Online ISSN
1750-0443
Micro & Nano Letters
Volume 6, Issue 7, July 2011
Volumes & issues:
Volume 6, Issue 7
July 2011
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- Author(s): Gwo-Bin Lee and Haixia Zhang
- Source: Micro & Nano Letters, Volume 6, Issue 7, page: 468 –468
- DOI: 10.1049/mnl.2011.0383
- Type: Article
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- Author(s): S. Murakami ; M. Konno ; T. Ikehara ; R. Maeda ; T. Mihara
- Source: Micro & Nano Letters, Volume 6, Issue 7, p. 469 –472
- DOI: 10.1049/mnl.2011.0097
- Type: Article
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Disc microresonators employing in-plane resonant modes are promising candidates as functional elements for high-sensitive mass sensing applications because they provide a high quality factor (Q) in air for the reduced air-damping effect. Furthermore, it has been reported that a disc resonator supported at fewer nodal points exhibited a higher Q. The authors have designed and fabricated two-point-supported annular micromechanical resonators employing the in-plane resonant modes, which shows two nodal points on the outer circumference, with an inner-to-outer radius ratio of 0.17. The beam structures to support the resonator were newly designed and connected to the two nodal points expected for a specified in-plane resonant mode to decrease the energy loss of the vibration through the supporting structures. The resonator was electrostatically driven and detected with 150 nm-wide vertical transducer gaps that were fabricated by trench etching of the single-crystal silicon using deep reactive ion etching with a resist mask patterned by electron beam lithography. The fabricated resonators show a resonant peak at 50.1 MHz with a Q of 3000 in air. The measured peak resonant frequency agreed well with the frequency predicted by finite-element simulations. - Author(s): Shuying Cheng and Hong Zhang
- Source: Micro & Nano Letters, Volume 6, Issue 7, p. 473 –475
- DOI: 10.1049/mnl.2011.0072
- Type: Article
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Tin sulphide (SnS) films with thicknesses of 65–580 nm have been deposited on glass substrates by thermal evaporation. The physical properties of the films were investigated using X-ray diffraction, scanning electron microscopy, atomic force microscopy, Raman spectroscopy and ultraviolet–visible–near-infrared spectroscopy measurements at room temperature. It is indicated that the deposited films mainly exhibit SnS phase, but they contain tiny SnO2. The deposited SnS films are pinhole free, smooth and strongly adherent to the surface of the substrate. With the increase of the film thickness from 65 to 580 nm, the colour of the SnS films changes from brown to dark brown to grey, and the grains and roughness of the films become larger and larger, but the direct bandgap decreases. All the films have larger direct bandgap of 1.55–2.28 eV, which is much larger than the 1.3 eV of bulk SnS. - Author(s): A. Kshirsagar ; S.P. Duttagupta ; S.A. Gangal
- Source: Micro & Nano Letters, Volume 6, Issue 7, p. 476 –481
- DOI: 10.1049/mnl.2011.0076
- Type: Article
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Modern lab-on-a-chip systems can benefit from integration of nanoelectromechanical system/microelectromechanical system (NEMS/MEMS) and complementary metal–oxide semiconductor technology with emphasis on low temperature processing. In the present work process, parameters for deposition of silicon oxide (SiOx) by inductively coupled plasma chemical vapour deposition (ICPCVD) at low temperature (70°C) are optimised. The sacrificial layer poly(methyl methacrylate) (PMMA) is in-house prepared and optimised. This PMMA sacrificial solution not only gives a low cost wide range of viscosity solutions, but it is also low temperature NEMS process compatible. With optimisations mentioned above, it has been possible to fabricate the whole device without exceeding the thermal budget 100°C. To the best of the authors' knowledge, this is the first report on sub-100°C, surface micromachined SiOx cantilevers deposited by ICPCVD and using PMMA as the sacrificial layer for low temperature NEMS applications. - Author(s): Lei-Guang Chen and Michael S.-C. Lu
- Source: Micro & Nano Letters, Volume 6, Issue 7, p. 482 –485
- DOI: 10.1049/mnl.2011.0117
- Type: Article
