Basic characteristics of metal-ferroelectric-insulator-semiconductor structure using a high-k PrOx insulator layer

Noda, Minoru,Kodama, Kazushi,Kitai, Satoshi,Takahashi, Mitsue,Kanashima, Takeshi,Okuyama, Masanori The Korean Institute of Electrical and Electronic 2003 전기전자재료 Vol.16 No.9

A metal-ferroelectric [SrBi$_2$Ta$_2$O$\_$9/ (SBT)-high-k-insulator(PrOx)-semiconductor(Si) structure has been fabricated and evaluated as a key part of metal-ferroelectric-insulator-semiconductor-field-effect-transistor MFIS-FET memory, aiming to improve the memory retention characteristics by increasing the dielectric constant in the insulator layer and suppressing the depolarization field in the SBT layer. A 20-nm PrOx film grown on Si(100) showed both a high of about 12 and a low leakage current density of less than 1${\times}$ 10e-8 A/$\textrm{cm}^2$ at 105 MV/cm. A 400-nm SBT film prepared on PrOx/Si shows a preferentially oriented (105) crystalline structure, grain size of about 130 nm and subface roughness of 3.2 nm. A capacitance-voltage hysteresis is confirmed on the Pt/SBT/PrOx/Si diode with a memory window of 0.3V at a sweep voltage width of 12 V. The memory retention time was about 1 104s, comparable to the conventional Pt/SBT/SiO$\_$x/N$\_$y/(SiO$\_$N/)/Si. The gradual change of the capacitance indicates that some memory degradation mechanism is different from that in the Pt/SBT/SiON/Si structure.

Sensitivity Change in Piezoelectric Ultrasonic Microsensors Caused by a Variation of Diaphragm Structures

Kaoru Yamashita,Minoru Noda,Tomoya Yoshizaki,Masanori Okuyama 한국물리학회 2009 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.55 No.2

Sensitivity changes in piezoelectric-type ultrasonic microsensors have been investigated for variations in the layered structures in their diaphragms. The structure variations have been designed for sensitivity improvement in sensors having statically downward-deflected diaphragms to reduce lateral strain cancellation on their piezoelectric layer by enhancing the strain of the structural expansion component and by suppressing the strain of the bending component. The piezoelectric layer on the front side of the diaphragm has been removed around the top electrode to make slits with various widths. Silicon-dioxide and silicon layers on the rear side of the diaphragm have been removed entirely. These two variations in the structures have been analyzed for their effectiveness in sensitivity improvement, the modified sensor structures have been fabricated, and their sensitivity have been evaluated. Sensitivity changes in piezoelectric-type ultrasonic microsensors have been investigated for variations in the layered structures in their diaphragms. The structure variations have been designed for sensitivity improvement in sensors having statically downward-deflected diaphragms to reduce lateral strain cancellation on their piezoelectric layer by enhancing the strain of the structural expansion component and by suppressing the strain of the bending component. The piezoelectric layer on the front side of the diaphragm has been removed around the top electrode to make slits with various widths. Silicon-dioxide and silicon layers on the rear side of the diaphragm have been removed entirely. These two variations in the structures have been analyzed for their effectiveness in sensitivity improvement, the modified sensor structures have been fabricated, and their sensitivity have been evaluated.

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.

Crystallization of BaTiO3 Thin Film at 140 $^circ$C by Metalorganic Decomposition Hydrothermal Method Using TiO2 Precursor

Zhiqiang Wei,Masanori Okuyama,Minoru Noda 한국물리학회 2003 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.42 No.IV

BaTiO3 thin lms with perovskite structure have been prepared on Pt/Ti/SiO2/Si substrate using a combined process of conventional MOD process and a hydrothermal treatment using TiO2 precursor. The BaTiO3 thin lms were crystallized on silicon by hydrothermal treatment at temperature of 140 C. The structure development, stoichiometry, spectroscopic, and dielectric properties of BaTiO3 thin lms have been systematically investigated. X-ray diraction patterns show that well-developed crystallites with perovskite phase have been formed. BaTiO3 thin lm obtained by the mono-treatment process shows (100) preferred orientation, but TiO2 peak still exists which indicated that the reaction is not completed. The stoichiometric BaTiO3 thin lms with a (110) preferred orientation were obtained by the multi-treatment process. AFM observation shows that the roughness of surface is improved with the multi-treatment process.The electric properties of the sample prepared by the multi-treatment process is better than that prepared by the mono-treatment process.

