57 research outputs found
Fei xian xing jie zhi he wai jia jing tai ci chang dui biao mian deng li zi se san guan xi de ying xiang
No full textLi, Ming Yip = 非線性介質和外加靜態磁場對表面等離子色散關係的影響 / 李銘業.Thesis M.Phil. Chinese University of Hong Kong 2014.Includes bibliographical references (leaves 88-91).Abstracts also in Chinese.Title from PDF title page (viewed on 01, November, 2016).Li, Ming Yip = Fei xian xing jie zhi he wai jia jing tai ci chang dui biao mian deng li zi se san guan xi de ying xiang / Li Mingye
Two-dimensional MoS₂ transistor and heterojunction synthesized by chemical vapor deposition
No full textSince the disclosure of the excellent carrier mobility in ultrathin monolayer graphene in 2004, an astounding amount of attention in the area of ultrathin two-dimensional (2D) semiconductor materials has been aroused. Molybdenum disulfide (MoS2), as a typical member of 2D transition-metal dichalcogenides (TMDs), has attracted significant research interest due to it prevailing over graphene in terms of acquiring a semiconducting band gap with layer-number-dependent properties. Most of the findings on MoS2-based devices were usually firstly demonstrated by exfoliated MoS2 because this is a fast and easy method of investigating the properties of MoS2 prototypes. Nevertheless, devices fabricated using micro-mechanical exfoliation or layer transfer are not preferred in manufacturing as the processes involved are complicated and result in an uncertain size, layer number and location of transferred MoS2. Chemical vapor deposition (CVD) has been indicated as a reliable and promising synthesis method of MoS2 with a comparable electrical performance to that of its natural crystals. This method can be used for deposited monolayers, discrete triangular islands and also continuous films from thin layers to thick layers. In this thesis, MoS2 isolated triangular islands on SiO2/Si substrate and large area continuous thin film on SiO2/p-GaN/Si substrate were grown independently using selectable CVD growth of MoS2 in a home-built furnace set-up. Back-gated FETs as well as top-gated FETs based on as-grown MoS2 triangular islands were fabricated and investigated on SiO2/Si substrate, while top-gated FETs and semiconductor/insulator/semiconductor (SIS) heterojunction diodes constructed from as-grown MoS2 few-layer film were also prepared and studied on SiO2/p-GaN/Si substrate. The FET devices on both substrates show a clear current saturation characteristic, which is crucial for its utilization in most circuit applications. For the SIS heterojunction diodes on SiO2/p-GaN/Si substrate, clear current-rectifying characteristics were shown, which are barely seen for devices based on as-grown MoS2 without layer transfer. This sheds light on future applications for large scale 2D heterostructure devices.</p
Two-dimensional MoS2 transistor and heterojunction synthesized by chemical vapor deposition
No full textInterface passivation and trap reduction via hydrogen fluoride for molybdenum disulfide on silicon oxide back-gate transistors
No full textLayered semiconductor molybdenum disulfide (MoS2) has recently emerged as a promising material for flexible electronic and optoelectronic devices because of its finite bandgap and high degree of gate control. Here, we report a hydrogen fluoride (HF) passivation technique for improving the carrier mobility and interface quality of chemical vapor deposited monolayer MoS2 on a SiO2/Si substrate. After passivation, the fabricated MoS2 back-gate transistors demonstrate a more than double improvement in average electron mobility, a reduced gate hysteresis gap of 3 V, and a low interface trapped charge density of ~5.8 × 1011 cm−2. The improvements are attributed to the satisfied interface dangling bonds, thus a reduction of interface trap states and trapped charges. Surface x-ray photoelectron spectroscopy analysis and first-principles simulation were performed to verify the HF passivation effect. The results here highlight the necessity of a MoS2/dielectric passivation strategy and provides a viable route for enhancing the performance of MoS2 nano-electronic devices
Transistors and tunnel diodes enabled by large-scale MoS<sub>2</sub> nanosheets grown on GaN
No full textWe report growth, fabrication, and device results of MoS2-based transistors and diodes implemented on a single 2D/3D material platform. The 2D/3D platform consists of a large-area MoS2 thin film grown on SiO2/p-GaN substrates. Atomic force microscopy, scanning electron microscopy, and Raman spectroscopy were used to characterize the thickness and quality of the as-grown MoS2 film, showing that the large-area MoS2 nanosheet has a smooth surface morphology constituted by small grains. Starting from the same material, both top-gated MoS2 field effect transistors and MoS2/SiO2/p-GaN heterojunction diodes were fabricated. The transistors exhibited a high on/off ratio of 105, a subthreshold swing of 74 mV dec-1, field effect mobility of 0.17 cm2 V-1 s-1, and distinctive current saturation characteristics. For the heterojunction diodes, current-rectifying characteristics were demonstrated with on-state current density of 29 A cm-2 and a current blocking property up to -25 V without breakdown. The reported transistors and diodes enabled by the same 2D/3D material stack present promising building blocks for constructing future nanoscale electronics.</p
The Hong Kong version of Montreal Cognitive Assessment for the Visually Impaired (HKMoCA-VI): Proposed cut-off and cognitive functioning survey of visually impaired elderly in residential homes.
