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Thin-film biological stimulation devices are a device that can be easily implanted into living bodies and stimulate living muscles, neurons, etc. In this study, we researched dependences of stimulation amperages on load resistance and phosphate buffered saline concentration. It was found that the stimulation device has a sufficient ability to stimulate the living body.
Neural networks are information processing models based on the human brain, and they have been activity studied. However, in order to realize the hardware of the neural network, it is necessary to achieve high integration. In this study, we fabricated synapses for neural networks using the Ga-Sn-O (GTO) thin films, which is rare-metal-free amorphous oxide semiconductor. The synapses are planar type,...
The flatpanel imager used for the new type magnifying viewer was able to detect the difference in brightness and succeed in character detection. However, the outline part of the character was blurred and the reading accuracy was low. In this research, a liquid crystal lens was used to reduce irregular reflection that is a cause of reduction in reading accuracy of the flat panel imager. As a result,...
Nuromorphic devices are powerful information processing systems and realize low power consumption. We proposed cellular neural networks with polycrystalline-silicon (Poly-Si) thin film transistors (TFTs). The neuron element consists of eight TFTs and the synapse element of only one TFT. We actually succeeded in confirming the operation of learning of logics. In this presentation, we succeeded the...
We have analyzed Hall effect in a thin-film transistor by actual experiments and device simulation. Particularly in this presentation, we show the sensitivity dependence on the applied voltage. These behaviors can be explained by the electric field in the channel layer for the operation regions. Additionally, the carrier mobilities and densities calculated using transistor equation and Hall effect...
We have developed a planar device using In-Ga-Zn-O (IGZO) semiconductor for synapse element in neural network. First, we formed the planar device on a glass substrate. Next, we formed it on an LSI wafer. Both devices shows proper uniformities of film thicknesses and sufficient degradations of electric characteristics, which can be utilized for modified Hebbian learning proposed by us. These results...
We have developed a cross-point device using In-Ga-Zn-O (IGZO) semiconductor for synapse element in neural network. Horizontal 80 and vertical 80 metal lines make 6400 cross-point synapse integrated on a glass substrate. The electrical conductance gradually degrades by flowing current, which is available for modified Hebbian learning.
We have evaluated optical and electrical characteristics of Ga-Sn-O (GTO) films deposited using mist chemical vapor deposition (CVD). It was found that the GTO film is transparent, which suggests the energy gap is wide. The X-ray diffraction (XRD) indicated that the GTO film was crystallized, but the crystal structure is not clarified now. It was also found that the sheet resistance decreases as the...
We have evaluated magnetoresistance (MR)effect of a Ga-Sn-O (GTO) film deposited using mist chemical vapor deposition (CVD). It is found that the as-deposited film shows negative MR effect, whereas the annealed film shows positive MR effect. We assume that this phenomenon occurs because the carrier transportation shifts from the Anderson localization to band transportation as the film structure changes...
We have succeeded in forming a Ga-Sn-O (GTO) film for a thin-film transistor (TFT) using radio-frequency (RF) magnetron sputtering at room temperature without annealing process. The field-effect mobility is 0.48 cm2·V−1·s−1 and the threshold voltage is 2.22 V. This result suggests a possibility of rare-metal free amorphous metal-oxide semiconductors.
Neural networks are computing models based on human brains. We propose a neural network using a field-programmable gate array (FPGA) for neurons and amorphous In-Ga-Zn-O (a-IGZO) thin films for synapses. It is found that electric current in the a-IGZO thin film gradually decreases along the time. On the other hand, the degradation does not occur when light is irradiated. These phenomena can be utilized...
We have developed a hybrid-type temperature sensor using thin-film transistors generating rectangle output waveform. The advantages of the hybrid-type temperature sensor are that the large temperature dependence of the off-leakage current can be utilized, and simultaneously only a digital circuit is required to count the digital pulse. However, the conventional hybrid-type sensor has a disadvantage...
We confirmed that photo-induced current in off region changes when we irradiate infrared light to N-type, P-type and PIN-type low-temperature poly-Si TFTs. In addition, we found that the photo-induced current is proportional to the gate width, whereas it does not depend on the gate length. We can indicate that it is possible to detect infrared light above certain intensity from the relationship between...
We have evaluated light and temperature dependences of transistor characteristics in n-type, p-type and pin-type poly-Si TFTs with and without infrared (IR) light illumination. It is found that light and temperature dependences of the off-leakage currents in the n-type and p-type TFTs are much larger than those of the on currents. Moreover, we confirmed that the light dependences with IR light illumination...
We have evaluated Ga-Sn-O (GTO) films fabricated using mist chemical vapor deposition (CVD). First, it is found that the GTO films are roughly transparent. Moreover, as the deposition temperature decreases, the transmittance becomes higher. Next, it is found that even if the carrier gas speed changes, the sheet resistance is roughly the same. However, as the composition ratio in the material solution...
We have evaluated characteristics of Ga-Sn-O (GTO) thin films deposited by RF magnetron sputtering with changing composition ratios of sputtering targets and deposition pressure. The optical transmittance is more than 80%, and the sheet resistance decreases as the deposition pressure increase for the thin films for Ga∶Sn=1∶3, On the other hand, for the thin films for Ga∶Sn=3∶1, both the transmittance...
We are developing cellular neural networks using thin-film transistors (TFTs). Although simplification of the circuits for the neurons and synapses is also needed for the cellular neural network, the detailed discussion is not sufficient for the cellular neural network. Particularly in this study, we tried simplification of synapse devices. We used discrete trimmer resistors and capacitors for the...
We are developing artificial retinas using poly-Si thin-film transistors (TFTs), which is suitable for the epiretinal implant on the curved human eyeballs. In this study, we have evaluated the wireless power supply to the artificial retinas using poly-Si TFTs. From simulation, it is found that the transmission efficiency can be 0.43 % currently. This value should be improved but acceptable because...
We are researching Ga-Sn-O (GTO) thin film as a potential material for future semiconductor devices. In this study, we investigate the GTO thin film using Hall measurement. A GTO film is deposited using RF magnetron sputtering, and annealed using electric-furnace annealing in air at temperature of 350 °C. We utilize van der Pauw method of the Hall measurement with slight modification, where the Hall...
We are developing neural networks using thin-film transistors (TFTs). By adopting an interconnect-type neural network and utilizing a characteristic degradation of poly-Si TFTs as a variable strength of synapse connection, which was originally an issue, we realized the neuron consisting of eight TFTs and synapse of only one TFT. Particularly in this presentation, we confirmed that the learning efficiency...
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