Browsing by Author "Jian, Wen-Bin"

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A Triode Device with a Gate Controllable Schottky Barrier: Germanium Nanowire Transistors and Their Applications
(1970-01-01)
Lin, Che-Yi
;
Chen, Chao-Fu
;
Chang, Yuan-Ming
;
Yang, Shih-Hsien
;
Lee, Ko-Chun
Electrical contacts often dominate charge transport properties at the nanoscale because of considerable differences in nanoelectronic device interfaces arising from unique geometric and electrostatic features. Transistors with a tunable Schottky barrier between the metal and semiconductor interface might simplify circuit design. Here, germanium nanowire (Ge NW) transistors with Cu3Ge as source/drain contacts formed by both buffered oxide etching treatments and rapid thermal annealing are reported. The transistors based on this Cu3Ge/Ge/Cu3Ge heterostructure show ambipolar transistor behavior with a large on/off current ratio of more than 10(5) and 10(3) for the hole and electron regimes at room temperature, respectively. Investigations of temperature-dependent transport properties and low-frequency current fluctuations reveal that the tunable effective Schottky barriers of the Ge NW transistors accounted for the ambipolar behaviors. It is further shown that this ambipolarity can be used to realize binary-signal and data-storage functions, which greatly simplify circuit design compared with conventional technologies.
A Versatile Method to Enhance the Operational Current of Air-Stable Organic Gas Sensor for Monitoring of Breath Ammonia in Hemodialysis Patients
(2019-04-01)
Yu, Shang-Yu
;
Tung, Tin-Wei
;
Yang, Hong-Yu
;
Chen, Guan-Yu
;
Shih, Che-Chi
Point-of-care (POC) application for monitoring of breath ammonia (BA) in hemodialysis (HD) patients has emerged as a promising noninvasive health monitoring approach. In this context, many organic gas sensors have been reported for BA detection. However, one of the major challenges for its integration with affordable household POC application is to achieve stable performance for accuracy and high operational current at low voltage for low-cost read-out circuitry. Herein, we exploited the stability of the Donor Acceptor polymer on the cylindrical nanopore structure to realize the sensors with a high sensitivity and stability. Then, we proposed a double active layer (DL) strategy that exploits an ultrathin layer of Poly(3-hexylthiophene-2,5-diyl) (P3HT) to serve as a work function buffer to enhance the operational current. The DL sensor exhibits a sustainable operational current of microampere level and a stable sensing response even with the presence of P3HT layer. This effect is carefully examined with different aspects, including vertical composition profile of DL configuration, lifetime testing on different sensing layer, morphological analysis, and the versatility of the DL strategy. Finally, we utilize the DL sensor to conduct a tracing of BA concentration in two HD patients before and after HD, and correlate it with the blood urea nitrogen (BUN) levels. A good correlation coefficient of 0.96 is achieved. Moreover, the feasibility of DL sensor integrated into a low-cost circuitry was also verified. The results demonstrate the potential of this DL strategy to be used to integrate organic sensor for affordable household POC devices.
Ambipolar MoTe2 Transistors and Their Applications in Logic Circuits
(2014-05-28)
Lin, Yen-Fu
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Xu, Yong
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Wang, Sheng-Tsung
;
Li, Song-Lin
;
Yamamoto, Mahito
We report ambipolar charge transport in a-molybdenum ditelluride (MoTe2) flakes, whereby the temperature dependence of the electrical characteristics was systematically analyzed. The ambipolarity of the charge transport originated from the formation of Schottky barriers at the metal/MoTe2 contacts. The Schottky barrier heights as well as the current on/off ratio could be modified by modulating the electrostatic fields of the back-gate voltage (V-bg) and drain-source voltage (V-ds). Using these ambipolar MoTe2 transistors we fabricated complementary inverters and amplifiers, demonstrating their feasibility for future digital and analog circuit applications.
Contact to ZnO and intrinsic resistances of individual ZnO nanowires with a circular cross section
(2007-05-28)
Lin, Yen-Fu
;
Jian, Wen-Bin
;
Wang, C. P.
