Browsing by Author "Chiu, Shao-Pin"

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Effects of atomic scale imperfection at the interfaces of CoSi2 and Si (100) on Schottky barrier contacts
(2015-01-01)
Chiou, Chien-Jyun
;
Chiu, Shao-Pin
;
Lin, Juhn-Jong
;
Chou, Yi-Chia
;
電子物理學系
We report here the correlation of electrical properties on Schottky barrier contacts and atomic scale imperfections based on the degree of lattice distortion and moire fringes at the interfaces of CoSi2 and Si. The I-V measurements showed that the higher levels of perfection of the interfaces gave better Schottky barrier characteristics and we discuss the implications of the transport property at Schottky barrier contacts.
Electrical conduction mechanisms in natively doped ZnO nanowires
(2009-01-07)
Chiu, Shao-Pin
;
Lin, Yong-Han
;
Lin, Juhn John
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電子物理學系
;
物理研究所
Single-crystalline zinc oxide (ZnO) nanowires (NWs) with diameters of 90-200 nm were synthesized by the thermal evaporation method. Four-probe Ti/Au electrodes were made by the standard electron-beam lithography technique, and the intrinsic resistivities, rho(T), of individual NWs were measured over a wide range of temperature from 300 down to 0.25 K. The temperature behavior of rho(T) between 300 and 5 K reveals that the intrinsic electrical-transport mechanisms through individual ZnO NWs are due to a combination of the thermal activation conduction and the nearest-neighbor hopping conduction processes. Three distinct activation and hopping contributions with discrete characteristic activation energies are observed. Above about 100 K, the charge transport mechanism is dominated by the thermal activation of electrons from the Fermi level, mu, to the conduction band. Between approximately 20 and 100 K, the charge transport mechanism is due to the activation of electrons from mu to the upper impurity (D(-)) band. Between approximately 5 and 20 K, the charge transport mechanism arises from the nearest-neighbor hopping conduction within the lower impurity (D) band. Such unique electrical conduction behaviors can be explained in terms of the intricate material properties (in particular, the presence of moderately high concentrations of n-type defects accompanied with a slight self-compensation) in natively doped ZnO NWs. In one heavily doped NW, a surface-related conduction process manifesting the two-dimensional attributes of quantum-interference transport phenomena is observed. The carrier concentrations in our NWs have been estimated, and they were found to lie close to the critical concentration for the Mott metal-insulator transition.
Electrical conduction mechanisms in natively doped ZnO nanowires (II)
(2010-04-09)
Tsai, Lin-Tzung
;
Chiu, Shao-Pin
;
Lu, Jia Grace
;
Lin, Juhn-Jong
;
電子物理學系
We have measured the intrinsic electrical resistivities, rho(T), of three individual single-crystalline ZnO nanowires (NWs) from 320 down to 1.3 K. The NWs were synthesized via carbon thermal chemical vapor deposition and the four-probe Pt contacting electrodes were made by the focused-ion-beam technique. Analysis of the overall temperature behavior of rho(T) confirms that the charge transport processes in natively doped ZnO NWs are due to a combination of the thermal activation conduction and the nearest-neighbor hopping conduction processes, as proposed and explained in a recent work (Chiu et al 2009 Nanotechnology 20 015203) where the ZnO NWs were grown by a different thermal evaporation method and the four-probe electrodes were made by the electron-beam lithography technique. Taken together, the observations of these two complementary studies firmly establish that the electrical conduction mechanisms in natively doped ZnO NWs are unique and now satisfactorily understood.
