Browsing by Author "Chen, Chia-Wei"

Now showing 1 - 15 of 15

A Pseudo-Differential OTA with Linearity Improving by HD3 Feedforward
(2009)
Chien, Chao-Liang
;
Hung, Chung-Chih
;
Chen, Chia-Wei
;
電子工程學系及電子研究所
;
Department of Electronics Engineering and Institute of Electronics
This paper presents a fully balanced structure of a CMOS operational transconductance amplifier (OTA) with high linearity for frequency up to 50MHz. The proposed circuit is based on a conventional pseudo-differential structure with a third-order harmonic distortion (HD3) feedforward technique to cancel out the output 3rd harmonic component. The OTA was fabricated in the TSMC CMOS 0.18 mu m technology. The measurement results show the HD3 of -62dB with 0.4-Vpp 50MHz input signal and the power consumption of 0.47mW at a 1.2-V voltage supply.
An indoor light-activated 3D cone-shaped MoS2 bilayer-based NO gas sensor with PPb-level detection at room-temperature
(2019-06-07)
Chen, Yu-Ze
;
Wang, Sheng-Wen
;
Yang, Chun-Chuan
;
Chung, Chieh-Han
;
Wang, Yi-Chung
Utilization of light to boost the performance of gas sensors allows us to operate sensor devices at room temperature. Here, we, for the first time, demonstrated an indoor light-activated 3D cone-shaped MoS2 bilayer-based NO gas sensor with ppb-level detection operated at room-temperature. Large-area coneshaped (CS)-MoS2 bilayers were grown by depositing 2 nm-thick MoO3 layers on a 2'' three-dimensional (3D) cone-patterned sapphire substrate (CPSS) followed by a sulfurization process via chemical vapor deposition. Because the exposed area of MoS2 bilayers is increased by 30%, the CS-MoS2 gas sensor (GS) demonstrated excellent performance with a response of 470% and a fast response time of 25 s after exposure to 1 ppm of NO gas illuminated by ultraviolet (UV) light with a wavelength of 365 nm. Such extraordinary performance at room temperature is attributed to the enhanced light absorption because of the light scattering effect caused by the 3D configuration and photo-desorption induced by UV illumination. For NO concentrations ranging from 2 ppm down to 0.06 ppm, the CS-MoS2 GS demonstrated a stable sensing behavior with a high response and fast response time (470% and 25 s at 2 ppm NO) because of the light absorption enhanced by the 3D structure and photo-desorption under constant UV illumination. The CS-MoS2 GS exhibits a high sensitivity (189.2 R% ppm-1), allowing the detection of NO gas at 0.06 ppm in 130 s. In addition, the 3D cone-shaped structure prolonged the presence of sulfur vapor around MoO3, allowing MoO3 to react with sulfur completely. Furthermore, the CS-MoS2 GS using an indoor lighting to detect NO gas at room temperature was demonstrated for the first time where the CS-MoS2 GS exhibits a stable cycling behavior with a high response (165% at 1 ppm NO) in 50 s; for concentration as low as 0.06 ppm, the response of 75% in 150 s can be achieved.
Beacon Jointed Packet Reconstruction Scheme for Mobile-Phone Based Visible Light Communications Using Rolling Shutter
(2017-12-01)
Wang, Wei-Chung
;
Chow, Chi-Wai
;
Chen, Chia-Wei
;
Hsieh, Hsiang-Chain
;
Chen, Yen-Ting
Mobile-phone based visible light communication (VLC) is an attractive method for optical wireless communication. However, the data rate is typically limited by the complementary metal-oxide-semiconductor image sensor frame rate and the processing time gap in the rolling shutter mode operation. Here, we propose and demonstrate a packet-reconstruction scheme, known as beacon jointed rolling shutter pattern scheme. The mobile-phone based VLC data rate can be increased to a record 10.32 kb/s. The implementation algorithm is discussed; and the bit-error-rate experimental evaluations at different transmission distances and horizontal offsets are performed.
