. 39 –43
- DOI: 10.1049/mnl:20080059
- Type: Article
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Assuming the ambient atoms and ablated particles are elastic hard-spheres, the transportation of Si particles produced by single-pulsed laser ablation in the mixture of two inert gases is numerically simulated via Monte Carlo method. The influence of the mixed atomic ratio (MAR) of the two gases on the oscillating stabilisation time (OST) of the high density mixed region of Si vapour and ambient gas is investigated. The result shows that the MAR, satisfying that average atomic mass of the ambient sufficiently approaches to Si atomic mass, induces the shortest OST and therefore the smallest average size of Si nanoparticles, as indicated in the previous experimental observation. - Author(s): W.-L. Li
- Source: Micro & Nano Letters, Volume 4, Issue 1, p. 44 –47
- DOI: 10.1049/mnl:20090003
- Type: Article
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A modified Reynolds equation, which includes the effect of flow rheology, is derived to describe the flow behaviour of lubricant between the space of a magnetic head slider and a disk. Under the assumptions of a small vibration of the spacing, and zero contact angle of the liquid–solid interface, the dynamics of a liquid meniscus disk of finite radius is analysed. The time-dependent modified Reynolds equation is linearised, and solved, under the boundary condition considering Laplace pressure. The results show that the pressure and load carrying capacity consist of three terms, that is, the static meniscus force term, the spring term by the dynamic Laplace pressure, and time-dependent damping term by the flow rheology of the fluid. The flow rheology affects the static meniscus forces and the damping forces significantly as compared to the spring forces. The effects of flow rheology on the load carrying capacity are also discussed. - Author(s): S. Lihong ; W. Yiguang ; Q. Shengru ; Z. Jiaoqiang ; Z. Xu ; G. Lingjun ; S. Lihua ; S. Yujie ; A. Yanling ; C. Qin
- Source: Micro & Nano Letters, Volume 4, Issue 1, p. 48 –52
- DOI: 10.1049/mnl:20080055
- Type: Article
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As more and more nanoparticles are synthesised and applied in industry and society, their safety has started to become an environmental concern. The solubility of Co3O4 particles with different morphology and sizes were investigated. The solubility of the mono-dispersed Co3O4 nanoparticle was discovered to be much lower than that of its micrometre counter-partners. A mechanism was proposed to interpret the inconsistency of this finding with the traditional soluble dynamic equilibrium theory. The nanometre particles exist during surface tension interaction because of their small size. The traditional Ostwald–Freundlich relationship cannot apply to nanometre sizes, as it does not include the interface dispersion force interaction. - Author(s): M. Hajj-Hassan ; V.P. Chodavarapu ; S. Musallam
- Source: Micro & Nano Letters, Volume 4, Issue 1, p. 53 –58
- DOI: 10.1049/mnl:20090007
- Type: Article
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The authors describe a simple dry-etch silicon microfabrication process to develop an array of electrodes with multiple recording sites suitable for neural recording applications. This new high-yield fabrication process uses commercially available ultra-thin silicon wafers as substrate material. A xenon difluoride system is used to etch the silicon substrate to form the electrode structures. The novel concept of structural reinforcement to produce elongated and reliable probe electrodes is introduced. The authors demonstrate recording silicon electrodes that can reach lengths longer than 10 mm having only 50 µm thicknesses and an 100 µm average width. This new microfabrication process illustrates a simple, cost-effective and mass-producible method for developing ultra-long silicon probes for deep brain implantation and neural recording. - Author(s): B. Huo ; L. Hu ; H. Zhang ; Q. Fu ; J. Zhu ; X. Chen
- Source: Micro & Nano Letters, Volume 4, Issue 1, p. 59 –62
- DOI: 10.1049/mnl:20080058
- Type: Article
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A porous MgO film was grown on sapphire by pulsed-laser deposition. First, small islands of ZnO are grown, and then MgO at a high temperature and high vacuum is deposited. The shortest distance between the two pores is about 5 um. The ZnO grains are grown at the bottom of the pore. The ZnO grains at the rim of the bottom are thinner than that of the centre at the bottom, at which the grains look like thin nano-rods. It is evident that MgO would not be deposited on ZnO small islands at a high vacuum and high temperature when the substrate is sapphire. This morphology can be used for fabricating the materials in which the shortest distance between the two nanoparticles is about 5 um. It seems that other porous materials can also be realised by this method. - Author(s): Q. Zou and M.Z. Wang
- Source: Micro & Nano Letters, Volume 4, Issue 1, p. 63 –68
- DOI: 10.1049/mnl:20080056
- Type: Article
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Atmospheric pressure microplasma was produced in a scanning electron microscope (SEM) chamber for synthesising carbon nanomaterials. The SEM observation is convenient for both adjusting the gap length and observing the electrode surface before and after experiments. After adjusting the gap length, the electrodes were housed in a small removable gas cell equipped in the SEM chamber and CH4 discharge gas was introduced into the gas cell. It was found that the discharge was pulsated automatically because of slow discharge through a large ballast resistor and fast discharge through gas breakdown, even though a DC voltage was applied. The peak pulse current density was almost 60 kA/cm2, the peak power density in the microplasma volume was approximately 555 MW/cm3 and the pulse width was 10 ns typically. Spherical and nanotube-like carbon nanomaterials were found on the cathode surface after microplasma discharge for 1–5 s. With the discharge time increasing, the spherical substance changes into nanotube-like carbon nanomaterials.
Carbon nanofibres from diamond film using Ar-ion bombardment and their field emission property
Surface texturing for Maxwell–Wagner polarisation engineering
Dynamic characteristics of micro-optothermal expansion and optothermal microactuators
Design and performance analysis of a nanoscaled inverter based on wrap-around-gate nanowire MOSFETs
Fabrication of arrays of carbon micro- and nanostructures via electrochemical etching
Assembly of multi-functional nanocomponents on periodic nanotube array for biosensors
Process flow improvement on a bulk micromachined gyroscope
Dynamical transportation of Si particles produced by pulsed laser ablation in the mixture of two inert gases
Dynamics of liquid meniscus bridge of a vibrating disk: consideration of flow rheology
Co3O4 mono-dispersed nanoparticle solubility in high-purity water
Microfabrication of ultra-long reinforced silicon neural electrodes
Porous MgO film grown on sapphire by pulsed-laser deposition
Fabrication of carbon nanomaterials by atmospheric pressure microplasma
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