Fabrication and Antireflection properties of Biomimetic GaAs nanograss

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活動日期：101 年 5 月 19 日(星期六)

活動地點：日月山景農場(彰化市水月台路 218 號) 活動網址：http://140.120.11.1/LDS/index.htm 主辦單位：彰化師範大學科技研究總中心

彰化師範大學台灣自旋科技研究中心彰化師範大學物理系

協辦單位：中興大學物理學系東海大學物理學系嘉義大學電子物理學系

中正大學台灣自旋科技研究中心雲林科技大學台灣自旋科技研究中心聯絡人：吳憲昌助理教授、蕭輔力助理教授

技術委員：洪連輝教授、吳仲卿教授、石豫臺副教授秘書：陳奕樺小姐、潘昭倩小姐

地點：日月山景農場(彰化市水月台路 218 號)

電話：04-7370949

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如何前往：

1、從彰化市來的遊客:

路線一：可由公園路→虎崗路→環山路→看到台 74 甲線紅綠燈左轉即可看到本農場指示標。

路線二：可由中興路(往彰化縣體育場)→寶山路→環山路→看到台 74 甲線紅綠燈左轉即可看到本農場指示標。

2、南彰化的遊客：

可走省道台一線中山路北上，至花壇時可看到右轉往台中(台 74 甲線彰化市東外環) 指示標，右轉延路均有本農場指標，本農場位於台 74 甲線彰化市東外環旁。

3、台中或走國道三號下快官交流道的遊客：

可下快官交流道下快官匝道後，接中彰快速道路(台 74 線)直行進入東外環道(台 74 甲線)，即可到達本農場。本農場位於東外環右手邊。

4、本農場水月台路為新編道路名稱，某些導航業者並未將此道路更新到導航軟體內，請遊客先行更新衛星導航圖資，確認圖資為最新版本輸入座標前，請先確認衛星導航座標格式是否為度分秒，農場座標為：N 24 度 03 分 22.3 秒；E 120 度 35 分 12.9 秒

會議地點

用餐地點

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8:30~9:00 Registration

9:00~9:10 Opening Ceremony 9:10~10:00 Lecture

彭維鋒教授

Photo-conductivity and electronic structures of Au-nanoparticle embedded silica-nanowire system Chair：吳仲卿教授

10:00~ 10:10 Break

Session A Chair：徐嘉宏博士

Number Time Speaker Title

A 1* 10:10 ~ 10:35 ^Strikanth_Ravipati Fabrication and Antireflection properties of Biomimetic GaAs nanograss

A 2 * 10:35 ~ 11:00 ^李玟頡 Atomistic simulation for C84 monolayer on Silicon (111) surface under nanoindentation

A 3 11:00 ~ 11:15 林宥宸 Measurment and applications of synthesized zinc oxide nanowires A 4 11:15 ~ 11:30 胡晉瑋 Modulation-bias-induced image distortion in Scanning

Capacitance Microscopy

A 5 11:30 ~ 11:45 古硯涵 Properties of nano-rod tips deposited by a scanning electron beam

A 6 11:45 ~ 12:00 余政德 Effects of thermal annealing on P3HT-PCBM solar cells 12:00 ~ 13:30 Lunch & Photo

Session B Chair：郭政宜博士候選人

B 1* 13:30 ~ 13:55 李柏瀚 A study of field enhancement factors of closed single-walled carbon nanotubes enhanced by Cs adsorption

B 2* 13:55 ~ 14:20 蘇志川 Defects Induce Water Adsorption and Dissociation on ZnO Surface

B 3 14:20 ~ 14:35 翁怡鍵 The exchang coupling between ferromagnetic layers in

CoFeB/MgO/CoFeB tunnel structure with perpendicular magnetic anisotropy

B 4 14:35 ~ 14:50 陳柏羽 Characterization of conductive AFM probes with a coating of a Pt layer

B 5 14:50 ~ 15:05 ^黃瑞傑 Well vertically aligned Fe-doped ZnO nanorods array grown by

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Session C Chair：趙建都博士候選人

C 1* 15:45 ~ 16:10 黃昭憲 Study of vortex configuration and switching behavior in submicro-scaled asymmetric Permalloy ring

C 2 16:10 ~ 16:25 ^王正侖 The study of large-area antidot array of magnetic nanostructure on AAO template

