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Indian Journal of Pure and Applied Physics

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[This special issue is based on the papers presented at the Indo-Chinese Workshop on Micro Electro Mechanical Systems (MEMS) and Related Technologies held at National Physical Laboratory, New Delhi 110 012 during April 5-7, 2006]

 

Volume 45                                                                    Number 4                                                 APRIL 2007

CODEN : IJOPAU 45 (4) 265-414                                                                                           ISSN : 0019-5596

 

CONTENTS

Foreword

267

 

Vasudev K Aatre

 

Preface

268

        Vikram Kumar & V K Jain

Papers

 

Piezoelectrically actuated array microjet for biomedical purpose

273

Xu Qiang, Zhou Zhaoying*, Zhu Junhua, Feng Yanying, Lin Dong & Du Guibin

 

Piezoelectric microvalve

278

P V M Ramanamurthy, R Ahrens & S Karmalkar*

 

Measurement and simulation of carbon nanotube’s piezoresistance property by a micro/nano combined structure

282

Xing Yang, Zhaoying Zhou*, Ying Wu, Mingfei Xiao, Qingqing Luo, Chenren Shao,
Jin Zhang & Yingying Zhang

 

Affinity cantilever sensors for cardiac diagnostics

287

Manoj Joshi, Nitin Kale, S Mukherji, R Lal & V Ramgopal Rao*

 

Piezoresistive effects of resonant tunneling structure for application in micro-sensors

294

Wendong Zhang*, Chenyang Xue, Jijun Xiong, Bin Xie, Tianjie Wei & Yong Chen

 

Development of silicon and quartz based MEMS high precision accelerometers

299

Santiram Kal* & Soumen Das

 

Uncooled infrared detectors based on MEMS technologies

304

V K Jain

 

Wafer bonding — A powerful tool for MEMS

311

K N Bhat*, A Das Gupta, P R S Rao, N Das Gupta, E Bhattacharya, K Sivakumar, V Vinoth Kumar,
L Helen Anitha, J D Joseph, S P Madhavi & K Natarajan

 

Silicon-based MEMS fabrication techniques and standardization

317

Yilong Hao

 

Fabrication of MEMS composite-polymer gas sensor arrays for electronic nose

321

B D Pant*, Mahesh Kumar, Subha Lakshmi, Anil Arora, Mahanth Prasad, Akshdeep Sharma,
Mohan Patel, S Radhakrishnan & V K Dwivedi

 

MEMS prototyping using RF sputtered films

326

Sudhir Chandra*, Vivekanand Bhatt, Ravindra Singh, Preeti Sharma & Prem Pal

 

Design and electro-thermal simulation of a polysilicon microheater on a suspended membrane for use in gas sensing

332

V K Khanna*, Mahanth Prasad, V K Dwivedi, Chandra Shekhar, A C Pankaj & J Basu

 

Micromachined conductor backed coplanar waveguides for millimeter wave circuit application

336

Shiban K Koul*, Abhishek Kumbhat & Ananjan Basu

 

Advances in chemical sensors, biosensors and microsystems based on ion-sensitive field-effect transistor

345

V K Khanna

 

Electrochemical actuator from conductive electroactive polymer polypyrrole deposited on gold

354

Dayanand Sutar*, D K Aswal, S K Gupta & J V Yakhmi

 

Material selection for MEMS devices

358

Rudra Pratap* & A Arunkumar

 

Fabrication of single-walled carbon-nanotube with metallic electrodes

368

Ying Wu, Zhaoying Zhou*, Xing Yang, Mingfei Xiao, Qingqing Luo, Jin Zhang,
Ying Ying Zhang & Yagang Yao

 

Measurement of novel micro bulk defects in semiconductive materials based on Mie scatter

372

You Zheng*, Li Yingpeng & Chen Jun

 

Stress evaluation of RF sputtered silicon dioxide films for MEMS

377

Vivekanand Bhatt, Sudhir Chandra*, Sushil Kumar, C M S Rauthan & P N Dixit

 

Microfabrication and characterization of gallium arsenide membranes for force sensor applications

382

Niranjana Goswami*, Krishan Lal, J Miao & H L Hartnagel

 

Studies on RF MEMS shunt switch

387

Preeti Sharma*, Shiban K Koul & Sudhir Chandra

 

Nano-structured ZnO films by sol-gel process

395

Harish Bahadur*, A K Srivastava, Divi Haranath, Harish Chander, A Basu, S B Samanta,
K N Sood, Ram Kishore, R K Sharma, Rashmi, Vivekanand Bhatt, Prem Pal & Sudhir Chandra

 

Deposition of low stress polysilicon thin films using low-pressure chemical vapour deposition

400

Mahesh Kumar*, Mahant Parsad, Niranjana Goswami, Anil Arora, B D Pant & V K Dwivedi

 

Variation of the surface layer during chemical mechanical polish

403

Luo Jianbin

 

Development of ferrofluid and its possible applications in MEMS

406

Vinod Kumar, R P Pant, S K Halder* & M S Yadav

 

___________

*The corresponding author has been indicated by (*) mark in case of papers with more than one author.

