Browsing by Author "Dhananjay"

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Ambipolar transport behavior in In(2)O(3)/pentacene hybrid heterostructure and their complementary circuits
(2008-07-21)
Dhananjay
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Ou, Chun-Wei
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Yang, Chuan-Yi
;
Wu, Meng-Chyi
;
Chu, Chih-Wei
In this Letter, ambipolar transport properties of a bilayer of In(2)O(3) and a pentacene heterostructure have been realized. While In(2)O(3) thin film transistors exhibited a n-channel behavior, pentacene presumed p-channel characteristics on bare SiO(2)/p-Si substrates. However, when a bilayer of In(2)O(3)/pentacene was realized on the gate dielectrics, the hybrid structure exhibited both n- and p-channel conductions, depicting an ambipolar transistor behavior. When two identical ambipolar transistors were integrated to establish an inverter structure, a voltage gain of 10 was obtained. The results indicate that these heterostructures can be utilized for the complementary circuits. (C) 2008 American Institute of Physics.
Balancing the ambipolar conduction for pentacene thin film transistors through bifunctional electrodes
(2008-06-23)
Yang, Chuan-Yi
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Dhananjay
;
Cheng, Shiau-Shin
;
Ou, Chun-Wei
;
Chuang, You-Che
We report an effective way to equilibrate hole and electron transport in ambipolar pentacene thin film transistors (TFTs). It was achieved by inserting an ultra thin lithium fluoride (LiF) layer at the electrode/organic interface to form a bifunctional source/drain electrode. It can be observed that the presence of ultrathin LiF layer will facilitate the injection of electrons from source/drain electrodes to organic semiconductor, resulting in a significant enhancement of the n-channel conduction, without sacrificing p-channel conduction for ambipolar pentacene TFTs. These factors make them potential candidates for the organic complementary circuits and inverter circuits of these ambipolar TFTs are also demonstrated. (c) 2008 American Institute of Physics.
Complementary inverter circuits based on p-SnO(2) and n-In(2)O(3) thin film transistors
(2008-06-09)
Dhananjay
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Chu, Chih-Wei
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Ou, Chun-Wei
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Wu, Meng-Chyi
;
Ho, Zhong-Yo
Thin film transistors (TFTs) of indium oxide (In(2)O(3)) and tin oxide (SnO(2)) were fabricated on SiO(2) gate dielectric using reactive evaporation process. Structural investigation of the films revealed that In(2)O(3) films were polycrystalline in nature with preferred (222) orientation and SnO(2) films exhibited amorphous nature. The x-ray photoelectric spectroscopy measurements suggest that SnO(2) films were oxygen rich and presume mixed oxidation states of Sn, namely Sn(2+) and Sn(4+). While the In(2)O(3) based TFTs possess n-type channel conduction, SnO(2) based TFTs exhibited anomalous p-type conductivity. Integration of these n- and p-type devices resulted in complementary inverter with a gain of 11. (C) 2008 American Institute of Physics.
Complementary inverter circuits based on p-SnO2 and n-In2O3 thin film transistors
(2008-06-09)
Dhananjay
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Chu, Chih-Wei
;
Ou, Chun-Wei
;
Wu, Meng-Chyi
;
Ho, Zhong-Yo
Thin film transistors (TFTs) of indium oxide (In2O3) and tin oxide (SnO2) were fabricated on SiO2 gate dielectric using reactive evaporation process. Structural investigation of the films revealed that In2O3 films were polycrystalline in nature with preferred (222) orientation and SnO2 films exhibited amorphous nature. The x-ray photoelectric spectroscopy measurements suggest that SnO2 films were oxygen rich and presume mixed oxidation states of Sn, namely Sn2+ and Sn4+. While the In2O3 based TFTs possess n-type channel conduction, SnO2 based TFTs exhibited anomalous p-type conductivity. Integration of these n- and p-type devices resulted in complementary inverter with a gain of 11. (C) 2008 American Institute of Physics.
Dependence of channel thickness on the performance of In(2)O(3) thin film transistors
(2008-05-07)
Dhananjay
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Cheng, Shiau-Shin
;
Yang, Chuan-Yi
;
Ou, Chun-Wei
;
Chuang, You-Che
Bottom gate and top contact thin film transistors were fabricated using In(2)O(3) thin films as active channel layers. Thin films of varying thicknesses in the range 5 - 20 nm were deposited on an SiO(2) gate dielectric by the thermal evaporation process in the presence of high purity oxygen. The results of atomic force microscopy show that all the films exhibit dense grain distribution with a root-mean-square roughness in the range 0.6-8.0 nm. Irrespective of the thickness of the channel layer, the on/off ratio of the device is 10(4). The channel mobility and resistivity were found to be a strong function of the thickness of the active layer. The Levinson model was used to calculate the trap density and the grain boundary mobility. The low processing temperature shows the possibility of utilizing these devices on flexible substrates such as polymer substrates.
Dependence of channel thickness on the performance of In2O3 thin film transistors
(2008-05-07)
Dhananjay
;
Cheng, Shiau-Shin
;
Yang, Chuan-Yi
;
Ou, Chun-Wei
;
Chuang, You-Che
Bottom gate and top contact thin film transistors were fabricated using In2O3 thin films as active channel layers. Thin films of varying thicknesses in the range 5 - 20 nm were deposited on an SiO2 gate dielectric by the thermal evaporation process in the presence of high purity oxygen. The results of atomic force microscopy show that all the films exhibit dense grain distribution with a root-mean-square roughness in the range 0.6-8.0 nm. Irrespective of the thickness of the channel layer, the on/off ratio of the device is 10(4). The channel mobility and resistivity were found to be a strong function of the thickness of the active layer. The Levinson model was used to calculate the trap density and the grain boundary mobility. The low processing temperature shows the possibility of utilizing these devices on flexible substrates such as polymer substrates.
Realization of ambipolar pentacene thin film transistors through dual interfacial engineering
(2008-05-01)
Yang, Chuan-Yi
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Cheng, Shiau-Shin
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Ou, Chun-Wei
;
Chuang, You-Che
;
Wu, Meng-Chyi
Ambipolar conduction of a pentacene-based field-effect transistor can be attributed to dual interface engineering, which occurs at the dielectric/semiconductor interface and electrode/semiconductor interface. While the former was realized by utilizing a hydroxyl-free gate dielectric, the latter was made feasible by the use of appropriate metal source and drain electrodes. The field-effect hole and electron mobilities of 0.026 and 0.0023 cm(2)/V s, respectively, were extracted from the transfer characteristics of pentacene organic field-effect transistors utilizing polymethyl methacrylate as the trap-reduction interfacial modified layer and Al as the source and drain (S/D) electrodes. We demonstrated a complementarylike inverter by using two identical ambipolar transistors and it can be operated both in the first and third quadrants with a high output voltage gain of around 10. (C) 2008 American Institute of Physics.
Realization of In2O3 thin film transistors through reactive evaporation process
(2007-09-24)
Dhananjay
;
Chu, Chih-Wei
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光電工程學系
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Department of Photonics
In2O3 thin films have been grown by reactive evaporation of indium in ambient oxygen. The films were structurally characterized by x-ray diffraction (XRD) and atomic force microscopy techniques. The results of XRD revealed that the films were polycrystalline in nature with preferred (222) orientation. The as-grown films were subjected to various annealing treatments to modulate the conductivity of the films for thin film transistors (TFTs). TFTs fabricated on SiO2 gate dielectric exhibited an on/off ratio of 10(4) and a field-effect mobility of 27 cm(2)/V s. High on-state current makes them potential candidates for flat-panel display devices. (c) 2007 American Institute of Physics.