Global ETD Search

1	Study On Resistive Switching Mechanism Of Hafnium-doped Silicon Oxide Thin Film Chu, Tian-Jian 28 August 2012 (has links) In this study,The bottom electrode(TiN),middle insulator(Hf:SiOx),and top electrode(Pt) were deposited respectively by sputtering technique for fabricating the RRAM with MIM structure.The mole fraction of hafnium were about 5%.Instead of non-doped SiO2 base device has no switching characteristic,the Hf-doped SiO2 RRAM could be operator over 100 times and resistive state was kept stable over 104 second. In this researches,the double layer structure(Pt/Hf:SiO2/Hf:SiO2(doped N2 and NH3)).The Resistance switching characteristics of double layer structure device has particular I-V characteristics due to the doping of N.The doping of NH3 cause hydrogen plasma treatment on double layer device also bring about particular I-V characteristics. The physical mechanism we had proposed were proof by the Current-Voltage fitting and the material analysis.By control stop-voltage,the double layer structure device can operation by multi-bit. The detail physical mechanism is studied by the stable RRAM device(Ti/HfO2/TiN).In this study,the model of reset process we had proposed were proof by the special measurement methods(Constant-voltage sampling) and the principle of chemical reaction mechanism. doped SiO2 physical mechanism double layer structure hydrogen plasma treatment Hf
2	Effect of double-layer structure in intramucosal gastric signet-ring cell carcinoma on lymph node metastasis: a retrospective, single-center study / 胃粘膜内印環細胞癌における二層構造とリンパ節転移との関連性：単施設後ろ向き研究 Murai, Katsuyuki 23 May 2023 (has links) 京都大学 / 新制・論文博士 / 博士(医学) / 乙第13552号 / 論医博第2281号 / 新制\|\|医\|\|1067(附属図書館) / (主査)教授武藤学, 教授小濱和貴, 教授佐藤俊哉 / 学位規則第4条第2項該当 / Doctor of Medical Science / Kyoto University / DFAM Stomach neoplasms Signet-ring cell carcinoma Lymph node metastasis Double-layer structure 490
3	Electrical properties of amorphous selenium based photoconductive devices for application in x-ray image detectors Belev, Gueorgui Stoev 14 February 2007 In the last 10-15 years there has been a renewed interest in amorphous Se (a-Se) and its alloys due to their application as photoconductor materials in the new fully digital direct conversion flat panel x-ray medical image detectors. For a number of reasons, the a-Se photoconductor layer in such x-ray detectors has to be operated at very high electric fields (up to 10 Volts per micron) and one of the most difficult problems related to such applications of a Se is the problem of the dark current (the current in the absence of any radiation) minimization in the photoconductor layer. <p>This PhD work has been devoted to researching the possibilities for dark current minimization in a-Se x-ray photoconductors devices through a systematic study of the charge transport (carrier mobility and carrier lifetimes) and dark currents in single and multilayered a-Se devices as a function of alloying, doping, deposition condition and other fabrication factors. The results of the studies are extensively discussed in the thesis. We have proposed a new technological method for dark current reduction in single and multilayered a-Se based photoconductor for x-ray detector applications. The new technology is based on original experimental findings which demonstrate that both hole transport and the dark currents in a-Se films are a very strong function of the substrate temperature (Tsubstrate) during the film deposition process. We have shown that the new technique reduces the dark currents to approximately the same levels as achievable with the previously existing methods for dark current reduction. However, the new method is simpler to implement, and offers some potential advantages, especially in cases when a very high image resolution (20 cycles/mm) and/or fast pixel readout (more than 30 times per second) are needed. <p>Using the new technology we have fabricated simple single and double (ni-like) photoconductor layers on prototype x-ray image detectors with CCD (Charge Coupled Device) readout circuits. Dark currents in the a-Se photoconductor layer were not a problem for detector operation at all tested electric fields. Compared to the currently available commercial systems for mammography, the prototype detectors have demonstrated an excellent imaging performance, in particular superior spatial resolution (20 cycles/mm). Thus, the newly proposed technology for dark current reduction has shown a potential for commercialization. amorphous state amorphous semiconductors photoconductivity a Se photoconductors medical imaging radiation detectors high resolution digital mammography thick films experimental study electron hole pair lifetime localized states carrier lifetime trapping drift mobility carrier mobility charge carrier trapping alloying fabrication property relation arsenic additions doping chlorine additions deposition rate deposition conditions boat temperature substrate temperature annealing time-of-flight method dark current metal electrodes blocking layers double layer structure
4	Electrical properties of amorphous selenium based photoconductive devices for application in x-ray image detectors Belev, Gueorgui Stoev 14 February 2007 (has links) In the last 10-15 years there has been a renewed interest in amorphous Se (a-Se) and its alloys due to their application as photoconductor materials in the new fully digital direct conversion flat panel x-ray medical image detectors. For a number of reasons, the a-Se photoconductor layer in such x-ray detectors has to be operated at very high electric fields (up to 10 Volts per micron) and one of the most difficult problems related to such applications of a Se is the problem of the dark current (the current in the absence of any radiation) minimization in the photoconductor layer. <p>This PhD work has been devoted to researching the possibilities for dark current minimization in a-Se x-ray photoconductors devices through a systematic study of the charge transport (carrier mobility and carrier lifetimes) and dark currents in single and multilayered a-Se devices as a function of alloying, doping, deposition condition and other fabrication factors. The results of the studies are extensively discussed in the thesis. We have proposed a new technological method for dark current reduction in single and multilayered a-Se based photoconductor for x-ray detector applications. The new technology is based on original experimental findings which demonstrate that both hole transport and the dark currents in a-Se films are a very strong function of the substrate temperature (Tsubstrate) during the film deposition process. We have shown that the new technique reduces the dark currents to approximately the same levels as achievable with the previously existing methods for dark current reduction. However, the new method is simpler to implement, and offers some potential advantages, especially in cases when a very high image resolution (20 cycles/mm) and/or fast pixel readout (more than 30 times per second) are needed. <p>Using the new technology we have fabricated simple single and double (ni-like) photoconductor layers on prototype x-ray image detectors with CCD (Charge Coupled Device) readout circuits. Dark currents in the a-Se photoconductor layer were not a problem for detector operation at all tested electric fields. Compared to the currently available commercial systems for mammography, the prototype detectors have demonstrated an excellent imaging performance, in particular superior spatial resolution (20 cycles/mm). Thus, the newly proposed technology for dark current reduction has shown a potential for commercialization. amorphous state amorphous semiconductors photoconductivity a Se photoconductors medical imaging radiation detectors high resolution digital mammography thick films experimental study electron hole pair lifetime localized states carrier lifetime trapping drift mobility carrier mobility charge carrier trapping alloying fabrication property relation arsenic additions doping chlorine additions deposition rate deposition conditions boat temperature substrate temperature annealing time-of-flight method dark current metal electrodes blocking layers double layer structure

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