http://nopr.niscair.res.in/handle/123456789/2305 Search the Channel search http://nopr.niscair.res.in/simple-search http://nopr.niscair.res.in/handle/123456789/2343 Title: Deposition of low stress polysilicon thin films using low-pressure chemical vapour deposition <br/> <br/>Authors: Kumar, Mahesh; Parsad, Mahant; Goswami, Niranjana; Arora, Anil; Pant, B D; Dwivedi, V K <br/> <br/>Abstract: 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. <br/> <br/>Page(s): 400-402 http://nopr.niscair.res.in/handle/123456789/2342 Title: Nano-structured ZnO films by sol-gel process <br/> <br/>Authors: Bahadur, Harish; Srivastava, A K; Haranath, Divi; Chander, Harish; Basu, A; Samanta, S B; Sood, K N; Kishore, Ram; Sharma, R K; Rashmi; Bhatt, Vivekanand; Pal, Prem; Chandra, Sudhir <br/> <br/>Abstract: 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. <br/> <br/>Page(s): 395-399 http://nopr.niscair.res.in/handle/123456789/2341 Title: Studies on RF MEMS shunt switch <br/> <br/>Authors: Sharma, Preeti; Koul, Shiban K; Chandra, Sudhir <br/> <br/>Abstract: 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. <br/> <br/>Page(s): 387-394 http://nopr.niscair.res.in/handle/123456789/2340 Title: Microfabrication and characterization of gallium arsenide membranes for force sensor applications <br/> <br/>Authors: Goswami, Niranjana; Lal, Krishan; Miao, J; Hartnagel, H L <br/> <br/>Abstract: 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 > 2 μm 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 Ω cm and breakdown voltage of ~ 60 V. An ~ 100 μm 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 K⍺₁ X-ray beam of very narrow lateral width (~ 10 μm) 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. <br/> <br/>Page(s): 382-386