Integrated Magnetic Sensing of Electrostatically Actuated Thin-Film Microbridges

2002 ◽  
Vol 729 ◽  
Author(s):  
J. Gaspar ◽  
Haohua Li ◽  
P.P. Freitas ◽  
V. Chu ◽  
J.P. Conde
Keyword(s):  
Thin Film ◽  
Low Temperatures ◽  
Counter Electrode ◽  
Spin Valve ◽  
Metal Gate ◽  
Electrostatically Actuated ◽  
Glass Substrates ◽  
Hydrogenated Amorphous ◽  
Bridge Length ◽  
The Magnetic Field

AbstractBilayer microbridges of aluminum and hydrogenated amorphous silicon are fabricated using thin film technology and surface micromachining at low temperatures on glass substrates. The microstructure is electrostatically actuated by applying a voltage between the bridge and a metal gate counter electrode placed beneath it. The movement is measured with a precision close to 0.1 Å by sensing the magnetic field of a permanent magnet, deposited and patterned on top of the microbridge, with an integrated spin valve magnetic sensor. The deflection of the bridge is at the same time monitored using an optical setup. The deflection of the structures is studied as a function of the driving applied gate voltage and bridge length and experimental results are analyzed with an electromechanical model.

Thin Film Silicon Microbridges for DNA Detection

2005 ◽  
Vol 872 ◽  
Author(s):  
T. Adrega ◽  
J. Gaspar ◽  
F. Fixe ◽  
V. Chu ◽  
D.M.F. Prazeres ◽  
...  
Keyword(s):  
Thin Film ◽  
Resonance Frequency ◽  
Specific Binding ◽  
Molecular Layer ◽  
Mass Loading ◽  
Initial State ◽  
Molecular Sensors ◽  
Electrostatically Actuated ◽  
Glass Substrates ◽  
Hydrogenated Amorphous

AbstractThin-film MEMS molecular sensors are fabricated at temperatures below 110°C on glass substrates. The microelectromechanical structure consists of a surface micromachined bilayer bridge of phosphorous-doped hydrogenated amorphous silicon and aluminum with a patterned SiO2 layer on the top. Specific binding of DNA to functionalized SiO2 on the bridge is confirmed using fluorescence microscopy. Microbridges are electrostatically actuated and the resonance frequency measurements are performed in vacuum in the initial state after fabrication, after the chemical functionalization of the SiO2surface and after DNA immobilization. The sensor is able to detect the functionalization molecular layer, the cross-linker molecular layer, and the DNA molecules attached to the surface through a shift in its resonance frequency. The binding of molecules to the surface results in a shift of the resonance frequency due to contributions from surface stresses and mass loading.

Microstructure Characterization of Amorphous Silicon Films by Effusion Measurements of Implanted Helium

2013 ◽  
Vol 1536 ◽  
pp. 175-180 ◽  
Author(s):  
W. Beyer ◽  
W. Hilgers ◽  
D. Lennartz ◽  
F.C. Maier ◽  
N.H. Nickel ◽  
...  
Keyword(s):  
Thin Film ◽  
Amorphous Silicon ◽  
Low Temperatures ◽  
Plasma Deposition ◽  
Hydrogenated Amorphous Silicon ◽  
Silicon Films ◽  
Hot Wire ◽  
Common Features ◽  
Hydrogenated Amorphous

ABSTRACTAn important property of thin film silicon and related materials is the microstructure which may involve the presence of interconnected and isolated voids. We report on effusion measurements of implanted helium (He) to detect such voids. Several series of hydrogenated and unhydrogenated amorphous silicon films prepared by the methods of plasma deposition, hot wire deposition and vacuum evaporation were investigated. The results show common features like a He effusion peak at low temperatures attributed to He out-diffusion through a compact material or through interconnected voids, and a He effusion peak at high temperatures attributed to He trapped in isolated voids. While undoped plasma-grown device-grade hydrogenated amorphous silicon (a-Si:H) films show a rather low concentration of such isolated voids, its concentration can be rather high in doped a-Si:H, in unhydrogenated evaporated material and others.

