著者

Cui Guodong Han Dedong Yu Wen Shi Pan Zhang Yi Huang Lingling Cong Yingying Zhou Xiaoliang Zhang Xiaomi Zhang Shengdong Zhang Xing Wang Yi

出版者

Institute of Physics

雑誌

Jpn. J. Appl. Phys. (ISSN:00214922)

巻号頁・発行日

vol.55, no.4, 2016-03-22

被引用文献数

3

---

By applying a novel active layer of titanium zinc oxide (TiZO), we have successfully fabricated fully transparent thin-film transistors (TFTs) with a bottom gate structure fabricated on a flexible plastic substrate at low temperatures. The effects of various oxygen partial pressures during channel deposition were studied to improve the device performance. We found that the oxygen partial pressure during channel deposition has a significant impact on the performance of TiZO TFTs, and that the TFT developed under 10% oxygen partial pressure exhibits superior performance with a low threshold voltage (V<inf>th</inf>) of 2.37 V, a high saturation mobility (μ<inf>sat</inf>) of 125.4 cm²V⁻¹s⁻¹, a steep subthreshold swing (SS) of 195 mV/decade and a high I<inf>on</inf>/I<inf>off</inf>ratio of 3.05 × 10⁸. These results suggest that TiZO thin films are promising for high-performance fully transparent flexible TFTs and displays.

著者

Fukagawa Miki Koshiba Yausko Morimoto Masahiro Ishida Kenji

出版者

Institute of Physics

雑誌

Jpn. J. Appl. Phys. (ISSN:00214922)

巻号頁・発行日

vol.56, no.4, 2017-01-25

被引用文献数

5

---

The structural, ferroelectric, and piezoelectric properties of poly(vinylidene fluoride–trifluoroethylene) [P(VDF–TrFE)] gels fabricated using poly(pyridinium-1,4-diyliminocarbonyl-1,4-phenylenemethylene thiocyanate) (PICPM-SCN) as a gelator are investigated in this study. The P(VDF–TrFE)/PICPM-SCN composites formed thermally reversible physical gels and their analysis by Fourier transform infrared spectroscopy revealed that the P(VDF–TrFE) molecules in these gels exhibit predominantly the ferroelectric phase I (Form β). Furthermore, the polarization switching peaks of the P(VDF–TrFE)/PICPM-SCN gel films were clearly observed. The coercive electric field for these gel films was estimated to be 2 MV/m, which is dramatically lower than the values typically observed for P(VDF–TrFE) solid films (50 MV/m). Finally, the P(VDF–TrFE)/PICPM-SCN gel films exhibited a piezoelectric response, and the highest piezoelectric coefficient was determined to be ∼53 pm/V at an applied voltage frequency of 4 kHz.

著者

Horike Shohei Misaki Masahiro Koshiba Yasuko Morimoto Masahiro Saito Takeshi Ishida Kenji

出版者

Institute of Physics

雑誌

Appl. Phys. Express (ISSN:18820778)

巻号頁・発行日

vol.9, no.8, 2016-07-06

被引用文献数

9

---

The tuning of the Seebeck coefficient of a single-walled carbon nanotube (SWCNT) film was achieved by using the dipole field of a ferroelectric polymer. The Seebeck coefficient was positive under an up-poling dipole field, but negative under a down-poling dipole field, whereas the control remained positive. This tunable behavior can be explained by selective carrier injection and accumulation, which was confirmed by the temperature dependence of electrical conductivity. Connecting p- and n-type SWCNT films tuned by dipole fields to create a π module resulted in a significant improvement in output voltage owing to the temperature difference between the two.

著者

Sato-Iwanaga Junko Yu Zhiping Dutton Robert Tsuchiya Hideaki

出版者

Institute of Physics

雑誌

Jpn. J. Appl. Phys. (ISSN:00214922)

巻号頁・発行日

vol.55, no.4, 2016-02-29

被引用文献数

1

---

The nonlinear characteristics arising from the third-order intermodulation distortion (IMD3) of MOSFETs are investigated by harmonic-balance device simulation. First, to identify the spatial location in a MOSFET, where IMD3 is mostly generated, a conventional n-MOSFET structure is simulated, and it is found that IMD3 generation is located at the top surface over the channel–drain p–n junction where a high lateral electric-field exists. Second, to alleviate the impact of IMD3, we proposed and simulated three types of n-MOSFET structures with a low lateral electric-field around the channel–drain junction. We demonstrated that a low-distortion MOSFET can be realized by optimizing the doping concentration profile at the channel–drain junction. In particular, the introduction of a thin layer of a low-doped n-type surface-channel and a low-doped n-type drain at the top of p-type well and n-type drain regions resulted in a marked IMD3 reduction of as much as 8 dBm in IMD3 power characteristics, in comparison with a conventional structure.

