Online ISSN
1750-0443
Micro & Nano Letters
Volume 5, Issue 2, April 2010
Volumes & issues:
Volume 5, Issue 2
April 2010
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- Author(s): M. Hajj-Hassan ; M. Cheung ; V. Chodavarapu
- Source: Micro & Nano Letters, Volume 5, Issue 2, p. 63 –69
- DOI: 10.1049/mnl.2009.0107
- Type: Article
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The authors report the fabrication of porous silicon material using a xenon difluoride (XeF2) dry etching technique. Using a XeF2 fabrication process, porous silicon can be formed selectively on silicon by employing a standard hard-baked photoresist layer as a masking layer. The authors demonstrate porous silicon with different pore sizes and configurations rendering this material as an attractive candidate for a wide spectrum of potential applications. The pore size, porosity and thickness of the various developed porous silicon samples were characterised with electron microscopy and optical reflectance measurements. This XeF2 etching technique offers flexible and straightforward fabrication of porous silicon and could allow simple monolithic integration of porous silicon devices with microelectronic circuitry, following the current trend of integrated microsystems. - Author(s): M. Saremi and M. Yeganeh
- Source: Micro & Nano Letters, Volume 5, Issue 2, p. 70 –75
- DOI: 10.1049/mnl.2009.0111
- Type: Article
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Nanostructured copper was deposited on oxidised p-type (100) single crystal silicon using radio frequency (RF) sputtering technique. The morphology and crystal orientation of the deposited films were examined by scanning electron microscopy (SEM) and X-ray diffraction (XRD), respectively. Corrosion behaviour of these films was studied by potentiodynamic polarisation and electrochemical impedance spectroscopy (EIS) methods. Results showed that the corrosion resistance of copper thin film produced by RF sputtering was higher than the copper sheet because of its higher ability to form a passive layer and protective cuprous oxide on its surface. - Author(s): D.M. Han ; G.L. Dai ; W.P. Jia ; H.D. Liang
- Source: Micro & Nano Letters, Volume 5, Issue 2, p. 76 –80
- DOI: 10.1049/mnl.2009.0114
- Type: Article
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A Cu2+-doped 2, 4-dichlorophenol (2, 4-DCP) molecularly imprinted TiO2–SiO2 nanocomposite catalyst was prepared by molecular imprinting technique in combination with sol–gel methods. The prepared material was characterised by X-ray diffraction (XRD), infrared spectroscopy (IR), scanning electron microscopy (SEM), transmission electron microscopy (TEM) and N2 adsorption measurements. The photocatalytic ability and selectivity of the material was also evaluated. The results show that the Cu2+-doped imprinted material not only has good capacity but also favourable selectivity towards the photocatalytic degradation of the target pollutant, which was shown to be promising for selective removal of 2, 4-DCP from environmental samples. - Author(s): Y.-H. Tseng ; C.-S. Kuo ; C.-H. Huang ; T. Hirakawa ; N. Negishi ; H.-L. Bai
- Source: Micro & Nano Letters, Volume 5, Issue 2, p. 81 –84
- DOI: 10.1049/mnl.2010.0003
- Type: Article
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81
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TiO2 thin film photocatalysts coated onto glass plates were prepared by thermal decomposition of tetraisopropyl orthotitanate with a dip-coating process. In this Letter, the mechanism for photoinduced hydrophilicity of TiO2 film is clarified by adding the extra H2O2 on TiO2 surface. Results show that the photoinduced hydrophilicity of TiO2 film is inhibited with the presence of H2O2. The amount of Ti–OH bonds on the surface oppositely increased by the addition of H2O2. It indicates the photoinduced hydrophilicity of TiO2 results from surface oxygen vacancy, not Ti–OH bonds. - Author(s): S.M. Firdaus ; I.A. Azid ; O. Sidek ; K. Ibrahim ; M. Hussien
- Source: Micro & Nano Letters, Volume 5, Issue 2, p. 85 –90
- DOI: 10.1049/mnl.2009.0105
- Type: Article
