Browsing by Author "Tang, Mau-Tsu"

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30 nm resolution x-ray imaging at 8 keV using third order diffraction of a zone plate lens objective in a transmission microscope
(2006-11-27)
Yin, Gung-Chian
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Song, Yen-Fang
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Tang, Mau-Tsu
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Chen, Fu-Rong
;
Liang, Keng S.
A hard x-ray transmission microscope with 30 nm spatial resolution has been developed employing the third diffraction order of a zone plate objective. The microscope utilizes a capillary type condenser with suitable surface figure to generate a hollow cone illumination which is matched in illumination range to the numerical aperture of the third order diffraction of a zone plate with an outmost zone width of 50 nm. Using a test sample of a 150 nm thick gold spoke pattern with finest half-pitch of 30 nm, the authors obtained x-ray images with 30 nm resolution at 8 keV x-ray energy. (c) 2006 American Institute of Physics.
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.
Hard X-ray nanoprobe and time-resolved XEOL to observe increasing luminescence of ZnO and GaN epitaxial structures
(2019-10-21)
Lin, Bi-Hsuan
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Wu, Yu-Hao
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Wu, Tai-Sing
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Wu, Yung-Chi
;
Li, Xiao-Yun
Hard X-ray excited optical luminescence (XEOL) with a nanofocused beam provides both excellent spatial resolution and high enough peak power density, which makes XEOL mapping and luminescence dynamics study achievable. We present here the time and X-ray intensity dependence of the near-band-edge (NBE) luminescence from the nonpolar a-plane MgZnO/ZnO multiple quantum wells (MQWs): the emission intensity increases more than 10 times after high X-ray irradiation. Different from the well-known NBE emission lifetime of ZnO (less than 1 ns), the long decay time gradually decreases from 130 ns to 35 ns with the increasing X-ray irradiation time. We attribute the observed changes in NBE luminescence to the excitation of the Mg-related energy state by the high energy X-ray nanobeam. This suggestion was further confirmed in the XEOL spectra of the Mg-doped and Si-doped c-plane GaN epi-films. Published under license by AIP Publishing.
Investigation of Cavity Enhanced XEOL of a Single ZnO Microrod by Using Multifunctional Hard X-ray Nanoprobe
(2019-01-18)
Lin, Bi-Hsuan
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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
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Wu, Yu-Hao
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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
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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
Polarization-dependent XEOL: Comparison of peculiar near-band-edge emission of non-polar alpha-plane GaN and ZnO wafers
(2019-03-04)
Lin, Bi-Hsuan
;
Wu, Yung-Chi
;
Lee, Jyh-Fu
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Tang, Mau-Tsu
;
Hsieh, Wen-Feng
Polarization-dependent hard X-ray excited optical luminescence (XEOL) spectroscopy was used to study the properties of near-band-edge (NBE) emission of non-polar alpha-GaN and alpha-ZnO wafers. We found similar behaviors of alpha-GaN with alpha-ZnO that include the positive intensity jump and the blue shift of the NBE emission peak in the XEOL spectrum following the polarization-dependent X-ray absorption near-edge structure (XANES) as the X-ray energy is tuned across the Ga or Zn K-edge. Furthermore, as the X-ray energy is set above the K-edges, different oscillations of XEOL, also following the XANES, were observed depending upon the directions of the excitation X-ray electric field. However, the blue shift of alpha-ZnO is about two times larger than that of alpha-GaN that results from the larger polar field in alpha-ZnO than that in alpha-GaN. For both alpha-GaN and alpha-ZnO, the above K-edge excited oscillations in XANES and XEOL spectra, where the polarization is set parallel to the pi-axis, are attributed to simultaneous excitations of the p-bond along the pi-axis and in-plane sigma-bonds, whereas only the in-plane sigma-bonds are excited for the polarization perpendicular to the pi-axis. Therefore, these polarization dependent oscillation features of XEOL yields that follow the fluorescence yields can be used as an alternative way to determine the crystallographic orientations. Published under license by AIP Publishing.
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
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Chen, Huang-Yeh
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Tseng, Shao-Chin
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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.