Huang Qing-an

Effect of (2×1) Surface Reconstruction on Elasticity of a Silicon Nano-Plate

A semi-continuum approach is developed to describe the effect of (2 × 1) surface reconstruction on the elastic modulus of the silicon nano-plate. Youngs moduli of a (001) silicon nano-plate along the high-symmetry [100] direction are obtained with and without considering (2 × 1) surface reconstruction. The approach predicts that the nano-plate with unreconstructed (001) surface is elastically softer than the bulk while it exhibits the opposite behaviour with (2 × 1) reconstructed surface. On the (001) surface, the (2 × 1) reconstructed surface dominates the plate as the thickness of the plate scaling decreases to several tens of nanometre. Whether the nano-plate is softer or stiffer depends on bond loss, bond saturation and direction of bond alignment, which have major impacts on the mechanics of the nano-plate.

Theoretical study of electromechanical property in a p-type silicon nanoplate for mechanical sensors

Electromechanical property of a p-type single-crystal silicon nanoplate is modelled by a microscopic approach where the hole quantization effect and the spin–orbit coupling effect are taken into account. The visible anisotropic subband structures are calculated by solving self-consistently the stress-dependent 6 × 6 κ p Schrodinger equation with the Poisson equation. The strong mixing among heavy, light, and split-off holes is quantitatively assessed. The influences of the thickness and the temperature on the piezoresistive coefficient are quantitatively investigated by using the hole concentrations and the effective masses from the complex dispersion structure of the valence band with and without stresses. Our results show that the stress determines the extent to which the band is mixed. The hole quantization effect increases as the thickness decreases, and therefore the valence band is strongly reshaped, resulting in the size-dependent piezoresistivity of the silicon nanoplate. The piezoresistive coefficient increases almost 4 times as the thickness reduces from the bulk to 3 nm, exhibiting a promising application in mechanical sensors.

GaAs piezoelectric modulated resistors for sensor

The authors report the development of GaAs piezoelectric modulated resistors which are very sensitive to stress. A model of the resistors is presented, and simple cantilever experiments confirm that the piezoelectric modulated effect exists in GaAs. The effect is expected to be applied to the monolithic integration of mechanical sensors and signal processing circuits.<<ETX>>

A dynamic macromodel for distributed parameter magnetic microactuators

This paper presents a reduced-order model to describe the mechanical behaviour of microbeam-based magnetic devices. The integration for magnetic force is calculated by dividing the microbeam into several segments, and the nonlinear equation set has been developed based on the magnetic circuit principle. In comparison with previous models, the present macromodel accounts for both the micro-magnetic-core reluctance and the coupling between the beam deflection and magnetic force. This macromodel is validated by comparing with the experimental results available in some papers and finite-element solutions.

A novel SOI MOSFET electrostatic field sensor

A novel low temperature solid state electric field sensor is demonstrated as a promising sensor. The sensor is a type of constant voltage Wheatstone bridge whose resistors are four direct gate SOI MOSFET devices. It is demonstrated in theory that the output voltage signal is proportional to the electric field E, the temperature drift is about zero when the temperature is in the range from 200 to 400 K, and the doping concentration is in the range from 1 × 1014 to 1 × 1016 cm−3. The experiment results indicate that the resolution of the sensor is about 3.27 mV for a 1000 V/m electric field at 300 K, and the voltage drift by an amount is about 47 V/m field signal when the degree temperature is in the range from 300 to 370 K, which is much smaller than the current drift of a single MOSFET which is about 10000 V/m field signal.

Requirement of silicon flatness for silicon direct bonding technology

The influence of silicon slice flatness on bonding technology and the relation between a foreign particle and resulting bubble are quantitatively presented by the elastic theory. It is demonstrated experimentally by X-ray double crystal diffractometry and infrared imager.

A simple approach to the calculation of the mechanical stress in silicon devices

The residual mechanical stress in SiO2 films results in the degradation of mobilities in MOSFETs. Based on the edge force approximation in SiO2 films, the stress field in MOS devices is calculated. The results here are in agreement with those measured by the Raman spectrum method.