Dissipation Mechanisms in Thin-Film Silicon Microresonators on Glass Substrates

2003 ◽  
Vol 782 ◽  
Author(s):  
J. Gaspar ◽  
V. Chu ◽  
J. P. Conde
Keyword(s):  
Thin Film ◽  
Energy Dissipation ◽  
Chemical Vapor ◽  
Quality Factors ◽  
Resonance Amplitude ◽  
Electrostatically Actuated ◽  
Glass Substrates ◽  
Thin Film Silicon ◽  
Resonance Frequencies ◽  
Phosphorus Doped

ABSTRACTThe fabrication and characterization of thin-film silicon resonators processed at temperatures below 110°C on glass substrates is described. The microelectromechanical structures consist of surface micromachined bridges of phosphorus-doped hydrogenated amorphous silicon (n+-a-Si:H) deposited by plasma-enhanced chemical vapor deposition (PECVD) suspended over a metallic gate counterelectrode. The structures are electrostatically actuated. Resonance frequencies in the MHz range and quality factors as high as 5000 are observed in vacuum. The effect of the geometrical dimensions of the bridges and of the measurement pressure on the resonance amplitude and frequency is studied. The elementary energy dissipation processes in a-Si:H-based resonators are discussed. At atmospheric pressure, air damping dominates the energy dissipation. In vacuum, intrinsic mechanisms, such as clamping losses and surface losses, control the energy dissipation.

Electrolyte-Gate a-Si:H Thin Film Transistors

2005 ◽  
Vol 862 ◽  
Author(s):  
Dina I. Gonçalves ◽  
Duarte M. Prazeres ◽  
Virginia Chu ◽  
João P. Conde
Keyword(s):  
Thin Film ◽  
Thin Film Transistors ◽  
Drain Current ◽  
Chemical Sensitivity ◽  
Metal Gate ◽  
Pt Electrode ◽  
Ph Variation ◽  
Voltage Range ◽  
Hydrogenated Amorphous

AbstractThis paper presents the fabrication and characterization of electrolyte-gate (EG) hydrogenated amorphous silicon (a-Si:H) thin film transistors (TFTs). In these devices, the metal gate is replaced by a Pt electrode immersed in an electrolyte. The source-drain current of these devices is modulated by the voltage applied through the Pt electrode. Device characteristics are compared with structurally equivalent top-gate a-Si:H TFTs. The EG devices show higher mobility and smaller subthreshold slope than their counterparts with metal gate and work in a narrower voltage range. EG-TFTs show chemical sensitivity, illustrated by a voltage shift in the transfer curve as a consequence of pH variation. The sensitivity of the devices to pH is different depending on whether the top layer in contact with the electrolyte is SiO2 or SiNx.

Thin-Film Electrostatic Actuators on Flexible Plastic Substrates

2003 ◽  
Vol 782 ◽  
Author(s):  
J. Gaspar ◽  
V. Chu ◽  
J. P. Conde
Keyword(s):  
Thin Film ◽  
Resonance Frequency ◽  
Actuation Voltage ◽  
Quality Factors ◽  
Electrostatic Actuators ◽  
Plastic Substrates ◽  
Electrostatically Actuated ◽  
Glass Substrates ◽  
Resonance Frequencies ◽  
Silicon Based

ABSTRACTThin-film silicon micromachined bridge actuators are fabricated at temperatures below 110°C on flexible polyethylene terephthalate plastic substrates. The micromechanical structures are electrostatically actuated both at the resonance frequency and at below-resonance frequencies, and the resulting deflection is optically monitored. Deflections up to 100 nm are measured below the resonance frequency with subnanometric precision. Resonance frequencies in the MHz range are observed in vacuum with quality factors of the order of 100. The movement is studied as a function of the geometrical dimensions of the actuators, of the actuation voltage and of the measurement pressure. The experimental data are analyzed using an electromechanical model. The performance of hydrogenated amorphous silicon based resonators on PET substrates is compared to that of similar microstructures on glass substrates.