Four-probe electrical-transport measurements on single indium tin oxide nanowires between 1.5 and 300 K
(2009-03-11)
Chiu, Shao-Pin
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Chung, Hui-Fang
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Lin, Yong-Han
;
Kai, Ji-Jung
;
Chen, Fu-Rong
Single-crystalline indium tin oxide (ITO) nanowires (NWs) were grown by the standard thermal evaporation method. The as-grown NWs were typically 100-300 nm in diameter and a few mu m long. Four-probe submicron Ti/Au electrodes on individual NWs were fabricated by the electron-beam lithography technique. The resistivities of several single NWs have been measured from 300 down to 1.5 K. The results indicate that the as-grown ITO NWs are metallic, but disordered. The overall temperature behavior of resistivity can be described by the Bloch-Gruneisen law plus a low-temperature correction due to the scattering of electrons off dynamic point defects. This observation suggests the existence of numerous dynamic point defects in as-grown ITO NWs.
Gate tunable spin-orbit coupling and weak antilocalization effect in an epitaxial La2/3Sr1/3MnO3 thin film
(2017-08-28)
Chiu, Shao-Pin
;
Yamanouchi, Michihiko
;
Oyamada, Tatsuro
;
Ohta, Hiromichi
;
Lin, Juhn-Jong
Epitaxial La2/3Sr1/3MnO3 (LSMO) films have been grown on SrTiO3 (001) substrates via pulsed laser deposition. In a 22-nm-thick LSMO film with a low residual resistivity of rho(0) approximate to 59 mu Omega cm, we found a zero-field dip in the magnetoresistance (MR) below 10 K, manifesting the weak antilocalization (WAL) effect due to strong spin-orbit coupling (SOC). We have analyzed the MR data by including the D'yakonov-Perel' spin-relaxation mechanism in the WAL theory. We explain that the delocalized spin-down electron sub-band states play a crucial role for facilitating marked SOC in clean LSMO. Moreover, we find that the SOC strength and gate voltage tunability are similar to those in a two-dimensional electron gas at the LaAlO3/SrTiO3 interface, indicating the presence of an internal electric field near the LSMO/SrTiO3 interface. In a control measurement on a 5-nm-thick high resistivity (rho(0) approximate to 280 mu Omega cm) LSMO film, we observe only a small zero-field peak in MR from weak localization effect, indicating negligible SOC.
Long electron dephasing length and disorder-induced spin-orbit coupling in indium tin oxide nanowires
(2010-11-15)
Hsu, Yao-Wen
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Chiu, Shao-Pin
;
Lien, An-Shao
;
Lin, Juhn-Jong
;
電子物理學系
We have measured the quantum-interference magnetoresistances in two single indium tin oxide (ITO) nanowires between 0.25 and 40 K, by using the four-probe configuration method. The magnetoresistances are compared with the one-dimensional weak-(anti)localization theory to extract the electron dephasing length L-phi. We found, in a 60-nm-diameter nanowire with a low resistivity of rho(10 K) =185 mu Omega cm, that L-phi is long, increasing from 150 nm at 40 K to 520 nm at 0.25 K. Therefore, the nanowire reveals strict one-dimensional weak-localization effect up to several tens of degrees of kelvin. In a second 72-nm-diameter nanowire with a high resistivity of rho(10 K)=1030 mu Omega cm, the dephasing length is suppressed to L-phi(0.26 K)=200 nm, and thus a crossover of the effective device dimensionality from one to three occurs at about 12 K. In particular, disorder-induced spin-orbit coupling is evident in the latter sample, manifesting weak-antilocalization effect at temperatures below similar to 4 K. These observations demonstrate that versatile quantum-interference effects can be realized in ITO nanowires by controlling differing levels of atomic defects and impurities.