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Suen, Yuen-Wuu
;
Wu, Zhong-Yi
Single crystalline ZnO nanowires (NWs) with a circular cross section and similar to 40 nm in diameter have been synthesized and utilized to fabricate two-contact ZnO NW devices. The electrical properties of the NW devices can be categorized into two classes according to the magnitude of their room-temperature resistances. I-V curves of low-resistance devices exhibit downward bending features and their temperature dependent resistances demonstrate thermal activation transport in the ZnO NWs. The high-resistance NW devices can be modeled as back-to-back Schottky contacts and the electron transport through the contacts reveals a variable-range-hopping mechanism. (C) 2007 American Institute of Physics.
Demonstration of 40-nm Channel Length Top-Gate p-MOSFET of WS2 Channel Directly Grown on SiOx/Si Substrates Using Area-Selective CVD Technology
(2019-12-01)
Chung, Yun-Yan
;
Lu, Kuan-Cheng
;
Cheng, Chao-Ching
;
Li, Ming-Yang
;
Lin, Chao-Ting
For high-volume manufacturing of 2-D transistors, area-selective chemical reaction deposition (CVD) growth is able to provide good-quality 2-D layers and may be more effective than exfoliation from bulk crystals or wet/dry transfer of large-area as-grown 2-D layers. We have successfully grown continuous and uniform WS2 film comprising around seven layers by area-selective CVD approach using patterned tungsten source/drain metals as the seeds. The growth mechanism is inferred and supported by the transmission electron microscope (TEM) images, as well. The first top-gate MOSFETs of CVD-WS2 channels on SiOx/Si substrates are demonstrated to have good short channel electrical characteristics: ON-/OFF-ratio of 10(6), a subthreshold swing of 97 mV/decade, and nearly zero drain-induced barrier lowering (DIBL).
Dielectrophoretic placement of quasi-zero-, one-, and two-dimensional nanomaterials into nanogap for electrical characterizations
(2012-08-01)
Lin, Yen-Fu
;
Chiu, Shao-Chien
;
Wang, Sheng-Tsung
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Fu, Sheng-Kai
;
Chen, Chien-Hsiang
DEP is one of promising techniques for positioning nanomaterials into the desirable location for nanoelectronic applications. In contrast, the lithography technique is commonly used to make ultra-thin conducting wires and narrow gaps but, due to the limit of patterning resolution, it is not feasible to make electrical contacts on ultra-small nanomaterials for a bottom-up device fabrication. Thus, integrating the lithography and dielectrophoresis, a real bottom-up fabrication can be achieved. In this work, the device with the nanogap in between two nanofinger-electrodes is made using electron-beam lithography from top down and the ultra-small nanomaterials, such as colloidal PbSe quantum dots, polyaniline nanofibers, and reduced-graphene-oxide flakes, are placed in the nanogap by DEP from bottom up. The threshold electric field for the DEP placement of PbSe nanocrystals was roughly estimated to be about 8.3 x 104 V/cm under our experimental configuration. After the DEP process, several procedures for reducing contact resistances are attempted and measurements of intrinsic electron transport in versatile nanomaterials are performed. It is experimentally confirmed that electron transport in both PbSe nanocrystal arrays and polyaniline nanofibers agrees well with Prof. Ping Sheng's model of granular metallic conduction. In addition, electron transport in reduced-graphene-oxide flakes follows Mott's 2D variable-range-hopping model. This study illustrates an integration of the electron-beam lithography and the DEP techniques for a precise manipulation of nanomaterials into electronic circuits for characterization of intrinsic properties.