Fabrication and characterization of SrBi$_2$Ta$_2$O$_9$-Bi$_2$SiO$_5$ Thin Films by Pulsed Laser Deposition

Yoshihide Toyoshima,Masanori Okuyama,Minoru Noda,Mitsue Takahashi 한국물리학회 2003 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.42 No.IV

SrBi2Ta2O9-Bi2SiO5 (SBT-BSO) thin lms have been prepared on Pt/Ti/SiO2/Si substrate by pulsed laser deposition at low temperature, 300 to 450 C . We succeeded in crystallizing SBT at 350 C and P-E hysterisis loops of SBT-BSO thin lm were observed and the curve was almost the same as that of SBT. Binding state of BSO has been investigated by XPS spectra, Raman spectra and AFM. As a result it is conrmed that the binding state of BSO in ceramics is dierent from that in lms prepared by PLD. Moreover we tried to anneal SBT and SBT-BSO thin lms in high pressure O2 atmosphere, and succeeded in improve ferroelectric properties about SBT.

Oxygen Annealing Effects in Natural-Superlattice-Structured Ferroelectric Bi$_4$Ti$_3$O$_{12}$-SrBi$_4$Ti$_4$O$_{15}$ Thin Films

Akira Shibuya,Masanori Okuyama,Minoru Noda 한국물리학회 2003 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.42 No.IV

Bi4Ti3O12-SrBi4Ti4O15 thin lms have been prepared on Pt/Ti/SiO2/Si by pulsed laser deposition (PLD) and their crystalline and electrical properties have been characterized. After oxygen annealing, X-ray diraction (XRD) patterns and grain sizes in atomic force microscopy (AFM) images did not change very much. But P-E hysteresis loop measured at 60 Hz has been improved very much after oxygen annealing. The values of 2Pr and 2Ec were 32 C/cm2 and 190 kV/cm, respectively, after oxygen annealing while 2Pr and 2Ec were 20 C/cm2 and 145 kV/cm, respectively, before oxygen annealing. C-V hysteresis loops shows reasonable results compared with P-E hysteresis loops both before and after oxygen annealing. The relative dielectric constant and dielectric loss were 433 and 0.037, respectively, after oxygen annealing while 595 and 0.071 before post annealing. The dielectric constant of BIT-SBTi lm approaches to that of the ceramics which is around 100 at room temperature after oxygen annealing. This improvement of ferroelectrics is mainly attributed to reduction of oxygen vacancies.p탾

Ferroelectric and Magnetic Properties of Multiferroic BiFeO3 Thin Films Prepared by Pulsed Laser Deposition

Kwi-Young Yun,Dan Ricinschi,Masanori Okuyama,Minoru Noda,Saburo Nasu 한국물리학회 2005 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.46 No.1

Multiferroic BiFeO3 thin flms have been deposited on Pt/TiO2/SiO2/Si substrates by pulsedlaser deposition. From the X-ray diffraction analysis, the BiFeO3 thin lm consists of perovskite single-phase and shows a tetragonal structure with a space group P4mm. Ferroelectric hysteresis saturate well and a remanent polarization is 73 C/cm2 for a maximum applied voltage of 4 V. A saturated ferromagnetic hysteresis loop has been also obtained and a saturation magnetization is 3.5 emu/cm3 for a maximum magnetic feld of 10 kOe at room temperature.

Effects of Annealing Atmosphere on Crystallization and Electrical Properties in BiFeO3 Thin Films by Chemacal Solution Deposition (CSD)

Kwi-Young Yun,Masanori Okuyama,Minoru Noda 한국물리학회 2003 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.42 No.IV

BiFeO3 (BFO) thin lms have been prepared on platinized silicon substrates by chemical solution deposition (CSD) and annealed at 600 C for 1 hour under various atmospheres, i.e., O2, Air and N2. Eects of annealing atmospheres on the crystallization and electrical properties of BFO lms were investigated. Crystallization behavior and electrical properties of BFO lms depend on the oxygen partial pressure of the annealing atmosphere. The BFO thin lm annealed in N2 atmosphere showed a good crystallinity. The surface roughness of the BFO lm decreased with lowering oxygen partial pressure of the annealing atmosphere. Low leakage current density and P-E hysteresis were found only in the BFO lm annealed at 600 C under N2 atmosphere. Leakage current density, polarization (at zero electric eld) and electric eld (at zero polarization) of the BFO lm annealed at 600 C under N2 are 510..7A/cm2 at 1 V, 0.2 C/cm2 and 15 kV/cm, respectively.