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The glass-based thin film transistor (TFT) process, as widely known for making liquid crystal displays, is utilised to make integrated capacitive sensors for dopamine detection. The interface capacitance change, after binding of dopamine and immobilised 4-carboxyphenylboronic acid, is detected through interdigitated microelectrodes and integrated sensing circuits. The associated impedance changes are analysed by an equivalent circuit model. Three designs with microelectrode capacitances of 28, 37 and 57 fF showed measured sensitivities of −3.9, −5.4 and −7.2 fF/mM, respectively. The minimum detectable capacitance changes were 12.7, 14.7 and 13.5 aF, equivalent to detectable dopamine concentrations of 3.2, 2.7 and 1.9 µM, respectively. - Author(s): Honglong Chang ; Jianbing Xie ; Qianyan Fu ; Qiang Shen ; Weizheng Yuan
- Source: Micro & Nano Letters, Volume 6, Issue 7, p. 486 –489
- DOI: 10.1049/mnl.2011.0120
- Type: Article
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A reduced micromachined inertial measurement unit (MIMU) was fabricated by a proposed two-step release silicon-on-insulator (SOI) process to meet the requirements of land vehicle navigation. The release process consists of two steps, that is, dry release using notching effect and wet release using hydrogen fluoride (HF) solution. By applying the presented layout design rules, most of the area of the device was released in the dry-etching process, but boundaries of the proof mass and the suspension beams were not released until the wet etching. Through such a process configuration, a smooth surface was obtained under some thickness-senstive structures such as suspension beams and a rough surface under some thickness-non-sensitive structures such as proof mass. The smooth surface avoids both the defects and the loss to the thickness brought about by the notching effect that is helpful to improve the reliability of the MEMS devices. The rough surface avoids the stiction under structures with a large area. A reduced MIMU was fabricated by such a process. The test results showed that scale factors of the X/Y-axis accelerometer and Z-axis gyroscope were about 19.11 mV/g and 15.6 mV/°/s at one atmosphere, respectively. The bias stability of the gyroscope was about 129.6°/h with a resolution of 0.0224°/s/√Hz. - Author(s): Senlin Jiang ; Dacheng Zhang ; Longtao Lin ; Zhenchuan Yang ; Guizhen Yan
- Source: Micro & Nano Letters, Volume 6, Issue 7, p. 490 –493
- DOI: 10.1049/mnl.2011.0128
- Type: Article
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A single-crystal silicon probe for micromechanical surface profilers is presented, which uses a double-ended tuning fork (DETF) resonator as the displacement-sensing element. In addition, a two-stage micro-leverage mechanism for force amplification is introduced to increase the overall sensitivity. The frequency shift of the DETF caused by the induced axial stress is directly proportional to the displacement input. The probe was fabricated through a standard silicon-on-glass process, which can realise high aspect ratio single-crystal silicon structures. The experimental results indicated that the probe had a nominal resonant frequency of 54.5 kHz under atmosphere at room temperature. The scale factor and linearity of the probe with the input range of 0–10 µm were evaluated to be 359.7 Hz/µm and 6.3%, respectively. The measured scale factor shows good agreement with the simulated value of 330 Hz/µm using ANSYSTM. - Author(s): C.K. Chung ; S.L. Lin ; S.Y. Cheng ; K.P. Chuang ; H.Y. Wang
- Source: Micro & Nano Letters, Volume 6, Issue 7, p. 494 –497
- DOI: 10.1049/mnl.2011.0133
- Type: Article
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The crystalline structure of titanium dioxide (TiO2) is very much related to its properties. The sol–gel process and CO2 laser annealing instead of conventional furnace annealing have been performed to investigate the crystalline TiO2 formation. The sol–gel solution was mixed by tetraisopropyl orthotitanate (TTIP), acetonylacetone, distilled water and alcohol at various molar ratios and spin-coated on the p-Si(100) substrate. Then the CO2 laser annealing in air at powers of 0.5, 1.5 and 3.0 W in the defocus mode was performed on the coatings for studying the crystallisation of titanium oxide. The