著者

Koshiba Yasuko Nishimoto Mihoko Misawa Asuka Misaki Masahiro Ishida Kenji

出版者

Institute of Physics

雑誌

Jpn. J. Appl. Phys. (ISSN:00214922)

巻号頁・発行日

vol.55, no.3, 2016-02-12

被引用文献数

4

---

The thermal behavior of 1,2,4,5-tetracyanobenzene (TCNB), the synthesis of metal-2,3,9,10,16,17,23,24-octacyanophthalocyanine–metal [MPc(CN)<inf>8</inf>–M] (M = Cu, Fe, Ni) complexes by the tetramerization of TCNB, and the growth of MPc(CN)<inf>8</inf>–M nanorods were investigated. By chemical vapor deposition (CVD) in vacuum, MPc(CN)<inf>8</inf>molecules were synthesized and MPc(CN)<inf>8</inf>–M nanorods were formed on all substrates. Among them, CuPc(CN)<inf>8</inf>molecules were synthesized in high yield, and CuPc(CN)<inf>8</inf>–Cu nanorods were deposited uniformly and in high density, with diameters and lengths of 70–110 and 200–700 nm, respectively. The differences in the growth of MPc(CN)<inf>8</inf>–M nanorods were mainly attributed to the stability of the MPc(CN)<inf>8</inf>–M complex, the oxidation of ultrathin metal films, and the diffusion of metal atoms. Additionally, the tetramerization of TCNB by CVD at atmospheric pressure was performed on ultrathin Cu films, and the synthesis of CuPc(CN)<inf>8</inf>molecules was observed by in situ UV–vis spectroscopy. CVD under atmospheric pressure is also useful for the synthesis of CuPc(CN)<inf>8</inf>molecules.

著者

Inoue Takaaki Mori Akimitsu Koshiba Yasuko Misaki Masahiro Ishida Kenji

出版者

Institute of Physics

雑誌

Appl. Phys. Express (ISSN:18820778)

巻号頁・発行日

vol.8, no.11, 2015-10-14

被引用文献数

3

---

The ferroelectric properties of perpendicularly oriented, highly crystalline vinylidene fluoride (VDF) oligomer thin films were investigated by using a planar device configuration consisting of comblike Cr–Au electrodes with a 1 µm gap. In-plane polarization switching was induced by the rotation of the VDF oligomer. As the measurement temperature was increased from 295 to 380 K, the coercive field (E<inf>c</inf>) decreased drastically from 124 to 7.7 MV/m. Furthermore, the thermal stability of our device significantly improved compared with that of conventional sandwiched devices utilizing VDF oligomer films with a parallel orientation.

著者

Ide T Isozaki H Nakata S Siltanen S

出版者

Institute of Physics

雑誌

Inverse problems (ISSN:02665611)

巻号頁・発行日

vol.26, no.3, pp.035001, 2010-03

被引用文献数

12 12

---

Assume one is given a three-dimensional bounded domain with an unknown conductivity distribution inside. Further, suppose that the conductivity consists of a known background and unknown anomalous regions (inclusions) where conductivity values are unknown and different from the background. A method is introduced in Ide et al (2007 Commun. Pure Appl. Math. 60 1415–42) for locating inclusions approximately from noisy localized voltage-to-current measurements performed at the boundary of the body. The method is based on the use of complex geometrical optics solutions and hyperbolic geometry; numerical testing is presented in the aforementioned paper for the two-dimensional case. This work reports the results of computational implementation of the method in dimension three, where both the simulation of data and the computerized inversion algorithm are more complicated than in dimension two. Three new regularizing steps are added to the algorithm, resulting in significantly better robustness against noise. Numerical experiments are reported, suggesting that the approximate location of the inclusions can be reliably recovered from the data with a realistic level of measurement noise. Potential applications of the results include early diagnosis of breast cancer, underground contaminant detection and nondestructive testing.

