Typically, each element in a large-area flat-panel X-ray image sensor consists of a photodetector and amorphous silicon (a-Si) thin-film transistor (TFT) switches. In order to reduce noise, increase sensor dynamic range, and increase carrying capacity, the low-temperature polycrystalline-silicon (LTPS) TFTs have been proposed as a candidate to replace the a-Si TFTs. However, there are concerns regarding the impact of X-ray radiation in LTPS-TFTs, and several studies have been conducted to inquire into the same. In this paper, we show that LTPS TFTs with small channel length (<2 µm) are almost immune to X-ray radiation.
A photo-electronic fog counter has been developed on the principle of counting flashes of light scattered from individual fog droplets with a photomultiplier. Since a photomultiplier appears to act very rapidly and reponse in a time of the order of 10-8 sec. is possible, the maximum counting rate is limited only by the sealer which is associated with the counter. If a Berkeley Sealer (Model 1000B) is used, this counter is capable of counting fog droplets at a rate of 300,000/min. with very small error and the chance of coincidence countings is therefore small. This counter will prove useful for even very dense fogs or any other kind of aerosols. The optical theory of scattering which may lead to the determination of particle size from size of electric pulse has been introduced.Preliminary experiments show the applicability of this counter for droplet size measurement. There seems to be of no doubt that this counter could register the smallest droplets that occur in natural fogs (i.e., of the order of r≈1 micron) and a better sensitivity can be achieved by reducing stray-light noise level and improving signal to noise ratio. Possibilities of further improvements of the present instrument both as a fog counter and as a droplet size indicator have been discussed.
In this paper, high-performance Zinc oxide (ZnO) thin-film transistors (TFTs) with bottom-gate (BG) structure and artificially location-controlled lateral grain growth have been prepared by low-temperature hydrothermal method. As the proper design of source/drain structure of ZnO/Ti/Pt thin films, the lateral grain growth can be artificially controlled in the desired location and the vertical grain boundary perpendicular to the current flow in the channel region can be reduced to single one. As compared with the conventional sputtered ZnO BG-TFTs, the proposed locationcontrolled hydrothermal ZnO BG-TFTs (W/L = 250 µm/10 µm) demonstrated the higher field-effect mobility of 6.09 cm 2 /V·s, lower threshold voltage of 3.67 V, larger on/off current ratio above 10 6 , and superior current drivability, which can be attributed to the high-quality ZnO thin films with the reduced vertical grain boundaries in the channel region.
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