Electrical & Computer Engineering

Trapping and releasing of telecom rainbow

We show how the graded grating structures developed for “trapped rainbow” in THz domain can be transferred to telecom frequencies for future possible optical communication and various nano photonic applications.

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Monday, October 20th, 2008 Electrical & Computer Engineering Comments Off

Novel MEMS-Based Technology for Measuring the Mechanical Properties of a Live Biological Cell

This paper presents an experimental platform for measuring the mechanical properties of live biological cells. The polymer-based MEMS device integrates a V-shaped electrothermal actuator (ETA) array, a force sensor, a displacement sensor, a thermal sensor, and a cell-positioning system in a single chip. The integrated cell-positioning system based on dielectrophoresis precisely places a cell to a designed spot, the MEMS ETA array provides a predefined deformation to the cell, the force and displacement sensors measure the magnitude of the force applied to the cell and the corresponding cell deformation, and the thermal sensor monitors temperature in the liquid cell medium environment during the experiment. This MEMS device was able to compress a NIH3T3 fibroblast cell and cause 25% mechanical strain.

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Polymer MEMS System for Measuring the Mechanical Modulus of a Biological Cell

The measurements of the mechanical modulus of biological cells are critical to studies of pathophysiology and the research for an effective treatment. This research has developed a rapid and cost effective technique in order to measure the Poissons ratio and mechanical modulus of a live biological cell by utilizing microelectromechanical system (MEMS) techniques in a biological application. The design, fabrication, and characterization of a polymer-based MEMS system that integrates a V-shaped electrothermal actuator array and a cell-positioning system in a single microelectronics chip are presented here. This BioMEMS device compressed a NIH3T3 fibroblasts cell and caused up to 25% mechanical strain.

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Effect of mechanical strain on mobility of polycrystalline silicon thin-film transistors fabricated on stainless steel foil

The effect of uniaxial tensile strain parallel to the channel on mobility of polycrystalline silicon thin-film transistors on stainless steel foil has been investigated. The electron mobility increases by 20% while the hole mobility decreases by 6% as the strain increases to 0.5% and both followed by saturation as the strain increases further. The off current decreases for both types TFTs under strain. All TFTs remained functional at the applied strain of 1.13%.

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Monday, December 17th, 2007 Electrical & Computer Engineering Comments Off

A Quantum Mechanical Mobility Model for Scaled NMOS Transistors with Ultra-thin High-K Dielectrics and Metal Gate Electrodes

At the ITRS 45nm technology node, NMOS transistors with high-K dielectrics have an effective oxide thickness (EOT) less than 1nm. Electron mobility in these devices is affected by quantization of carrier energy and a redistribution of carriers at the semiconductor and gate dielectric interface due to the decrease of the gate dielectric layer thickness and the increase of substrate doping. Electron mobility is also affected by surface roughness and Coulomb scattering rising from the interface traps and fixed charges in the high-K layer. We develop a quantum mechanical model for electron mobility, including Coulomb scattering of carriers and surface roughness in scaled high-K, metal-gate, NMOS transistors, which predicts an increase in Coulomb scattering mobility and a slow decrease of surface roughness mobility with increasing the gate voltage. The total mobility is limited by the bulk mobility because of the need for highly-doped substrates for scaled 45nm node transistors.

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Wednesday, December 12th, 2007 Electrical & Computer Engineering, Physics Comments Off