No full textBackgroundVisual impairment has been strongly associated with the incidence of dementia. Appropriate cognitive screening for the elderly with visual impairment is crucial for early identification of dementia and its management. Due to challenges in processing visually presented stimuli among participants, the cut-off score of the Hong Kong version of the Montreal Cognitive Assessment for the Visually Impaired (HKMoCA-VI), also known as MoCA-BLIND or MoCA-22, was unknown. Besides, the cognitive status of elderly with visual impairment residing in care homes is rarely investigated. The current study aimed to 1) establish the cut-off score for HKMoCA-VI and 2) examine the general cognitive functioning of elderly with visual impairment living in residential homes in Hong Kong in terms of MoCA-VI percentile scores.MethodHKMoCA-VI and the Cantonese version of the Mini-Mental State Examination (CMMSE) were administered to 123 visually impaired elderly residents in care homes in Hong Kong. Percentile scores of HKMoCA-VI by age and education level were determined, and the concurrent validity, sensitivity, and specificity of HKMoCA-VI were assessed.ResultsA cut-off score 12 was suggested for HKMoCA-VI, which yielded a sensitivity and specificity of 89.29% and 83.58%, respectively. Moreover, it strongly correlated with CMMSE, indicating satisfactory concurrent validity.ConclusionsHKMoCA-VI is suggested to be a viable cognitive screening tool for elderly individuals with visual impairment in residential homes. Further modifications to enhance the sensitivity and specificity of the measure are proposed
Di li kong jian de yi yi: Zhu Tianwen xiao shuo zhong de "xing lü" shu xie yan jiu = The meaning of geographical spaces : a study of travel writing in Chu Tien Wen’s fiction
No full textPh.D.朱天文是當代台灣重要的作家之一。朱天文從七十年代開始創作，並與文友成立「三三文學集團」，出版《三三集刊》，影響力遍及亞洲。朱天文曾出版五本短篇小說集、兩部長篇小說與四本散文集，其中第一部長篇小說《荒人手記》奪得「時報百萬小說獎首獎」，奠定她在文壇的地位。朱天文的作品不僅受到台灣文學界的重視，更被翻譯為英文、法文、日文，在國際文壇亦得到好評。除文學創作，朱天文還長期擔任侯孝賢、陳坤厚等台灣導演的編劇，是現時少數同時兼及文學與電影創作的作家。現時研究朱天文小說的方向多集中在性別、國族、身份、「張派」等，一般忽略朱天文小說中跨地域、跨文化的特質，而這正是「行旅」所關注的重心。在朱天文的小說中，「行旅」不限於觀光，還包括朝聖、離散，更可以是在想像或虛擬的時空中移動。故此本論文以「行旅」這個議題出發，探討朱天文小說中描述的地理位置與其相關意義，從而展示空間與人物心理狀態的微妙關係。本論文共分七章。第一章為導論，簡介本論文的研究目的、方法與主題。第二章至第六章以朱天文小說為分析對象，每章節的討論線索都以朱天文小說中重複書寫的地理空間為主。第二章從具有宗教情調的「印度」，看朱天文如何看待朝聖與「行旅」的關係。第三章探討「香港」這個商業化的都市，如何影響朱天文小說中人物的行為與心理。第四章討論的「日本」與朱天文生活的台灣關係較為複雜，在殖民文化的影響下，朱天文有意或無意地對保留與發揚傳統文化的日本表達欣賞與讚歎。第五章以「中國」為主要分析的地理位置，顯示不同時代的人物，在離散返鄉後的內心變化。第六章回到朱天文當下生活的「台灣」，科技媒介已經滲入台灣生活的各個部分，如何溝通成為現代人的一大問題，朱天文對這類現代文明表達深切的焦慮。第七章總結上述各章的分析，可見朱天文的小說中除了細緻地描述這些地理空間的獨特風貌，還透過「行旅」過程呈現生活的情感與意義。Chu Tien Wen is one of the most important writers in Taiwan. Her first novel “huangren shouji” (荒人手記) received the first prize of the “shibao baiwan xiaoshuo jiang” (時報百萬小說獎), which established her position in the literary scene. Chu was also one of the founders of the significant literary association “san san literary group ” (三三文學集團), which published the influential journal “san san jikan” (《三三集刊》). Chu has published five short story collections, two novels, and four prose collections up- to- date. Her works are well-received not only in Taiwan, but also throughout the world with their English, French and Japanese translation. Chu is also a scriptwriter working with renown Taiwan directors, such as Hou Hsiao Hsien (侯孝賢)and Chen Kun Hou(陳坤厚).The existing research on Chu mainly focuses on gender, nationality, identity, and the “school of Chang” (the followers of Eileen Chang), while the notion of “travel,” including the intercultural and interregional characteristics of Chu’s works, has received little attention. In Chu’s fiction, “travel” means more than just tourism, or other kinds of “physical” travel, e.g. pilgrimage, diaspora, etc. Chu expands the definition of “travel” to “virtual” travel. For this reason, this thesis aims to study the topic of “travel” in Chu’s fiction. By analyzing the features of different geographical spots in the fiction of Chu, this thesis explains the subtle relationship between spaces and the inner states of the respective characters.This thesis comprises seven chapters. Chapter one introduces the