著者

Meng Jianwei Jiang Jun Geng Wenping Chen Zhihui Zhang Wei Jiang Anquan

出版者

Institute of Physics

雑誌

Jpn. J. Appl. Phys. (ISSN:00214922)

巻号頁・発行日

vol.54, no.2, 2015-01-19

被引用文献数

3

---

We fabricated (00l) BiFeO<inf>3</inf>(BFO) thin films in different growth modes on SrRuO<inf>3</inf>/SrTiO<inf>3</inf>substrates using a pulsed laser deposition technique. X-ray diffraction patterns show an out-of-plane lattice constant of 4.03 Å and ferroelectric polarization of 82 µC/cm²for the BFO thin film in a layer-by-layer growth mode (2D-BFO), larger than 3.96 Å and 51 µC/cm²for the thin film in the 3D-island formation growth mode (3D-BFO). The 2D-BFO thin film at 300 K shows switchable on/off diode currents upon polarization flipping near a negative coercive voltage, which is nevertheless absent from the above 3D-BFO thin film. From a positive-up–negative-down pulse characterization technique, we measured domain switching current transients as well as polarization–voltage (P<inf>f</inf>–V<inf>f</inf>) hysteresis loops in both semiconducting thin films. P<inf>f</inf>–V<inf>f</inf>hysteresis loops after 1 µs-retention time show the preferred domain orientation pointing to bottom electrodes in a 3D-BFO thin film. The poor retention of the domains pointing to top electrodes can be improved considerably in a 2D-BFO thin film. From these measurements, we extracted domain switching time dependence of coercive voltage at temperatures of 78–300 K. From these dependences, we found coercive voltages in semiconducting ferroelectric thin films much higher than those in insulating thin films, disobeying the traditional Merz equation. Finally, an equivalent resistance model in description of free-carrier compensation of the front domain boundary charge is developed to interpret this difference. This equivalent resistance can be coincidently extracted either from domain switching time dependence of coercive voltage or from applied voltage dependence of domain switching current, which drops almost linearly with the temperature until down to 0 in a ferroelectric insulator at 78 K.

著者

Kim Yoon Shim Won Park Byung-Gook

出版者

Institute of Physics

雑誌

Jpn. J. Appl. Phys. (ISSN:00214922)

巻号頁・発行日

vol.54, no.6, 2015-05-26

被引用文献数

2

---

In this paper, we report the fabrication and analysis of the gated twin-bit NAND flash memory with a nitride charge-trapping layer. This device is based on the recessed channel structure, and it has an additional cut-off gate that enables 2-bit operation. Therefore, the density of the array can be doubled without any difficulty in patterning. The fabrication method for gated twin-bit (GTB) silicon–oxide–nitride–oxide–silicon (SONOS) memories and their electrical characteristics are described in this paper. Program/erase characteristics are observed and the 2-bit operation is verified by the forward–reverse reading scheme.

著者

Ma Yitao Miura Sadahiko Honjo Hiroaki Ikeda Shoji Hanyu Takahiro Ohno Hideo Endoh Tetsuo

出版者

Institute of Physics

雑誌

Jpn. J. Appl. Phys. (ISSN:00214922)

巻号頁・発行日

vol.55, no.4, 2016-03-29

被引用文献数

13

---

A novel associative processor using magnetic tunnel junction (MTJ)-based nonvolatile memories has been proposed and fabricated under a 90 nm CMOS/70 nm perpendicular-MTJ (p-MTJ) hybrid process for achieving the exceptionally low-power performance of image pattern recognition. A four-transistor 2-MTJ (4T-2MTJ) spin transfer torque magnetoresistive random access memory was adopted to completely eliminate the standby power. A self-directed intelligent power-gating (IPG) scheme specialized for this associative processor is employed to optimize the operation power by only autonomously activating currently accessed memory cells. The operations of a prototype chip at 20 MHz are demonstrated by measurement. The proposed processor can successfully carry out single texture pattern matching within 6.5 µs using 128-dimension bag-of-feature patterns, and the measured average operation power of the entire processor core is only 600 µW. Compared with the twin chip designed with 6T static random access memory, 91.2% power reductions are achieved. More than 88.0% power reductions are obtained compared with the latest associative memories. The further power performance analysis is discussed in detail, which verifies the special superiority of the proposed processor in power consumption for large-capacity memory-based VLSI systems.

