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M. Sohgawa,M. Yoshida,M. Okuyama,T. Kanashima 한국물리학회 2005 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.46 No.1
SrBi2Ta2O9 (SBT)/SiO2/Si structures have been characterized by photore ectance spectroscopy (PRS) without electrode formation. SBT lm was deposited on SiO2/n-Si by the metal-organic decomposition (MOD) method and annealed in O2 atmosphere at 600 C. The voltage was applied by attaching ITO transparent electrodes during PRS measurement. The PRS spectral intensity of SBT/SiO2/Si structure has hysteresis characteristics as well as a C-V curve. Additionally, the spectral intensity gradually decreases with time, in a similar way to reduction of the capacitance. These results mean that the spectral intensity indicates the ferroelectricity of SBT flm in SBT/SiO2/Si structure, so that it is considered that characterization of MFIS structure without electrode can be measured by PRS.
박정민,Masayuki Sohgawa,Takeshi Kanashima,Masanori Okuyama,Seiji Nakashima 한국물리학회 2013 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.62 No.7
Epitaxial BiFeO<sub>3</sub> (BFO) thin films have been prepared on La-doped (001) SrTiO<sub>3</sub> substrates (La-STO) by using magnetic-field-assisted pulsed laser deposition. X-ray diffraction patterns of the epitaxial BFO thin films prepared under magnetic fields of 0, 0.1, and 0.4 T show only (00l) diffraction peaks without secondary phases. From the results of reciprocal space mapping for all epitaxial BFO thin films, (003) reflections show splitting spots, and asymmetric spots of (−103) and (103) reflections exhibit a rhombohedral structure. The microstructure of the epitaxial thin films was modified by the strength of magnetic field, and a columnar structure was shown in the film prepared under a high deposition rate for a magnetic field of 0.4 T. The polarization versus electric field hysteresis loops were obtained at room temperature (RT) in all the epitaxial films; in particular, the remanent polarization for the epitaxial film prepared under a magnetic field of 0.1 T was 46 μC/cm<sup>2</sup> at RT while the current density was reduced in comparison with those of other epitaxial films.
Takeshi Kanashima,Koji Ikeda,Masanori Okuyama,Masayuki Sohgawa,Taizo Tada 한국물리학회 2005 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.46 No.1
High-k HfO2 thin lms have been prepared mainly at 400 C in O2 atmosphere by pulsed laser deposition (PLD), and defects in the lm have been characterized by electron spin resonance (ESR). Two ESR peaks are found at g ' 2:003 and 2:006. The g ' 2:006 peak intensity is higher in the sample deposited at target-sample distance of 45 mm than in that deposited at 60 mm. This is because part of the substrate and the lm are exposed to high-energy particles ablated during deposition and are hence damaged. Moreover, the peak at g ' 2:006 is related to the interface state density calculated from the high-frequency C V curve. On the other hand, the peak at g ' 2:003 is related to the thickness of the interfacial layer, and thus may be attributed to defects in the interfacial layer.
Characterization of Si Interface in FIS Structure by Photoreflectance Spectroscopy
Hirofumi Kanda,Akira Fujimoto,Masanori Okuyama,Masayuki Sohgawa,Takeshi Kanashima,Yoshihide Toyoshima 한국물리학회 2003 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.42 No.IV
SrBi2Ta2O9(SBT) thin lm grown on SiO2/Si by a pulsed laser deposition was evaluated by photore ectance spectroscopy (PRS) which is one of the non-destructive techniques to characterize an interface. The stress of a SiO2/Si interface of ferroelectric-insulator-semiconductor (FIS) structure has been evaluated by using this method. As a result, there is a tensile stress which is larger than that before deposition, and the stress becomes large according to increasing SBT thickness. Moreover, when ferroelectric thin lm is poled, the stress becomes small with increase of the voltage.
Miniature Ultrasonic and Tactile Sensors for Dexterous Robot
Okuyama, Masanori,Yamashita, Kaoru,Noda, Minoru,Sohgawa, Masayuki,Kanashima, Takeshi,Noma, Haruo The Korean Institute of Electrical and Electronic 2012 Transactions on Electrical and Electronic Material Vol.13 No.5
Miniature ultrasonic and tactile sensors on Si substrate have been proposed, fabricated and characterized to detect objects for a dexterous robot. The ultrasonic sensor consists of piezoelectric PZT thin film on a Pt/Ti/$SiO_2$ and/or Si diaphragm fabricated using a micromachining technique; the ultrasonic sensor detects the piezoelectric voltage as an ultrasonic wave. The sensitivity has been enhanced by improving the device structure, and the resonant frequency in the array sensor has been equalized. Position detection has been carried out by using a sensor array with high sensitivity and uniform resonant frequency. The tactile sensor consists of four or three warped cantilevers which have NiCr or $Si:B^+$ piezoresistive layer for stress detection. Normal and shear stresses can be estimated by calculation using resistance changes of the piezoresitive layers on the cantilevers. Gripping state has been identified by using the tactile sensor which is installed on finger of a robot hand, and friction of objects has been measured by slipping the sensor.
Miniature Ultrasonic and Tactile Sensors for Dexterous Robot
Masanori Okuyama,Kaoru Yamashita,Minoru Noda,Masayuki Sohgawa,Takeshi Kanashima,Haruo Noma 한국전기전자재료학회 2012 Transactions on Electrical and Electronic Material Vol.13 No.5
Miniature ultrasonic and tactile sensors on Si substrate have been proposed, fabricated and characterized to detect objects for a dexterous robot. The ultrasonic sensor consists of piezoelectric PZT thin film on a Pt/Ti/SiO2 and/or Si diaphragm fabricated using a micromachining technique; the ultrasonic sensor detects the piezoelectric voltage as an ultrasonic wave. The sensitivity has been enhanced by improving the device structure, and the resonant frequency in the array sensor has been equalized. Position detection has been carried out by using a sensor array with high sensitivity and uniform resonant frequency. The tactile sensor consists of four or three warped cantilevers which have NiCr or Si:B+ piezoresistive layer for stress detection. Normal and shear stresses can be estimated by calculation using resistance changes of the piezoresitive layers on the cantilevers. Gripping state has been identified by using the tactile sensor which is installed on finger of a robot hand, and friction of objects has been measured by slipping the sensor.
T. Kanashima,M. Okuyama,H. Kanda,K. Ikeda,M. Sohgawa 한국물리학회 2003 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.42 No.IV
High-k thin lms of ZrO2, PrOx of 10 nm thickness have been prepared by pulsed laser deposition, and characterized in microscopic structure and electrical properties. Crystallization is promoted in ZrO2 lms deposited above 400 C, but a signicant XRD peak was not observed in the ZrO2 lm grown below 400 C. The leakage current is decreased by increasing growth temperature, but an equivalent-oxide thickness (EOT) obtained from accumulation capacitance of C .. V characteristics becomes large. The lms deposited at 400 C were annealed at 400 C in O2 gas to reduce the leakage. The leakage current change to be small, but the EOTs become large. Oxygen radical annealing is carried out to reduced the leakage, and is eective for ZrO2 thin lm. On the other hand, only small improvement is observed in the PrOx lms.