Browsing by Author "Yeh, Sheng-Shiuan"

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1/f noise in micrometer-sized ultrathin indium tin oxide films
(2013-09-16)
Yeh, Sheng-Shiuan
;
Hsu, Wei-Ming
;
Lee, Jui-Kan
;
Lee, Yao-Jen
;
Lin, Juhn-Jong
We have measured the low-frequency noises of ultrathin indium tin oxide films to investigate the effect of post annealing on the noise level. The noises obtained obey an approximate 1/f law in the frequency range f approximate to 0.1-20 Hz. The microstructures and grain sizes of our films were altered by adjusting the annealing conditions. An enhancement of the noise level was observed for those samples comprising smaller grains, where numerous grain boundaries exist. This enhancement in the noise level is ascribed to atomic diffusion along grain boundaries or dynamics of two-level systems near the grain boundaries. (C) 2013 AIP Publishing LLC.
Activation Energy Distribution of Dynamical Structural Defects in RuO2 Films
(2018-09-05)
Yeh, Sheng-Shiuan
;
Gao, Kuang Hong
;
Wu, Tsung-Lin
;
Su, Ta-Kang
;
Lin, Juhn-Jong
Ruthenium dioxide (RuO2) is an important metal widely used in nanoelectronic devices. It plays indispensable roles in applications such as catalysts and supercapacitors. A good understanding of the origin of the flicker or 1/f noise in RuO2 will advance the design and efficiency of these applications. We demonstrate in a series of sputtered RuO2 polycrystalline films that the 1/f noise originates from fluctuating oxygen vacancies which act as dynamical structural defects, i.e., moving scattering centers. Reducing the number of oxygen vacancies by adjusting thermal annealing conditions significantly reduces the noise magnitude gamma, the Hooge parameter. We quantify the activation energy distribution function, g(E), and calculate the oxygen vacancy density, n(TLS), from the measured gamma value. We show that g(E) can be explicitly expressed in terms of gamma(T) and the electronic parameters of the metal, where T denotes temperature. The inferred n(TLS) value is in line with the oxygen content determined from the x-ray photoelectron spectroscopy studies.
Bistable transport properties of a quasi-one-dimensional Wigner solid on liquid helium under continuous driving
(2017-11-27)
Rees, David G.
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Yeh, Sheng-Shiuan
;
Lee, Ban-Chen
;
Kono, Kimitoshi
;
Lin, Juhn-Jong
We investigate low-frequency fluctuations in the transport characteristics of a quasi-1D Wigner solid (WS) moving along a liquid helium substrate in response to a sinusoidal driving voltage. The fluctuations occur between distinct transport modes in which the decoupling of the WS from ripplonic polarons (or "dimple lattice," DL) formed on the helium surface does, or does not, occur during each ac cycle. We demonstrate that a Gaussian-like distribution in the decoupling threshold force gives rise to this bistability, as the low-frequency switching occurs when the probability of decoupling during each ac cycle is small but finite. We attribute the distribution in the decoupling threshold force to the range of structural configurations allowed for the quasi-1D electron lattice, which influences the strength of the WS-DL coupling. Hence, the switching rate between the ac transport modes is extremely sensitive to the microscopic properties of the electron solid.
Conductivity and tunneling density of states in granular Cr films
(2010-08-12)
Sun, Yu-Chen
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Yeh, Sheng-Shiuan
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Lin, Juhn-Jong
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電子物理學系
;
物理研究所
We have measured the tunneling differential conductances, G(V), of four Al/AlOx/Cr planar tunnel junctions as well as the conductivities, sigma(T), of the Cr electrodes at liquid-helium temperatures. The Cr electrodes were made to be granular with dimensionless intergrain tunneling conductance spanning from g similar or equal to 1 to g >> 1, and the dimensionality of the granular array d=3. For the samples with g >> 1, we found that the measured G(V) curves display large zero-bias singularities which obey a ln V law at low bias voltages (less than or similar to a few millielectron volt) while crossing over to a root V law at high bias voltages. Simultaneously, the conductivities of the Cr electrodes reveal ln T dependence below a characteristic temperature. These results are explained in terms of the recent theory of granular metals. In a sample with g similar or equal to 1, in addition to the conductivity dependence sigma proportional to ln T, we observed a universal scaling behavior of the normalized differential conductance [G(V, T) -G(0, T)]/root T with the combined parameter root e vertical bar V vertical bar/k(B)T in a wide temperature interval of 2.5-32 K. This result is not yet understood.
Dynamical decoupling and recoupling of the Wigner solid to a liquid helium substrate
(2020-08-24)
Rees, David G.
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Yeh, Sheng-Shiuan
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Lee, Ban-Chen
;
Schnyder, Simon K.