C 3 16:25 ~ 16:40 ^蔡宗存 Particle blockade sensing in a flow by using microwave resonators C 4 16:40~ 16:55 ^王新斐 Magneto-optical characteristics of nanostructured magnetic thin films C 5 16:55~ 17:10 ^張嘉訓 Fluorescence quenching of quantum dots on luminant silver

nanoparticles

17:10~17:30 Closing Remarks Chair：洪連輝教授

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Photo-conductivity and electronic structures of Au-nanoparticle embedded silica-nanowire system

W. F. Pong (彭維鋒)

Department of Physics, Tamkang University, Tamsui, Taiwan

Abstract

Silica nanowires (SiO_x-NWs) embedded with Au peapods have been studied by energy-filtered scanning transmission electron microscopy (EFTEM), O K- and Au L₃-edge x-ray absorption near-edge structure (XANES) and extended x-ray absorption fine structure (EXAFS), x-ray emission spectroscopy (XES) and scanning photoelectron microscopy. XANES and XES data show that band gaps of Au-peapod embedded and pure SiO_x-NWs were 6.8 eV. In additional, XANES and EXAFS results indicate illumination induced electron transfer from Au-peapod to SiO_x-NWs and does not show any feature attributable to the formation of Au-Si bonding in the Au peapod embedded in SiO_x-NWs with or without illumination. Photo-response and EFTEM measurements show that green light has more significant enhancement of photo conductivity than red and blue light due to surface plasmon resonance and suggest that transport of electrons across SiO_x-NWs is via Mott-variable-range hopping mechanism through localized or defect states.

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A1*

Fabrication and Antireflection properties of Biomimetic GaAs nanograss

Srikanth Ravipati,¹ Jiann Shieh,² Fu-Hsiang Ko,¹ Chen-Chieh Yu,³ Hsuen-Li Chen,³ Chia-Tien Wu,¹ and Szu-Hung Chen⁴

1Institute of Nanotechnology, Department of Materials Science & Engineering, National Chiao Tung University, Hsinchu 30010, Taiwan (ROC).

2Department of Materials Science & Engineering, National United University, Miaoli 36003, Taiwan (ROC).

3Department of Materials Science and Engineering, National Taiwan University, Taipei 10617, Taiwan (ROC).

4National Nano Device Laboratories, Hsinchu 30078, Taiwan (ROC).

Abstract

The fabrication of GaAs nanograss with diameter less than 20 nm to mimic the moth-eye structure have been demonstrated using a simple, one-step, and mask-less plasma etching based approach. The GaAs nanograss exhibits remarkable broadband antireflection properties, which arise from the graded refractive index between air and GaAs substrate by nanograss layer. Moreover, GaAs nanograss show less sensitivity to transverse electric polarized light and transverse magnetic polarized light over a wide range of incident angles compared to the strong variation in bare GaAs substrate. These effects show an enhanced absorption of 98%-100% as the incident energy is larger than the GaAs band gap (λ=240-873 nm) and 72%-98% at incident energy less than the band gap (λ=873-2400 nm) for sub-20 nm GaAs nanograss with a length ~200 nm. Our simple, one-step, and mask-less plasma etching method opens up promising approach for the direct implementation of broad omnidirectional antireflective surfaces on solar cells and various optoelectronic devices to improve the device performance.

References

1. M. C. Yang, J. Shieh, C. C. Hsu and T. C. Cheng, Electrochem. Solid-State Lett., 8, C131, (2005).

2. S. Ravipati, C. J. Kuo, J. Shieh, C. T. Chou and F. H. Ko, Microelectro. Relia., 50, 1973, (2010).

3. Y. M. Song, S. J. Jang, J. S. Yu and Y. T. Lee, Small, 6, 984, (2010).

4. Y. M. Song, S. Y. Bae, J. S. Yu and Y. T. Lee, Opt. Lett., 34, 1702, (2009).

Figure 1. Measured reflectance at an angle of incidence of 5° as a function of wavelength for different etching times of GaAs nanograss.

Figure 2. Angle-dependent reflectance of AOI covering 20 to 60 at 400 nm, 600 nm and 800 nm.

The TE and TM polarization of bare GaAs and 120 min etched samples are presented.