Indian Journal of Pure & Applied Physics

Vol. 45, April 2007, pp. 273-277

 

 

Piezoelectrically actuated array microjet for biomedical purpose

 

Xu Qiang, Zhou Zhaoying, Zhu Junhua, Feng Yanying, Lin Dong & Du Guibin

State Key Laboratory of Precision Measurement Technology and Instruments,Tsinghua University, Beijing, China 100 084

E-mail: serzha@gmail.com

Received 7 June 2006; revised 4 December 2006; accepted 3 January 2007

This paper presents a micromachining-based piezoelectrically actuated array microjet for biomedical purposes such as inhalation drug therapy (IDT) and drug microencapsulation. The microjet consists of a reservoir and a fluid chamber, which is formed by a piezoelectric transducer bonded to a silicon chip with numerous micro nozzles. Inside the fluid chamber, a continuous pressure wave generated by the piezoelectric transducer propagates towards the silicon chip and squeezes the liquid out through the nozzles. The pressure wave in fluid chamber is numerically simulated using finite elements method to give a reference for nozzles arrangement. Diameter and velocity measurements of droplets, temperature estimations on working device and a preliminary animal experiment of IDT are done to characterize the microjet. As a result, the microjet could be a promising tool in biomedicine field.

Keywords: Microjet, Inhalation drug therapy, Piezoelectric transducer

IPC Code: B06B1/06, A61K

 

Indian Journal of Pure & Applied Physics

Vol. 45, April 2007, pp. 278-281

Piezoelectric microvalve

 

P V M Ramanamurthy1, R Ahrens2 & S Karmalkar3

1, 3 Department of Electrical Engineering, Indian Institute of Technology Madras, 600 036

2 Institute for Microstructure Technology, Forschungszentrum Karlsruhe, Germany

3E-mail: karmal@ee.iitm.ac.in Ph: 044-2257-6409 Fax: 044-2257-4402

Received 7 June 2006; revised 28 December 2006; accepted 2 January 2007

A normally closed microvalve is a very important component of a microfluidic system. The fabrication of an active, normally-closed piezoelectric microvalve useful for automated drug delivery or control of fluids in microreactor systems has been studied. The microvalve has dimensions of 19 mm ´ 19 mm ´ 7 mm, an inlet diameter of 200 µm, a dead volume of 0.33 µl and has a steady-state flow-rate of about 240 sccm.

Keywords: Piezoelectric microvalve, Microreactor

IPC Code:     H01L41/00

Indian Journal of Pure & Applied Physics

Vol. 45, April 2007, pp. 282-286

 

 

 

 

 

 

 

 

 

Measurement and simulation of carbon nanotube’s piezoresistance property
by a micro/nano combined structure

 

Xing Yang1,2, Zhaoying Zhou1,2, Ying Wu1,2, 4, Mingfei Xiao1,2, Qingqing Luo1,2, Chenren Shao1,2

1MEMS Lab, Department of Precision Instruments & Mechanology, Tsinghua University, P R China

2 State Key Lab of Precision Measurement Technology and Instrumentation, Tshinghua University, P R China

4 Chongqing University of Science and Technology, chongqing, P R China

Jin Zhang3, Yingying Zhang3

3Department of Chemistry, Peking University, P R China

Received 7 June 2006; accepted 3 January 2007

In this paper, the present status of carbon nanotube’s electromechanical properties was reviewed. The relationships among the carbon nanotube’s resistance, gauge factor and the rates of change of the band gaps with strain (dEg/de) were analyzed and simulated. Then, a micro/nano combined device and method for measuring the piezoresistance property of carbon nanotube were proposed. The device is consisted of a silicon chip and a printed circuit board which is used for loading and leading wire. The microelectrodes were fabricated on the silicon chip by FIB and a CVD-growth single-wall carbon nanotube was connected with the microelectrodes. The voltage-current characteristic of the carbon nanotube was measured using the proposed device. The relationship between the current and the voltage is basically linear, which demonstrates that the carbon nanotube is metallic. The experimental results show that the micro/nano combined device can be used for measuring the piezoresistance of carbon nanotube in our future work.

