Browsing by Author "Kuan, Chieh-Hsiung"

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High-density one-dimensional well-aligned germanium quantum dots on a nanoridge array
(2008-08-25)
Chen, Yan-Ru
;
Kuan, Chieh-Hsiung
;
Suen, Yuen-Wuu
;
Peng, Yu-Hwa
;
Chen, Peng-Shiu
The selective growth of high-density one-dimensional well-aligned Ge quantum dots (QDs) on the top of nanoridges patterned on Si substrate is reported. The period of ridge array is 150 nm, the width of each ridge is 80 nm, and the depth of the trench is 20 nm. The areal density of QDs is about 5.4 x 10(9) cm(-2). Simulations of the chemical potential show that a proper distribution of the surface curvature may give rise to a suitable chemical potential minimum helping positioning the QDs. These ridges can also be used to control the shape and the uniformity of QDs. (C) 2008 American Institute of Physics.
Influence of patterned sapphire substrates with different symmetry on the light output power of InGaN-based LEDs
(2014-11-03)
You, Yao-Hong
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Su, Vin-Cent
;
Ho, Ti-En
;
Lin, Bo-Wen
;
Lee, Ming-Lun
This paper aims to investigate the light output power (LOP) of InGaN-based light-emitting diodes (LEDs) grown on patterned sapphire substrates (PSSs) with different symmetry. The GaN epitaxial layers grown on the hexagonal lattice arrangement PSS (HLAPSS) have a lower compressive strain than the ones grown on the square lattice arrangement PSS (SLAPSS). The quantum-confined Stark effect (QCSE) is also affected by the residual compressive strain. Based on the experimentally measured data and the ray tracing simulation results, the InGaN-based LED with the HLAPSS has a higher LOP than the one with the SLAPSS due to the weaker QCSE within multiple-quantum wells (MQWs).
Resonance-enhanced dipolar interaction between terahertz photons and confined acoustic phonons in nanocrystals
(2008-03-03)
Liu, Tzu-Ming
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Lu, Ja-Yu
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Chen, Hung-Ping
;
Kuo, Chung-Chiu
;
Yang, Meng-Ju
Taking advantage of the specific core-shell charge separation structure in the CdSe/CdTe core-shell type-II nanocrystals, we experimentally observed and verified the existence of the resonance-enhanced dipolar interaction between terahertz photons and their corresponding confined acoustic phonons. From the measured terahertz transmission spectra, we found that the photon frequency of the terahertz resonant absorption is inversely proportional to the diameter D of the nanocrystals and agrees with that of dipolar active l=1, n=0 confined acoustic modes. The corresponding absorption cross section shows a D(4) dependence, supporting a charged simple-harmonic-oscillator model. These facts verify the occurrence of dipolar interaction between terahertz photons and confined terahertz acoustic phonons. (c) 2008 American Institute of Physics.
Resonant-enhanced dipolar interaction between THz-photons and confined acoustic phonons in nanostructures
(2008-01-01)
Liu, Tzu-Ming
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Lu, Ja-Yu
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Kuo, Chung-Chiu
;
Yang, Meng-Ju
;
Lai, Chih-Wei
By using a frequency-controlled narrow band THz source, a Fourier Transform Infrared (FTIR) spectroscopy system, and a frequency-controlled terahertz (THz) emitter, for the first time, we studied the THz photon absorption related to the THz confined acoustic vibrations in semiconductor nanocrystals. Through a specific charge separation in the CdSe/CdTe type-II nanocrystals and a piezoelectric coupling in the wurtzite CdSe nanocrystals, the THz photons can be resonantly coupled with (l=1) dipolar modes and the (l=0) breathing modes, respectively. Our results provide new mechanisms for low dimensional systems to convert a THz photon into a phonon of the same frequency.