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A2*

Atomistic simulation for C

84

monolayer on Silicon (111) surface under nanoindentation

Wen-Jay Lee (李玟頡)¹ , Wan-Sheng Su(蘇萬生)^1,2*,Chih-Chuan Su(蘇志川)² and Mon-Shu Ho(何孟書)^2,3*

1National Center for High-Performance Computing, Hsin-Shi, Tainan 74147, Taiwan

2Department of Physics, National Chung Hsing University, Taichung 402, Taiwan

3Center of Nanoscience and Nanotechnology National Chung Hsing University, Taichung 402, Taiwan.

Abstract

In this work, molecular dynamics (MD) was employed to investigate the nanoindentation of the C84 monolayer embedded on the Si(111) surface. LAMMPS, an open source software, was employed to perform our simulation. In the calculations, Tersoff and AIREBO potentials were utilized to describe the Si-Si, Si-C, and C-C interactions. The reported hardness and Young’s modulus of the substrate are derived from the force-distance curves of indentation. Our findings reveal that the hardness of such Si(111) surfaces with embedded C84 monolayer is softer than that of the pure Si(111) surface. Moreover, the resulting structure of the C84 monolayer under indentation is explored and presented. Finally, the deformed C84 molecules behave like a punctured soccer, which significantly influences the slop of the force-distance curves.

Figure 1 Force-distance curve for C84 monolayer on Si(111) surface under nanoindentation.

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A3

Measurment and applications of synthesized zinc oxide nanowires

Y.-C. Lin(林宥辰), W.-H. Chen(陳韋豪), M.-S. Ho(何孟書)

Department of Physics, National Chung Hsing University, Taichung 402, Taiwan

Abstract

In recent years, many researches are fabricated the photoelectric sensor based on Zinc Oxide nanowires, because ZnO is a direct wide-band gap semiconductor. In this report, we use Vapor-liquid-solid method to fabricate ZnO nanowires and control different growth factors to adjust the size of ZnO for nanowire device manufacture.

We use different analyzing instruments to determine the material properties. scanning electron microscope (SEM) was used to determine the morphology, energy dispersive spectrometer (EDS) was used to determine the composition, transmission electron microscope (TEM) and X-ray diffraction (XRD) were used to determine the crystal structure and grown orientation. After all, we used focus ion beam (FIB) to deposit Pt Electrodes and used four-point probe measurement system to determine the electronic properties.

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A4

Modulation-bias-induced image distortion in Scanning Capacitance Microscopy

Chin-Wei Hu and Mao-Nan Chang

Department of Physics, National Chung Hsing University, Taichung 402, Taiwan

Abstract

Direct observation of electrical junctions provides important informations for electronic devices, [1] such as junction widths, carrier concentration distributions, channel lengths, and electrical uniformity. Typically, scanning capacitance microscopy (SCM) can qualitatively provide images regarding the above informations. Unfortunately, it has been found that photoperturbations from the SCM setup may distort SCM images of electrical junctions. [2] In this work, we employed a dark-mode SCM to avoid photoperturbations and used a solid-metal probe to investigate the influence of the SCM modulation bias on the observed junction images. The negligible impedance of solid-metal probes allowed us to precisely control the modulation biases and to obtain higher signal intensities. With the dark-mode SCM, it is revealed that higher modulation biases may narrow the observed junction regions and distort the images of carrier concentration profiles. In addition, our experimental results also suggested that dark-mode SCM with a solid-metal probe working at a modulation bias lower than 0.4 V is a reliable setup for the SCM measurements on electrical junctions.

References

[1] J. J. Kopanski, J. F. Marchiando, D. W. Berning, R. Alvis, and H. E. Smith, J. Vac. Sci. Technol.

B 16, 339 (1998).

[2] M. N. Chang, C. Y. Chen, F. M. Pan, J. H. Lai, W. W. Wan, and J. H. Liang, Appl. Phys. Lett. 82, 3955 (2003).