Keywords: Piezoresistance, Carbon nanotube, Micro/nano combined device

IPC Code: B82B; H01L41/00

 

Indian Journal of Pure & Applied Physics

Vol. 45, April 2007, pp. 287-293

 

Affinity cantilever sensors for cardiac diagnostics

Manoj Joshi, Nitin Kale, S Mukherji, R Lal & V Ramgopal Rao*

Micro-fabrication Laboratory, Indian Institute of Technology Bombay, Mumbai 400 076

* E-mail: rrao@ee.iitb.ac.in

Received 7 June 2006; accepted 9 February 2007

Cardiac problems are on the rise in the Indian sub-continent due to the changing life styles and food habits. Acute Myocardial Infraction (AMI) is becoming a major concern. In this paper, we report the development of affinity cantilever based sensors for the detection of AMI with optical and electrical readouts. We designed, simulated and fabricated these cantilevers with various micro fabricated materials such as silicon dioxide, silicon nitride and SU-8. Thin films such as silicon nitride and p-type polysilicon are deposited using hot wire CVD technique. For electrical detection, p-type polysilicon was used as a piezoresistive layer. The mechanical and electrical performance parameters of these cantilevers were investigated using Atomic Force Microscope (AFM) set-up. The top surface of these cantilevers was selectively immobilized with the antibodies. Following this, antibody specific antigens were allowed to react with the cantilever surface in the liquid cell of AFM set-up for the optical detection. For electrical signal detection, microcontroller based signal conditioning and digital readout circuit was developed.

Keywords:  Cantilever sensors, Cardiac diagnostics, Myocardial infraction, Piezoresistive layer, Atomic force microscope

IPC Code:  A61B5/04, H02N2/00

 

 

 

 

 

Indian Journal of Pure & Applied Physics

Vol. 45, April 2007, pp. 294-298

 

 

Piezoresistive effects of resonant tunneling structure for application in micro-sensors

Wendong Zhang¹, Chenyang Xue¹, Jijun Xiong¹, Bin Xie¹, Tianjie Wei¹ & Yong Chen²

¹Kay Lab of Instrumentation Science & Dynamic Measurement of Ministry of Education,

North University of China, Taiyuan, Shanxi 030051, China, wdzhang@nuc.edu.cn

²Ecole Normale Supérieure, 24 rue Lhomond, Paris 75231, France, yong.chen@ens.fr

Received 7 June 2006; revised 2 January 2007; accepted 5 February 2007

In this paper, piezoresistive properties of resonant tunneling structure made of undoped InGaAs/AlAs double-barrier quantum layers have been experimentally investigated, and the resonant tunneling structure was grown by molecular beam epitaxy (MBE) on semi-insulation (001)-oriented GaAs substrate. We found that the piezoresistivity of such quantum layers is about one order higher than that of the commonly used silicon structures. Micro accelerometers based on InGaAs/AlAs double-barrier resonant tunneling structures have also been designed and fabricated by control hole technique.

Keywords:  Resonant tunneling, Piezoresistor, Double-barrier microstructure, Superlattice

IPC Code:  B06B1/06; C30B

 

Indian Journal of Pure & Applied Physics

Vol. 45, April 2007, pp. 299-303

 

Development of silicon and quartz based MEMS high precision accelerometers

 

Santiram Kal* & Soumen Das

Advanced Technology Centre, Department of Electronics & ECE, Indian Institute of Technology, Kharagpur 721 302, India

*E Mail: srkal@ece.iitkgp.ernet.in

Received 7 June 2006; revised 9 October 2006; accepted 4 December 2006

Conventional electro-mechanical inertial sensors are being replaced by MEMS versions which are miniature in size, light weight, cost effective, more reliable and sensitive, low power consuming and VLSI compatible. Although silicon is the most widely used material for MEMS, quartz has some advantage for realizing inertial sensors due to its piezoelectric property. The R&D activities undertaken in the authors’ laboratory in the area of MEMS based silicon and quartz acceleration sensors have been described. While the silicon accelerometer is based on the piezoresistive technique, the quartz double ended tuning fork (DETF) accelerometer works on the stress dependence of vibration frequency.

Keywords: MEMS, High precision accelerometers, Silicon, Quartz

IPC Code: B81B7/02, H05H

Indian Journal of Pure & Applied Physics

Vol. 45, April 2007, pp. 304-310

 

 

 

 

 

 

 

 

 

 

 

Uncooled infrared detectors based on MEMS technologies

V K Jain

CSIO (Delhi Centre), CSIR Complex, Pusa Campus, New Delhi 110 012

E-mail: Vk_mems@yahoo.com

Received 7 June 2006 ; revised 11 December 2006 ; accepted 9 January 2007

Uncooled infrared (IR) detectors are gaining importance over the HgCdTe based IR photon detectors because of their room temperature operation, low power consumption and smaller in size. Silicon micromachining has made it possible to make micro bolometer base IR detector. In a focal plane array (FPA), there is a two dimensional assembly of bolometers and each bolometer acts as a thermally sensitive pixel. The detector element consists of thermal sensitive material suspended above the readout electronics having an air gap of 2 micron and supported by thermally isolated hinges. The most important task is to design the structure of the sensor having the lowest possible thermal conductance. The characterization gives that thermal conductance and thermal mass are the deciding factors for the higher responsivity and detectivity. This paper presents a modified design based on thermal characterization of the membranes of micro bolometer. Based on our theoretical analysis, the required thermal conductance can be achieved even with short hinges. This can be done by reducing the thermal conductivity of the material of hinges. Our experimental investigations are in good agreement with this concept. This will also enhance the fill factor of the two dimensional IR array.