microstructure and phase transformation of titanium dioxide were examined by X-ray diffraction pattern. Increasing TTIP concentration and decreasing laser power were favourable for anatase phase formation. The grain size of titanium dioxide calculated using Scherrer's formula was between 10 and 32 nm, which increased with increasing laser power. The ANSYS simulation was employed to calculate the temperature distribution of films to correlate with the phase transformation of titanium dioxide. This sol–gel processing combined with CO2 laser annealing had advantages of low cost, controllable titanium dioxide phase, selective area annealing and easy operating at room temperature. - Author(s): Jian-Yang Lin and Pai-Yu Chang
- Source: Micro & Nano Letters, Volume 6, Issue 7, p. 498 –502
- DOI: 10.1049/mnl.2011.0130
- Type: Article
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The formation of Si trenches with anisotropic wet etching of (100) Si wafers for light-emitting diode electrode arrays has been investigated. An alkali etchant, potassium hydroxide (KOH), was used as the anisotropic etchant for the Si etching in this study. Experimental results show that the KOH etching process not only etches the Si surface, but also etches the SiO2 film on the wafer surface. Electrode arrays of 25 columns by 25 rows, providing a total of 625 trenches in the Si wafer, were produced with well-controlled anisotropy. Finally, Silvaco TCAD software was used to simulate the thermal power variation of the LED die in the Si trench. Heat distribution simulation analysis showed that this design improves the heat dissipation problem in subsequent manufacturing processes, such as assembly and packaging. - Author(s): Chia-Feng Liu ; Ming-Kun Chen ; Ling-Sheng Jang
- Source: Micro & Nano Letters, Volume 6, Issue 7, p. 503 –509
- DOI: 10.1049/mnl.2011.0131
- Type: Article
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When cell impedance measurements are conducted at low frequency, the current passes through the outside wall of the cell membrane. The capacitance effect of the double layer and the position of the cell change the impedance. Therefore the pathological change inside the cell cannot be investigated. To overcome the shortcomings of low-frequency measurements, this Letter proposes a method that uses a dielectrophoretic (DEP) trapping technique to position single cells and a coplanar waveguide electrode to measure the impedance of a single HeLa cell (human cervical epithelioid carcinoma) in the frequency range of 1 MHz–1 GHz. Two materials (a double-sided printed circuit board and glass) are used to fabricate the measurement microelectrodes. Trapping microelectrodes are deposited on the glass substrate near the measurement microelectrodes to trap single cells using the DEP force. The electrical characterisation of a single cell is demonstrated using a two-port vector network analyser. The electrical equivalent model used in this work is validated through measurements of cell impedance in phosphate buffer solution and through electrical simulations of a single HeLa cell. - Author(s): Qifang Hu ; Chengchen Gao ; Yilong Hao ; Yangxi Zhang ; Gang Yang
- Source: Micro & Nano Letters, Volume 6, Issue 7, p. 510 –514
- DOI: 10.1049/mnl.2011.0137
- Type: Article
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This Letter presents the design and implementation of a highly symmetric microelectromechanical system sandwich accelerometer using a double-device-layer silicon-on-insulator (D-SOI) wafer. The proof mass of though-wafer-thickness is suspended by eight L-shaped beams mirror-symmetrically. The suspension system provides flexible mechanical suspension without large chip area consumption. Therefore the accelerometer is immune from trade-off between sensing capacitance and structure flexibility. The sensing mode (first vibration mode) of the accelerometer is successfully decoupled from other variation modes that followed. Thereby, the accelerometer is insensitive to the lateral acceleration and the rotation disturbance. The symmetric beam-mass structure is fabricated from both sides of the D-SOI wafer symmetrically using a combination of anisotropic wet etching and dry etching process. The accelerometer has high opened-loop capacitance sensitivity of 55 pF/±1 g. The closed-loop sensitivity is 1.096 v/g and the cross-axis sensitivity is 0.356%. The resolution of the accelerometer is 4.167 µg/√Hz (0–200 Hz at 1 atm). - Author(s): Hsinwha Liu ; Je-Chuang Wang ; Chen Hsu