Design of novel TiO2-SiO2 core-shell helical nanostructured anti-reflective coatings on Cu(In,Ga)Se-2 solar cells with enhanced power conversion efficiency
(2019-05-14)
Chen, Chia-Wei
;
Tsai, Hung-Wei
;
Wang, Yi-Chung
;
Su, Teng-Yu
;
Yang, Chen-Hua
Introducing an anti-reflective coating (ARC) is the last step of fabricating Cu(In,Ga)Se-2 solar cells with enhanced photo-generated current by reducing the reflectance of visible light. The use of nanostructures in ARC has been intensively investigated because this can prolong the optical path length by a scattering effect or by the formation of a refractive index gradient. Herein, we proposed the use of TiO2 helical nanostructures using glancing angle deposition (GLAD), and then synthesized SiO2 surrounding the helical nanostructures to further decrease the reflectance by producing a refractive index gradient. The optimized values of TiO2 and SiO2 thicknesses are 150 nm and 3 nm determined by the finite-difference time-domain (FDTD) simulation on Cu(In,Ga)Se-2 solar cells. The suppression of reflectance led to enhanced light absorption across a broad wavelength range, and boosted the J(SC) from 20.66 to 22.51 mA cm(-2), resulting in improved power conversion efficiency (PCE) from 6.32 to 7.00% after applying the TiO2-SiO2 core-shell nanostructures as the ARC. This 10.75% PCE enhancement suggests that the novel TiO2-SiO2 core-shell nanostructures have great potential as ARC for Cu(In,Ga)Se-2 solar cells, and it would be beneficial for development in the photovoltaic field in both research and applications.
Direct Synthesis and Practical Bandgap Estimation of Multilayer Arsenene Nanoribbons
(2016-01-26)
Tsai, Hsu-Sheng
;
Wang, Sheng-Wen
;
Hsiao, Ching-Hung
;
Chen, Chia-Wei
;
Ouyang, Hao
Efficient demodulation scheme for rolling-hutter-patterning of CMOS image sensor based visible light communications
(2017-10-02)
Chen, Chia-Wei
;
Chow, Chi-Wai
;
Liu, Yang
;
Yeh, Chien-Hung
;
光電工程學系
Recently even the low-end mobile-phones are equipped with a high-resolution complementary-metal-oxide-semiconductor (CMOS) image sensor. This motivates using a CMOS image sensor for visible light communication (VLC). Here we propose and demonstrate an efficient demodulation scheme to synchronize and demodulate the rolling shutter pattern in image sensor based VLC. The implementation algorithm is discussed. The bit-error-rate (BER) performance and processing latency are evaluated and compared with other thresholding schemes. (C) 2017 Optical Society of America
Electrochemically active novel amorphous carbon (a-C)/Cu3P peapod nanowires by low-temperature chemical vapor phosphorization reaction as high efficient electrocatalysts for hydrogen evolution reaction
(2019-09-20)
Manikandan, Arumugam
;
Sriram, Pavithra
;
Hsu, Kun-Chieh
;
Wang, Yi-Chung
;
Chen, Chia-Wei
Toward finding low-cost electrocatalysts with high catalytic properties to replace noble metals as high efficient electrocatalysts in electrochemical hydrogen evolution reaction (HER) of total water splitting plays a vital role to approach the green and sustainable energy supply. Here, we demonstrate the direct growth of novel copper phosphide coated with amorphous carbon, namely heterostructured a-C/Cu3P peapod nanowires from chemically synthesized copper nanowires (Cu NWs) followed by a chemical vapor phosphorization reaction (CVPR) process at a low temperature of 400 degrees C. The heterostructured a-C/Cu3P peapod nanowires exhibit a superior electrocatalytic activity by a lower overpotential of 287 mV at a current density of 10 mA cm(-2) with a low Tafel slope of 72 mV dec(-1) and excellent stability over 1000 cycles. The superior electrocatalytic performance can be explained by the superior contact of the electrolyte with active sites on the heterostructured a-C/Cu3P due to the high surface area of peapod nanowire structure covered by defective edges of graphene with the encapsulated amorphous carbon layer, which can tremendously enhance electrical conductivity at the surface. (C) 2019 Published by Elsevier Ltd.