Keywords: Infrared detectors, MEMS, Uncooled IR detectors, Silicon micromachining

IPC Code: H01L, B81B7/02

 

Indian Journal of Pure & Applied Physics

Vol. 45, April 2007, pp. 311-316

 

 

Wafer bonding  — A powerful tool for MEMS

 

K N Bhat+, A Das Gupta, P R S Rao, N Das Gupta, E Bhattacharya, K Sivakumar, V Vinoth Kumar,
L Helen Anitha, J D Joseph, S P Madhavi & K Natarajan*

Electrical Engineering Department, Indian Institute of Technology Madras, Chennai 600 036

+Present address: ECE Department, Indian Institute of Science Bangalore 560 012

*Bharat Electronics Ltd, Jalahalli, Bangalore 560 013

Received 7 June 2006; accepted 16 October 2006

Wafer bonding techniques play a key role in the present day silicon bulk micromachining for MEMS based sensors and actuators. Various silicon wafer bonding techniques and their role on MEMS devices such as pressure sensors, accelerometers and micropump have been discussed. The results on the piezoresistive pressure sensors monolithically integrated with a MOSFET differential amplifier circuit have been presented to demonstrate the important role played by the Silicon Fusion Bonding technique for integration of sensors with electronics on a single chip.

Keywords: Silicon fusion bonding, Silicon on insulator, Piezoresitive pressure sensor, MOSFET amplifier integration with sensor

IPC Code: B81B7/02

 

 

 

 

 

Indian Journal of Pure & Applied Physics

Vol. 45, April 2007, pp. 317-320

 

 

Silicon-based MEMS fabrication techniques and standardization

Yilong Hao

National key Lab of Micro/Nano Fabracation Technology,
Institute of Microelectronics, Peking University, Beijing, 100 871

E-mail: ylhao@ime.pku.edu.cn

Received 7 June 2006; accepted 2 January 2007

The silicon-based MEMS fabrication technology, including bulk micromachining and sacrificial layers technology have been developed and studied. The 3-D fabrication and integration of silicon-based MEMS and standard process fabrication have been studied in the present paper.

Keywords: MEMS, Silicon-based MEMS, Micromachining

IPC Code: B81B7 /02

 

 

 

Indian Journal of Pure & Applied Physics

Vol. 45, April 2007, pp 321-325

 

 

Fabrication of MEMS composite-polymer gas sensor arrays for electronic nose

 

B D Pant, Mahesh Kumar, Subha Lakshmi, Anil Arora, Mahanth Prasad, Akshdeep Sharma, Mohan Patel,
S Radhakrishnan* & V K Dwivedi

MEMS Laboratory, Central Electronics Engineering Research Institute, Pilani 333 031, Rajasthan

*Polymer Science and Engineering, National Chemical Laboratory, Pune 411 008

Received 7 June 2006; accepted 6 February 2007

Sensor arrays capable of sensing different gases combined with a sampling system and a means of pattern classification and recognition comprise a basic system for an ‘Electronic Nose’ In the present work, a complete process for the fabrication of micro-cavities with sensing electrodes and volumes ranging from 2.5 to 12 nano-liters for the development of polymer gas sensors has been reported. An array of eight sensing cells in four sizes have been fabricated using SU-8 negative
tone resist through UV-LIGA process developed at CEERI, Pilani. The length and width of the SU-8 cavities are: 250 ´ 250, 300 ´ 300, 500 ´ 500 and 500 ´ 600 micron and the depth of each of them was optimized to be 40 micron. These cavities filled with different polymer composites comprise the basic sensing cells for a variety of gases. The current paper presents the salient features of the fabrication process in detail and the results obtained in ethanol and methanol ambient using a polymer composite developed through dissolution of styrene and polyaniline in PMMA. A number of other composites such as Pc-Ppy, Pr-Ppy, Fc+-PPy have also been synthesized and tested for a high sensitivity in carbon monoxide.

Keywords: Polymer gas sensor, Composite polymer, Conducting polymer, Electronic nose, Sensor array, Sensitivity, Selectivity

IPC Code: B81B7/02

 

 

Indian Journal of Pure & Applied Physics

Vol. 45, April 2007, pp. 326-331

 

MEMS prototyping using RF sputtered films

Sudhir Chandra, Vivekanand Bhatt, Ravindra Singh, Preeti Sharma & Prem Pal*

Centre for Applied Research in Electronics, Indian Institute of Technology Delhi, Hauz-khas, New Delhi 110 016

*Yonsei Microsystems Laboratory, Yonsei University, Seoul, South Korea

E-mail: schandra@care.iitd.ernet.in

Received 7 June 2006; accepted 7 February 2007

In the present work, the deposition and characterization of dielectric, piezoelectric, semiconductor and conductor films by RF diode / RF magnetron sputtering process for applications in MEMS fabrication have been reported. Thin films of silicon dioxide, silicon nitride, amorphous silicon, zinc oxide and lanthanum doped lead zirconate titanate (PLZT) were prepared by RF sputtering process and extensively characterized for their structural, optical, and electrical properties. Thin films of conducting materials which are commonly used in MEMS fabrication (Cr, Au, Ti, and Pt) were also prepared by the same process. A few applications of these films in MEMS are demonstrated. It has been concluded that RF sputtering can be advantageously used for rapid prototyping of MEMS and demonstrating new ideas especially by researchers who do not have access to a well-established MEMS foundry.