- Source: Micro & Nano Letters, Volume 6, Issue 7, p. 515 –518
- DOI: 10.1049/mnl.2011.0139
- Type: Article
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The optical behaviour of nanostructured nanoporous alumina anodic oxide thin film (AAOF) on sapphires was investigated. The AAOF was intentionally nanostructured by varying the nanopore diameters, as a result, the distance between neighbour pores decreased. The resultant nanostructured nanoporous patterns cause super-paramagnetism and the excited photoluminescence splits into two wavelengths of near blue and green peaks. This light modulation could be related to the super-paramagnetic magnetisation of the patterns upon in nanoscale. With increasing the nanopore size by the reaming method, the super-paramagnetic susceptibility first decreases and then increases. Once the super-paramagnetic susceptibility deviates from that of the as-received AAOF, the green peak would be excited. On the other hand, strong super-paramagnetism facilitates excitation of the blue peak. - Author(s): Yanlong Shang ; Junbo Wang ; Sheng Tu ; Lei Liu ; Deyong Chen
- Source: Micro & Nano Letters, Volume 6, Issue 7, p. 519 –522
- DOI: 10.1049/mnl.2011.0129
- Type: Article
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The design, fabrication and testing of a z-axis micro-machined resonant accelerometer with differential detection fabricated by silicon-on-insulator (SOI) microelectromechanical system technology are reported. The sensor chip was developed by a silicon-direct-bonding SOI wafer (10+2+290 µm). Z-axis acceleration is differentially detected by using two H-style vibrating beams through a frequency shift caused by the inertial force acting as bending stress loading. To improve the sensitivity of the accelerometer, an amplifying mechanism formed by vibrating beams, supporting beams and seismic-mass, which are respectively designed with their thickness as 10, 30 and 300 µm, is adopted, from which the transformation efficiency between the external acceleration and the bending stress of the vibrating beams would be improved obviously. The electromagnetically excitation and detection is adopted to make the closed-loop control of the sensor easier. Testing results show that the Q-factors of the two vibrating beams are about 400 in the air and the differential sensitivity measured by two H-style resonators can reach to 584 Hz/g. - Author(s): V. Lin ; H.-C. Wei ; H.-T. Hsieh ; J.-L. Hsieh ; G.-D.J. Su
- Source: Micro & Nano Letters, Volume 6, Issue 7, p. 523 –526
- DOI: 10.1049/mnl.2011.0132
- Type: Article
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Presented is a microlens array (MLA) with long focal length (millimetre range) in various structures and arrangements using thermal reflow process for Shack–Hartmann wavefront sensors (SHWSs). The microlens focal length is usually of the same order of the lens diameter or several 100 µm. To extend the focal length, the authors made a photoresist MLA covered by polydimethysiloxane (PDMS) film on a glass substrate. Since the refractive index difference between the PDMS and MLA interface is lower than that of air and the MLA interface, the light is less bended when passing through it and focuses in a far distance. The exerimental result shows a 235 and 135 µm diameter MLA with 5.27 and 1.81 mm focal lengths, which is around six times longer than the conventional thermal reflow method. Other specific focal lengths could be realised by modifying the refractive index difference. After the long-focal-length MLA film was fabricated, it could be integrated with an image sensor to build a SHWS. The authors evaluated the performance of their sensor by measuring a progressive addition lens wavefront aberration. - Author(s): Xi Li ; Jiawen Li ; Jinjin Li ; Yi Liu ; Wenhao Huang
- Source: Micro & Nano Letters, Volume 6, Issue 7, p. 527 –529
- DOI: 10.1049/mnl.2011.0124
- Type: Article
