We have implemented the time-resolved technique at frequency domain on a laser scanning microscope to investigate light emitting diodes. Leds are not high-speed device, so we use e-o modulator to change its frequency of Laser and finish the experiment. In this way, temporal response of a device can be mapped at high spatial resolution. We are using a Ti : sapphire laser and a high frequency phase sensitive lock-in loop to achieve time-resolved the dynamics properties of the light emitting devices.Laser used to excite carriers in the depletion region detected form the contract signal for scanning imaging. We can observe the OBIC effect and measure the response time of light emitting devices.

The fabrication characteristic of focused ion beam (FIB) for fused quartz was investigated. With the progress of nanotechnology, new technologies and devices are invented constantly. In nanofabrication, FIB has several advantages such as high material removal rate, high resolving power and direct fabrication in some selected areas without etching mask. Therefore, it had been studied in detail to fabricate nano-structures by FIB. In this study, we found out the effect of nano-machining by adjusting the parameters of FIB system such as: beam current, overlap, and dwell time. The fabricated features together with their surface morphology and profile were investigated by scanning electron microscope (SEM) and atomic force microscope (AFM). Results show that when beam current was smaller, overlap was 50% and dwell time was 10£gs could get best performance by FIB.

Ocean ambient noise is one of factors that can affect the performance of sonar and underwater communication system, it can degrade the performance of sonar system on listening or active detection, and also can affect the quality of underwater communication. Due to the variation of temperature and density in the ocean which make ambient noise has directionality. Beamforming can analyze the directionality of noise energy. Conventional beamforming is based on the assumption of plane wave sound field, so the energy from each angle is obtained by linear accumulation of every element. However plane wave assumption may not be satisfied because of the boundary interactions of sound propagation and energy attenuation of water column, therefore conventional beamforming may have poor beam resolution and SNR in applications. This research is to study of the influence of spatial coherence of ambient noise on beam resolution, and to improve the beam resolution by using the adaptive algorithm from the communication system theory. Firstly, simulations were performed to study spatial coherence between plane wave and non-plane wave in ambient noise, and the results were compared with beam resolution. This research also analyzes the influence of different conditions of noise spatial coherence on beamforming with ASIAEX data. The results showed that ambient noise has lower spatial coherence at high frequency, and the beamforming has poor beam resolution because of the lower spatial coherence in noise. Therefore, the adaptive beamforming were performed to improve the beam resolution, and compared with the conventional beamforming. The results showed that the highest improvement on beam resolution is 42.9 %, and increased SNR by 6 dB. On the other hand, the application of ASIAEX data show that, the highest improvement on beam resolution is 40.0 %, and increased SNR by 8 dB. The noise notch of ambient noise became more significant by increasing in beam resolution, and it also promoted the accuracy of analysis on noise directionality.

We have observed a large spin-splitting in device made of AlxGa1-xN/GaN quantum wires. Based on this observation, we proposed a new spintronic application, the spin-hall quantum-ring interferometer, by the spin-Hall effect, Rashba and Dresselhaus effects. This device we use the ICP Etch System to etch the contact pattern, and then use the Multi-Target Sputter to deposit the protecting layer, and then use the E-Beam Evaporator to make the contact. Finally, using the Focus Ion Beam, we fabricate the quantum-ring and gate successfully. This thesis is focused on discussing the design of the fabrication and try to solve the problem in order to be able to detect the signal of the quantum-ring interferometer at low temperature and high magnetic condition.

<p>This thesis describes the development, characterization andoptimization of compact, high-brightness, liquid-jet-targetx-ray sources. Two different source types have been developedfor different wavelength regions and applications.</p><p>A laser-plasma source for generating soft x-ray andextreme-ultraviolet radiation has been further developed forsoft x-ray microscopy and extreme-ultraviolet lithography. Thiswork focused on improved target stability, increased conversionefficiency and decreased debris production. For x-raymicroscopy applications using carbon-containingliquid-jetdroplet targets, the droplet stability has beeninvestigated and a method for source stabilization introduced.This source has also been optimized in terms of flux per debriswith respect to target material and size. Forextreme-ultraviolet lithography applications, aliquid-xenon-jet-target laser-plasma source system has beengreatly improved, especially in terms of stability andconversion efficiency. This source has also been characterizedin terms of, e.g., source size, angular distribution, andrepetition-rate capability. For extremeultraviolet lithography,the possible use of tin as a target material has also beenstudied and conversion efficiency and debris measurementsperformed.</p><p>A new anode concept for electron-impact hard x-ray sourcesbased on high-speed liquidmetal jets has been introduced.Initial calculations show that this new target concept couldpotentially allow more than a hundred-fold increase in sourcebrightness compared to existing state-of-the-art technology. Alow-power, proof-of-principle, experiment has been performed,verifying the basic source concept. Scaling tohigh-poweroperation is discussed and appears plausible. A main obstaclefor high-power operation, the generation of a microscopichigh-speed jet in vacuum, is investigated usingdynamic-similarity experiments and shown to be feasible.Finally, initial medium-power experiments, approaching currentstate-of-the-art sources in terms of brightness, have beenperformed.</p>

The Institute of Ion Beam Physics and Materials Research (IIM) is one of the six institutes of the Forschungszentrum Dresden-Rossendorf (FZD), and contributes the largest part to its Research Program \"Advanced Materials\", mainly in the fields of semiconductor physics and materials research using ion beams. The institute operates a national and international Ion Beam Center, which, in addition to its own scientific activities, makes available fast ion technologies to universities, other research institutes, and industry. Parts of its activities are also dedicated to exploit the infrared/THz free-electron laser at the 40 MeV superconducting electron accelerator ELBE for condensed matter research. For both facilities the institute holds EU grants for funding access of external users.

Thesis (Ph. D.)--University of Hong Kong, 2001. / Includes bibliographical references (leaves 95-100).

Thesis (M.S.)--West Virginia University, 2002. / Title from document title page. Document formatted into pages; contains xi, 105 p. : ill. Includes abstract. Includes bibliographical references (p. 100-105).

Thesis (M. Phil.)--University of Hong Kong, 2002. / Includes bibliographical references (leaves 75-77).

A ”Haptic servo system” is here understood as a servo system whereforces from a controlled system are fed back to an operator. This thesis workis a design work where the work among other things comprises the choice ofsuitable motors, one for operating the beam and another one for operatingthe steering wheel. Data for the beam and ball are assumed to be known.Data for the feed back torque to the steering wheel is assumed to be specifiedin advance. Two models to represent the human response are suggested. Asimulation study is carried out to show that the system works according tosome specification. The ball and beam process is simulated with hardwarein the loop. The hardware in the loop is a Maxon motor. The motor is usedas the steering wheel and the motor will also propagate the torque feedbackto the operator.The task of the thesis work could then be formulated as: Can a human, withtorque feedback, manually control the ball on the beam without looking atthe ball and the beam?