Keywords: RF sputtering, Dielectric films, Piezoelectric films, Perfect convex corner, MEMS microstructures

IPC Code: G01L 9/06, B81B7/02

 

 

Indian Journal of Pure & Applied Physics

Vol. 45, April 2007, pp. 332-335

 

Design and electro-thermal simulation of a polysilicon microheater on a suspended membrane for use in gas sensing

V K Khanna*, Mahanth Prasad, V K Dwivedi, Chandra Shekhar, A C Pankaj & J Basu

Central Electronics Engineering Research Institute, Pilani 333 031

Central Mechanical Engineering Research Institute, Mahatma Gandhi Avenue, Durgapur 713 209

*E-mail: vkk@ceeri.ernet.in

Received 7 June 2006; revised 5 December 2006; accepted 8 February 2007

A microhotplate array comprising four 100 mm × 100 mm unit cells has been designed. It has a multi-layer structure: Si-thermal oxide-polySi-PECVD (plasma enhanced chemical vapour deposition) oxide-Sputtered Pt-Gas sensing film (SnO2). Electro-thermal simulation of the unit cell has been carried out using ANSYS. The simulations show that for an applied bias of 4 V a mean temperature of 706ºC is obtained at the centre of the heater area. The heat is assumed to flow from the hot plate to the surrounding air at an ambient temperature of 30ºC by conduction. The power dissipation is less than 50 mW. The paper presents the design methodology of the hotplate.

Keywords: Microhotplate, Gas sensor, Electro-thermal simulation

IPC Code: H 01 L, G 01

 

 

 

 

Indian Journal of Pure & Applied Physics

Vol. 45, April 2007, pp. 336-344

 

Micromachined conductor backed coplanar waveguides for millimeter wave circuit application

Shiban K Koul*, Abhishek Kumbhat & Ananjan Basu

Center for Applied Research in Electronics, Indian Institute of Technology Delhi, Hauz-Khas, New Delhi 110 016

*E-mail: shiban_koul@hotmail.com

Received  7 June 2006; revised  6 November 2006; accepted 14 February 2007

Conductor Backed Coplanar Waveguide (CBCPW) lines on Si micromachined substrate are in use for more than a decade, but their detailed analysis is still not available in the open literature. This paper presents design data and closed form expressions on characteristic parameters of CBCPW lines on Si-micromachined structures that are valid up to 40 GHz. Effect of various physical parameters are studied. Procedure for deriving lumped equivalent circuit models for discontinuities on Si-Micromachined substrate as a function of discontinuity physical parameters is also presented. Scattering parameters obtained from equivalent circuit models agree well with those obtained from full wave FEM for all the discontinuity structures. To show the usefulness of the data generated on discontinuities, design of a Ka-band band pass filter is described.  The results presented are useful in designing micromachined components at microwave and millimeter wave frequencies.

Keywords: Micromachined CBCPW line, RF MEMS, Discontinuity Models, Millimeter waves

IPC Code: B81B7/02, H01P

 

Indian Journal of Pure & Applied Physics

Vol. 45, April 2007, pp. 345-353

 

Advances in chemical sensors, biosensors and microsystems based on ion-sensitive field-effect transistor

V K  Khanna*

MEMS and Microsensors, Central Electronics Engineering Research Institute, Pilani 333 031

*Email: vkk@ceeri.ernet.in, vkk_ceeri@yahoo.com

Received 7 June 2006; accepted 2 January 2007

Introduced as a tool for electrophysiology three and a half decades ago, the ion-sensitive field-effect transistor (ISFET) is a generic electrochemical structure offering a family of analytical devices for applications in agriculture, food processing, medical diagnostics, pharmaceuticals, paper, pulp and chemical industries, and environmental control. Besides its use as a chemical sensor, this device has also served as the electrical transduction element for many enzyme and immunological biosensors. This paper presents the current status of this microelectronic device in terms of the theoretical understanding of its operational mechanism, the techniques used for its fabrication and the measurement circuits used in instrumentation. The state of the art of ISFET as a chemical and biosensor is examined, major problems in this area are discussed, perspectives of recent interesting developments are described and future research directions are indicated. Highlights of the work done on ISFET at our institute are presented.

