High Performance Gallium Tin Zinc Oxide Thin Film Transistors By Rf Magnetron Sputtering

With the growing need for large area display technology and the push for a faster and cheaper alternative to the current amorphous indium gallium zinc oxide (a-IGZO) as the active channel layer for pixel-driven thin film transistors (TFTs) display applications, gallium tin zinc oxide (GSZO) has shown to be a promising candidate due to the similar electronic configuration of Sn4+ and In3+. Post deposition annealing at 450 °C of the films in air was found to lead to a high atomic concentration of Sn4+ in the films as ascertained by x-ray photoelectron spectroscopy, which is one of the prerequisites for improved performance of the device. In this work a systematic and detailed study of GSZO TFTs with the channel annealed at 450°C has been carried out, and different effects have been investigated, including: oxygen flow, deposition contacts, further annealing in different ambients and presence of passivation layer on the TFT performance. The electrical and optical stability of the GSZO TFTs have also been the subject of study. These studies provided a more insight into the role of surface and interface states on the TFT performance and its degradation mechanism under stress. Improved device performance with VON of -3.5 V, ION/IOFF of 108, μFE = 4.36 V-1 s-1, and sub-threshold swing (SS) of 0.38 V/dec has been achieved, which is close to those of industrial standard IGZO TFTs. Thus, this work demonstrates GSZO based TFTs as a promising and viable option to the IGZO TFTs

Optimization in multi-relay wireless networks

The concept of cooperation in communications has drawn a lot of research attention in recent years due to its potential to improve the efficiency of wireless networks. This new form of communications allows some users to act as relays and assist the transmission of other users' information signals. The aim of this thesis is to apply optimization techniques in the design of multi-relay wireless networks employing cooperative communications. In general, the thesis is organized into two parts: ``Distributed space-time coding' (DSTC) and ``Distributed beamforming', which cover two main approaches in cooperative communications over multi-relay networks. In Part I of the thesis, various aspects of distributed implementation of space-time coding in a wireless relay network are treated. First, the thesis proposes a new fully-diverse distributed code which allows noncoherent reception at the destination. Second, the problem of coordinating the power allocation (PA) between source and relays to achieve the optimal performance of DSTC is studied and a novel PA scheme is developed. It is shown that the proposed PA scheme can obtain the maximum diversity order of DSTC and significantly outperform other suboptimal PA schemes. Third, the thesis presents the optimal PA scheme to minimize the mean-square error (MSE) in channel estimation during training phase of DSTC. The effect of imperfect channel estimation to the performance of DSTC is also thoroughly studied. In Part II of the thesis, optimal distributed beamforming designs are developed for a wireless multiuser multi-relay network. Two design criteria for the optimal distributed beamforming at the relays are considered: (i) minimizing the total relay power subject to a guaranteed Quality of Service (QoS) measured in terms of signal-to-noise-ratio (SNR) at the destinations, and (ii) jointly maximizing the SNR margin at the destinations subject to power constraints at the relays. Based on convex optimization techniques, it is shown that these problems can be formulated and solved via second-order conic programming (SOCP). In addition, this part also proposes simple and fast iterative algorithms to directly solve these optimization problems

Enhance the trust of citizen on government by applying electronic government services

There is the trend that trust of citizens in the government declined from over the world because of many of reasons. It requires many efforts from government to rebuild the confidence of the people in the government system. The topic of this thesis relates to enhancing the trust of the citizen on government by applying electronic government services. This thesis employs qualitative and quantitative methods to conduct the research. When we finish this study, we revealed that the e-service quality, public administration and attitude of citizens towards e-government affect the trust of people in the government system of Ho Chi Minh City. Based on the findings of this research, policy makers, public sector managers can concentrate on the improvement of e-service quality, civil service and the attitude towards e-government to enhance the trust of citizens in government. Shortly, other researchers, managers in the public sector in Ho Chi Minh City can do further research on this topic. It would be very meaningful to rebuild, to gain the trust of the public in government

An Alternative Approach to Classify Illegal Logging: The Case in Vietnam

This article examines the different kinds of illegal logging that takes place in Vietnam, challenging the typical approaches to understanding and classifying the various criminal activities involved. We argue that either overlooking the classification of illegal logging or relying solely on illegal timber volumes and legal descriptions to categorise the crime is not sufficient to comprehend its diverse nature. This leads to inappropriate measures to tackle the crime. Instead, this study suggests that illegal logging should be categorised into three types, which are fundamentally distinctive, not only with regard to the volumes of illicit timber and the legislative definitions of the crime, but also (and more importantly) with reference to the attributes of harvesters, the degree of their involvement and their motivations, and the level of organisation involved in criminal commissions