Long electron dephasing length and disorder-induced spin-orbit coupling in indium tin oxide nanowires
(2010-11-15)
Hsu, Yao-Wen
;
Chiu, Shao-Pin
;
Lien, An-Shao
;
Lin, Juhn-Jong
;
電子物理學系
We have measured the quantum-interference magnetoresistances in two single indium tin oxide (ITO) nanowires between 0.25 and 40 K, by using the four-probe configuration method. The magnetoresistances are compared with the one-dimensional weak-(anti)localization theory to extract the electron dephasing length L(phi). We found, in a 60-nm-diameter nanowire with a low resistivity of rho(10 K) =185 mu Omega cm, that L(phi) is long, increasing from 150 nm at 40 K to 520 nm at 0.25 K. Therefore, the nanowire reveals strict one-dimensional weak-localization effect up to several tens of degrees of kelvin. In a second 72-nm-diameter nanowire with a high resistivity of rho(10 K)=1030 mu Omega cm, the dephasing length is suppressed to L(phi)(0.26 K)=200 nm, and thus a crossover of the effective device dimensionality from one to three occurs at about 12 K. In particular, disorder-induced spin-orbit coupling is evident in the latter sample, manifesting weak-antilocalization effect at temperatures below similar to 4 K. These observations demonstrate that versatile quantum-interference effects can be realized in ITO nanowires by controlling differing levels of atomic defects and impurities.
Nanomechanical, structural, and transport properties of Bi3Se2Te thin films
(2016-09-15)
Phuoc Huu Le
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Chiu, Shao-Pin
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Jian, Sheng-Rui
;
Luo, Chih Wei
;
Lin, Jiunn-Yuan
New ternary phase of Bi3Se2Te thin films were successfully grown through pulsed laser deposition with a single Bi2Se2Te crystal as the target. Bi-rich and Se-and Te-deficient compositions deposited at a substrate temperature (T-s) of 250 degrees C and helium gas pressures (P-He) ranging from 2.0 x 10(-5) to 6.5 x 10(-1) Torr aided the formation of the dominant Bi-rich phase: Bi3Se2Te. The films were grown epitaxially on Al2O3 (001) substrates with Bi3Se2Te [001]//Al2O3 [001] and Bi3Se2Te [110]//Al2O3 [210]. An increase in P-He remarkably enhanced the hardness and Young\'s modulus of the films, primarily because of the decrease in nanograin size, following the HallePetch relationship. Moreover, the Bi3Se2Te films present linear magnetoresistance under a high perpendicular magnetic field (B >= 4 T) and twodimensional weak antilocalization effect under a low B (+/- 1 T) which may be attributed to topological insulator surface state (TSS). Clearly, further theoretical calculations and experiments are needed to confirm the suggested interpretation. (C) 2016 Elsevier B.V. All rights reserved.
Probing Thermally Activated Atomic and Nanocrystalline Defect Motion Through Noise Processes in RuO2 Nanowires
(2020-08-18)
Yeh, Sheng-Shiuan
;
Yu, Cheng-Ya
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Lee, Yi-Te
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Chiu, Shao-Pin
;
Lin, Juhn-Jong
The present-day nanodevice dimensions continuously shrink, with the aim to prolong Moore's law. As downsizing meticulously persists, undesirable dynamic defects, which cause low-frequency noise and structural instability, play detrimental roles on limiting the ultimate performance and reliability of miniaturized devices. A good understanding and a meaningful control of the defect kinetics then become fundamental and urgent issues. Here we report observations of thermally activated atomic defect motion as well as nanocrystalline defect motion through electrical noise processes in metallic RuO2 rutile nanowires around room temperature. First, we extract the energy-distribution function and the number density of mobile atomic defects (oxygen vacancies). Second, we obtain the geometrical size, grain-boundary bonding strength, and relaxation times of dynamic nanocrystallites. Our results show clearly a powerful probe for effective and noninvasive characterizations of nanostructures and nanomaterials for which quantitative information about mechanical hardness, breakdown current density, and/or resistance noise is essential.
