Browsing by Author "Lin, Yong-Han"

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Effect of ion-milled barriers on electron transport in micrometer-sized tunnel junctions
(2014-03-12)
Lee, Yen-Chi
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Lin, Yong-Han
;
Wu, Jong-Ching
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Lin, Juhn-Jong
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電子物理學系
We studied the electron transport properties of micrometre-sized all-Al tunnel junctions (TJs) between 2 and 300 K, in which the AlOx layer grown by O-2 plasma was moderately Ar-ion-milled prior to top electrode deposition. In contrast to the direct tunnelling in the TJs whose barriers are intact (not ion-milled), the zero-bias conductances and the current-voltage characteristics of the TJs as processed are found to be best described by the fluctuation-induced tunnelling conduction mechanism. This observation indicates the formation of nanoscopic incomplete pinholes in the AlOx layer, owing to large junction-barrier interfacial roughness introduced by the ion-milling process. Topographical features revealed by the cross-sectional transmission electron microscopy imaging of the TJ stack conform to this result. This study is of relevance to cases in which ion-milling techniques are applied in tailoring the TJ properties.
Electrical conduction mechanisms in natively doped ZnO nanowires
(2009-01-07)
Chiu, Shao-Pin
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Lin, Yong-Han
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Lin, Juhn John
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電子物理學系
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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.
Fluctuation-induced tunneling conduction through RuO(2) nanowire contacts
(2011-09-15)
Lin, Yong-Han
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Lin, Juhn-Jong
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電子物理學系
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物理研究所
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Department of Electrophysics
A good understanding of the electronic conduction processes through nanocontacts is a crucial step for the implementation of functional nanoelectronic devices. We have studied the current-voltage (I-V) characteristics of nanocontacts between single metallic RuO(2) nanowires and contacting Au electrodes, which were pre-patterned by simple photolithography. Both the temperature behavior of contact resistance in the low-bias voltage ohmic regime and the I-V curves in the high-bias voltage non-ohmic regime have been investigated. We found that the electronic conduction processes in the wide temperature interval 1-300 K can be well described by the fluctuation-induced tunneling (FIT) conduction theory. Taken together with our previous work [Lin et al., Nanotechnology 19, 365201 (2008)], where the nanocontacts were fabricated by delicate electron-beam lithography, our study demonstrates the general validity of the FIT model in characterizing electronic nanocontacts. (C) 2011 American Institute of Physics. [doi:10.1063/1.3638707]
Fluctuation-induced tunneling conduction through RuO2 nanowire contacts
(2011-09-15)
Lin, Yong-Han
;
Lin, Juhn-Jong
;
電子物理學系
;
物理研究所
;
Department of Electrophysics
A good understanding of the electronic conduction processes through nanocontacts is a crucial step for the implementation of functional nanoelectronic devices. We have studied the current-voltage (I-V) characteristics of nanocontacts between single metallic RuO2 nanowires and contacting Au electrodes, which were pre-patterned by simple photolithography. Both the temperature behavior of contact resistance in the low-bias voltage ohmic regime and the I-V curves in the high-bias voltage non-ohmic regime have been investigated. We found that the electronic conduction processes in the wide temperature interval 1-300 K can be well described by the fluctuation-induced tunneling (FIT) conduction theory. Taken together with our previous work [Lin et al., Nanotechnology 19, 365201 (2008)], where the nanocontacts were fabricated by delicate electron-beam lithography, our study demonstrates the general validity of the FIT model in characterizing electronic nanocontacts. (C) 2011 American Institute of Physics. [doi:10.1063/1.3638707]
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
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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.
Growth of single-crystalline RuO2 nanowires with one- and two-nanocontact electrical characterizations
(2007-01-01)
Liu, Yee-Lang
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Wu, Zong-Yi
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Lin, Kuei-Jiun
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Huang, Jr-Jeng
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Chen, Fu-Rong
Single-crystalline RuO2 nanowires were grown by using a thermal evaporation method. A control of the sizes (width and length) and the length-to-width ratio of the nanowires were achieved by tuning the growth time. A transmission electron microscope-scanning tunneling microscope technique invoking one-nanocontact electrical characterization was adopted to determine the room-temperature resistivity (similar to 100 mu Omega cm) of the nanowires. An e-beam lithography technique facilitating two-nanocontact measurements was performed to establish the metallic characteristic of individual nanowires. The authors found that a nanocontact may introduce high contact resistance, nonlinear current-voltage characteristics, and even semiconducting behavior in the temperature dependent resistance. (c) 2007 American Institute of Physics.
Metallic conduction and large electron-phonon-impurity interference effect in single TiSi nanowires
(2012-09-05)
Hsu, Wei-Che
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Chen, Chao-Chun
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Lin, Yong-Han
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Lin, Huang-Kai
;
Chiu, Hsin-Tien
We report on the first electrical characterizations of single-crystalline TiSi nanowires (NWs) synthesized by chemical vapor deposition reactions. By utilizing the focused-ion-beam-induced deposition technique, we have delicately made four-probe contacts onto individual NWs. The NW resistivities have been measured between 2 and 300 K, which reveal overall metallic conduction with small residual resistivity ratios in the NWs. Surprisingly, we find that the effect due to the interference processes between the elastic electron scattering and the electron-phonon scattering largely dominates over the usual Boltzmann transport even at room temperature. Such prominent electron-phonon-impurity interference effect is ascribed to the presence of large amounts of disorder and high Debye temperatures in TiSi NWs.
Observation of fluctuation-induced tunneling conduction in micrometer-sized tunnel junctions
(2012-09-01)
Lai, Yu-Ren
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Yu, Kai-Fu
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Lin, Yong-Han
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Wu, Jong-Ching
;
Lin, Juhn-Jong
Micrometer-sized Al/AlOx/Y tunnel junctions were fabricated by the electron-beam lithography technique. The thin (approximate to 1.5-2 nm thickness) insulating AlOx layer was grown on top of the Al base electrode by O-2 glow discharge. The zero-bias conductances G(T) and the current-voltage characteristics of the junctions were measured in a wide temperature range 1.5-300 K. In addition to the direct tunneling conduction mechanism observed in low-G junctions, high-G junctions reveal a distinct charge transport process which manifests the thermally fluctuation-induced tunneling conduction (FITC) through short nanoconstrictions. We ascribe the experimental realization of the FITC mechanism to originating from the formations of "hot spots" (incomplete pinholes) in the AlOx layer owing to large junction-barrier interfacial roughness. Copyright 2012 Author(s). This article is distributed under a Creative Commons Attribution 3.0 Unported License. [http://dx.doi.org/10.1063/1.4749251]
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
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Chiu, Shao-Pin
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Lin, Juhn-Jong
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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.
Time-dependent universal conductance fluctuations in IrO2 nanowires
(2012-12-13)
Lin, Yong-Han
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Wang, Lu-Yao
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Lin, Juhn-Jong
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電子物理學系
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物理研究所
Single-crystalline iridium dioxide nanowires show the time-dependent universal conductance fluctuations (TUCFs) at cryogenic temperatures. The conductance fluctuations persist up to temperature T as high as nearly 10 K. The root-mean-square TUCF magnitudes increase with decreasing T, reaching approximately 0.1 e (2) / h at 1.7 K. We ascribe these conductance fluctuations to originating from the conduction electrons scattering upon mobile defects (moving scattering centers). Our measured TUCF characteristics are satisfactorily explained in terms of the existing TUCF theory in its three-dimensional form. The extracted electron dephasing length L (phi) (1.7 K) a parts per thousand integral 90 nm is smaller than the diameter (a parts per thousand 180 nm) of our nanowires.