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According to the emerging requirement in the nanofabrication field of obtaining the quantitative relationship between the nanostructure and the colour exhibited, a sphere-size colour model has been proposed and proved by experiments. The photonic crystal structures of SiO2 nanospheres with different diameters are fabricated on glass substrate by the self-assembly method. Simulation is carried out by thin film principle using the plane segmentation method, and a model is fitted to express the relationship between the peak wavelength and the diameter of the nanospheres. The result shows good agreement with that by the improved Bragg equation, and matched the experimental results quite well. Thus, the characteristics of its colour can be determined by the spectra obtained and the colorimetric principle. Finally, according to the model, the linear relationship between the sphere size and the peak wavelength, namely the colour of the sample, has been built. - Author(s): Jiawen Li ; Qi Han ; Yuhang Chen ; Jiaru Chu ; Wenhao Huang
- Source: Micro & Nano Letters, Volume 6, Issue 7, p. 530 –533
- DOI: 10.1049/mnl.2011.0109
- Type: Article
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Colloidal crystals can exhibit distinct structural colours that resulted from incomplete photonic bandgap. In this Letter, two kinds of colloidal crystals are fabricated and used to realise tunable colour by changing lattice distance and refractive index contrast between the particles and the medium among the particles. Through experiment and simulation analysis, the stop band characteristic of colloidal crystal is affected by the refractive index contrast and the lattice distance. The shift of peak position is nearly linear to the lattice distance even if the refractive index contrast is different. Longer tunable colour range and narrower bandwidth can be obtained in the colloidal crystal with lower refractive index contrast. Colloidal crystal with lower refractive index contrast has lower reflective intensity. The peak intensity is also related to lattice distance and there is an optimal lattice distance where colloidal crystal can obtain highest peak intensity. Such an investigation can help to acquire nice tunable colour by changing the stop band characteristic on the colloidal crystal. - Author(s): Jin-Chern Chiou ; Lei-Chun Chou ; You-Liang Lai ; Ying-Zong Juang ; Sheng-Chieh Huang
- Source: Micro & Nano Letters, Volume 6, Issue 7, p. 534 –536
- DOI: 10.1049/mnl.2011.0122
- Type: Article
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The present study focuses on implementing a complementary metal–oxide semiconductor (CMOS) microelectromechanical system thermal switch by using the commercially available Taiwan Semiconductor Manufacturing Company (TSMC) 0.35 µm two-poly four-metal CMOS process. There are two novel designs: first, the soft contact structure and post-processing fabrication; second, a new design of thermal actuator. To create the soft contact structure, residual stress effect has been utilised to make different bending curvatures. According to the experiments, the layer metal-1 has the largest residual stress effect that can achieve the largest deflection in the z-axis. Because the residual stress of the layer metal-1 is negative, the structure will bend down after release, hence providing larger contact area, which has been set up to obtain the lowest contact miss ability. In the post-processing fabrication, 0.3 µm thickness gold will be patterned at the contact tips. Since gold, rather than aluminium, has no oxidation issue, it has more reliability in preventing the problem of oxidation than aluminium. In the new thermal actuator design, the authors designed a novel folded-flexure with the electrothermal excitation to turn the switch on or off. In the prototype, the device size is 500×400 µm and the gap between two contact pads is 9 µm in off-state. Depending on the simulation results, the switch can work stably at 3 V, and the working temperature and operating bandwidth are individually 20–200°C. - Author(s): Dong F. Wang ; Xiaoqiang Li ; Ryutaro Maeda
- Source: Micro & Nano Letters, Volume 6, Issue 7, p. 537 –539
- DOI: 10.1049/mnl.2011.0081
- Type: Article