area of study, objectives, methodology and defines the main concept of the thesis – “travel.” The major part of the thesis, chapters two to six, investigate Chu’s fictional works. Each chapter explores a place where Chu has written about twice or more. Chapter two concentrates on the discussion of a religious nation, India, so as to show how Chu distinguishes the difference between pilgrimage and travel. Chapter three analyses how the commercial city, Hong Kong, affects the behavior and psychology of the characters in Chu’s fiction. Chapter four focuses on the colonizer of Taiwan – Japan. Therein, Chu shows her exclamation and appreciation of the traditional Japanese culture. Chapter five raises a discussion on China, with special interest on the matter of location. It reveals that the different backgrounds of the Chinese causes them to have different experiences after “returning home.” Chapter six examines Taiwan, a key place in the fiction by Chu. In Chu’s understanding of Taiwan, the development of technology is an essential issue; however, Chu has expressed reservations for such technological development as it appears to hinder the effectiveness of communication. Chapter seven concludes the study. Chu’s fiction not only notices and describes the uniqueness of different geographical spaces, but also shows its affections toward life through “travel.”葉嘉詠.Parallel title from added title page.Thesis Ph.D. Chinese University of Hong Kong 2009.Includes bibliographical references (leaves 215-231).Abstracts in English and Chinese.Title from PDF title page (viewed on April 20, 2020).Ye Jiayong
Selectable synthesis of 2-D MoS2 and its electronic devices : from isolated Triangular Islands to large-area continuous thin film
No full textWe report on the controllable and selectable synthesis of two-dimensional (2-D) molybdenum disulfide (MoS2 ) by molybdenum trioxide sulfurization with chemical vapor deposition. By controlling the sulfurization timing and substrates positions, the selectable growth of MoS2 isolated triangular islands and continuous thin film was successfully performed independently with the same home-built furnace setup. Also, we found that the hydrofluoric acid substrate treatment took effects on MoS2 nucleation seed densities and modulated the sizes of the triangular islands. Atomic force microscopy and Raman and photoluminescence spectroscopy were used to characterize and compare the properties of MoS2 triangular islands and continuous thin film. The MoS2 triangular islands were monolayers and highly crystalline in nature; where the continuous thin film was formed by small grain size MoS2 nanosheets with smooth surface morphology and a large covered area of up to centimeters. Back-gated field effect transistors (FETs) of as-grown MoS2 triangular islands and continuous thin film were fabricated to analyze their electrical properties. The electron mobilities were measured to be 11.42 and 4.04 cm2/V·s respectively, and with an excellent on/off current ratio up to over 108, which demonstrated the good quality of the as-grown MoS2 samples. Furthermore, both the MoS2 triangular islands and continuous thin film FETs exhibited a near ideal current saturation characteristic, which shows the real potential of future applications for 2-D electronic devices.Department of Applied Physic
Structural and Functional Insights into the Pilotin-Secretin Complex of the Type II Secretion System
No full textPMCID: PMC3276575This is an open-access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited
Predicting adherence to antiretroviral therapy and retention to HIV care : effects of baseline biopsychosocial status and neuropsychological functioning
No full textThese drugs have demonstrated efficacy in improving immune function and reducing HIV-related morbidity and mortality, and while a cure is not available, patients on treatment may live longer, healthier lives. However, early optimism has been tempered by the growing recognition that meticulous adherence is a prerequisite for optimal clinical response and prevention of drug resistance
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