Browsing by Author "Chen, Bo-Yi"

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Capabilities of time-resolved X-ray excited optical luminescence of the Taiwan Photon Source 23A X-ray nanoprobe beamline
(2020-01-01)
Lin, Bi-Hsuan
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Wu, Yu-Hao
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Li, Xiao-Yun
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Hsu, Hsu-Cheng
;
Chiu, Yu-Cheng
Time-resolved X-ray excited optical luminescence (TR-XEOL) was developed successfully for the 23A X-ray nanoprobe beamline located at the Taiwan Photon Source (TPS). The advantages of the TR-XEOL facility include (i) a nano-focused X-ray beam (<60 nm) with excellent spatial resolution and (ii) a streak camera that can simultaneously record the XEOL spectrum and decay time. Three time spans, including normal (30 ps to 2 ns), hybrid (30 ps to 310 ns) and single (30 ps to 1.72 mu s) bunch modes, are available at the TPS, which can fulfil different experimental conditions involving samples with various lifetimes. It is anticipated that TR-XEOL at the TPS X-ray nanoprobe could provide great characterization capabilities for investigating the dynamics of photonic materials.
High Optical Conversion Capability within the Interface between Graphene and Si under Zero Bias and Visible to Near Infrared Regime
(2016)
Hsiao, Chin-Chiang
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Wei, Mao-Qugn
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Ren, Ting-Ting
;
Chen, Bo-Yi
;
Li, Mei-Yi
In this study, we demonstrate the high performance few-layer graphene-Si sensor with high photoresponsivity of 95 mA/W, operation behaviors with external bias as low as 0 V, and broadband operating light wavelength from 400 nm to 1000 nm by combining high transparency of few-layer graphene and n-type silicon. Although external bias benefits the photoresponsivity, the larger dark current is the price to pay. Under zero bias, the different Si substrate, n-type or p-type, provides variant Schottky barrier height guiding different photoelectrical behavior also be investigated in this work. According to the experimental results, few-layer graphene over p-type silicon (FLG p-Si) has one order higher the dark current of the few-layer graphene over n-type silicon (FLG n-Si) to ensure that the detection region between few-layer graphene and n-type silicon profits high optical-to-electrical conversion. Further, the capability of photocurrent-to-photovoltage conversion directly in one device is also provided and verified to profit the integration proposed device with periphery circuit easily.
High Photothermal Properties in Silicon Nanostructures
(2016)
Ren, Ting-Ting
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Wei, Mao-Qugn
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Hsiao, Chin-Chiang
;
Chen, Bo-Yi
;
Li, Mei-Yi
This research describes the p-type nanostalactites (p-type NS) with high photothermal conversion capability has been demonstrated by rapid INC process without extra heat treatment. In optical property, p-type NS has ultralow reflectance below 5 % and high light absorption due to rough structures in the broadband wavelength (350 nm -1100 nm). It looks like a black body. Silicon, an indirect band material, can release thermal energy during the recombination process of photo-generated electron-hole pairs. P-type NS converts photon energy into heat rapidly and then photothermal effect occurs. Then, the temperature change of p-type NS is faster in 10 second than bulk p-type silicon. These nanostructures can not only enhance thermal conversion efficiency but be regarded as a great heat absorber.
Investigation of Cavity Enhanced XEOL of a Single ZnO Microrod by Using Multifunctional Hard X-ray Nanoprobe
(2019-01-18)
Lin, Bi-Hsuan
;
Li, Xiao-Yun
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Lin, Dai-Jie
;
Jian, Bo-Lun
;
Hsu, Hsu-Cheng
The multifunctional hard X-ray nanoprobe at Taiwan Photon Source (TPS) exhibits the excellent ability to simultaneously characterize the X-ray absorption, X-ray excited optical luminescence (XEOL) as well as the dynamics of XEOL of materials. Combining the scanning electron microscope (SEM) into the TPS 23A end-station, we can easily and quickly measure the optical properties to map out the morphology of a ZnO microrod. A special phenomenon has been observed that the oscillations in the XEOL associated with the confinement of the optical photons in the single ZnO microrod shows dramatical increase while the X-ray excitation energy is set across the Zn K-edge. Besides having the nano-scale spatial resolution, the synchrotron source also gives a good temporal domain measurement to investigate the luminescence dynamic process. The decay lifetimes of different emission wavelengths and can be simultaneously obtained from the streak image. Besides, SEM can provide the cathodoluminescence (CL) to be a complementary method to analyze the emission properties of materials, we anticipate that the X-ray nanoprobe will open new avenues with great characterization ability for developing nano/microsized optoelectronic devices.