"Dielectrophoretic placement of quasi-zero-, one-, and two-dimensional nanomaterials into nanogap for electrical characterizations"
(2012-08-01)
Lin, Yen-Fu
;
Chiu, Shao-Chien
;
Wang, Sheng-Tsung
;
Fu, Sheng-Kai
;
Chen, Chien-Hsiang
"DEP is one of promising techniques for positioning nanomaterials into the desirable location for nanoelectronic applications. In contrast, the lithography technique is commonly used to make ultra-thin conducting wires and narrow gaps but, due to the limit of patterning resolution, it is not feasible to make electrical contacts on ultra-small nanomaterials for a bottom-up device fabrication. Thus, integrating the lithography and dielectrophoresis, a real bottom-up fabrication can be achieved. In this work, the device with the nanogap in between two nanofinger-electrodes is made using electron-beam lithography from top down and the ultra-small nanomaterials, such as colloidal PbSe quantum dots, polyaniline nanofibers, and reduced-graphene-oxide flakes, are placed in the nanogap by DEP from bottom up. The threshold electric field for the DEP placement of PbSe nanocrystals was roughly estimated to be about 8.3 x 104 V/cm under our experimental configuration. After the DEP process, several procedures for reducing contact resistances are attempted and measurements of intrinsic electron transport in versatile nanomaterials are performed. It is experimentally confirmed that electron transport in both PbSe nanocrystal arrays and polyaniline nanofibers agrees well with Prof. Ping Sheng's model of granular metallic conduction. In addition, electron transport in reduced-graphene-oxide flakes follows Mott's 2D variable-range-hopping model. This study illustrates an integration of the electron-beam lithography and the DEP techniques for a precise manipulation of nanomaterials into electronic circuits for characterization of intrinsic properties."
Effects of cross-sectional area on the tunneling-junction array in octahedral PbSe colloidal-nanocrystal solids
(2013)
Chiu, Shao-Chien
;
Jhang, Jia-Sin
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Chen, Jenn-Fang
;
Fang, Jiye
;
Jian, Wen-Bin
Octahedral PbSe colloidal nanocrystals (NCs) are used to assemble a solid. Because of the special feature of the apexes of the octahedrons, the cross-sectional area of the inter-dot tunneling junctions is much smaller than that formed between spherical NCs. The inter-dot separation between NCs is easily adjusted by mild thermal treatment. Like a spherical NC-solid, the resistance of the octahedral NC-solid is exponentially dependent on the inter-dot separation. On the contrary, due to the difference in the cross-sectional area between the NCs, electron transport in the octahedral NC-solid does not follow the same model used for the explanation of electron transport in a spherical NC-solid. Through analyses of current-voltage and resistance-temperature behaviors, we have confirmed that the model of fluctuation-induced tunneling conduction fits very well with all of the data and explains the variation in the electrical properties of octahedral PbSe colloidal NC-solids after thermal annealing.
Effects of Thermal Annealing and Solvent Annealing on the Morphologies and Properties of Poly(3-hexylthiophene) Nanowires
(2015-01-01)
Fu, Chuan-Min
;
Jeng, Kai-Sheng
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Li, Yu-Hsun
;
Hsu, Yuan-Chen
;
Chi, Mu-Huan
In recent years, poly(3-hexylthiophene) (P3HT) nanowires have attracted great interest because of their unique physical and electronic properties. The annealing effects on the properties and morphologies of P3HT nanowires, however, are still not fully understood. In this work, the effects of thermal annealing and solvent annealing on the morphologies and crystallinities of P3HT nanowires prepared by the whisker method are studied. P3HT is first dissolved in heated p-xylene, followed by a cooling process to room temperature, and P3HT nanowires are formed by self-assembly. The crystallinities of the P3HT nanowires are observed to increase by both thermal annealing and solvent annealing, as confirmed by differential scanning calorimetry and X-ray diffraction. The device performances of organic field-effect transistors based on the annealed nanowires are also examined. After annealing, an enhancement of the charge mobility by one order is observed.
Electron hopping transport in 2D zinc oxide nanoflakes
(2017-06-01)
Jian, Dunliang
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Lai, Jian-Jhong
;
Lin, Yen-Fu
;
Zhai, Jianpang
;
Li, Irene Ling
A sequential hydrothermal process was used to synthesize ZnO nanostructures on Si substrates. The synthesized ZnO nanostructures were inspected and presented a morphology of 2D structures, named nanoflakes. These ZnO nanoflakes had a thickness of tens of nanometers. An energy dispersive x-ray spectrum revealed their composition of only Zn and O elements. In addition, its crystalline structure was investigated by high-resolution transmission electron microscopy. The nanoflakes were then dispersed for another morphology measurement using atomic force microscopy and their average thickness was determined. The dispersed nanoflakes were further contacted with metal electrodes for electron transport measurements. Through the analysis of temperature-dependent resistivity, it was confirmed that the electron transport in such ZnO nanoflakes agrees well with the theory of Mott's 2D variable range hopping. The nature of the 2D electron system in the ZnO nanoflakes points to potential applications of this 2D semiconductor as a new channel material for electronics.