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A5

Properties of nano-rod tips deposited by a scanning electron beam

Y. H. Ku,¹ M. N. Chang,¹ P. L. Chen,² C. Y. Su,² and C. T. Wu³

1Department of Physics, National Chung Hsing University, Taichung, Taiwan

2Instrument Technology Research Center, National Applied Research Laboratories, Hsinchu, Taiwan

3National Nano Device Laboratories, National Applied Research Laboratories

Abstract

In this work, we employed scanning electron beam induced deposition (SEBID) to deposit a high-aspect-ratio carbon nano-rod at the tip apex of an atomic force microscopy (AFM) probe and investigated the chemical and mechanical properties of the carbon nano-rod. Electron energy-loss spectroscopy reveals that the SEBID-modified nano-rod is diamond-like carbon (DLC). The sp³/sp² hybridization ratio in EELS increases with the electron-beam accelerating voltage, implying that the increase of the electron-beam accelerating voltage may enhance the strength of the DLC nano-rod.

From the linear region of the AFM force curves, the force constant of the DLC nano-rod 200 nm in length was about 28 N/m higher than the force constant of typical silicon cantilever for tapping-mode AFM. Applying a vertical force of 1152 nN, the elastic deformation of the DLC nano-rod can be up to 39 nm even if the aspect ratio of the nano-rod tip is up to 10. It is expected that the SEBID-modified tip has enough strength and lifetime for practical AFM measurements in high-aspect-ratio and high-resolution applications.

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A6

EFFECTS OF THERMAL ANNEALING ON P3HT-PCBM SOLAR CELLS

Allen Cheng-En Cheng^1,2, Chen-Te Yu², Hua-Wei Shih², Ming-Hsien Chung², Ko-Wei Lin², Chang-Shiung Chang¹, Zingway Pei³ and Forest Shih-Sen Chien²

1Departmant of Photonics, National Chiao Tung University, Hsinchu, 301, Taiwan; 2

Department of Physics, Tunghai University, Taichung, 407, Taiwan;

3Graduate Institute of Opoelectronic Engineering, Department of Electrical Engineering, National Chung Hsin University, 402, Taichung, Taiwan

E-mail: s922143@gmail.com, fsschien@thu.edu.tw

INTRODUCTION

Recently, several researches have addressed the post-treatment effects on P3HT-PCBM solar cell. In most lectures, they claimed the post-annealing treatment leading the P3HT self-organization and PCBM diffusion to reach an optimal phase separation for the transportation of excited electrons.

Moreover, the fibrillate P3HT would increase the carrier mobility. Herein, we take a serier optical and electrical characterizations at different treatment temperature. We study the impedance spectrum of the P3HT-PCBM solar cell at each temperature to investigate the electrical properties after the post-treatment.

METHODS

The ITO/PEDOT:PSS/P3HT-PCBM/Al solar cells were used in this study. After the device preparing procedure, we characterized the optical and electrical properties in a serier post-treatment temperature, from room-temperature to 200ôC. From the photovoltaic performance measurement, we observed the highest power conservation efficiency (PCE) and short circuit current density (J_SC) at about 120ôC (Fig.1a). The highest absorption also occured at 120ôC (Fig. 1b). In addition, we discovered the higher suface roughness from the AFM morphology of the composite blend and suggested that was contributed from the P3HT self-organization.

From the optical and electrical experiments, we observed the optimal performance of polymer solar cell after a post-annealing treatment at 120^oC. We suggested such treatment would induce the P3HT self-organization and PCBM diffusion in the composite blend, resulting in the increase of carrier mobility and the appropriate phase separation respectively. We believe, that are the key points for the optimization of P3HT-PCBM solar cell

55 70

nce (%) ^RT

120^oC 160^oC 2

3 4

erage PCE (%)

PCE (b)

(a)

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B1*

A study of field enhancement factors of closed single-walled carbon nanotubes enhanced by Cs adsorption

Po-Han Lee (李柏翰)¹ and Cheng-Ying Chiang (江政穎)¹ and Wan-Sheng Su (蘇萬生)²

1 The Affiliated Senior High School of National Taiwan Normal University, Taipei 106, Taiwan

2National Center for High-Performance Computing, Tainan 741, Taiwan

Abstract

With the method of the first-principles, the effects of alkali-metal Cs adsorption on the field enhancement factors of finite-length (3,3) and (5,0) single-walled carbon nanotubes with capped ends were investigated. Calculations exhibited the fact that the field enhancement factor of pristine capped (3,3) nanotubes is slightly greater than that of pristine capped (5,0) nanotubes, mainly due to the degree of the sharpness of tubes. Moreover, through the treatment of adsorption of alkali-metal Cs, the enhanced field enhancement factors of either capped (3,3) or (5,0) nanotubes can be achieved

effectively. What we find such a manipulated process that results in the modulation of the dipoles at the tips plays a dominated role in the reduction of work functions and in the improvement of the corresponding field enhancement factors.