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A study on a fabricated piezoresistive micro-electro-mechanical systems (MEMS) cantilever for a mass-based sensor has been carried out to enhance sensor sensitivity by introducing the stress concentration region (SCR). Three types of SCR geometry designs were first analysed using finite element analysis (FEA) software ANSYS® to study the effect of stress and its distribution when varying mass is applied at the free end. FEA results show that the rectangular SCR design has the highest stress. Then, the length of rectangular SCR is varied from 1000 µm (A1) to 3000 µm (A3) to study the stress distribution along the cantilever. The piezoresistive MEMS cantilever with rectangular SCR A3 produced the highest stress and was thus selected for fabrication along with the piezoresistive MEMS cantilever without SCR. From the testing results, the piezoresistive MEMS cantilever with rectangular SCR A3 successfully enhanced sensitivity by 1.97 times as compared to the piezoresistive MEMS cantilever without SCR when varying mass is applied. Therefore this SCR approach appears to be suitable for enhancing the sensitivity of a mass-based piezoresistive MEMS cantilever sensor. - Author(s): K. Michelakis ; T. Prodromakis ; C. Toumazou
- Source: Micro & Nano Letters, Volume 5, Issue 2, p. 91 –94
- DOI: 10.1049/mnl.2009.0106
- Type: Article
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This Letter aims to promote basic research into memristors, which will help provide theorists with much-needed reliable benchmarks and will also aid the technology progress. It addresses an information gap presently in the literature on simple microfabrication techniques for the realisation of such devices. Consequently, a fabrication method is reported for implementing the full active-material stack, requiring a single lithography and evaporation step. A cost-effective technique that can reliably shrink device lateral dimensions towards the nanoscale is also demonstrated. Experimental results confirm the suitability of the proposed methods for fabricating memristors of varying dimensions that exhibit consistent electrical characteristics. - Author(s): M. Li ; R. Zhang ; H. Zhang ; W. Feng ; X. Liu
- Source: Micro & Nano Letters, Volume 5, Issue 2, p. 95 –99
- DOI: 10.1049/mnl.2009.0092
- Type: Article
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CeO2 nanoparticles were prepared by a simple co-precipitation method and the structural and magnetic properties were studied. X-ray diffraction, Raman and selected area electron diffraction results indicate that the samples have the cubic fluorite structure without other impurity phases. Magnetisation measurements indicate that the CeO2 nanoparticles calcined at different temperatures exhibit room temperature ferromagnetism (RTFM). The result of energy-dispersed X-ray spectrometry (EDS) analysis indicates that ferromagnetic impurities could not be responsible for the magnetic signals and that ferromagnetism (FM) is an inherent property of the material. It is found that the saturation magnetisation (Ms) of CeO2 nanoparticles increases after annealing in reducing ambience and decreases after annealing in a rich-oxygen atmosphere, which confirms that the oxygen vacancies may play an important role in introducing FM. - Author(s): S.S. Kawar and B.H. Pawar
- Source: Micro & Nano Letters, Volume 5, Issue 2, p. 100 –104
- DOI: 10.1049/mnl.2009.0108
- Type: Article
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Zinc sulphide (ZnS) thin films with nanoscale grains of about 8–113 nm were deposited on glass substrates by chemical bath deposition technique using aqueous solution of zinc acetate [Zn (CH3COO)2] and Thiourea. The structure, surface morphology and optical characteristics of the deposited films were investigated for photovoltaic device applications. The crystallinity of the thin films was characterised by X-ray diffraction and they all appeared to be polycrystalline. Scanning electron microscopy (SEM) studies gives the average grain size to be small (8–130 nm) with an uneven surface feature. Fourier transform infrared spectroscopy (FTIR) and UV–VIS measurements showed that the films had more than 65% transmittance in the wavelength larger than 350 nm. The fundamental absorption edge shifted to a shorter wavelength, which corresponds to an increase in the energy band gap ranging from 3.59 to 3.72 eV. The physical conditions were kept identical while growing all the samples. It was found that ZnS films are suitable for use as the buffer layer of CIS solar cells, and it is a viable alternative for replacing CdS in the photovoltaic cell structure. - Author(s): Xiaoqing Yang ; Dingcai Wu ; Ruowen Fu
- Source: Micro & Nano Letters, Volume 5, Issue 2, p. 105 –109
- DOI: 10.1049/mnl.2010.0001
- Type: Article
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p.