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Micro/nanofabrication of magnetic materials is becoming a crucial technology for future magnetic systems/devices such as high-density magnetic recording heads, high-density-patterned media, magnetic quantum devices, micro/nanomagnetic smart systems and so on. This work reports a prototype of mesa-structure, micromachined by sputtering NiFe alloys on SiO2 stripes, for potential applications in ensemble detection of nuclear spins. The status of the magnetic field present around the array of NiFe alloys was stimulated by ANSYS analysis. Subsequently, the mesa-structure array design was carried out according to the stimulated results of ANSYS analysis to obtain a strong magnetic gradient with homogeneous magnetic-flux density which was essential to the ensemble detection of nuclear spins. SiO2 stripes and the final mesa-structure were micromachined by means of micro-electro-mechanical systems technologies. The scanning electron microscope images demonstrated that the NiFe alloys were finely sputtered on SiO2 stripes with the ellipse-like shape. The final morphology of mesa-structure alloy was impacted by the vacuum degree in the sputtering process. - Author(s): B.P. Mahale ; D. Bodas ; S.A. Gangal
- Source: Micro & Nano Letters, Volume 6, Issue 7, p. 540 –542
- DOI: 10.1049/mnl.2011.0082
- Type: Article
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The development of a poly(vinyldifluoride) (PVdF)-based dynamic pressure sensor for low-pressure application is reported. β-phase PVdF film of thickness 10 µm is fabricated using the spin coating method with thermally evaporated Al electrodes (200 nm) on both sides of the film. The film is polled and packaged in a poly(dimethyl siloxane) block. The exposed area of the pressure sensor is ∼500 µm in diameter. A signal conditioning circuit is designed to amplify the signal and a NI DAQ card with LabVIEW software is used to acquire the signal on a PC. The dynamic pressure response of the sensor is recorded which shows linearity in detection. Pressure measured by the sensor is in the range of 10–150 kPa. - Author(s): Chia-Hao Kuo ; Chia-Wei Hsu ; Horng-Chih Lin ; Tiao-Yuan Huang
- Source: Micro & Nano Letters, Volume 6, Issue 7, p. 543 –545
- DOI: 10.1049/mnl.2011.0090
- Type: Article
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A novel suspended nanowire (NW) channel thin-film transistor (TFT) with sub-100 nm air gap has been fabricated and characterised. With a simple and low-cost over-etching-time-controlled reactive ion etching technique and a buffered-oxide etch wet-etching process, a suspended NW of 27 nm and an air gap of 10 nm were achieved. The resultant suspended-NW-channel TFTs showed an ultra-low subthreshold swing (52 mV/dec) and considerable hysteresis window (3.7 V). Finally, the impacts of device dimensions on the characteristics of suspended NW TFTs were also investigated. - Author(s): DaeYoung Kong ; Changtaeg Seo ; Bonghwan Kim ; Chan Seob Cho ; Jonghyun Lee
- Source: Micro & Nano Letters, Volume 6, Issue 7, p. 546 –548
- DOI: 10.1049/mnl.2011.0096
- Type: Article
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Recently, the important issues relating to the photovoltaic cell have featured low cost and high efficiency. To make a low-cost and high-efficiency photovoltaic cell, there are many aspects such as the development of inexpensive wafers, process simplification and improvement of optical and electrical properties. In this study, the two-step texturing method using a microblaster was developed to decrease the reflection of incident lights. Bridge-type electrode structures are suggested to expand the effective surface area and decrease the series resistance of finger electrodes. The authors decided to use 10 µm size powders since the efficiency of the solar cell could rather be reduced by using 50 µm size powders because of their extremely rough surface. And the surface of the wafer after microblaster etching was treated with a chemical etching method using HNA (HF:HNO3:CH3COOH=4:9:7) solution, a dry etching method using reactive ion etching and a oxide etching method. - Author(s): Chun-Ying Lin and Jin-Chen Chiou
- Source: Micro & Nano Letters, Volume 6, Issue 7, p. 549 –552
- DOI: 10.1049/mnl.2011.0100
- Type: Article