.

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B2*

Defects Induce Water Adsorption and Dissociation on ZnO Surface

C.-C. Su¹, S.-Y. Chang², N.-H. Yang³, C.-Y. Liu^*2 and M.-S. Ho^*1

2Department of Materials Science and Engineering, National Chung Hsing University, Taichung, Taiwan

3Department of Materials Science and Engineering, National Tsing Hua University, Hsinchu, Taiwan

Abstract

In 2011, Chang et al. found that ZnO nanostructure can spontaneously growth near the stress-caused defects of ZnO film. The process needs no precursors, chamber, oven nor other equipments. By introduce some indentations or scratches on the surface of ZnO film, the single-crystal ZnO nanostructure can spontaneously growth in ambient atmosphere at room

temperature. The adsorption and dissociation of water on defects was believed to be the first stage of the growth. A ultrahigh vacuum scanning tunneling microscope (UHV-STM) was used to observe the surface of ZnO. The status of water adsorption and dissociation on the defect of ZnO surface was also investigated.

Reference:

1. S. Y. Chang et al., Journal of Materials Chemistry 21, 4264 (2011).

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B3

The exchang coupling between ferrmagnetic layers in CoFeB/MgO/CoFeB tunnel structure with perpendicular magnetic anisotropy

Yi-Chien Weng

Abstract

磁性隨機記憶體(Magnetic Random Access Memory, MRAM)元件的發展中，垂直異向性 (Perpendicular Magnetic Anisotropy, PMA)的應用對於熱穩定性的改善是非常重要的關鍵。

MRAM 最重要的特性是必須展現出不同的高低阻態,這個重要的特性最具代表性的就是巨磁阻

（GMR, giant magnetoresistance）以及穿隧磁阻（TMR, tunnel magnetoresistance）兩種不同效應, 在結構上巨磁阻及穿隧磁阻式非常相似,都是以鐵磁層/間隔層/鐵磁層的形式呈現,最大的差異是在於間隔層的不同,巨磁阻使用的是非磁性金屬材料而穿隧磁阻使用的是絕緣材料。

在這些三層系統中各層間存在著耦合效應,FM/NM/FM 的系統以 RKKY 的形式來產生耦合效應,RKKY 主要是藉由非鐵磁層的自由電子產生耦合且有震盪的現象並隨非鐵磁層厚度增加而減少週期為2π/K_F,在 Fe/Cr/Fe 或 Co/Ru/Co 系統中耦合強度約為 1erg/cm²,這些耦合效應也是產生巨磁阻效應的起源,還有其他如"Orange peel"的耦合存在, Orange peel 耦合主要是因為介面不平整所形成的,因為介面的不平整導致介面上的電子形成偶極而產生耦合,強度約為 0.1~1

erg/cm², Orange peel 通常都是以鐵磁耦合的形式存在但是當垂直方向的異向能增加時則會轉變

為反鐵磁耦合。

本論文將探討Co₄₀Fe₄₀B₂₀/MgO/Co₂₀Fe₆₀B₂₀磁穿隧結(p-MTJ, perpend -icular magnetic tunnel junction)各層之間的介面耦合效應(IEC, interlayer exchange coupling)主要分為下列三部進行探討：