;
Williams, Francis I. B.
We investigate the dynamical interaction between an electron crystal trapped above the surface of liquid helium and surface waves ('ripplons') excited by its motion. At rest, the electron system is 'dressed' by static ripplons to form 'ripplopolaron' states. As the electrons move, resonant ripplon scattering results in a growth of the ripplopolaron effective mass, on timescales comparable with the inverse of the ripplon frequency (similar to 100 ns). Under sufficient driving force, the electron system decouples from the surface waves and moves at high velocity, before decelerating sharply when the electron solid and surface excitations recouple to form a 'new' ripplopolaron system. The mass of the newly formed ripplopolarons is similar to that in the initial static case.
Negative correlation between charge carrier density and mobility fluctuations in graphene
(2014-08-26)
Lu, Jianming
;
Pan, Jie
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Yeh, Sheng-Shiuan
;
Zhang, Haijing
;
Zheng, Yuan
By carrying out simultaneous longitudinal and Hall measurements in graphene, we find that the 1/f noise for the charge carrier density is negatively correlated to that of mobility, with a governing behavior that differs significantly from the relation between their mean values. The correlation in the noise data can be quantitatively explained by a single-parameter theory whose underlying physics is the trapping and detrapping of the fluctuating charge carriers by the oppositely charged Coulomb scattering centers. This can alter the effective density of long-range scattering centers in a transient manner, with the consequent fluctuating effect on the mobility.
Probing nanocrystalline grain dynamics in nanodevices
(2017-06-01)
Yeh, Sheng-Shiuan
;
Chang, Wen-Yao
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Lin, Juhn-Jong
;
電子物理學系
;
物理研究所
Dynamical structural defects exist naturally in a wide variety of solids. They fluctuate temporally and hence can deteriorate the performance of many electronic devices. Thus far, the entities of these dynamic objects have been identified to be individual atoms. On the other hand, it is a long-standing question whether a nanocrystalline grain constituted of a large number of atoms can switch, as a whole, reversibly like a dynamical atomic defect (that is, a two-level system). This is an emergent issue considering the current development of nanodevices with ultralow electrical noise, qubits with long quantum coherence time, and nanoelectromechanical system sensors with ultrahigh resolution. We demonstrate experimental observations of dynamic nanocrystalline grains that repeatedly switch between two or more metastable coordinate states. We study temporal resistance fluctuations in thin ruthenium dioxide (RuO2) metal nanowires and extract microscopic parameters, including relaxation time scales, mobile grain sizes, and the bonding strengths of nanograin boundaries. These material parameters are not obtainable by other experimental approaches. When combined with previous in situ high-resolution transmission electron microscopy, our electrical method can be used to infer rich information about the structural dynamics of a wide variety of nanodevices and new two-dimensional materials.
Probing Thermally Activated Atomic and Nanocrystalline Defect Motion Through Noise Processes in RuO2 Nanowires
(2020-08-18)
Yeh, Sheng-Shiuan
;
Yu, Cheng-Ya
;
Lee, Yi-Te
;
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.
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.
Two-channel Kondo effects in Al/AlO(x)/Sc planar tunnel junctions
(2009-01-01)
Yeh, Sheng-Shiuan
;
Lin, Juhn-Jong
;
電子物理學系
;
物理研究所
;
Department of Electrophysics
We have measured the differential conductances G(V, T) in several Al/AlO(x)/Sc planar tunnel junctions between 2 and 35 K. As the temperature decreases to similar to 16 K, the zero-bias conductance G(0, T) crosses over from a standard -ln T dependence to a novel -root T dependence. Correspondingly, the finite bias conductance G(V, T) reveals a two-channel Kondo scaling behavior between similar to 4 and 16 K. The observed two-channel Kondo physics is ascribed to originating from a few localized spin-1/2 Sc atoms situated slightly inside the AlO(x)/Sc interface.
Two-channel Kondo effects in Al/AlOx/Sc planar tunnel junctions
(2009-01-01)
Yeh, Sheng-Shiuan
;
Lin, Juhn-Jong
;
電子物理學系
;
物理研究所
;
Department of Electrophysics
We have measured the differential conductances G(V, T) in several Al/AlOx/Sc planar tunnel junctions between 2 and 35 K. As the temperature decreases to similar to 16 K, the zero-bias conductance G(0, T) crosses over from a standard -ln T dependence to a novel -root T dependence. Correspondingly, the finite bias conductance G(V, T) reveals a two-channel Kondo scaling behavior between similar to 4 and 16 K. The observed two-channel Kondo physics is ascribed to originating from a few localized spin-1/2 Sc atoms situated slightly inside the AlOx/Sc interface.
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.