Electron transport in high-resistance semiconductor nanowires through two-probe measurements
(2010)
Lin, Yen-Fu
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Chen, Tzu-Han
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Chang, Chia-Hung
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Chang, Yu-Wei
;
Chiu, Yi-Cheng
Since the successful fabrication of semiconductor nanowires, various techniques have been developed to contact these nanowires and to probe their intrinsic electrical properties. Although many novel quasi one-dimensional materials such as Pb(1-x)Mn(x)Se nanoarrays were recently produced, their intrinsic electron transport properties have not been extensively studied so far. In this work, we demonstrate that an ordinary source-drain configuration of field-effect transistors or the two-probe measurement can be applied to the exploration of the intrinsic properties of nanowires. This two-probe measurement approach also works on highly resistive nanowires without an Ohmic contact issue. By using this method, electron transport behavior, resistivity, and carrier concentrations of ZnO, InP, GaP, and Pb(1-x)Mn(x)Se semiconductor nanowires have been investigated. Due to the tiny cross-section and few conducting channels, a nanomaterial usually reveals an ultra high resistance. This technique demonstrates a two-probe characterization of nanostructures, paving the simplest way toward electrical characterizations of all high-resistance nanomaterials such as deoxyribonucleic acid (DNA), molecules and organics.
Electron transport in the two-dimensional channel material - zinc oxide nanoflake
(2018-03-01)
Lai, Jian-Jhong
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Jian, Dunliang
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Lin, Yen-Fu
;
Ku, Ming-Ming
;
Jian, Wen-Bin
ZnO nanoflakes of 3-5 mu m in lateral size and 15-20 nm in thickness are synthesized. The nanoflakes are used to make back-gated transistor devices. Electron transport in the ZnO nanoflake channel between source and drain electrodes are investigated. In the beginning, we argue and determine that electrons are in a two-dimensional system. We then apply Mott's two-dimensional variable range hopping model to analyze temperature and electric field dependences of resistivity. The disorder parameter, localization length, hopping distance, and hopping energy of the electron system in ZnO nanoflakes are obtained and, additionally, their temperature behaviors and dependences on room-temperature resistivity are presented. On the other hand, the basic transfer characteristics of the channel material are carried out, as well, and the carrier concentration, the mobility, and the Fermi wavelength of two-dimensional ZnO nanoflakes are estimated.
Electron Transport Properties of ZnO, InP, GaP, and Pb Se Nanowires By Two-Probe Measurements
(2010)
Lin, Yen-Fu
;
Jiye-Fang
;
Jian, Wen-Bin
;
電子物理學系
;
Department of Electrophysics
Nanowires (NWs) of four different materials, including ZnO, InP, GaP, and Pb1-xMnxSe, have been used for the fabrication of two-probe electronic devices to study electrical transport properties. The average diameters of ZnO, InP, GaP, and Pb1-xMnxSe NWs are about 40, 25, 25, 70 nm, respectively. Both electron-beam lithography and dielectrophoresis techniques are employed to either deposit two Ti/Au electrodes on single NW or positioned the NW into nanometer gap between two electrodes. Temperature dependent behaviors of resistance of two-probe devices are measured to explore the electron transport either in the NW or in the nanocontact formed in the interface between the NW and the Ti/Au electrodes. Two-probe devices with high and low room-temperature resistance are used to inspect and distinguish the interplay between the nanocontact and the NW. After the separation of NW-dominated devices from contact-dominated ones, the thermally activated transport in semiconductor ZnO, MP, and GaP NWs and the temperature independent tunneling conduction in Pb1-xMnxSe NWs have been revealed. On the other hand, the contact-dominated devices display electron hopping transport in the nanocontact. Moreover, the fluctuation-induced tunneling conduction in the overlapped Pb1-xMnxSe NWs has been observed.