Enhanced Photocarrier Generation with Selectable Wavelengths by M-Decorated-CuInS2 Nanocrystals (M = Au and Pt) Synthesized in a Single Surfactant Process on MoS2 Bilayers
(2019-02-22)
Tang, Shin-Yi
;
Medina, Henry
;
Yen, Yu-Ting
;
Chen, Chia-Wei
;
Yang, Tzu-Yi
A facile approach for the synthesis of Au- and Pt-decorated CuInS2 nanocrystals (CIS NCs) as sensitizer materials on the top of MoS2 bilayers is demonstrated. A single surfactant (oleylamine) is used to prepare such heterostructured noble metal decorated CIS NCs from the pristine CIS. Such a feasible way to synthesize heterostructured noble metal decorated CIS NCs from the single surfactant can stimulate the development of the functionalized heterostructured NCs in large scale for practical applications such as solar cells and photodetectors. Photodetectors based on MoS2 bilayers with the synthesized nanocrystals display enhanced photocurrent, almost 20-40 times higher responsivity and the On/Off ratio is enlarged one order of magnitude compared with the pristine MoS2 bilayers-based photodetectors. Remarkably, by using Pt- or Au-decorated CIS NCs, the photocurrent enhancement of MoS2 photodetectors can be tuned between blue (405 nm) to green (532 nm). The strategy described here acts as a perspective to significantly improve the performance of MoS2-based photodetectors with the controllable absorption wavelengths in the visible light range, showing the feasibility of the possible color detection.
Environmentally and Mechanically Stable Selenium 1D/2D Hybrid Structures for Broad-Range Photoresponse from Ultraviolet to Infrared Wavelengths
(2018-10-17)
Chen, Yu-Ze
;
You, Yen-Ting
;
Chen, Pin Jung
;
Li, Dapan
;
Su, Teng-Yu
Selenium (Se) is one of the potential candidates as photodetector because of its outstanding properties such as high photoconductivity (similar to 8 x 10(4) S cm(-1)), piezoelectricity, thermoelectricity, and nonlinear optical responses. Solution phase synthesis becomes an efficient way to produce Se, but a contamination issue that could deteriorate the electric characteristic of Se should be taken into account. In this work, a facile, controllable approach of synthesizing Se nanowires (NWs)/films via a plasma-assisted growth process was demonstrated at the low substrate temperature of 100 degrees C. The detailed formation mechanisms of nanowires arrays to thin films at different plasma powers were investigated. Moreover, indium (In) layer was used to enhance the adhesive strength with 50% improvement on a SiO2/Si substrate by mechanical interlocking and surface alloying between Se and In layers, indicating great tolerance for mechanical stress for future wearable devices applications. Furthermore, the direct growth of Se NWs/films on a poly(ethylene terephthalate) substrate was demonstrated, exhibiting a visible to broad infrared detection ranges from 405 to 1555 nm with a high on/off ratio of similar to 700 as well as the fast response time less than 25 ms. In addition, the devices exhibited fascinating stability in the atmosphere over one month.
Fabrication of Multilayer Borophene on Insulator Structure
(2016-10-12)
Tsai, Hsu-Sheng
;
Hsiao, Ching-Hung
;
Lin, Yu-Pin
;
Chen, Chia-Wei
;
Ouyang, Hao
Phase-Engineered PtSe2-Layered Films by a Plasma-Assisted Selenization Process toward All PtSe2-Based Field Effect Transistor to Highly Sensitive, Flexible, and Wide-Spectrum Photoresponse Photodetectors
(2018-05-09)
Su, Teng-Yu
;
Medina, Henry
;
Chen, Yu-Ze
;
Wang, Sheng-Wen
;
Lee, Shao-Shin
The formation of PtSe2-layered films is reported in a large area by the direct plasma-assisted selenization of Pt films at a low temperature, where temperatures, as low as 100 degrees C at the applied plasma power of 400 W can be achieved. As the thickness of the Pt film exceeds 5 nm, the PtSe2-layered film (five monolayers) exhibits a metallic behavior. A clear p-type semiconducting behavior of the PtSe2-layered film (approximate to trilayers) is observed with the average field effective mobility of 0.7 cm(2) V-1 s(-1) from back-gated transistor measurements as the thickness of the Pt film reaches below 2.5 nm. A full PtSe2 field effect transistor is demonstrated where the thinner PtSe2, exhibiting a semiconducting behavior, is used as the channel material, and the thicker PtSe2, exhibiting a metallic behavior, is used as an electrode, yielding an ohmic contact. Furthermore, photodetectors using a few PtSe2-layered films as an adsorption layer synthesized at the low temperature on a flexible substrate exhibit a wide range of absorption and photoresponse with the highest photocurrent of 9 mu A under the laser wavelength of 408 nm. In addition, the device can maintain a high photoresponse under a large bending stress and 1000 bending cycles.