Keywords: ISFET, Chemical sensor, Biosensor, Microsystem, Analytical instrumentation.

IPC Code: C 12, C 25, G 01, H01 L

 

 

 

 

Indian Journal of Pure & Applied Physics

Vol. 45, April 2007, pp. 354-357

 

Electrochemical actuator from conductive electroactive polymer polypyrrole deposited on gold

Dayanand Sutar, D K Aswal, S K Gupta & J V Yakhmi*

Technical Physics & Prototype Engineering Division, Bhabha Atomic Research Center, Trombay, Mumbai 400 085

Received 7 June 2006; accepted 2 January 2007

Electrochemical bilayer actuators were fabricated from conductive electroactive polymer polypyrrole deposited by electrochemical polymerization. Films of polypyrrole doped with dodecylbenzene sulphonate (PPy-DBS) and with gold coating on one side were prepared by galvanostatic electrochemical polymerization of pyrrole. Polystyrene sheet (used for over-head-projector) with thermally deposited gold film, was used as working electrode. The strong interaction of pyrrole with gold was made use of to get a freestanding polypyrrole film with gold coating on one side (PPy-DBS/Au). Bilayer actuators, were fabricated from these freestanding films and tested in 1 M LiClO4 solution. The actuator showed bending of up to 90º on both sides on electrochemical reduction/oxidation under an applied potential of 2-3 V. The applied voltage determined the response time, which was 2 to 3 s. The actuator action was also observed with low frequency ac signal.

Keywords: Electrochemical actuator, Electroactive polymer polypyrrole, Electrochemical polymerization

IPC Code:  C08

 

 

 

Indian Journal of Pure & Applied Physics

Vol. 45, April 2007, pp. 358-367

 

 

 

Material selection for MEMS devices

 

Rudra Pratap & A Arunkumar

CranesSci MEMS Lab, Department of Mechanical Engineering, Indian Institute of Science,
Bangalore 560 012

Received 7 June 2006; accepted 1 November 2006

As MEMS design matures and migrates from process centric design to performance based design, MEMS designers would need a rational method for selecting an appropriate material that is not based on ease of processing alone. While there is a growing number of thin film materials that can be used in micromachining for MEMS devices, the selection of a particular material is rarely based on quantifiable criterion that relates directly to the optimum performance of the device. In this study, we present a methodology for creating material related device performance indices that can be used for selecting best possible material for a device. This study is inspired by the Ashby approach and its extension to the microworld in recent studies, where materials are graded on material performance indices and the most appropriate material is selected from the Ashby charts so created. We extend this concept further in this paper and create device performance indices that can be used to grade MEMS materials in performance parameter space. We first create and discuss a material index for thermoelastic damping, an important index for vacuum packed dynamic MEMS devices that has been missing from the list of performance indices previously considered. We present two case studies of material selection, for a MEMS gyroscope and a MEMS ultrasound transducer, to illustrate the methodology and show two different approaches for creating optimality criterion in the presence of several competing performance indices.

Keywords: MEMS devices, Material performance indices, Thermoelastic damping, MEMS gyroscope, MEMS ultrasound transducer

IPC Code: B81B7/02

 

Indian Journal of Pure & Applied Physics

Vol. 45, April 2007, pp. 368-371

 

Fabrication of single-walled carbon-nanotube with metallic electrodes

Ying Wu1, 2, Zhaoying Zhou1, Xing Yang1, Mingfei Xiao1,, Qingqing Luo1, Jin Zhang3, Ying Ying Zhang3 & Yagang Yao3

1State Key Lab. of Precision Measurement Technology and Instrumentation, Tshinghua University, Beijing, 100084, P R China

2 Chongqing University of Science and Technology, chongqing, 400050, P R China

3Coll Chem & Mol Engn, Ctr Nanoscale Sci & Technol, Peking Univ, Beijing, 100871, P R China

Received 7 June 2006; accepted 3 January 2007

Aligned array of single-walled carbon nanotubes on a substrate is synthesized by chemical vapour deposition of methane. The combined synthesis and FIB technique presented here demonstrated the nanotube devices with metallic electrodes. Sample characterization was carried out with SEM pictures and I-V curves, which show that the nanotube with metallic electrodes may be widely used in both basic research and applications.

Keywords: Carbon nanotubes, Single-walled carbon nanotubes, Metallic electrodes, Chemical vapour deposition

IPC Code: B82B

 

 

 

 

Indian Journal of Pure & Applied Physics

Vol. 45, April 2007, pp. 372-376

 

Measurement of novel micro bulk defects in semiconductive
materials based on Mie scatter

 

You Zheng, Li Yingpeng & Chen Jun

Department of Precision Instruments, Tsinghua University, Beijing, China

Received 7 June 2006; accepted 6 February 2007

This paper introduces a new micro bulk defects measurement method in semiconductive materials, which scales the defects by analyzing scattering light distribute based on Generalized Lorenz and Mie Theory (GLMT). A method named character recognition and pick up two characters as defect criterions have been presented. Moreover, a set of experimental apparatus is built to prove the detect method and defect criterions. The micro bulk defects in semiconductive materials have been detected experimentally.