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A new type of nanoporous carbon material by pyrolysis of styrene-acrylonitrile random copolymer (SAN)/multiwalled carbon nanotube (MWCNT) composite was prepared. The thermal decomposable styrene component of the SAN could act as a soft template to form abundant nanopores with the help of the pristine nanotubular framework of the MWCNT. The measured Brunauer–Emmett–Teller surface area of the SAN/MWCNT-based carbon was up to 376 m2/g with a MWCNT content of 10 wt%, 11 and 14 times as large as those of SAN-based and polyacrylonitrile/MWCNT-based carbons, respectively. As a result, the highest specific capacitance of an as-prepared SAN/MWCNT-based carbon reached 118 F/g, which is much higher than those of the latter two. - Author(s): P. Kumar
- Source: Micro & Nano Letters, Volume 5, Issue 2, p. 110 –116
- DOI: 10.1049/mnl.2010.0007
- Type: Article
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p.
110
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Surfaces of single crystal [311] silicon, germanium and GaAs were nanostructured by a DC electric field (0.1–1.5 kV/cm). Spark threshold was found to be 1.33, 0.66 and 0.33 kV/cm for GaAs, silicon and germanium, respectively. Field nanostructuring results in the formation of nanoparticles of grain size in the range of 30–200 nm showed the nanoparticle size increasing with the increase in field value. Electric field treatment of the silicon surface gives rise to a lack of long-range crystalline order for surfaces. The effect of such a nanostructuring process is to make more absorbing and surface-oxidised nanocrystalline photoluminescent surfaces. Electric field treatment gives rise to local and directional nanostructuring. - Author(s): S. Takei ; T. Ogawa ; R. Deschner ; M. Hanabata ; C.G. Willson
- Source: Micro & Nano Letters, Volume 5, Issue 2, p. 117 –120
- DOI: 10.1049/mnl.2010.0014
- Type: Article
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117
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Step and flash nanoimprint lithography has many advantages such as high resolution, low line edge roughness and easy operation. However, resist peeling and defects present challenges that must be resolved in order to mass-produce advanced devices. A new approach using a spin-on UV-sensitive hard mask underlayer material with terminal methacrylate groups has been developed successfully, in order to obtain high adhesion by radical polymerisation between acrylate groups of the resist material and methacrylate groups of the underlayer during UV irradiation. The obtained high adhesion between the resist and underlayer was acceptable to improve the generated resist peeling and contamination problem when the template was removed from the resist after UV irradiation. The first demonstrated underlayer material indicated great properties, such as 80 nm straight profiles on 20 nm thin residual thickness and nanoimprint patterning replication on 200 mm wafer. - Author(s): M. Aljada and A. Asthana
- Source: Micro & Nano Letters, Volume 5, Issue 2, p. 121 –124
- DOI: 10.1049/mnl.2010.0019
- Type: Article
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In this Letter, the authors demonstrate fabrication of multilevel microstructures using inductively coupled plasma deep reactive ion etcher (ICP-DRIE) in conjunction with dry film photoresist (DFR) as etch mask. By limiting the usage of photoresist on the layers, both the chances of introducing contamination as well as wastage of photoresist are reduced. Thus, combining DFR with DRIE in microfabricating of multilevel microstructure has the potential to significantly reduce fabrication time, cost and contamination. - Author(s): S.K. Tripathi ; N. Shukla ; N.S. Rajput ; S. Dhamodaran ; V.N. Kulkarni
- Source: Micro & Nano Letters, Volume 5, Issue 2, p. 125 –130
- DOI: 10.1049/mnl.2010.0015
- Type: Article