Electron Transport Properties of ZnO, InP, GaP, and Pb(1-x)Mn(x)Se Nanowires By Two-Probe Measurements
(2010)
Lin, Yen-Fu
;
Jiye-Fang
;
Jian, Wen-Bin
;
電子物理學系
;
Department of Electrophysics
Nanowires (NWs) of four different materials, including ZnO, InP, GaP, and Pb(1-x)Mn(x)Se, have been used for the fabrication of two-probe electronic devices to study electrical transport properties. The average diameters of ZnO, InP, GaP, and Pb(1-x)Mn(x)Se NWs are about 40, 25, 25, 70 nm, respectively. Both electron-beam lithography and dielectrophoresis techniques are employed to either deposit two Ti/Au electrodes on single NW or positioned the NW into nanometer gap between two electrodes. Temperature dependent behaviors of resistance of two-probe devices are measured to explore the electron transport either in the NW or in the nanocontact formed in the interface between the NW and the Ti/Au electrodes. Two-probe devices with high and low room-temperature resistance are used to inspect and distinguish the interplay between the nanocontact and the NW. After the separation of NW-dominated devices from contact-dominated ones, the thermally activated transport in semiconductor ZnO, MP, and GaP NWs and the temperature independent tunneling conduction in Pb(1-x)Mn(x)Se NWs have been revealed. On the other hand, the contact-dominated devices display electron hopping transport in the nanocontact. Moreover, the fluctuation-induced tunneling conduction in the overlapped Pb(1-x)Mn(x)Se NWs has been observed.
Exploration and characterization of the memcapacitor and memristor properties of Ni-DNA nanowire devices
(2017-09-01)
Chu, Hsueh-Liang
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Lai, Jian-Jhong
;
Wu, Li-Ying
;
Chang, Shen-Lin
;
Liu, Chia-Ming
A 2-mu m-long Ni ion-chelated DNA molecule (Ni-DNA) was found for the first time to possess both memcapacitor and memristor properties; this Ni-DNA molecule is known as a dual memory circuit element (memelement). As a memelement, the state of impedance on Ni-DNA is proportional to the unit number of Ni ions containing a base pair complex (Ni-bp), which is determined by the previously applied external voltage. Interestingly, the impedances of Ni-DNA change in response to a change in the sweeping frequencies of the external bias. Our simulation results also indicate that changes in the effective resistance and capacitance of Ni-bp may be attributed to changes in the Ni ion redox species in the Ni-bp of a Ni-DNA nanowire. Therefore, the working mechanism of a nanowire-type memcapacitor and memristor is revealed. In summary, the Ni-DNA nanowire is shown to be a multi-dimensional memory device, whose memory state depends on the length of DNA and applied external voltages/frequencies.
Exposure of the Hidden Anti-ferromagnetism in Paramagnetic CdSe:Mn Nanocrystals
(2015-01-01)
Zou, Shou-Jyun
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Wang, Sheng-Tsung
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Wu, Ming-Fan
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Jian, Wen-Bin
;
Cheng, Shun-Jen
We present theoretical and experimental investigations of the magnetism of paramagnetic semiconductor CdSe:Mn nanocrystals and propose an efficient approach to the exposure and analysis of the underlying anti-ferromagnetic interactions between magnetic ions therein. A key advance made here is the development of an analysis method with the exploitation of group theory technique that allows us to distinguish the anti-ferromagnetic interactions between aggregative Mn2+ ions from the overall pronounced paramagnetism of magnetic-ion-doped semiconductor nanocrystals. By using the method, we clearly reveal and identify the signatures of anti-ferromagnetism from the measured temperature-dependent magnetisms and furthermore determine the average number of Mn2+ ions and the fraction of aggregative ones in the measured CdSe:Mn nanocrystals.