1. Co40Fe40B20(1.2) /MgO(X) /Co20Fe60B20(1.2) 改變不同 MgO 厚度觀察耦合效應和 MgO 厚度的關係。

當MgO 範圍在 X=0.9~1.5nm 之間我們觀察到一個類似週期性的變化, MgO 為 1nm 時沒有

耦合現象, MgO 為 1.2 nm 時為反鐵磁耦合, 1.2 5 nm 時為鐵磁耦。

2. Co40Fe40B20(1.2) /MgO(X) /Co20Fe60B20(1.2)改變不同退火溫度觀察耦合效應和退火溫度的關係。

本實驗MgO 範圍為 1~1.5nm,在 MgO 為 1~1.4nm 時耦合現象會隨著退火溫度增加而往反

鐵磁耦合改變,當 MgO 為為 1.5nm 時耦合現象會隨著退火溫度增加先往鐵磁耦合改變當溫

度達285℃時改往反鐵磁耦合轉變。

3. 改變鐵磁層厚度觀察耦合效應和鐵磁層的關係,結構分別為改變下層鐵磁層厚度

Co₄₀Fe₄₀B₂₀(1.2) /MgO(X) /Co₂₀Fe₆₀B₂₀(X)以及改變上層鐵磁層厚度 Co₄₀Fe₄₀B₂₀(X) /MgO(1) /Co₂₀Fe₆₀B₂₀(1.2)兩種實驗。當退火溫度為225℃時可以看到隨 CoFeB 厚度增加耦合效應有週期性的震盪,當退火溫度達 255℃時週期性將會消失。

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B4

Characterization of conductive AFM probes with a coating of a Pt layer

Bo-Yu Chenâ,b, Jia-Mou Leeâ,, Lin-Xiu Yeâ, Ching-Ming Lee^{a, b}, Shao-Tang Dingâ,b, Te-ho Wuâ,b,c

aTaiw n SPIN Research Center, National Yunlin University of Science and Technology, Douliou, 64002, Taiwan.

bGraduate School of Materials Science, National Yunlin University of Science and Technology, Douliou, 64002, Taiwan.

cGraduate School of Information Technology, Overseas Chinese University, Taichung, 407, Taiwan.

Abstract

Conducting atomic force microscope (Conducting AFM or CAFM) has been used to measure the magnetization switching induced by spin transfer torque (STT) for nanopillars of magnetic tunnel junctions. For reliable STT measurements, the probe features such as tip wear and contact resistance are crucial. In present study we present the effect of tip wear and the contact resistance on STT measurements. The AFM probes were coated a Pt layer by sputtering to deliver up several milliamps for spin-transfer switching measurement. Figure 1(a) show the SEM micrographs of the tips with different times of wear test. The wear test times varied from 0 to 350. The tip has worn obviously with increased the wear test times. The curvature radius and the contact resistance as a function of wear test times are shown in Fig. 1(b). One can see that both the curvature radius and the contact resistance of tips increased with increasing wear test times. The curvature radius was changed from 93 to 441 nm after 350 wear tests. As the wear test times increasing, the contact area of Pt layer was reduced due to the outcrop of the Si tip. Hence the contact resistance increased from 39 　 to 268 　.

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B5

Well vertically aligned Fe-doped ZnO nanorods array grown by hydrothermal synthesis method

Ruei-Jie Huang (黃瑞傑)², Chung-Wei Liu(劉宗維)^1,3, Shoou-Jinn Chang(張守進)^1,3, Chih-Hung Hsiao(蕭至宏)^1,3, Chun-Chu Liu(劉春菊)², Yan-Shen Lin(林延信)², Min-Chia Su(蘇泯嘉)², Peng-han Wang(王鵬漢)² and Kuang-Yao Lo(羅光耀)².

1 Institute of Microelectronics & Department of Electrical Engineering and

Center for Micro/Nano Science and Technology, National Cheng Kung University, Tainan 701, Taiwan.

2 Department of Electrophysics, National Chia Yi University, Chia Yi 600, Taiwan.

3Advanced Optoelectronic Technology Center, National Cheng Kung University, Tainan 701, Taiwan.

Abstract

Well vertically aligned Fe-doped ZnO nanorods array was grown on glass substrate by using hydrothermal synthesis method at different growth temperature. At the growth temperature of 80o, well vertical ZnO nanorods was formed and Fe readily substitutes Zn in the ZnO nanorods array. The weak room temperature ferromagnetism (RTFM) in the Fe-doped ZnO nanorod arrays was revealed by magnetization measurement. The quality of Fe-doped ZnO nanorods was examined by transmission electron microscopy (TEM),elemental mapping under electron microprobe and x-ray diffraction (XRD).

