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This paper considers the energy consumed by charging and discharging a width-variable capacitor. The capacitor with plate distance d is coupled with repulsive mechanical potential energy, which is proportional to 1/dn. In this capacitor model, there is a stable point between attractive electrical force and repulsive mechanical force. All energies, including the electrostatic energy, potential energy, and energy dissipation, are proportional not to the ordinary value V2 but to V2/(n-1)+2, where V is the abrupt power supply voltage. We apply N-stepwise adiabatic charging to the width-variable capacitor system. It is shown that the energy consumption after charging and discharging (or recycling) can be 1/N times smaller than that of the conventional abrupt operation. By increasing the step number N, the adiabatic operation can ideally charge and discharge the width-variable capacitor system with absolutely no energy dissipation, although the voltage dependence of energies is quite different from the usual one. Adiabatic charging is very promising for realizing dissipationless operation in the proposed system. [ABSTRACT FROM AUTHOR]

A circuit for adiabatically charging and discharging a supercapacitor was designed. A microprocessor sets the duty ratio of the switching transistors that control the inductor current. Changing the duty ratio in a stepwise fashion causes the output voltage to change in a similar fashion. Stepwise voltage changes enable adiabatic charging and discharging. Current measurements showed that the eight-step charging and discharging of a supercapacitor reduced the energy dissipation to one-eighth of that for a constant-voltage process. The circuit enables precise voltage control in small steps. [ABSTRACT FROM AUTHOR]

Abstract: Thin film Al2O3/Al-rich Al2O3/SiO2 structures were fabricated on p-Si substrates. Radio-frequency magnetron co-sputtering was used to form Al-rich Al2O3 thin film as the charge-trapping layer of nonvolatile Al2O3 memory. Capacitance–voltage measurements showed a large hysteresis due to charge trapping in the Al-rich Al2O3 layer. The charge trap density was estimated to be 42.7×1018 cm−3, which is the largest value ever reported for an Al-rich Al2O3 layer; it is six times larger than that of a conventional metal–nitride–oxide–silicon memory. Thermal annealing was found to reduce the leakage current of the Al2O3 blocking layer, thereby providing this structure with better data retention at room temperature than an as-deposited one. In addition, the annealed structure was found to exhibit good data retention even at 100°C. [Copyright &y& Elsevier]

Abstract: A thin-film structure comprising Al2O3/Al-rich Al2O3/SiO2 was fabricated on Si substrate. We used radio-frequency magnetron co-sputtering with Al metal plates set on an Al2O3 target to fabricate the Al-rich Al2O3 thin film, which is used as a charge storage layer for nonvolatile Al2O3 memory. We investigated the charge trapping characteristics of the film. When the applied voltage between the gate and the substrate is increased, the hysteresis window of capacitance–voltage (C–V) characteristics becomes larger, which is caused by the charge trapping in the film. For a fabricated Al–O capacitor structure, we clarified experimentally that the maximum capacitance in the C–V hysteresis agrees well with the series capacitance of insulators and that the minimum capacitance agrees well with the series capacitance of the semiconductor depletion layer and stacked insulator. When the Al content in the Al-rich Al2O3 is increased, a large charge trap density is obtained. When the Al content in the Al–O is changed from 40 to 58%, the charge trap density increases from 0 to 18×1018 cm −3, which is 2.6 times larger than that of the trap memory using SiN as the charge storage layer. The device structure would be promising for low-cost nonvolatile memory. [Copyright &y& Elsevier]