32 research outputs found
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žçŽ æµéæ¯(=O_2/(Ar+O_2))4.2%ã§æ倧ãšãªã£ããããã«ç±åŠçå¹æã«ã€ããŠæ€èšãããšããã500â10ç§éã®çæéç±åŠçã§ã¯ãSiçé¢ã®SiO_xå±€ããããã«å¢å ããããåæã«ZrO_2èã®æ§é æ¬ é¥ãé€å»ãããã®çµæèªé»çãå¢å€§ããå
šäœãšããŠSiO_2æç®èåã¯1.5nm1ãã1.15nmã«å°ãããªã£ãããããã700â以äžã®ç±åŠçã§ã¯ãSiO_xå±€ãå¢å€§ãæŒãé»æµç¹æ§ã¯æ¹åããããSiO_2æç®èåã¯å¢å€§ããã以äžæ¬ç 究ã«ãããŠã極èZrO_2èäœè£œã«ãããæé©æ¡ä»¶ãæããã«ãããA new sputtering film deposition method, named Limtted Reaction Sputtering Technique, was developed and investigated. Using this technique, YSZ and ZrO2 dielectric films were synthsized for gate materials of next generation MOSFETs. The Si substrate surface oxidation was suppressed consequently a high specific dielectric constant as high as over 20 was obtained. On conventional sputtering technique using oxide target, oxigen ions and radicals are easily to be generated, thus Si is oxidized significantly. However, this teconique does not genarate them, resulting in clear interface between Si substrate and deposited films.ç 究課é¡/é åçªå·:13650338, ç 究æé(幎床):2001-2002åºå
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±é³Ž)æ³ãçšããŠæ°ŽçŽ ãã©ãºããå±èµ·ããããã«SiH_4ã¬ã¹ãæ¥è§Šå解ãããSiã®ãšãã¿ãã·ã£ã«æé·ãè¡ã£ãããã®æ°ŽçŽ ãã©ãºãã¯ãSiH_4ã¬ã¹ã®å解ã ãã§ãªããå ç©ããSièã®äžéšããšããã³ã°ããŠããããšããã³ãã®äœçšããšãã¿ãã·ã£ã«æé·ãä¿é²ããŠããããšãé床ã®ãšããã³ã°ã¯çµæ¶æ¬ é¥ãåŒãèµ·ããããšãæããã«ãªã£ããäžæ¹ãé©åœãªå ç©æ¡ä»¶ãèšå®ããã°ãSiO_2åºæ¿äžã«ã¯Sièã¯æé·ãããSiåºæ¿ã®ã¿ã«Siã®ãšãã¿ãã·ã£ã«æé·ãèµ·ããããšãã§ãããããããéžæãšãã¿ãã·ã£ã«æé·ãå¯èœã§ããããšãèŠãã ããããIt is possible to reduce the base resistance by introducing wider energy bandgap emitter than a base region. This can make operation speed of bipolar transistor faster. We proposed amorphous SiC (a-SiC) and microcrystalline Si (mu c-Si) for the emitter material and fabricated prototype devices using those. For only using mu c-Si the device showed low current gain because of epitaxial growth which forms the Si homojunction. Whereas, we fabricated devices with a a-SiC ultra-thin film before deposition of a mu c-Si film, resulting in 20-30 times larger current gain than that of the mu c-Si device. However emitter resistance of the a-SiC device increased, which degraded high frequency performance.Nextly, we attempted to fabricate devices having SiGe base as a narrow bandgap base. SiGe films were formed by sputtering Si and Ge targets using an Ar ion beam. Epitaxial temperature went down by adding Ge. For example, the epitaxial temperature was as low as 400ïŸC for composition of Si_Ge_.Furthermore, we investigated low temperature Si epitaxial growth by ECR (Electron Cycrotron Resonance) plasma CVD method. In the film growth process, not only deposition process but also etching process was found to proceed. The later process was found to be effective for enhancing epitaxial growth. Moreover, selective epitaxial growth was successfully carried out by controlling the deposition conditions.ç 究課é¡/é åçªå·:07650394, ç 究æé(幎床):1995-1996åºå
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Feasibility of Ultra-Thin Films for Gate Insulator by Limited Reaction Sputtering Process
A new sputtering technique named "limited reaction sputtering" is proposed and the feasibility toward an ultra-thin gate insulator is investigated. 5-10 nm thick ZrO 2 films were prepared on Si(100) substrates and analyzed by XPS, HR-RBS and RHEED. Significant Zr diffusion into the Si substrate and interface oxidation were not observed. An optimum film was obtained at growth temperature of 300°C, oxygen flow rate of 4.2% and 500°C-10 sec RTA. The equivalent oxide thickness of 2 nm was realized with leakage current of 10 -7 A/cm 2 at 1.5 MV/cm
3D neuromelanin-sensitive magnetic resonance imaging with semi-automated volume measurement of the substantia nigra pars compacta for diagnosis of Parkinson's disease