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A nano-mechanical switch has been fabricated and its switching action has been demonstrated. The device utilises the phenomenon of bending of Pt nanopillars and cantilevers induced by focused ion beam (FIB). Two skew Pt pillars with equal lengths and different cross-sections have been fabricated subtending an angle of approximately 100° with each other using FIB-chemical vapour deposition (CVD). One of the pillars is initially made to bend towards the adjacent pillar to achieve a physical contact with it, and then is bent in opposite direction from it. The pillar has been bent along the desired orientation by appropriately choosing the ion beam irradiation directions. The switching action has been demonstrated by applying constant voltage across the Pt pillars and measuring the current passing through it, as a function of time during ion beam scanning. These nano-mechanical switches would find useful applications during the in-situ electrical characterisation of micro- and nano-structures fabricated by FIB. - Author(s): A. Roy and J. Bhattacharya
- Source: Micro & Nano Letters, Volume 5, Issue 2, p. 131 –134
- DOI: 10.1049/mnl.2010.0020
- Type: Article
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This Letter reports a process of preparation and characterisation of Ca(OH)2 nanoparticles without using any surfactant. Ca(OH)2 is frequently used as precipitant, catalyst, paint, toxic-waste remediation agent, adsorbent and so on. To prepare stable Ca(OH)2 nanoparticles, a simple hydrolysis method was applied using Ca(NO3)2·4H2O as the precursor, aqueous NaOH as the precipitant and ethane-1,2-diol (ED) as the medium. The nanoparticles were characterised by X-ray diffraction (XRD), Fourier transform infrared (FTIR) spectroscopy, high-resolution transmission electron microscope (HRTEM) and field emission scanning electron microscopy (FESEM). The results showed that the nanoparticles are of about 47 nm in diameter and P3m1 hexagonal structure. The method is simple and effective so that nanoparticles are stable up to 45 days, confirmed by the XRD pattern. - Author(s): A. Tavakoli ; M. Sohrabi ; C.J. Choi ; A. Kargari
- Source: Micro & Nano Letters, Volume 5, Issue 2, p. 135 –139
- DOI: 10.1049/mnl.2009.0109
- Type: Article
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Nanosized iron powders have been synthesised by the chemical vapour condensation (CVC) method. The effects of various operating parameters, such as decomposition temperature, bubbler temperature, carrier gas flow rate, precursor flow rate and pressure on the particle's size and properties, were investigated. The phase analysis and morphology of samples were determined by X-ray diffraction (XRD) and transmission electron microscopy (TEM), respectively. The effects and contributions of the process pertinent parameters on particle size and interactions between the parameters were determined using Taguchi experimental design method. It was observed that the decomposition temperature was the most significant process parameter affecting the particle size. - Author(s): G. Hwang ; S. Haliyo ; S. Régnier
- Source: Micro & Nano Letters, Volume 5, Issue 2, p. 140 –145
- DOI: 10.1049/mnl.2010.0012
- Type: Article
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Although two-dimensional thin-film nanostructures such as graphene are extremely promising for future optical or electronic devices, the required manufacturing technologies are still lacking. Herein the authors introduce a robotically controlled electro-osmotic spray deposition method of colloids with a high electric potential to create optoelectronic devices directly onto the surface of graphene. Since the process does not require a clean room or lithography method, pure graphene optoelectronic devices can be manufactured at a low cost. Moreover, preliminary experiments revealed that the manufactured graphene optoelectronic devices have excellent photoelectric properties in the infrared wavelengths. - Author(s): DongEn Zhang ; Qing Xie ; HongXiang Cai ; ShanZhong Li ; XiaoBo Zhang ; GuiQuan Han ; AiLing Ying ; ZhiWei Tong
- Source: Micro & Nano Letters, Volume 5, Issue 2, p. 146 –149
- DOI: 10.1049/mnl.2010.0011
- Type: Article
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A facile route using simple hydrothermal reaction and sequential calcinations to synthesise three-dimensional flower-like Cd(OH)2 architectures without employing templates or matrix for self-assembly is presented. X-ray diffraction (XRD) patterns of the as-synthesised samples reveal clearly that all diffraction peaks match well with the hexagonal phase of Cd(OH)2. The flower-like structures are composed of nanosheets with a thickness of about 50 nm, which is verified by the field-emission electron microscopy. Every flake is curled and thin, has a smooth surface and a large surface area. - Author(s): T.A. Hilder ; R. Yang ; V. Ganesh ; D. Gordon ; A. Bliznyuk ; A.P. Rendell ; S.-H. Chung