Keywords: Non-destructive detection, Semiconductive material, Micro bulk defect, Generalized Lorenz, Mie Theory (GLMT), Near-infrared laser, Scattering

IPC Code: B81B7/02

 

 

 

 

 

 

 

 

 

 

Indian Journal of Pure & Applied Physics

Vol. 45, April 2007, pp 377-381

 

 

Stress evaluation of RF sputtered silicon dioxide films for MEMS

Vivekanand Bhatt, Sudhir Chandra*, Sushil Kumar1, C M S Rauthan1 & P N Dixit1

Centre for Applied Research in Electronics, Indian Institute of Technology Delhi, New Delhi 110 016
1National Physical Laboratory, New Delhi 110 012

*E-mail: schandra@care.iitd.ernet.in

Received 7 June 2006; revised 21 November 2006; accepted 7 February 2007

In the present work, the stress evaluation of RF sputtered silicon dioxide films for MEMS applications has been reported. The films were deposited in argon atmosphere in the pressure range 5-20 mtorr at 300 W RF power using a 3 inch diameter silicon dioxide target. The stress measurements were carried out using wafer curvature technique. All the deposited films show compressive stress except the film having thickness less than 5000 Å. It is observed that sputtering pressure, film thickness and annealing temperature affect the stress in SiO2 films. The dependence of deposition rate and etch rate on the deposition parameters were also investigated. To obtain the minimum stress in the film, the deposition parameters are optimized. An array of cantilever beams of sputtered silicon dioxide film was fabricated. It was observed that beams up to 500 micron length show no upward or downward bending indicating low stress in the films deposited under optimized conditions.

Keywords: RF sputtering, Stress measurement, Silicon dioxide, Cantilever beams

IPC Code: G 01 N

 

 

Indian Journal of Pure & Applied Physics

Vol. 45, April 2007, pp. 382-386

 

 

Microfabrication and characterization of gallium arsenide membranes
for force sensor applications

 

Niranjana Goswamia, Krishan Lala, J Miaob & H L Hartnagelb

aNational Physical Laboratory, New Delhi 110 012

bInstitute für Hochfrequenztechnik, Technische Hochschule Darrmstadt, 64283 Darmstadt, Germany

E-mail: ngoswami@mail.nplindia.ernet.in; klal@mail.nplindia.ernet.in

Received 7 June 2006; revised 23 October 2006 ; accepted 6 December 2006

High-precision force sensors based on membranes of semi-insulating gallium arsenide with stable structures had been fabricated by micromachining. Their structural quality had been evaluated by high-resolution X-ray diffraction techniques. Free hanging membranes with thicknesses of > 2mm have been synthesized by utilizing photolithography, implantation and selective etching. Starting wafers were (100) n-type GaAs crystals with n = 3.5 × 1017 cm-3. Implantation by 4 MeV N2+ (dose » 1015 cm-2) produced N compensated semi-insulating GaAs with a resistivity of 109 W cm and breakdown voltage of ~ 60 V. An ~ 100 mm deep cavity below the membrane was produced by selective etching. A typical sensor was coiled shaped with five segments. The five-crystal X-ray diffractometer developed at NPL was employed in (+, -, +) configuration for structural characterization of the final device structures. A highly monochromated and well-collimated Mo Ka1 X-ray beam of very narrow lateral width (~ 10 mm) was employed as the exploring beam. Specimens were studied in symmetric as well as in highly asymmetric Bragg geometries with (400) and (511) diffracting lattice planes, respectively. Crystalline quality, tilt between adjoining sensor segments and the level of stress in the specimens were determined.

Keywords: Force sensors, Micro-machining, Semi-insulating gallium arsenide High-resolution X-ray diffraction

IPC Code: C30B; H05G

 

 

 

Indian Journal of Pure & Applied Physics

Vol. 45, April 2007, pp. 387-394

 

Studies on RF MEMS shunt switch

Preeti Sharma, Shiban K Koul* & Sudhir Chandra

Center for Applied Research in Electronics, Indian Institute of Technology Delhi, Hauz-Khas, New Delhi 110 016

*E-mail: shiban_koul@hotmail.com

Received  7 June 2006; revised 12 December 2006; accepted 14 February 2007

Radio Frequency Micro-Electro-Mechanical-Systems (RF MEMS) based switches are expected to play a key role in the field of microwave switching. Traits like low-loss performance; zero-power consumption and very low inter-modulation distortion have made these switches well suitable for high-performance microwave and millimeter-wave circuits.   The design of RF MEMS switches, however, require sophisticated modeling techniques because of their complicated 3-D geometries with critical aspect ratios and strong in-homogeneities.  In this paper, the effect of various geometric dimensional parameters on the electromagnetic and mechanical behaviour of a shunt capacitive MEMS switch using finite element method based Ansoft High Frequency Structure Simulator (HFSS) software tool has been presented. This exercise will provide a better insight into designing a reliable and high-performance MEMS shunt switch.

