Department of Electrical Engineering

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Fluid continuity theory is used to describe the dynamic response of open Micro-Electro-Mechanical-System (MEMS) devices. For a packaged device, at low pressure, the fluid continuity theory is no longer valid and a rarefication theory based on a Knudsen number is used. In an open MEMS device, the characteristic length which determines the Knudsen number is represented by the gap between the MEMS bridge and underneath actuation electrodes. On the other hand, for a packaged device, effective characteristic length is modified with the packaging cavity height. In this paper, for a packaged MEMS device, effective characteristic length with reference to the packaging height is derived. © 2016 Author(s).

World University root node

AIP Conference Proceedings

Change of characteristic length with packaging for torsional MEMS switch

In the present work, HfO2 thin film (100 nm) has been deposited by sputtering technique and annealed at various temperatures ranging from 400 to 1000 °C (in step of 200 °C) in O2 ambient for 10 min. The samples have been characterized using XRD, FTIR, EDAX, AFM and Laser Ellipsometer. The impact of annealing temperatures in O2 ambient on structural properties such as crystallite size, phase, orientation, stress have been studied using XRD. The Hf–O phonon peaks in the infrared absorption spectrum are detected at 512, 412 cm−1. The stretching vibration modes at 720 and 748 cm−1 correspond to HfO2. AFM data show mean grain size in the range of 38–67 nm. The film reveals variation in structural properties, which appears to be responsible for variation in oxygen percentage, refractive index (1.96–2.01) at 632 nm wavelength and roughness (6.13–16.40 nm). Annealing temperature as well as ambient condition has significant effects on stress, crystal size and thus the arrangement of atoms. For good quality film, annealing temperature larger than 600 °C is desired. © 2016, Springer Science+Business Media New York.

Fulltext

Journal of Materials Science: Materials in Electronics

Impact of post deposition annealing in O2 ambient on structural properties of nanocrystalline hafnium oxide thin film

This paper presents a novel design approach of T-type RF MEMS switch cross over junction, implemented using symmetric toggle switch (STS) as a basic building block. T-type switches are key elements for designing redundancy switch matrices. Proposed design is a dual type switch, i.e. under operation same bridge is used as an ohmic series switch as well as a capacitive shunt switch. This reconfigurable switch constitutes the cross over junction part for the T-type switch. Simulated results show an insertion loss of < 0.2 dB upto 10 Ghz and isolation is better than -20 dB over a band of 5 Ghz through capacitive path and is better than -80 dB up-to 10 Ghz through ohmic contact path. STS as a building block is used for designing cross over junction and is a technologically mature device. The designed actuation voltage of this cross over switch is 4.75 Volts and simulated resonant frequency is 3.253 KHz. © 2016 Author(s).

Design of MEMS based 'cross over junction' for T-type switch

This paper presents design, simulation results and envisaged fabrication process for a versatile MEMS bimorph actuator with large out of plane displacement and high resolution. A comparative study of mechanical, thermal and electrical response of the micro-actuator is presented by using two well-known MEMS simulation tools. The bimorph structure measuring 700 × 1280 mm2 is fully integrable with CMOS fabrication process. It is indented for tunable filter applications where the precise vertical motion of the payload, the top metallic electrode anchored rigidly to bimorph 'springs' spans the vertical range of 250-300 microns with submicron resolution. Each bimorph spring resembles a hair pin structure and is composed of materials with large difference in thermal expansion coefficients e.g. electroplated gold and polysilicon for optimal out-of-the plane deflection. The novel structure can also be configured for analog micro-mirror based optical and IR spectroscopy applications by controlling the actuation bias and top electrode surface parameters. © 2016 Author(s).

A versatile MEMS bimorph actuator with large vertical displacement and high resolution: Design and fabrication process

This paper presents a new type of capacitive shunt RF-MEMS switch. In the proposed design, float metal concept is utilized to reduce the RF overlap area between the movable structure and central conductor of CPW for improving the insertion loss of the device. This has been achieved without affecting the down-state response. Further, float metal also makes the down-state behavior predictable in terms of resonant frequency. For reducing the pull-in voltage, the switch is implemented with cantilever type of structure on either side of the transmission line. This structure also has the capability to inductively tune the isolation optimum value to the different bands and thus can be used in the reconfigurable RF systems. The device shows an insertion loss less than 0.10 dB, a return loss below 36.80 dB up to 25 GHz as compared to 1.00 dB insertion, 7.67 dB return loss for the conventional switch. In the OFF state, proposed device shows two isolation peaks i.e. 48.80 dB at 4.5 GHz and 54.56 dB at 9.7 GHz, when either or both cantilevers are electro-statically actuated to the down-state position respectively. The conventional device has a single isolation peak in the X-band. In addition, improvement of around 3 times in the bandwidth has also been achieved. The designed switch can be used at device and sub-system level for the future multi-band communication applications. © 2015 Karabuk University

Engineering Science and Technology, an International Journal

A novel design for low insertion loss, multi-band RF-MEMS switch with low pull-in voltage

In this paper, coupled beam bandpass Disk filter is designed for 1 MHz bandwidth. Filter electrical equivalent circuit simulation is performed using circuit simulators. Important filter parameters such as insertion loss, shape factor and Q factor aresetimated using coventorware simulation. Disk resonator based radial contour mode filter provides 1.5 MHz bandwidth and unloaded quality factor of resonator and filter as 233480, 21797 respectively. From the simulation result it's found that insertion loss minimum is 151.49 dB, insertion loss maximum is 213.94 dB, and 40 dB shape factor is 4.17. © 2016 Author(s).