- Source: Micro & Nano Letters, Volume 5, Issue 2, p. 150 –156
- DOI: 10.1049/mnl.2009.0112
- Type: Article
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Past molecular dynamics (MD) studies of boron nitride nanotubes (BNNTs) have used van der Waals parameters from generic force fields, combined with various values for the partial charges on the boron and nitrogen atoms. This study explores the validity of these parameters by first using quantum chemical packages Car-Parrinello molecular dynamics (CPMD) and Gaussian to compute partial charges for isolated and periodic BNNTs, both with and without water. Then in order to test the accuracy of the molecular mechanics force field using our computed charges, the authors calculate the interaction energy between each water molecule in a hydrated nanotube with the nanotube itself using two methods: first using a quantum chemical calculation, and secondly using the molecular mechanics force field. The authors show that in order to obtain satisfactory agreement in the interaction energies the boron and nitrogen Lennard-Jones parameters must be adjusted from their usual values. Modified Lennard-Jones parameters and partial charges, obtained by fitting, are presented as candidates for future MD simulations of hydrated BNNTs. - Author(s): Xing Yang ; Zhaoying Zhou ; Fuzhong Zheng ; Ying Wu
- Source: Micro & Nano Letters, Volume 5, Issue 2, p. 157 –161
- DOI: 10.1049/mnl.2010.0005
- Type: Article
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Considering the electron–phonon scattering mechanisms as well as the number of conduction channels, the long single-walled carbon nanotube (SWCNT) has larger temperature coefficient of resistivity than that of the short SWCNT or that of the multi-walled carbon nanotube (CNT). A tens of micrometres length, suspended SWCNT array-based temperature sensor was proposed, and its fabrication technique was presented. The theoretical analysis and the experimental results showed that the long SWCNT array device had high sensitivity and low power consumption than ordinary platinum thermal resistor. The long SWCNT array sensor also featured a simple and application-oriented process and was easier to use than a single CNT-based device. Thus, it has the potential to be applied in high sensitivity temperatures or flow measurements in an ultra small scale.
Dry etch fabrication of porous silicon using xenon difluoride
Investigation of corrosion behaviour of nanostructured copper thin film produced by radio frequency sputtering
Preparation and photocatalytic activity of Cu2+-doped 2, 4-dichlorophenol molecularly imprinted SiO2–TiO2 nanocomposite
Photoinduced hydrophilicity of TiO2 film as the effect of H2O2 addition
Enhancing the sensitivity of a mass-based piezoresistive micro-electro-mechanical systems cantilever sensor
Cost-effective fabrication of nanoscale electrode memristors with reproducible electrical response
Synthesis, structural and magnetic properties of CeO2 nanoparticles
Zinc sulphide thin films having nanometre grain size for photovoltaic applications
Nanoporous carbon produced from a styrene-acrylonitrile random copolymer/carbon nanotube composite
Nanostructured semiconductor surfaces induced by an electric field
Advanced step and flash nanoimprint lithography using UV-sensitive hard mask underlayer material
Fabrication of multilayer microstructures using dry film resist and deep reactive ion etcher
Fabrication of nano-mechanical switch using focused ion beam for complex nano-electronic circuits
Synthesis of Ca(OH)2 nanoparticles by wet chemical method
Effects of pertinent operating parameters on the size of iron nanoparticles synthesised by chemical vapour condensation method applying experimental design procedure
Infrared-photovoltaic properties of graphene revealed by electro-osmotic spray direct patterning of electrodes
Complex-controlled morphosynthesis of ring-like Cd(OH)2 superstructures
Validity of current force fields for simulations on boron nitride nanotubes
High sensitivity temperature sensor based on a long, suspended single-walled carbon nanotube array
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