Neuromelanin-sensitive MRI has been reported to be used in the diagnosis of Parkinson's disease (PD), which results from loss of dopamine-producing cells in the substantia nigra pars compacta (SNc). In this study, we aimed to apply a 3D turbo field echo (TFE) sequence for neuromelanin-sensitive MRI and to evaluate the diagnostic performance of semi-automated method for measurement of SNc volume in patients with PD. We examined 18 PD patients and 27 healthy volunteers (control subjects). A 3D TFE technique with off-resonance magnetization transfer pulse was used for neuromelanin-sensitive MRI on a 3T scanner. The SNc volume was semi-automatically measured using a region-growing technique at various thresholds (ranging from 1.66 to 2.48), with the signals measured relative to that for the superior cerebellar peduncle. Receiver operating characteristic (ROC) analysis was performed at all thresholds. Intra-rater reproducibility was evaluated by intraclass correlation coefficient (ICC). The average SNc volume in the PD group was significantly smaller than that in the control group at all the thresholds (P 2.0), the area under the curve of ROC (Az) increased (0.88). In addition, we observed balanced sensitivity and specificity (0.83 and 0.85, respectively). At lower thresholds, sensitivity tended to increase but specificity reduced in comparison with that at higher thresholds. ICC was larger than 0.9 when the threshold was over 1.86. Our method can distinguish the PD group from the control group with high sensitivity and specificity, especially for early stage of PD
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ã«çµæ¶åãé²ããšæçžã解ã移åãå¯èœã«ãªãæµæçã¯æžå°ãããããããé«æž©æé·ã§ã¯çµæ¶æ§ãè¯ãçæ§åå°äœãšãªããããã£ãªã¢ãçæããã«ãããªããæµæçãåã³äžæãããšè§£éããããçµæ¶æé·ãéå§ãã400âã§ã¯ãé©åºŠãªçµæ¶æ¬ é¥ãååšãããããã£ãªã¢ãçæããçµæ¶åããé åãäŒå°ããããæµæçã®äœäžãèŠããããšèãããããã»ãŒãŒããã¯ä¿æ°äœè£œããSiGeèã¯ã1.5-2mV/Kãšãããã«ã¯SiGeã®3å以äžã®ç±èµ·é»èœã瀺ãããæµæã®äœãè©Šæã§ãããŒãŒããã¯ä¿æ°ãå°ãããªã£ãããäœè£œæž©åºŠãçµæ¶æ§ãšã®çžé¢ã¯èŠ³ãããªãã£ããã»ç±é»æ§èœæž¬å®ãããæµæçãšãŒãŒããã¯ä¿æ°ãããã®ææããåãåºããæèœé»åããªãã¡ãã¯ãŒãã¡ã¯ã¿ãŒãèŠç©ãã£ããšããã7.2x10^Wm^K^ãšããéåžžã«å€§ããªå€ãåŸãããããŸãããã«ã¯SiGeã®ç±äŒå°çãçšããŠç¡æ¬¡å
æ§èœææ°ãèšç®ãããšZT=1.3ãæ±ããããææãªç±é»ææã§ããããšã瀺ãããCrystallinity :Crystalline growth of SiGe films was slightly observed to take place at 400â from XRD measurement. Below that the films were amorphous structure. The films were confirmed epitaxially grown from RHEED observation. Above 500â, crystallinity was improved.Resistivity :Until 400â, film resistivity decreased with increasing growth temperature but above that, resistivity was increased again. This phenomena is explained that at low temperature carrier is not generated because of the amorphous structure. While crystalline growth proceeds, carrier comes to be generated. Under almost perfect crystalline structure, however, resistivity increases again because of intrinsic semiconductor resulting in no carrier genneration. The reason of low resistivity at 400â is considered that appropriate crystalline defects generated carriers, which could conduct within the crystallized region.Seebeck coefficient :SiGe films prepared showed large Seebeck coefficients of 1.5-2.0mV/K which is more than 3 times larger than that of bulk SiGe. No special coreration was observed on Seebeck coefficient with samples.Thermo-electric performances :Power factor was estimated from the Seebeck coeffcient and resistivity and showed as high as 7.2x10^Wm^K^. Moreover, the non-dimensional figure of merit Z reached ZT=1.3 at room temperature. This value shows useful for practical use.ç 究課é¡/é åçªå·:15360161, ç 究æé(幎床):2003 â 2005åºå
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