Keywords:          MEMS shunt switch, Finite-element method, Coplanar Waveguide, RF MEMS

IPC Code: B81B7/02

 

Indian Journal of Pure & Applied Physics

Vol. 45, April 2007, pp. 395-399

 

Nano-structured ZnO films by sol-gel process

Harish Bahadur, A K Srivastava, Divi Haranath, Harish Chander, A Basu, S B Samanta, K N Sood, Ram Kishore,
R K Sharma, Rashmi, Vivekanand Bhatt*, Prem Pal* & Sudhir Chandra*

National Physical Laboratory, Dr K S Krishnan Road, New Delhi 110 012

*Centre for Applied Research in Electronics, Indian Institute of Technology,

Hauz Khas, New Delhi 110 016

Received 7 June 2006; revised 28 December 2006; accepted 4 January 2007

Thin films of ZnO grown by sol-gel spin method using two different precursors viz. zinc nitrate and zinc acetate have been characterized for their crystalline nature and associated nanostructures. In some cases, the films consist of nanostructures in the form of nanocrystals and nanoneedles of dimensions in the range 15-60 nm. A comparison between the physical characterization and the nanostructures of the films grown by two different precursor materials has been presented and the results are discussed in terms of the fundamental considerations governing the growth kinetics of the ZnO films.

Keywords: ZnO films, Sol-gel, Scanning electron microscopy, XRD, Transmission electron microscopy, Nano-structured ZnO thin films

IPC Code: H01F41/30

 

 

 

 

 

Indian Journal of Pure & Applied Physics

Vol. 45, April 2007, pp. 400-402

 

 

Deposition of low stress polysilicon thin films using low-pressure
chemical vapour deposition

 

Mahesh Kumar, Mahant Parsad, Niranjana Goswami*, Anil Arora, B D Pant & V K Dwivedi

Central Electronics Engineering Research Institute, Pilani

*National Physical Laboratory, New Delhi 110 012

Received 7 June 2006; revised 5 November 2006; accepted 5 February 2007

The deposition of polysilicon thin films on silicon wafers using low-pressure chemical vapour deposition (LPCVD) was carried out and the process parameters were optimized to obtain normal and low stress films. The films of thickness 150 nm to 2 microns were deposited on 4¢¢ and 6¢¢ silicon wafers and the thickness uniformity was measured using Dektak 6M surface profiler. The thickness variation across the wafer was found to be in 5-10% range. Stress measurements were carried out using X-ray diffraction method. We were able to deposit low stress films with stress ~14 MPa. The quality of the films was found to be good and they were used in fabrication of MEMS based silicon devices.

Keywords: Polysilicon thin films, Thin films, MEMS, Chemical vapour deposition

IPC Code: B81B7/02, C30B

 

 

 

          Indian Journal of Pure & Applied Physics

Vol. 45 April 2007, pp. 403-405

Variation of surface layer during chemical mechanical polish

Luo Jianbin

State Key Laboratory of Tribology, Tsinghua University, Beijing 100084, China

Received 7 June 2006; accepted 1 February 2007

Nanoparticles have been widely used in oils and polish slurry such as chemical mechanical polish (CMP) process. The movement of nanoparticles in liquid and the interaction between nano-particles and solid surface are very important to obtain an atomic smooth surface in CMP process. This paper presents both experimental and theoretical studies on the movement of nanoparticles in fluid and the collision between nanoparticles as well as that between the particles and solid surfaces in two phases flowing process.

Keywords: Tribology, Two phases flow, Wear, Chemical mechanical polish

IPC Code: B82B

 

 

 

 

 

 

Indian Journal of Pure & Applied Physics

Vol. 45, April 2007, pp. 406-410

 

 

Development of ferrofluid and its possible applications in MEMS

Vinod Kumar, R P Pant*, S K Halder & M S Yadav#

X-ray Section, National Physical Laboratory, Dr K S Krishnan Marg, New Delhi 110 012

#Department of Physics, Kurukshetra University, Harayana

Received 7 June 2006; revised 21 December 2006; accepted 2 January 2007

In micro-fluidic devices, fluid control plays a crucial role in its operation. The input and output in the device must pass through control surface. Synthesized nano magnetic fluid is characterized by X-ray diffraction (XRD), transmission electron microscope (TEM) and vibrating sample magnetometer (VSM) techniques for its potential applications in MEMS devices as gas pressure valve. Operation of gas pressure valve was monitored at varying electromagnetic actuation level.

Keywords: Ferrofluid, MEMS, Micro-valve, Crystallite size

IPC Code: B81B7/02