A MEMS disk resonator-based band pass filter electrical equivalent circuit simulation

Ruthenium is deposited by DC magnetron sputtering at different powers and is characterized. The effect of sputtering power on the electrical and structural properties of the film is investigated experimentally. High resolution X-ray diffraction is used to characterize the microstructure of Ru films deposited on SiO2 surface. The peak (002) is more sharp and intense with full width at half maximum (FWHM) of 0.37° at 250W. The grain size increases with increase in sputtering power improving the crystallinity of the film. The film deposited at high sputtering power also showed lower resistivity (12.40 μΩ-cm) and higher mobility (4.82 cm2/V.s) as compared to the film deposited at low power. The surface morphology of the film is studied by atomic force microscopy (AFM). © 2016 Author(s).

Effect of sputtering power on the growth of Ru films deposited by magnetron sputtering

Owing to recent well-known trends, renewable resources are becoming increasingly prominent in the complex energy market mosaic. As long as their penetration level is low, they can be handled easily by the current infrastructure, but at present incremental rates, this will not be the case in the future. The intermittent nature of solar and wind generation will require a far more flexible compensation mechanism than is currently available. Because of this, large battery banks that act as buffers between the generator and the grid invariably accompany today’s renewable energy installations. Wind power, in particular, is not only intermittent but also it has no day-average predictability, as winds can differ hour-to-hour as easily at night as during the day, adding an extra amount of irregularity to an already varying load. This suggests that plug-in electric vehicles (PEVs) will be called on to perform, not only the more manageable regulation tasks, but also aid in providing peak power. As noted earlier, this might not find approval with PEV owners unless the pricing model is modified. Nevertheless, it is reasonable to ask whether a large PEV contracted fleet could perform this task on a national (US) level. Studies have shown that the answer is yes. With an overconfident 50% estimation for the market penetration of wind energy and 70 million PEVs available, peak power could be provided at the expense of approximately 7 kWh of battery energy per day or about 10%-20% of an average PEV reserve. © The Institution of Engineering and Technology 2016.

Power Electronic Converters and Systems: Frontiers and Applications

Automotive energy systems

Synthesis of orthorhombic (α) MoO3 nano-flakes by dry oxidation of RF sputtered Mo thin film is presented. The influence of Mo thickness variation, oxidation temperature and time on the crystallographic structure, surface morphology and roughness of MoO3 thin films was studied using SEM, AFM, XRD and Raman spectroscopy. A structural study shows that MoO3 is polycrystalline in nature with an α phase. It was noticed that oxidation temperature plays an important role in the formation of nano-flakes. The synthesis technique proposed is simple and suitable for large scale productions. The synthesis parameters were optimized for the fabrication of sensors. Chrome gold-based IDE (interdigitated electrodes) structures were patterned for the electrical detection of organic vapors. Sensors were exposed to wide range 5-100 ppm of organic vapors like ethanol, acetone, IPA (isopropanol alcohol) and water vapors. α-MoO3 nano-flakes have demonstrated selective sensing to acetone in the range of 10-100 ppm at 150 °C. The morphology of such nanostructures has potential in applications such as sensor devices due to their high surface area and thermal stability. © 2016 IOP Publishing Ltd.

Semiconductor Science and Technology

Synthesis of α-MoO3 nano-flakes by dry oxidation of RF sputtered Mo thin films and their application in gas sensing

Selective detection of trace level water vapours by functionalized porous silicon (PS) using photoluminescence (PL) quenching technique is reported. This sensitive technique provides sensing data through optical probing on a surface with a submicron surface area. PS samples were prepared via electrochemical etching and were functionalized using ammonium sulphide and UV exposure which brought about major changes in the surface properties. Samples were examined using SEM, FTIR, contact angle and PL spectroscopy. These samples were tested as sensors in the presence of linear aliphatic alcohols and water vapours in the wide range of 0-400 ppm. An increasing trend of sensor response with increase in alcohol chain length and minimal response to water vapours was observed from sensors based on as-anodized PS samples whereas post functionalization, sensors portrayed an opposite response wherein selective response to water vapours and minimal response to alcohols was indicated. The role of surface nitridation is highlighted in selective sensing of water vapours. A correlation between the sensing response and surface chemistry of samples has been established. It is implicated that sensing is directly linked to both the chemical properties of the sensing surface and analytes. A highly sensitive sensor for detection of water vapours at low ppm is presented. A simple and compact design of portable optical sensors, applicable for water vapour sensing is proposed. © 2016 The Royal Society of Chemistry.