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In the present paper, guided four beam (G4B) piezoelectric transducers with enhanced sensitivities have been designed. Based on the suggested G4B structures, piezoelectric energy harvesters (PEHs) and acceleration transducers with higher voltages than their previously reported counterparts and with lower displacements than the single-cantilever PEHs (SC-PEHs) have been proposed. We have shown that it is possible to arrive at much more output voltages in comparison with the conventional PEHs by redesigning the structure of the cantilever beams. In 1 g acceleration, the maximum output voltage obtained from the proposed PEHs has been 13.49 V whereas the output voltage for the conventional G4B-PEH is 2.87 V. This paper for the first time proposes G4B-PEHs with smaller displacements and larger voltages compared to a SC-PEH. The same G4B framework has been studied as a piezoelectric acceleration transducer. The effect of piezoelectric length on the extracted voltage in both unimorph and bimorph cantilevers has been discussed and the optimized length has been calculated. An analytical method is developed to compute the resonance frequencies of different beam shapes whose results are in a good agreement with numerical simulations.

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Optimized architectures for carbon nanotube field-effect transistors (CNTFETs) with lightly doped source and drain have been proposed. Simulations are based on self-consistent solution of two dimensional non-equilibrium Green's function (NEGF) with Poisson's equation. By utilizing special designs in the lightly doped regions of the CNTFETs, their characteristics could be improved. Four CNTFET structures have been designed and compared to the conventional CNTFET which are lightly doped source and drain (LD_CNTFET), double lightly doped source and drain (DLD_CNTFET), linear lightly doped source and drain (LLD_CNTFET) and step-linear lightly doped source and drain (SLLD_CNTFET). In order to get to the optimized electrical characteristics, for the first time, the geometry and the doping of the new designed CNTFETs have been optimized. The target of optimizations has been achieving the best Ion/Ioff, cutoff Frequency and transconductance independently. The proposed designs have been optimized based on particle swarm optimization (PSO) method. The optimized length and doping level of source and drain lightly doped regions then have been used and the features of the proposed optimized CNTFETs have been compared. The results show that with the help of the proposed designs, great improvements have been achieved in the dc and ac characteristics of CNTFETs compared to the conventional CNTFETs.