Browsing by Author "Liu, Da-Ren"

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Characteristics of atomic-layer-deposited Al(2)O(3) high-k dielectric films grown on Ge substrates
(2008)
Cheng, Chao-Ching
;
Chien, Chao-Hsin
;
Luo, Guang-Li
;
Liu, Jun-Cheng
;
Kei, Chi-Chung
This paper describes the structural and electrical properties of Al(2)O(3) thin films grown through atomic layer deposition onto Ge substrates over a wide deposition temperature range (50-300 degrees C). From grazing-incidence X-ray reflectivity and X-ray photoelectron spectroscopy, we found that increasing the deposition temperature improved the Al(2)O(3) film density and its dielectric stoichiometry; nevertheless, dielectric intermixing between main Al(2)O(3) and interfacial GeO(2) appeared at temperatures above 200 degrees C, along with degradation of the GeO(2)/Ge interface. Accordingly, a relatively large gate leakage current (J(g)) and a high density of interfacial states D(it) (> 10(13) cm(-2) eV(-1)) were observed as a result of deterioration of the entire Al(2)O(3)/Ge structure at higher deposition temperatures. In addition, although subsequent high-temperature processing at 600 degrees C in a N(2) ambient could relieve the oxygen-excessive behavior further, i.e., to provide a more stoichiometric film, the accompanying GeO(x) volatilization close to the dielectric interface caused greater damage to the electrical performance. Only forming gas annealing (H(2)/N(2), 1:10) at low temperature (300 degrees C) improved the capacitance-voltage characteristics of the Pt/Al(2)O(3)/Ge structure, in terms of providing a lower value of D(it) (ca. 6 x 10(11) cm(-2) eV(-1)), a lower value of J(g), and a reduced hysteresis width.
Compact motorized circular wheel of polarization optics for ultra-broadband polarization state generation
(2012)
Weng, Chun-Jen
;
Liu, Da-Ren
;
Hsu, Ken-Yuh
;
Chen, Yung-Fu
;
光電工程學系
This study proposes an innovative optical mechanism with a miniature motorized circular wheel for polarization optics for an ultra-broadband polarization state generator. The proposed apparatus can be suitable for a polarimetric microspectrophotometer for measurements of micro optics and metamaterials with circular dichroism and linear dichroism. Different types of micro optics have their own wavelength dependence, meaning different curves in the broadband range of light. This study presents an ultra-broadband platform for measuring and identifying micro optics such as chiral metamaterials, plasmonics, micro polarizers, and patterned retarders. The key component of a polarimetric microspectrophotometer is a polarization state generator (PSG). A simple PSG consists of a polarizer and a waveplate. An arbitrary polarization state can be created by rotating either the polarizer or the waveplate. Sheet polarizers and achromatic waveplates have a limited bandwidth range. For the ultra-broadband measurement range of 400 nm to 1700 nm, the PSG needs at least three sheet polarizers and three achromatic waveplates: 400 nm-700 nm, 700 nm-1000 nm, and 1000 nm-1700 nm. This optical mechanism, which consists of only one control motor and two high precision unidirectional bearings, includes several polarizers and waveplates arranged in a matrix on a circular wheel. This apparatus can shift one of the polarizers and waveplates to a predetermined position and rotate all the polarizers to change the polarization status. An ultra-broadband polarimetric microspectrophotometer with a compact motorized wheel is an advanced polarization optical instrument for research on chiral metamaterials, plasmonics, micro polarization optics, green optics, and bio optics.
Confocal displacement sensor with varifocal lens
(2015)
Weng, Chun-Jen
;
Lan, Tzu-Hsien
;
Hwang, Chi-Hung
;
Liu, Da-Ren
;
Chen, Chih-Yen
a confocal displacement sensor with a varifocal lens and a multi-wavelength rainbow laser was established in this study. The surface curvature of varifocal lens was varied by different current driving so that the focal length can be easily changed. Thus, we can quickly measure the distance between the sensor head and targets by detecting the reflective power according to the principle of confocal laser. This rainbow laser can operate at four different wavelengths. The laser beams with different colors can be used to measure the dispersion of varifocal lens. The range of measuring displacement with 20X objective lens in this displacement sensor is from 4.9mm to 5.9mm. The FWHM resolution of displacement is about 70 mu m. The step-height aluminate plate was measured by this system and the error of measuring distance is less than 35 mu m (0.75%).