Application of Thin-Film Micromachining on Glass

1998 ◽  
Vol 507 ◽  
Author(s):  
M. Boucinha ◽  
V. Chu ◽  
J.P. Conde
Keyword(s):  
Thin Film ◽  
Etch Rate ◽  
Sacrificial Layer ◽  
Three Dimensional ◽  
Electrical Characteristics ◽  
Microcrystalline Silicon ◽  
Large Area ◽  
Glass Substrates ◽  
Bridge Structures ◽  
Hydrogenated Amorphous

ABSTRACTThree dimensional microstructures have been made on glass substrates using surface micromachining techniques. Bridge structures were fabricated using both hydrogenated amorphous silicon and microcrystalline silicon. A low density silicon nitride with an etch rate of 100 Å/s in buffered HF was used as the sacrificial layer. As an example of how micromachining can be applied to large area electronics, thin film transistors (TFT) with the dielectric replaced by an air-gap were fabricated. The electrical characteristics of the first working devices are presented.

“In-Situ Raman Spectroscopy of Electronic Processes in Fullerene Thin Films

2002 ◽  
Vol 725 ◽  
Author(s):  
S.B. Phelan ◽  
B.S. O'Connell ◽  
G. Farrell ◽  
G. Chambers ◽  
H.J. Byrne
Keyword(s):  
Thin Film ◽  
Indium Tin Oxide ◽  
Low Temperatures ◽  
In Situ Raman Spectroscopy ◽  
State Reduction ◽  
In Situ Raman ◽  
Linear Behavior ◽  
Current Voltage ◽  
Solid State Reduction

AbstractThe current voltage characteristics of C60 thin film sandwich structures fabricated by vacuum deposition on indium tin oxide (ITO) with an aluminium top electrode are presented and discussed. A strongly non-linear behavior and a sharp increase in the device conductivity was observed at relatively low voltages (∼2V), at both room and low temperatures (20K). At room temperature the system is seen to collapse, and in situ Raman measurements indicate a solid state reduction of the fullerene thin film to form a polymeric state. The high conductivity state was seen to be stable at elevated voltages and low temperatures. This state is seen to be reversible with the application of high voltages. At these high voltages the C60 film was seen to sporadically emit white light at randomly localized points analogous to the much documented Electroluminescence in single crystals.

PREPARATION AND CHARACTERIZATION OF POLYVINYL ALCOHOL THIN FILMS FOR ORGANIC THIN FILM TRANSISTORS AND BIOMEDICAL APPLICATIONS

2018 ◽  
Vol 5 (2) ◽  
pp. 16-18
Author(s):  
Chandar Shekar B ◽  
Ranjit Kumar R ◽  
Dinesh K.P.B ◽  
Sulana Sundar C ◽  
Sunnitha S ◽  
...  
Keyword(s):  
Thin Film ◽  
Thin Films ◽  
Thin Film Transistors ◽  
Gravimetric Method ◽  
Dip Coating ◽  
Organic Thin Film Transistors ◽  
Poly Vinyl Alcohol ◽  
Organic Thin Film ◽  
Glass Substrates ◽  
Coating Method

Thin films of poly vinyl alcohol (PVA) were prepared on pre-cleaned glass substrates by Dip Coating Method. FTIR spectrum was used to identify the functional groups present in the prepared films. The vibrational peaks observed at 1260 cm-1 and 851 cm-1 are assigned to C–C stretching and CH rocking of PVA.The characteristic band appearing at 1432 cm-1 is assigned to C–H bend of CH2 of PVA. The thickness of the prepared thin films were measured by using an electronic thickness measuring instrument (Tesatronic-TTD20) and cross checked by gravimetric method. XRD spectra indicated the amorphous nature of the films.Surface morphology of the coated films was studied by scanning electron microscope (SEM). The surface revealed no pits and pin holes on the surface. The observed surface morphology indicated that these films could be used as dielectric layer in organic thin film transistors and as drug delivery system for wound healing.

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