著者

Ko Tsung-Shine Chen Zheng-Wen Lin Der-Yuh Suh Joonki Chen Zheng-Sheng

出版者

Institute of Physics

雑誌

Jpn. J. Appl. Phys. (ISSN:00214922)

巻号頁・発行日

vol.56, no.4, 2017-03-24

被引用文献数

4

---

In this study, Ni-doped MoS<inf>2</inf>was grown by chemical vapor transportation. Photoconductivity results reveal that Ni-doped MoS<inf>2</inf>has an obvious doping level of 1.2 eV and an electrical conductivity of σ ≅ 9.92 × 10⁻⁷S cm⁻¹at room temperature, which is lower than that of undoped MoS<inf>2</inf>(σ ≅ 7.913 × 10⁻⁵S cm⁻¹) owing to the impurity state caused by Ni atoms. Hall effect measurement results indicate that Ni-doped MoS<inf>2</inf>sample is of the n-type and has a higher resistance and a lower mobility than undoped MoS<inf>2</inf>. We further fabricated undoped and Ni-doped MoS<inf>2</inf>photodetectors to understand the operation characteristics of MoS<inf>2</inf>-based photodetectors. Persistent photoconductivity shows that both rise and fall times decreased from 0.33/0.68 to 0.14/0.43 s as Ni atoms were doped in MoS<inf>2</inf>PDs. This work shows that Ni atoms could cause small lattice imperfections to form trap states leading to high resistance, low mobility, small activation energy and short decay time. Therefore, doping Ni atoms in MoS<inf>2</inf>is beneficial for the application of photodetectors.

著者

Welch Adam Baranowski Lauryn Zawadzki Pawel Lany Stephan Wolden Colin Zakutayev Andriy

出版者

Institute of Physics

雑誌

Appl. Phys. Express (ISSN:18820778)

巻号頁・発行日

vol.8, no.8, 2015-07-06

被引用文献数

80

---

Recent technical and commercial successes of existing thin-film solar cell technologies encourage the exploration of next-generation photovoltaic (PV) absorber materials. Of particular scientific interest are compounds that do not exhibit conventional tetrahedral semiconductor bonding, such as CuSbSe<inf>2</inf>. CuSbSe<inf>2</inf>has a 1.1 eV optical absorption onset, a 10⁵cm⁻¹absorption coefficient, and a hole concentration of 10¹⁷cm⁻³. Here, we demonstrate CuSbSe<inf>2</inf>PV prototypes with efficiencies >3%, prepared by a self-regulated sputtering process using a conventional substrate device architecture. Bulk recombination, device engineering issues, and a nonideal CuSbSe<inf>2</inf>/CdS band offset likely limit the promising initial result.

著者

Kajihara Tadao Ueno Yoshikazu Tsujiura Yuichi Koshiba Yasuko Morimoto Masahiro Kanno Isaku Ishida Kenji

出版者

Institute of Physics

雑誌

Jpn. J. Appl. Phys. (ISSN:00214922)

巻号頁・発行日

vol.56, no.4, 2017-02-03

被引用文献数

8

---

We investigated piezoelectric vibration energy harvesters with poly(vinylidene fluoride/trifluoroethylene) films and the improved power generation from using multistacked and stretched ferroelectric films on the cantilevers. The energy harvesters generated electric power with a resonant frequency of approximately 25 Hz, which corresponded to the ambient vibration. The power density of four-layered harvesters was estimated to be 2.5 µW/m³, which was larger than the power density of previous harvesters. The output power of stretched-film harvesters was 3.6 times the output obtained from unstretched films. In addition, because organic ferroelectric films are flexible, the resonant frequency of each harvester was practically constant even when using the techniques of multistacking and stretching.

著者

Takahashi Hideyuki Okamoto Tsubasa Ohmichi Eiji Ohta Hitoshi

出版者

Institute of Physics

雑誌

Appl. Phys. Express (ISSN:18820778)

巻号頁・発行日

vol.9, no.12, 2016-10-27

被引用文献数

8

---

We present a method of broadening the dynamic range of optical interferometric detection of cantilever displacement. The key idea of this method is the use of a wavelength-tunable laser source. The wavelength is subject to proportional-integral control, which is used to keep the cavity detuning constant. Under this control, the change in wavelength is proportional to the cantilever displacement. Using this technique, we can measure large displacements (>1 µm) without degrading the sensitivity. We apply this technique to high-frequency electron spin resonance spectroscopy and succeed in removing an irregular background signal that arises from the constantly varying sensitivity of the interferometer.

著者

Kojima Yuta Hirose Tetsuya Tsubaki Keishi Ozaki Toshihiro Asano Hiroki Kuroki Nobutaka Numa Masahiro

出版者

Institute of Physics

雑誌

Jpn. J. Appl. Phys. (ISSN:00214922)

巻号頁・発行日

vol.55, no.4, 2016-03-16

被引用文献数

9

---

In this paper, we present a fully on-chip switched-capacitor DC–DC converter for low-voltage CMOS LSIs. The converter has three terminals of input, ground, and output, by developing control circuits with fully on-chip configuration. We employ an ultra low-power nanoampere bias current and voltage reference circuit to achieve ultra low-power dissipation of control circuits. It enables us to realize a highly efficient power conversion circuit at light-load-current applications. The converter achieves highly efficient and robust voltage conversion using a pulse frequency modulation control circuit and a start-up/fail-safe circuit. Measurement results demonstrated that the converter can convert a 3.0 V input into 1.2 V output successfully. The start-up and fail-safe operations were confirmed through the measurement. The efficiency was more than 50% in the range of 2–6 µA load current.