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Presented is a microelectromechanical system-based thermal actuating image stabiliser. The proposed stage has dimensions of 14.9×14.9×0.2 mm3 and contains a four-axis decoupling XY stage used for anti-shaking. The processes used to fabricate the stabiliser include silicon on isolator process, inductively coupled plasma process and flip-chip bonding technique. The maximum actuating distance of the stage is larger than 25 µm, which is sufficient to resolve the shaking problem in 3× optical zoom condition. According to the experiment results, the supplied voltage for the 25 µm moving distance is lower than 20 V, and the dynamic resonant frequency of the actuating device is 4.7 kHz. - Author(s): Dong-Yeon Lee ; Jaesool Shim ; Tae Song Kim ; Jae Hong Park
- Source: Micro & Nano Letters, Volume 6, Issue 7, p. 553 –558
- DOI: 10.1049/mnl.2011.0049
- Type: Article
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Pb(Zr0.52Ti0.48)O3 (PZT) thick film-based micro-transducers demonstrate excellent piezoelectric performances. However, its powder-based film requires very high sintering temperature to obtain high density and good electromechanical properties of the active film. High processing temperature enables inter-diffusion or reaction between PZT active materials and Si-based substrate to result in device failure via volatilisation of PbO especially over 800°C. Therefore the preventive solution to this problem should be considered in fabricating silicon-based piezoelectric microdevices for the better performance. In this research, compatibility in the interface stability and adhesion between the layers of the overall integrated piezoelectric thick-film devices were thoroughly investigated for the successful application of the process at high temperature. The Pt (or PtOx)/TiO2/SiNx/Si substrate represented the best interfacial properties among various combinations of structural substrates, so this structure is highly recommended to integrated piezoelectric thick-film microelectromechanical system devices. - Author(s): Shuai Zhang and Shuying Cheng
- Source: Micro & Nano Letters, Volume 6, Issue 7, p. 559 –562
- DOI: 10.1049/mnl.2011.0121
- Type: Article
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Cu-doped tin sulphide (SnS) films with a thickness of about 300 nm have been grown on glass substrates by thermal evaporation technique. Different Cu-doped SnS films were obtained by controlling the Cu evaporation time to roughly alter Cu-doping concentration in SnS films (from 5.7 to 23 atom%). Then they were annealed at a temperature of 250°C and a pressure of 5.0×10−3 Pa for 90 min. The structural, optical and electrical properties of the films were characterised by X-ray diffraction, atomic force microscopy, ultraviolet–visible–near infrared spectrometer and Hall-effect measurement system. All the films are polycrystalline SnS with orthorhombic structure, and the crystallites in the films are all exclusively oriented along (111) direction. Annealing can optimise the crystallinity of all the films. With the increase of Cu-doping concentration, the grain size of the films becomes larger and larger, but the roughness decreases. Meanwhile, the evaluated direct bandgap Eg of the SnS:Cu films initially decreases, reaches a minimum value of 1.38 eV with 15 atom% Cu and then increases thereafter. The carrier concentration of the films increases sharply, while the resistivity of the films decreases straightly. All the films are of p-type conductivity. Using the optimised conditions, it is possible to prepare SnS:Cu thin films suitable for absorbers of thin film solar cells. - Author(s): Zhonghua Yao ; Yen-Wen Lu ; Satish G. Kandlikar
- Source: Micro & Nano Letters, Volume 6, Issue 7, p. 563 –566
- DOI: 10.1049/mnl.2011.0136
- Type: Article
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A new technique utilising electrochemical deposition with the assistance of porous alumina membranes as the fabrication template is developed to directly grow metallic nanowires on different substrates. To emphasise the nanowire application in boiling enhancement, Cu nanowire (CuNW) has been successfully fabricated on Si, Au and Cu substrates with improved thermal properties and mechanical reliability. Several process parameters to control the CuNW growth have been discussed. The nanowire structures applied in pool boiling enhancement are further investigated and significant enhancements are observed with all the surfaces with nanowire structures. - Author(s): Dong-Hoon Lee ; Jung-Min Kim ; Jong-Wook Lee ; Yong-Song Kim
- Source: Micro & Nano Letters, Volume 6, Issue 7, p. 567 –570
- DOI: 10.1049/mnl.2011.0094
- Type: Article