References

1. B. Liu and H. C. Zeng, J. Am. Chem. Soc. 125, 4430 (2003).

2. L. Vayssieres, Adv. Mater. 15, 464 (2003).

3. Q. Li, V. Kumar, Y. Li, H. Zhang, T. J. Marks, and R. P. H. Chang, Chem. Mater. 17, 1001 (2005).

Figure1.Scan Electron Microscope Figure2. Magnetization measurement Cross section of Fe-doped ZnO nanow

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B6

Low-frequency Noise Properties of Amorphous In-Ga-Zn-O Thin-film Transistors

Y. L. Chen¹, T. C. Chang², and Y. W. Suen¹

2Department of Physics, National Sun Yat-Sen University, Kaohsiung, Taiwan

Abstract

We investigate the low-frequency noise properties of amorphous In-Ga-Zn-O (a-IGZO) thin-film transistors (TFTs) with the SiO_xgate dielectric. The gate voltage (Vgs) is provided by a home-made battery bank. The drain-source voltage (Vds) is given by the internal DC voltage source of the current amplifier (SR570). The drain-source current (Ids) is amplified by SR570 and then fed into DC couple low-noise voltage preamplifier (SR560). Finally, the time-domain signal is collected by a network signal analyzer (SR780). We can deduce the noise spectral density from the data of SR780 by programs. The electrical properties of a-IGZO TFTs are sensitive to the light, so the samples are placed in a dark chamber. We examine the noise behaviors at various Vgs or Vds conditions. At same Vgs, we find that the higher Vds is, the larger the noise becomes. In specific conditions, we even observe the Lorentzian noise.

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C1*

Study of vortex configuration and switching behavior in submicro-scaled asymmetric Permalloy ring

Chao-Hsien Huang,^1* Nian-Jia Cheng,² Feng-Sheng Wu,¹ Jong-Ching Wu,¹ and Lance Horng¹

1 Department of Physics and Taiwan SPIN Research Center, National Changhua University of Education, Changhua, Taiwan

2 Institute of Photonics, National Changhua University of Education, Changhua, Taiwan

Abstract

The influence of the asymmetry degree of a Permalloy ring on the switching behavior and the vortex configuration was studied by changing the diameters of circle and its shift length. The object oriented micromagnetic framework software was used to simulate the magnetic configurations and reversal processes in a single asymmetric Permalloy ring. By introducing an inner circle shifted from the center of outer circle by a shift length, an asymmetric ring and the asymmetric ratio are defined. The switching fields of vortex nucleation field (Hn) and vortex annihilation field (Han), analyzed from the simulated hysteresis loops of 300, 500, and 800 nm outer diameters, have linear relations to the asymmetric ratio. It is noteworthy that a linear relationship of Hn is independent on the variations of the inner diameters and only dependent on the asymmetric ratio. This result demonstrates that an asymmetric ring could determine not only the vortex chirality, but also the vortex nucleation and annihilation fields.

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C2

The study of large-area antidot array of magnetic nanostructure on AAO template

Jheng-Lun Wang(王正侖)¹, Lance Horng(洪連輝)², Jenn-Kai Tsai(蔡振凱)¹ , Teen-Hang Meen(閔庭輝)¹, Siou-huang Liou(劉秀凰)² ,Chien-Han Huang(黃建翰)¹, and Tian-Chiuan Wu(吳添全)^1*

1Department of Electronic Engineering, National Formosa University, Yunlin 632, Taiwan

2Department of Physics and Taiwan SPIN Research Center, National Changhua University of Education, Changhua 500, Taiwan

*eetcwu@nfu.edu.tw

Abstract

Porous anodic alumina has been used as a template for the growth of functional nanostructures due to the possibility of controlling its geometry by tuning the anodization processes. Obtained by a two-step anodization process , sing 0.3 M oxalic acid solution as electrolyte, an anodization voltage of 40 V, and a temperature of 20 . Nanohole films or antidot arrays of Permalloy have been prepared ℃ by the sputtering of Ni₈₀Fe₂₀ onto anodic alumina membrane templates. The film thickness varies from 30 to 40 nm and the antidot diameters go from 200 to 350 nm. A counterpart continuous thin film grown on a continuous glass substrate was also prepared. The coercivities of the antidot arrays are greater than those of unpatterned films and show only a weak dependence on antidot diameter.

Defects impede domain wall motion and therefore raise the coercivity with an effect that depends on the size and type of the defects.