Observation of anomalous emissions of nonpolar a-plane MgZnO and ZnO epi-films based on XEOL and time-resolved XEOL in hybrid bunch mode
(2020-08-01)
Lin, Bi-Hsuan
;
Wu, Yu-Hao
;
Wu, Yung-Chi
;
Liu, Wei-Rein
;
Lee, Chien-Yu
X-ray excited optical luminescence (XEOL) using an x-ray nanobeam operating in the hybrid bunch mode provides not only a sufficiently high peak power density but also high-quality temporal domain measurements for studying the luminescence dynamics of photonic materials and devices. We used these features to investigate the peculiar emission behavior of the as-grown and rapid thermal annealing (RTA)-treated a-plane MgZnO epi-films, from which an anomalous emission was observed at similar to 325 nm, along with a rapid increase in near-band edge (NBE) emission with increasing x-ray irradiation time. This peculiar emission behavior was also observed in the cathodoluminescence spectra obtained under electron beam excitation. Increases in the NBE emission intensity of the RTA-treated a-plane MgZnO epi-film were observed in terms of both photoluminescence and small anomalous emissions of XEOL. This can be explained by the effective transfer of Mg atoms from interstitial sites to suitable sites as a result of RTA treatment. Based on comparison with an a-plane ZnO epi-film without Mg, we conclude that the anomalous emission peak is caused by Mg-related energy states created by the high-dose x-ray or electron beam irradiation. Furthermore, the rapid increase in NBE emission and the reduction in the long decay lifetime can be attributed to charge transfer from the Mg clusters, which are thus responsible for the anomalous emissions.
Peculiar near-band-edge emission of polarization-dependent XEOL from a non-polar a-plane ZnO wafer
(2018-02-05)
Lin, Bi-Hsuan
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Wu, Yung-Chi
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Chen, Huang-Yeh
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Tseng, Shao-Chin
;
Wu, Jian-Xing
Polarization-dependent hard X-ray excited optical luminescence (XEOL) was used to study not only the optical properties but also the crystallographic orientations of a non-polar a-plane ZnO wafer. In addition to a positive-edge jump and extra oscillations in the near-band-edge (NBE) XEOL yield, we observed a blue shift of the NBE emission peak that follows the polarization-dependent X-ray absorption near-edge structure (XANES) as the X-ray energy is tuned across the Zn K-edge. This NBE blue shift is caused by the larger X-ray absorption, generating higher free carriers to reduce the exciton-LO phonon coupling, which causes a decrease in the exciton activation energy. The extra oscillations in XANES and XEOL as the polarization is set parallel to the c-axis is attributed to simultaneous excitations of the Zn 4p - O 2p pi-bond along the c-axis and the bilayer sigma-bond, whereas only the sigma-bond is excited when the polarization is perpendicular to the c-axis. The polarization-dependent XEOL spectra can be used to determine the crystallographic orientations. (c) 2018 Optical Society of America under the terms of the OSA Open Access Publishing Agreement
Probing the exciton-phonon coupling strengths of O-polar and Zn-polar ZnO wafer using hard X-ray excited optical luminescence
(2016-11-07)
Lin, Bi-Hsuan
;
Chen, Huang-Yeh
;
Tseng, Shao-Chin
;
Wu, Jian-Xing
;
Chen, Bo-Yi
The temperature-dependent hard X-ray excited optical luminescence (XEOL) spectroscopy was used to study the optical properties of O and Zn polarity of a c-plane single crystal ZnO wafer. By analyzing the XEOL and XRD, we found an unprecedented blue shift of the free exciton transition with increasing the excited carrier density as tuning the X-ray energy across the Zn K-edge, and the O-polar face possesses better crystal structure than the Zn-polar one. This spectral blue shift is attributed to the Coulomb screening of the spontaneous polarization by the excited free carriers that result in decreasing the exciton-phonon Frohlich interaction to reduce exciton binding energy. Published by AIP Publishing.