Research Of The Electromechanical Characteristics On Silicon Nanowire

NEMS resonators have been broadly applied in filters for information process and high sensitivity sensors, and have drawn lots of attentions because of these applications. It has become a research focus that the fabrication and detection of silicon nanoresonators, especially silicon nanowire resonators, and the quantum squeezing effects of NEMS resonators due to its typical dimensions of only several nanometers.However, as the dimension is so small, it is difficult for traditional methods to fabricate and detect the NEMS resonators. An air-gap TFT (thin film transistor) scheme can be used for vibration detection of the silicon beam and nanowire. In this method, mechanical stress (MS) will be introduced in the MOS-transistor, so that it is necessary to study the effect of MS and temperature on the MOSFETs. When detecting very weak physical quantities, the mechanical motion of a nano-resonator is comparable to the intrinsic quantum noise determined by Heisenberg relation. Quantum squeezing is an efficient way to decrease the system quantum noise to develop a high precision detection mechanism.Using MEMS and MOSFET technologies, this work has fabricated NEMS devices including nano-SOI (silicon on insulator) MOSFETs. Some experiments have been done to study the influence of MS (especially as large as GPa) and temperature on the MOSFETs. The fabrication of silicon nanowire has also been studied, and a new simple fabrication method for silicon nano-needles has been developed. The quantum squeezing of Si nanoresonators and sub-nano scale resonators based on graphene have been systemically studied.(1) NEMS devices with nano-SOI MOSFETs, which can be used to study the effects of the MS imposed on the MOSFETs, have been fabricated. After applying measurable mechanical stress, and temperature on the P-channel SOI-MOSFETs, the characteristic parameters, such as the threshold voltages, Uon/Ioff, sub threshold swing, have been theoretically studied. It is found that a 2 GPa MS can increase the gm of SOI-MOSFET by 197%. After removal of the stress, the gm is still 150% larger than before. The possible mechanism of this phenomenon is discussed.(2) It is found that a simple and low cost silicon nano-needle fabrication method can be developed using traditional MEMS TMAH etching techniques. We take advantage of the fact that the decrease of the silicon etch rate in TMAH solutions exhibits an inverse fourth power dependence on the boron doping concentration in our nano-needle fabrication. Silicon nano-needles, with high aspect ratios and sharp anglesθas small as 2.9°are obtained, which could be used for bio-sensors and nano-handling, such as penetrating living cells. An analytic model is proposed to explain the etching evolution of the experiment results, and the model can be used to predict the needle angle, length, and etching time. Based on our method, nano-needles with small acute angleθcan be obtained.(3) Using time-dependent pumping techniques, the quantum squeezing factor R can be much less than 1/2. Zero-point displacement uncertainty, or quantum noise, and quantum squeezing effects of nanoresonators have been studied. Quantum noise and quantum squeezing effects of Si nanoresonators has also been studied. By choosing a typical silicon nanowire resonator with L= 6μm, W= 20 nm, h= 12 nm, T= 50 mK and V= 4 V, the displacement uncertainty is reduced from 1.07×10-2 A to 1.27×10-3 A after squeezing. The reduction of quantum noise reaches 10.88 dB with Rgraphene≈0.1184. A scheme to obtain squeezed states was proposed through sub-nano graphene nanoresonators taking advantage of their thin thickness in principle. Zero-point displacement uncertainty and squeezing factors of strained multilayer graphene NEMS, are studied. The research promotes the measured precision limit of graphene-based nano-transducers by reducing quantum noises through squeezed states. By choosing a typical monolayer graphene nanoresonator with L= 1.8μm, W=0.2μm, d= 0.1 nm, T= 5 K, Q= 14000, and V= 2 V, the displacement uncertainty is reduced from 0.0044 nm to 0.0013 nm after squeezing. The reduction of quantum noise reaches 10.88 dB with Rgraphene≈0.2858. While the reduction can be as large as 36.90 dB at T = 50 mK and V= 4 V with Rgraphene≈0.0143.