Showing papers by "Chien-Hung Liu published in 2011"

Ultraviolet photodetectors based on MgZnO thin films

Abstract: In this work, Ti/Au Ohmic contacts to both Mg0.24Zn0.76O and ZnO film-based metal-semiconductor-metal (MSM) photodetectors (PDs) were fabricated on glass substrates for comparative analysis. The transmittance spectra measured around the optical energy gap revealed that Mg0.24Zn0.76O films have a larger optical energy gap (3.54 eV) than ZnO films (3.25 eV). Mg0.24Zn0.76O MSM-structured ultraviolet (UV) PDs show a much higher UV-to-visible rejection ratio of 2.78×103 than those made of ZnO films. This can be attributed to the low dark current (0.08 pA) of the Mg0.24Zn0.76O UV PDs and the small full width at half maximum (0.34°) of the Mg0.24Zn0.76O (002) x-ray diffraction peak, indicating better crystal quality than that of ZnO. With an applied bias of 5 V and illuminations at 350 and 380 nm, the Mg0.24Zn0.76O and ZnO film-based MSM PDs exhibited responsivities of 0.4 and 0.32 A/W, respectively.

Development of an optical three-dimensional laser tracker using dual modulated laser diodes and a signal detector.

Abstract: Laser trackers are widely used in industry for tasks such as the assembly of airplanes and automobiles, contour measurement, and robot calibration. However, laser trackers are expensive, and the corresponding solution procedure is very complex. The influence of measurement uncertainties is also significant. This study proposes a three-dimensional space position measurement system which consists of two tracking modules, a zero tracking angle return subsystem, and a target quadrant photodiode (QPD). The target QPD is placed on the object being tracked. The origin locking method is used to keep the rays on the origin of the target QPD. The position of the target QPD is determined using triangulation since the two laser rays are projected onto one QPD. Modulation and demodulation are utilized to separate the coupled positional values. The experiment results show that measurement errors in the X, Y, and Z directions are less than ±0.05% when the measured object was moved by 300, 300, and 200 mm in the X, Y, an...

Note: Development of a high resolution six-degrees-of-freedom optical vibrometer for precision stage

Abstract: A high resolution six degrees of freedom (6-DOF) optical vibrometer is proposed. 6-DOF vibrations can be simultaneously measured using the proposed optical vibrometer, which reduces measurement time and number. The performance of the proposed vibrometer is verified by experiments. The results show that the accuracy of the proposed optical vibrometer is ±30 nm/200 nm and ±0.04 arcsec/0.1 arcsec at 1000 Hz.

Characteristics of photodetectors with TiO 2 nanorod arrays

Abstract: TiO 2 is one of most widely studied and important materials for science application. A photodetectors (PDs) with TiO 2 nanorod arrays (TNAs) has been fabricated and characterized in this work. We report that the UV response of such a PDs has been enhanced about 4 orders of magnitude. This giant enhancement in photoresponsivity can be attributed to TNAs, because TNAs provide a directed path for electrical transport and increase optical absorption. The results indicate that TNAs are useful and attractive in the application of UV detectors.

Research on the Flows of Backspin Movement in Table Tennis

Abstract: This study discuss the distribution of the flows when the forced convection impacted on the spin and the static in table tennis; the research method is using the thermal flow in the experiment which the thermal flow will reflect according to the imaging principle when it passes through the spin sphere; this can be used to simulate the flows of balls in static condition and backspin ball in high-speed and low-speed rotation; the air flow passes through the spin sphere and generates the ball pressure which forms the quality variation of the spheres in table tennis competition; the results showed that it has a lower drag force, low fluid momentum and lower rectilinear speed when the sphere is in static condition , low Reynolds number; on the contrary, it has a higher drag force and increasing rectilinear speed of flows when the Reynolds number is high. When the ball is in backspin condition, the flows are symmetrical presented, and then the flows are gradually distributed, asymmetrical presented and are upward. The higher the Reynolds number is, the smaller the wake region is due to that the forced convection effect increased; the smaller the Reynolds number is, the ball will have more significant spin kinetic energy increasing rate when the spin speeds up.