Facet-controlled facilitation of PbS nanoarchitectures by understanding nanocrystal growth
(2015-01-01)
Loc, Welley Siu
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Quan, Zewei
;
Lin, Cuikun
;
Pan, Jinfong
;
Wang, Yuxuan
Nanostructured lead sulphide is a significant component in a number of energy-related sustainable applications such as photovoltaic cells and thermoelectric components. In many micro-packaging processes, dimensionality-controlled nano-architectures as building blocks with unique properties are required. This study investigates different facet-merging growth behaviors through a wet-chemical synthetic strategy to produce high-quality controlled nanostructures of lead sulphide in various dimensionalities. It was found that 1D nanowires or 2D nanosheets can be obtained by the merging of reactive {111}- or {110}-facets, respectively, while promoting {100} facets in the early stages after nucleation leads to the growth of 0D nanocubes. The influence of temperature, capping ligands and co-solvent in facilitating the crystal facet growth of each intermediate seed is also demonstrated. The novelty of this work is characterized by the delicate manipulation of various PbS nanoarchitectures based on the comprehension of the facet-merging evolution. The synthesis of facet-controlled PbS nanostructures could provide novel building blocks with desired properties for use in many applications.
Formation of Arrays of Free-Standing CdS Quantum Dots Using the Langmuir-Blodgett Technique
(2011-10-20)
Protasov, Dmitry Yu.
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Jian, Wen-Bin
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Svit, Kirill A.
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Duda, Tatyana A.
;
Teys, Sergei A.
Aggregation clusters of CdS quantum dots (QDs) on the highly ordered pyrolytic graphite substrate were investigated by atomic force microscopy and scanning tunneling microscopy. QDs were initially formed within Y-type Langmuir-Blodgett (LB) films of cadmium behenate. The LB matrix was then removed by annealing. To study the process of QD assembly, the density of QDs in the initial film was varied systematically by increasing the number of monolayers (MLs) 0 from 1 to 20 ML. It was found that, at a small LB ML number, only a small part of CdS molecules form into QDs by diffusion along the plane of LB layers. With an increase of the LB ML number, the interlayer diffusion arises that leads to almost full binding of CdS molecules into QDs. The individually standing QDs were formed on the substrate for 1 and 2 ML samples. The QD size distributions of the samples with a small ML number are broader than that predicted by the two-dimensional Lifshitz-Slezov diffusion model. With an increase of the LB matrix thickness, QDs begin to assemble into clusters, revealing a ribbon structure due to diffusion-limited aggregation, and for the 20 ML LB matrix, a submonolayer QD film arises. By analyzing the occurrence of QDs as a function of aggregation number, pair bondings were estimated to be about 34 and 62 meV for the 4 and 8 ML samples, respectively.
Growth of single-crystalline RuO2 nanowires with one- and two-nanocontact electrical characterizations
(2007-01-01)
Liu, Yee-Lang
;
Wu, Zong-Yi
;
Lin, Kuei-Jiun
;
Huang, Jr-Jeng
;
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.
High Mobilities in Layered InSe Transistors with Indium-Encapsulation-Induced Surface Charge Doping
(2018-11-02)
Li, Mengjiao
;
Lin, Che-Yi
;
Yang, Shih-Hsien
;
Chang, Yuan-Ming
;
Chang, Jen-Kuei
Tunability and stability in the electrical properties of 2D semiconductors pave the way for their practical applications in logic devices. A robust layered indium selenide (InSe) field-effect transistor (FET) with superior controlled stability is demonstrated by depositing an indium (In) doping layer. The optimized InSe FETs deliver an unprecedented high electron mobility up to 3700 cm(2) V-1 s(-1) at room temperature, which can be retained with 60% after 1 month. Further insight into the evolution of the position of the Fermi level and the microscopic device structure with different In thicknesses demonstrates an enhanced electron-doping behavior at the In/InSe interface. Furthermore, the contact resistance is also improved through the In insertion between InSe and Au electrodes, which coincides with the analysis of the low-frequency noise. The carrier fluctuation is attributed to the dominance of the phonon scattering events, which agrees with the observation of the temperature-dependent mobility. Finally, the flexible functionalities of the logic-circuit applications, for instance, inverter and not-and (NAND)/not-or (NOR) gates, are determined with these surface-doping InSe FETs, which establish a paradigm for 2D-based materials to overcome the bottleneck in the development of electronic devices.