Quantum-interference transport through surface layers of indium-doped ZnO nanowires
(2013-06-21)
Chiu, Shao-Pin
;
Lu, Jia Grace
;
Lin, Juhn-Jong
;
電子物理學系
;
物理研究所
We have fabricated indium-doped ZnO (IZO) nanowires (NWs) and carried out four-probe electrical-transport measurements on two individual NWs with geometric diameters of approximate to 70 and approximate to 90 nm in a wide temperature T interval of 1-70 K. The NWs reveal overall charge conduction behavior characteristic of disordered metals. In addition to the T dependence of resistance R, we have measured the magnetoresistance (MR) in magnetic fields applied either perpendicular or parallel to the NW axis. Our R(T) and MR data in different T intervals are consistent with the theoretical predictions of the one- (1D), two- (2D) or three-dimensional (3D) weak-localization (WL) and the electron-electron interaction (EEI) effects. In particular, a few dimensionality crossovers in the two effects are observed. These crossover phenomena are consistent with the model of a 'core-shell-like structure' in individual IZO NWs, where an outer shell of thickness t (similar or equal to 15-17 nm) is responsible for the quantum-interference transport. In the WL effect, as the electron dephasing length L-phi gradually decreases with increasing T from the lowest measurement temperatures, a 1D-to-2D dimensionality crossover takes place around a characteristic temperature where L-phi approximately equals d, an effective NW diameter which is slightly smaller than the geometric diameter. As T further increases, a 2D-to-3D dimensionality crossover occurs around another characteristic temperature where L-phi approximately equals t (
Structural order and melting of a quasi-one-dimensional electron system
(2016-07-29)
Rees, David G.
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Beysengulov, Niyaz R.
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Teranishi, Yoshiaki
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Tsao, Chun-Shuo
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Yeh, Sheng-Shiuan
We investigate the influence of confinement on the positional order of a quasi-1D electron system trapped on the surface of liquid helium. We find evidence that the melting of the Wigner solid (WS) depends on the confinement strength, as well as electron density and temperature. A reentrant solid-liquid-solid transition is observed for increasing electron density under constant electrostatic confinement. As the electron row number N-y changes, varying commensurability results in a modulation of the WS order, even when N-y is large (several tens). This is confirmed by Monte Carlo simulations.
Thermal fluctuation-induced tunneling conduction through metal nanowire contacts
(2008-09-10)
Lin, Yong-Han
;
Chiu, Shao-Pin
;
Lin, Juhn-Jong
;
電子物理學系
;
物理研究所
The temperature behavior of how electrons propagate through an insulating electronic contact formed at the interface between a submicron Cr/Au electrode and a metallic RuO(2) nanowire (NW) has been studied between 300 and 1 K. The NWs are typically of similar to 70 nm in diameter and a few microns long. The submicron electrodes were fabricated by the standard electron-beam lithography technique. By employing the two-probe method, the electronic contact resistances, R(c)(T), have been determined. We found that, in general, Rc increases rapidly with decreasing temperature but eventually saturates at liquid-helium temperatures. Such a temperature behavior can be well described by a thermal fluctuation-induced tunneling (FIT) conduction process which considers the crossover feature from thermal activation conduction at high temperatures to simple elastic tunneling conduction at low temperatures. The wide applicability of this FIT model has further been established by employing metallic IrO(2) and Sn-doped In(2)O(3-x) NWs. This work demonstrates that the underlying physics for the charge transport properties of an insulating electronic contact can be well understood.
Ultralow 1/f Noise in a Heterostructure of Superconducting Epitaxial Cobalt Disilicide Thin Film on Silicon
(2017-01)
Chiu, Shao-Pin
;
Yeh, Sheng-Shiuan
;
Chiou, Chien-Jyun
;
Chou, Yi-Chia
;
Lin, Juhn-Jong
High-precision resistance noise measurements indicate that the epitaxial CoSi2/Si heterostructures at 150 and 2 K (slightly above its superconducting transition temperature T-c of 1.54 K) exhibit an unusually low 1/f noise level in the frequency range of 0.008-0.2 Hz. This corresponds to an upper limit of Hooge constant gamma <= 3 X 10(-6), about 100 times lower than that of single-crystalline aluminum films on SiO2 capped Si substrates. Supported by high -resolution cross-sectional transmission electron microscopy studies, our analysis reveals that the 1/f noise is dominated by excess interfacial Si atoms and their dimer reconstruction induced fluctuators. Unbonded orbitals (i.e., dangling bonds) on excess Si atoms are intrinsically rare at the epitaxial CoSi2/Si(100) interface, giving limited trapping-detrapping centers for localized charges. With its excellent normal-state properties, CoSi2 has been used in silicon-based integrated circuits for decades. The intrinsically low noise properties discovered in this work could be utilized for developing quiet qubits and scalable superconducting circuits for future quantum computing.