Phase-Engineered Type-II Multimetal-Selenide Heterostructures toward Low-Power Consumption, Flexible, Transparent, and Wide-Spectrum Photoresponse Photodetectors
(2018-05-29)
Chen, Yu-Ze
;
Wang, Sheng-Wen
;
Su, Teng-Yu
;
Lee, Shao-Hsin
;
Chen, Chia-Wei
Phase-engineered type-II metal-selenide heterostructures are demonstrated by directly selenizing indium-tin oxide to form multimetal selenides in a single step. The utilization of a plasma system to assist the selenization facilitates a low-temperature process, which results in large-area films with high uniformity. Compared to single-metal-selenide-based photodetectors, the multimetal-selenide photodetectors exhibit obviously improved performance, which can be attributed to the Schottky contact at the interface for tuning the carrier transport, as well as the type-II heterostructure that is beneficial for the separation of the electron-hole pairs. The multimetal-selenide photodetectors exhibit a response to light over a broad spectrum from UV to visible light with a high responsivity of 0.8 A W-1 and an on/off current ratio of up to 10(2). Interestingly, all-transparent photodetectors are successfully produced in this work. Moreover, the possibility of fabricating devices on flexible substrates is also demonstrated with sustainable performance, high strain tolerance, and high durability during bending tests.
Polarization-Multiplexed Rolling Shutter Demodulation in Mobile-Phone Based Visible Light Communication
(2018-01-01)
Chang, Yuan-Chia
;
Chen, Chia-Wei
;
Liu, Yen-Chun
;
Shiu, Ruei-Jie
;
Chow, Chi-Wai
We propose and demonstrate using polarization-multiplexing of rolling-shutter-effect (RSE) based visible-light-communication (VLC) to increase the transmission capacity. Experimental net data rate of 11.52 kbit/s was achieved at typical room illuminance of 500 lux.
Visible light communications for the implementation of internet-of-things
(2016-06-01)
Chen, Chia-Wei
;
Wang, Wei-Chung
;
Wu, Jhao-Ting
;
Chen, Hung-Yu
;
Liang, Kevin
It is predicted that the number of internet-of-things (IoT) devices will be >28 billion in 2020. Due to the shortage of the conventional radio-frequency spectrum, using visible light communication (VLC) for IoT can be promising. IoT networks may only require very low-data rate communication for transmitting sensing or identity information. The implementation of a VLC link on existing computer communication standards and interfaces is important. Among the standards, universal asynchronous receiver/transmitter (UART) is very popular. We propose and demonstrate a VLC-over-UART system. Bit error rate analysis is performed. Different components and modules used in the proposed VLC-over-UART system are discussed. Then, we also demonstrate a real-time simultaneous temperature, humidity, and illuminance monitoring using the proposed VLC link. (C) 2016 Society of Photo-Optical Instrumentation Engineers (SPIE)
Wafer Scale Phase-Engineered 1T-and 2H-MoSe2/Mo Core-Shell 3D-Hierarchical Nanostructures toward Efficient Electrocatalytic Hydrogen Evolution Reaction
(2016-11-23)
Qu, Yindong
;
Medina, Henry
;
Wang, Sheng-Wen
;
Wang, Yi-Chung
;
Chen, Chia-Wei
The necessity for new sources for greener and cleaner energy production to replace the existing ones has been increasingly growing in recent years. Of those new sources, the hydrogen evolution reaction has a large potential. In this work, for the first time, MoSe2/Mo core-shell 3D-hierarchical nanostructures are created, which are derived from the Mo 3D-hierarchical nanostructures through a low-temperature plasma-assisted selenization process with controlled shapes grown by a glancing angle deposition system.