Self-assembled molecular magnets on patterned silicon substrates
(2006)
Chang, Chia-Ching
;
Sun, Kien-Wen
;
Lee, Shang-Fan
;
Kan, Lou-Sing
;
Kuan, Chieh-Hsiung
The paper reports the methods of preparing molecular magnets and pattering of the molecules on semiconductor surface. A highly magnetically aligned metallothionein containing Mn and Cd (Mn,Cd-MT-2) was first synthesized. Those molecules were then placed into nanopores prepared on silicon (001) surfaces using electron beam lithography and reactive ion etching techniques. We have observed self-assemble growth of those MT molecules on the patterned Si surface. The MT molecules have grown into rod or ring type nanostructures, depending on the patterned nanostructures on the surface. We also provide scanning electron microscopy (SEM) and atomic force microscopy (AFM) studied of those molecular nanostructures. This engineered molecule shows molecular magnetization and is biocompatible with conventional semiconductors. These features make Mn,Cd-MT-2 a good candidate for biological applications and sensing sources of new nano-devices.
Short-Term External Buckling With Pneumatic Retinopexy for Retinal Detachment With Inferior Retinal Breaks
(2013-04-01)
Cheng, Hui-Chen
;
Lee, Shui-Mei
;
Lee, Fenq-Lih
;
Liu, Jorn-Hon
;
Kuan, Chieh-Hsiung
PURPOSE: To introduce a new approach for short-term external scleral buckling with pneumatic retinopexy for the management of rhegmatogenous retinal detachment with inferior retinal breaks. DESIGN: Retrospective, noncomparative, interventional case series. METHODS: A review of 33 consecutive eyes of 31 patients who underwent external buckling with pneumatic retinopexy for uncomplicated rhegmatogenous retinal detachment with inferior, retinal breaks from December 2006 through December 2010. An external buckle was made of a 505 sponge sutured along the blunt side of a 279 tyre (MIRA Inc). The buckle was inserted deeply into the inferior fornix without suture after pneumatic retinopexy and was kept in place for 3 days. Primary and final anatomic outcomes, visual acuity, and adverse events were recorded. RESULTS: All patients tolerated the procedure. The mean follow-up period was 24.0 months (range, 9 to 61 months). Primary success, defined as successful retinal reattachment within 6 months without further treatment, was achieved in 29 (87.9%) eyes. All patients attained final retinal reattachment (100%). Overall, the mean best-corrected visual acuity improved significantly at the end of follow-up (0.30 logarithm of the minimal angle of resolution units; Snellen equivalent, 6/12), compared with the preoperative best-corrected visual acuity (0.82 logarithm of the minimal angle of resolution units; Snellen equivalent, 6/38; P < .001). CONCLUSIONS: Short-term external buckling with pneumatic retinopexy is a novel and effective treatment for rhegmatogenous retinal detachment with inferior retinal breaks, with a comparable success rate with other treatment methods. This approach also can avoid complications of long-term buckle implantation. Further comparative cohort studies may be necessary to compare the clinical efficacy with other conventional operations. (Am J Ophthalmol 2013;155:750-756. (C) 2013 by Elsevier Inc. All rights reserved.)
Suppression of "volcano" morphology and parasitic defect luminescence in AlGaN-based deep-UV light-emitting diode epitaxy
(2019-06-01)
Huang, Chia-Yen
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Liu, Tsung-Yen
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Huang, Shih-Ming
;
Chang, Kai-Hsiang
;
Tai, Tsu-Ying
In this study we overcame several critical growth issues related to epitaxy in AlGaN deep-ultraviolet lightemitting diodes. Irregular-shaped pits with dislocation clusters were observed in micron-thick layers of AlGaN on AlN. The strain-induced morphology and defects were suppressed after the insertion of superlattice transition layers between the AlGaN and AlN layers. The defect luminescence in the active region was governed by radiative recombination through the oxygen shallow donors and deep acceptors related to III-vacancies. After optimization of the growth conditions and a decrease in growth interruption, the intensity of the parasitic blueband emission was suppressed by up to 95%. Energy dispersive spectroscopy suggests that the desorption of gallium from the surface is the major source of the III-vacancies.
The Analysis of Nano-Patterned Sapphire Substrates-Induced Compressive Strain to Enhance Quantum-Confined Stark Effect of InGaN-Based Light-Emitting Diodes
(2013-01-01)
Chen, Po-Hsun
;
Su, Vincent
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You, Yao-Hong
;
Lee, Ming-Lun
;
Hsieh, Cheng-Ju
This paper demonstrates that the quantum-confined stark effect of InGaN-based light-emitting diodes can be enhanced by the means of using the hexagonal nano-post patterned sapphire substrates based on the increase of the post-duty cycle.