Ultralow 1/f Noise in a Heterostructure of Superconducting Epitaxial Cobalt Disilicide Thin Film on Silicon
(2017-01)
Chiu, Shao-Pin
;
Yeh, Sheng-Shiuan
;
Chiou, Chien-Jyun
;
Chou, Yi-Chia
;
Lin, Juhn-Jong
High-precision resistance noise measurements indicate that the epitaxial CoSi2/Si heterostructures at 150 and 2 K (slightly above its superconducting transition temperature T-c of 1.54 K) exhibit an unusually low 1/f noise level in the frequency range of 0.008-0.2 Hz. This corresponds to an upper limit of Hooge constant gamma <= 3 X 10(-6), about 100 times lower than that of single-crystalline aluminum films on SiO2 capped Si substrates. Supported by high -resolution cross-sectional transmission electron microscopy studies, our analysis reveals that the 1/f noise is dominated by excess interfacial Si atoms and their dimer reconstruction induced fluctuators. Unbonded orbitals (i.e., dangling bonds) on excess Si atoms are intrinsically rare at the epitaxial CoSi2/Si(100) interface, giving limited trapping-detrapping centers for localized charges. With its excellent normal-state properties, CoSi2 has been used in silicon-based integrated circuits for decades. The intrinsically low noise properties discovered in this work could be utilized for developing quiet qubits and scalable superconducting circuits for future quantum computing.
Variable-range-hopping conduction processes in oxygen deficient polycrystalline ZnO films
(2010-03-15)
Huang, Yung-Lung
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Chiu, Shao-Pin
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Zhu, Zhi-Xin
;
Li, Zhi-Qing
;
Lin, Juhn-Jong
We have fabricated oxygen deficient polycrystalline ZnO films by the rf sputtering deposition method. To systematically investigate the charge transport mechanisms in these samples, the electrical resistivities have been measured over a wide range of temperature from 300 K down to liquid-helium temperatures. We found that below about 100 K, the variable-range-hopping (VRH) conduction processes govern the charge transport properties. In particular, the Mott VRH conduction process dominates at higher temperatures, while crossing over to the Efros-Shklovskii (ES) VRH conduction process at lower temperatures. The crossover occurred at temperatures as high as a few tens degrees kelvin. Moreover, the temperature behavior of resistivity over the entire VRH conduction regime from the Mott-type to the ES-type process can be well described by a universal scaling law.
Weak antilocalization in topological insulator Bi2Te3 microflakes
(2013-01-16)
Chiu, Shao-Pin
;
Lin, Juhn-Jong
;
電子物理學系
;
物理研究所
;
Department of Electrophysics
We have studied the carrier transport in two topological insulator (TI) Bi2Te3 microflakes between 0.3 and 10 K and under applied backgate voltages (V-BG). Logarithmic temperature dependent resistance corrections due to the two-dimensional electron-electron interaction effect in the presence of weak disorder were observed. The extracted Coulomb screening parameter is negative, which is in accord with the situation of strong spin-orbit scattering as is inherited in the TI materials. In particular, positive magnetoresistances (MRs) in the two-dimensional weak-antilocalization (WAL) effect were measured in low magnetic fields, which can be satisfactorily described by a multichannel-conduction model. Both at low temperatures of T < 1 K and under high positive VBG, signatures of the presence of two coherent conduction channels were observed, as indicated by an increase by a factor of approximate to 2 in the prefactor which characterizes the WAL MR magnitude. Our results are discussed in terms of the (likely) existence of the Dirac fermion surface states, in addition to the bulk states, in the three-dimensional TI Bi2Te3 material. DOI: 10.1103/PhysRevB.87.035122