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Organic thin film transistors, owing to their low-costs fabrication process and potential to be devised on flexible substrate, can be used for varied applications such as radio frequency identification tags, flexible electronics, biosensors and integrated circuits. In this regard, the authors fabricated a pentacene organic rectifier consisting of a transistor diode and a bridge rectifier. The poly 4-vinylphenol (PVP)-based single layer, which is optimised for high current level, and polymethyl-methacrylate (PMMA)-PVP double-layer structure were compared with respect to their rectification efficiency. The electrical properties of the organic rectifier could be improved by use of the PMMA-PVP double layer as an insulator compared with a single layer of PVP. The device structure was further modified to include a diode and bridge rectifier. The rectification efficiency of the diode and bridge rectifier could be increased by 10%. - Author(s): Yu-Cheng Lin ; Po-Chien Chou ; Kuan-Chou Hou ; Stone Cheng ; Jin-Chern Chiou ; Hsi-Fu Shih
- Source: Micro & Nano Letters, Volume 6, Issue 7, p. 571 –574
- DOI: 10.1049/mnl.2011.0135
- Type: Article
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This Letter presents an optical module with a holographic optical element (HOE) for the small-form-factor pickup head. The proposed module is mounted on a novel seesaw swivel-drive mechanism with unique features, including a rotary actuator for track-following; in addition, a seesaw arm nutates along a pivot for laser focusing. Additionally, the actuating force is increased within the limit of actuator size constraints by using a Halbach-magnet-array in biaxial voice coil motors. Experimental assessment of the holographic module and actuator reveals that the HOE module ensures the optical performance and stability of the system, together with a performance superior to a classic hinge-type swing arm actuator, as attributed to enhanced durability and higher robustness.
Editorial
Fabrication of two-point-supported annular microresonators with vertical transducer gaps
Influence of thickness on structural and optical properties of evaporated tin sulphide films
Optimisation and fabrication of low-stress, low-temperature silicon oxide cantilevers
Glass-based integrated capacitive sensors for detection of the neurotransmitter dopamine
Micromachined inertial measurement unit fabricated by a SOI process with selective roughening under structures
Silicon probe for micromachined surface profilers
Effect of sol–gel composition ratio and laser power on phase transformation of crystalline titanium dioxide under CO2 laser annealing
KOH anisotropic etching of Si wafers for light-emitting diode electrode arrays
Design and fabrication of coplanar waveguide probes for single-cell impedance measurement using radio frequency
Low cross-axis sensitivity micro-gravity microelectromechanical system sandwich capacitance accelerometer
Light modulation of nanostructured alumina anodic oxide thin film on sapphire
Z-axis differential silicon-on-insulator resonant accelerometer with high sensitivity
Design and fabrication of long-focal-length microlens arrays for Shack–Hartmann wavefront sensors
Relationship between the size of SiO2 nanospheres and the structure colour
Tunable structural colour on the basis of colloidal crystal
Thermal switch design by using complementary metal–oxide semiconductor MEMS fabrication process
Magnetic mesa-structure array for ensemble detection applications of nuclear spins
Development of low-cost poly(vinyldifluoride) sensor for low-pressure application
Characterisation of a suspended nanowire channel thin-film transistor with sub-100 nm air gap
Air-bridge-type electrodes for high-efficiency photovoltaic cell
Design, fabrication and actuation of four-axis thermal actuating image stabiliser
Optimal materials and process conditions of functional layers for piezoelectric MEMS process at high temperature
Thermally evaporated SnS:Cu thin films for solar cells
Direct growth of copper nanowires on a substrate for boiling applications
Improved organic rectifier using polymethyl-methacrylate-poly 4-vinylphenol double layer
Optimising the performance of optical data storage drives based on a novel seesaw–swivel actuator for a holographic module
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