著者

Kimura Yoshinari Kitamura Masatoshi Kitani Asahi Arakawa Yasuhiko

出版者

Institute of Physics

雑誌

Jpn. J. Appl. Phys. (ISSN:00214922)

巻号頁・発行日

vol.55, no.2, 2016-01-22

被引用文献数

3

---

Pentacene-based organic thin-film transistors (TFTs) having a SiO<inf>2</inf>gate dielectric treated with oxygen plasma have been investigated for control of the threshold voltage. The threshold voltage changed in the wide range from −15 to 80 V, depending on plasma treatment time, AC power for plasma generation, and gate dielectric thickness. The threshold voltage change was attributed to negative charges induced on and/or near the surface of the gate dielectric. The threshold voltage change on the order of 1 V was particularly proportional to plasma treatment time. The predictable change enables the control of threshold voltage in this range. In addition, the effect of gate bias stress on threshold voltage was examined. The results suggested that gate bias stress does not negate the threshold voltage change induced by plasma treatment.

著者

Tatara Shingo Kuzumoto Yasutaka Kitamura Masatoshi

出版者

Institute of Physics

雑誌

Jpn. J. Appl. Phys. (ISSN:00214922)

巻号頁・発行日

vol.55, no.3, 2016-01-15

被引用文献数

19

---

The surface properties, including work function and wettability, of Au and Ag surfaces modified with various substituted benzenethiols have been investigated. Whereas the work functions of the modified Au surfaces ranged from 4.42 to 5.48 eV, those of the modified Ag surfaces ranged from 3.99 to 5.77 eV. The highest work function of 5.77 eV was obtained on the Ag surface modified with pentafluorobenzenethiol, and the lowest work function of 3.99 eV was obtained on the Ag surface modified with 4-methylbenzenethiol. The water contact angle on modified Au surfaces was found to be in a wide range from 30.9 to 88.3°. The water contact angle on the Au surface modified with a substituted benzenethiol was close to that on the Ag surface modified with the same benzenethiol. Furthermore, the tension of the modified Au surfaces was estimated from their contact angles of water and ethylene glycol.

著者

Kitani Asahi Kimura Yoshinari Kitamura Masatoshi Arakawa Yasuhiko

出版者

Institute of Physics

雑誌

Jpn. J. Appl. Phys. (ISSN:00214922)

巻号頁・発行日

vol.55, no.3, 2016-01-07

被引用文献数

9

---

The threshold voltage in p-channel organic thin-film transistors (TFTs) having dinaphthothienothiophene as a channel material has been investigated toward their applicability to logic circuits. Oxygen plasma treatment of the gate dielectric surface was carried out to control the threshold voltage. The threshold voltage changed in the range from −6.4 to 9.4 V, depending on plasma treatment time and the thickness of the gate dielectric. The surface charge after plasma treatment was estimated from the dependence of the threshold voltage. Operation of logic inverters consisting of TFTs with different threshold voltages was demonstrated as an application of TFTs with controlled threshold voltage.

著者

Horike Shohei Misaki Masahiro Koshiba Yasuko Saito Takeshi Ishida Kenji

出版者

Institute of Physics

雑誌

Jpn. J. Appl. Phys. (ISSN:00214922)

巻号頁・発行日

vol.55, no.3, 2015-12-18

被引用文献数

10

---

We have investigated the thermoelectric power of single-wall carbon nanotubes (SWCNTs) with an ionic liquid (IL). The SWCNT/IL films showed simultaneous increase in electrical conductivity and the Seebeck coefficient compared with the pristine SWCNT. No thermoelectric power was observed for the IL. The X-ray diffraction pattern and impedance diagram showed a unique behavior with the concentration of IL, which implies that the interaction between the SWCNTs and IL enhances the thermoelectric power of the SWCNTs. As a result of the simultaneous increase in these parameters, the power factor exhibited a 10-fold increase.

著者

compiled with commentary by Peter Day

出版者

Institute of Physics

巻号頁・発行日

1999