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C3

Particle blockade sensing in a flow by using microwave resonators

Tzung-Tsuen Tsai,¹ and Watson Kuo¹

1Department of Physics, National Chung Hsing University,Taichung 402, Taiwan, ROC

Abstract

In this study, microwave resonators are used to real-time detect blockade events of particle flowing through a pore. The resonantors are reflective microstrip resonators and double split ring resonators(DSRRs), fabricated on printed circuit boards(PCB). Their detection performance were systematically studied. By monitoring the microwave relection or transmission, we demonstrated the detection of 0.25mm-in-diameter particles suspended in water through the pore, which is 0.8mm in diameter at the position where the microwave electric field is strongest.

The microwave measurement is reliable since it is consistent with ion current measurement, which is a direct observation of the particle blockade. Also, the change in microwave signal is larger as the particle size increases. Sensitivity for amplitude and phase have different trend in their carrier frequency：for phase, the resonant frequency is the most sensitive operating point while for the amplitude, the most sensitive point is slightly off the resonance. If using the phase detection at the resonant frequency, we found MS resonantors more sensitive than DSRRs. This is because of the different electric field direction in the sensing area.

For detecting smaller particles, the microwave resonator and pore size should be reduced by micro fabrication techniques. Thus we tried to fabricate resonators on various substrates, and found that MS resonantors made on 50um-thick polyimides substrates displayed a good resonant property.

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C4

Magneto-optical characteristics of nanostructured magnetic thin films

S.F. Wang (王新斐)¹, Y.C Huang (黃郁宸)¹ ,W.K Lin(林瑋崗)¹, Lance Horng (洪連輝)², and J. C. Wu (吳仲卿)²

1 Institute of Photoncs, National Changhua University of Education, Changhua 500, Taiwan

2Department of Physics, National Changhua University of Education, Changhua 500, Taiwan

Abstract

Patterned magnetic elements have been widely investigated for developing spintronic devices.

One of the most important issues is the morphology of element by which the shape anisotropy is introduced to influence the behaviors of magnetization reversal. Herein, we report a size dependent magnetization reversal properties in an array of cascaded ellipses, the permalloy ellipses in series were fabricated by a standard electron beam lithography. The pattern dimensions are with fixed short axis of 100 nm and three segments of 300, 600, 300 nm, respectively, in long axes. The magnetization reversal processes of these permalloy thin film ellipses were investigated by using Magneto-Optical Kerr Effect (MOKE) measurments and Magnetic Force Microscopy (MFM). The switching behaviors are interpreted with the experimental data in conunction with a simulation using OOMMF software. It is found that the coercive field decreases as increasing the angle of external filed wit hrespect to long axis up 40 degrees. But the coercive field increases as increasing the angle from 60^o until 90^o at which the MOKE hysteresis loop shows a monotonically linear behavior. Details will be elaborated.

Figure 1. SEM image of the ellipses in series.

The dimensions are 100 nm in short axis and totally 1200 nm in long axis.

Figure 3. MOKE hysteresis loops measured with the external fields applied in various angles, from 0 degree to 90 degrees.

Figure 2. A schematic diagram of the external magnetic field applied in an angle with respect to

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C5

Fluorescence quenching of quantum dots on luminant silver nanoparticles

Chia-Hsun Chang¹, Yu-Chung Chang^1,*, Yang-Wei Lin², Chih Yi Liu³, Hsiang Chen Chui³,

¹Dept. of Electrical Engineering, National Changhua University of Education, Taiwan

2Dept. of chemistry, National Changhua University of Education, Taiwan

3Dept. of Photonics, National Cheng Kung University, Taiwan Presenting author’s e-mail address: abc110013@yahoo.com.tw

*corresponding author’s e-mail address: ycchang@cc.ncue.edu.tw

Abstract

Silver nanoparticles (size ~ 50 nm) were plated on the periodic nanostructures of anodized aluminum oxide (AAO). Strong fluorescence quenching effect of semiconductor nanocrystals (quantum dots, QDs) deposited on the silver nanoparticle plated nanostructure were observed. In addition, strong luminance signals were observed from the silver nanoparticles. In order to identify the origin of the luminance, we made silver nanoparticles with similar size but produced by a different chemical reaction. The newly-made silver nanoparticles showed similar spectral feature with the silver nanoparticles plated on AAO when excited by a 532 nm laser. The quenching of QDs was also verified by experiments conducted in aqueous conditions. Different concentrations of QDs and silver nanoparticles were mixed in the solution to determine the quenching strength of the nanoparticles.