| Co-Investigator(Kenkyū-buntansha) |
AIAWA Kouji Tokyo Institute of Technology・Precision and Intelligence Laboratory, Research As, 精密工学研究所, 助手 (40222450)
ASANO Tanemasa Kyushu Institute of Technology・Department of Computer Science and Electronics, P, 情報工学部, 教授 (50126306)
TOKUMITSU Eisuke Tokyo Institute of Technology・Precision and Intelligence Laboratory, Associate P, 精密工学研究所, 助教授 (10197882)
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| Research Abstract |
In this research project, in order to extract self-learning functions in electron devices we proposed a novel adaptive-learning neurodevice and a neuron circuit using ferroelectric materials. In the proposed neuron circuit, the adaptive-learning MISFETs are employed to realize synaptic operations and an UJT (uni-junction transistor) is used as a switching device to obtain the output signal.
First, we studied partial switching characteristics of PbZrTiO_3(PZT) films, which is a well-known ferroelectric material, when short input pulses are applied. It was found that ferroelectric PZT has adaptive-learning functions and it is applicable to neurodevices. Next, to fabricate the adaptive-learning neurodevices, we formed PZT films on Si substrates. However, it was shown tha the interdiffusion between PZT and Si was extremely serious and that PZT films with good-crystalline quality could not obtained. To overcome the difficulty, we proposed here to use a SrTiO_3(STO) as a buffer layr. The STO buffer layr suppressed the interdiffusion and PZT films with good crystalline quality were successfully grown on Si substrates. Furthermore, we studied on a new ferroelectric material, BaMgF_4(BMF) which can be grown on Si or GaAs substrates. BMF films were prepared on Si substrates by molecular beam epitaxy(MBE) and a remanent polarization of 1muC/cm^2 was obtained.
In addition, we experimentally and theoretically studied on UJTs, which are used in the neuron circuits. We fabricated various size of UJTs on SOI(silicon on insulator) substrates and demonstrated that the output frequency can be controlled by a CR time constant in the neuroncircuit. Furthermore, we theoretically calculated the electrical characteristics of UJTs and showed that the characteristics of UJTs were strongly affected by surface recombinations at the Si/SiO_2 interface.
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