第七十九期 2012年9月刊
 
 
 
发行人:林清富所长  编辑委员:陈奕君教授  主编:林筱文  发行日期:2012.09.20
 
 
 本所何志浩副教授指导光电所硕士生林冠中荣获「2012年度台大科林论文奖—硕士论文头等奖」,特此恭贺!

 

 
 
 
Theoretical Study of Surface Plasmon Coupling between a Radiating Dipole and a Metal Nanoparticle

Professor Y. W. Kiang’s Laboratory

Graduate Institute of Photonics and Optoelectronics, National Taiwan University

台湾大学光电所 江衍伟教授

We report the theoretical and numerical study results of surface plasmon (SP)-dipole coupling based on a simple coupling model between a radiating dipole and the SP induced on a nearby Ag nanoparticle (NP). To include the dipole strength variation effect caused by the field distribution built in the coupling system (the feedback effect), the radiating dipole is represented by a saturable two-level system. The spectral and dipole-NP distance dependencies of dipole strength variation and total radiated power enhancement of the coupling system are demonstrated and interpreted. The results show that the dipole-SP coupling can enhance the total radiated power. The enhancement is particularly effective when the feedback effect is included and hence the dipole strength is increased. Figure 1 shows the geometry of the dipole-NP system, including a spherical Ag NP with radius R (=10 nm) centered at the coordinate origin and a radiating dipole located at (0, 0, a), which is represented by an arrow. Figure 2 (3) shows the dipole strength enhancement ratios, , of the x-oriented (z-oriented) dipole as functions of wavelength when the distance between the dipole and the Ag NP center, a, varies from 40 through 120 nm. Figure 4 (5) shows the total radiated power enhancement ratios as functions of wavelength at several a values for the x-oriented (z-oriented) dipole. The power ratio is defined as the total radiated power of the dipole-NP system over that in the case without the Ag NP.

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

 

Structural properties of InAsPSb grown on GaAs

Professor Hao-Hsiung Lin

Graduate Institute of Photonics and Optoelectronics, National Taiwan University

台湾大学光电所 林浩雄教授

Previous studies have shown that bonds in alloy resemble their original lengths in binaries. Quaternary InAsPSb contains two bonds, InP and InSb, that are with very large mismatch in length. This mismatch leads to strong bond distortion in the quaternary, which could affect the structural, electronic and optical properties. In this work, we investigate the structural properties of InAsPSb grown on GaAs substrate using reciprocal space mapping (RSM) and P K-edge and In K-edge extended X-ray absorption fine structure (EXAFS). Valence force field (VFF) is used to simulate the bond distortion in the quaternary. Fig. 1 shows the Fourier transformed In K-edge EXAFS signals. Two peaks representing InP and InSb bonds are clearly seen when As composition is low and gradually merge into a broad peak with the increasing As composition. Detailed analysis show that the bond lengths are close to their original values in binaries. Fig. 2 shows RSM results of a InAsPSb samples. Although the lattice mismatch between of these alloys and GaAs is ~7% and the layer thicknesses are 1000 times thicker than the critical thicknesses, strong residual strain exists in these layers. We used VFF model to calculate the bond distortion. Fig. 3 shows the distortion energy as a function of az/axy for each sample. As can be seen, the distortion energy is much larger than the strain energy and the residual strain, in term of az/axy ratio, is proportional to the distortion energy. This finding suggests that the randomly oriented bond distortion could hinder the generation of dislocation in the alloy, leading to the observed residual strain.

Fig. 1 Fourier transformed In K-edge EXAFS signal of InAsPSb. Fig. 2 (004) and (-1-15) RSM measurements of InAs0.04P0.73Sb0.23 show a az/axy ratio of 1.017, resulting from the residual strain in the 1-mm-thick sample.
 

Fig. 3 Distortion energy as functions of az/axy for InAsPSb alloys. Symbols indicate the az/axy ratio obtained from RSM measurement for each samples.

 

     
 
 
论文题目:砷化铟镓量子点微碟激光之研究

姓名:钱皓哲   指导教授:毛明华教授

 

摘要

微碟(microdisk)共振腔由于其回音廊模态(whispering gallery mode)有良好的空间局限性,因此拥有高质量系数与低模态体积之特性,结合量子点主动材料,可在砷化镓材料系统实现光纤通讯用长波长激光,并具有低临界电流之潜力。

在我们的研究中,我们实现了质量系数高达14000的光激发式微碟共振腔激光,我们也利用两段式湿式蚀刻技术制作直径约为3微米的微碟激光,成功减少了模态的数量。在电注入式微碟共振腔激光的制作上,我们采取的是苯环丁烯聚合物包覆下的平坦化制程,并且透过光学量测,实现了世界上第一个室温下操作的量子点电注入式微碟共振腔激光,其SEM图如图一所示,室温下最低的临界电流是0.45毫安,其组件直径是6.5微米。我们另外对电注入式微碟共振腔激光讨论其动态的特性。在室温下电注入式微碟共振腔激光瞬时行为的量测中,我们发现微碟激光的起始时间很短暂,并且没有观察到弛逸震荡的现象,在大讯号直接调变的实验下,我们展示了此组件作为1 Gbps调变的可能(如图二),并且证实了此组件可以应用在高度积体化光收发器模块中,做为高频调变与单模操作的激光光源。

图一

图二

 

 

论文题目:氧化镉锌/氧化锌量子井生长、特性分析及发光二极管应用

姓名:丁绍滢   指导教授:杨志忠教授


摘要

在本研究中,我们使用分子束磊晶(Molecular-Beam Epitaxy)技术于p型氮化镓(p-GaN)上成长氧化镉锌/氧化锌(CdZnO/ZnO)多层量子井发光二极管结构。在结构表面有些V型凹陷存在,这显示在其底下存有贯穿式差排(threading dislocation),为了降低此漏电流通道,我们使用二氧化硅奈米颗粒将这些凹陷填满,并制作侧向式发光二极管(如图一(a))。量测结果发现组件开启电压为4伏特,组件电阻为224奥姆。另外我们制作出垂直式氧化锌/氧化镉锌量子井发光二极管组件(如图一(b)),我们拿它与侧向式发光二极管来做比较,发现垂直式发光二极管有较低的组件电阻、更小的漏电流、较弱的输出强度饱和、较高的光输出强度以及相对低的缺陷放光(如图二)。

图一:(a)垂直式氧化锌发光二极管结构 (b)侧向式氧化锌发光二极管结构

图二:垂直式发光二极管与侧向式发光二极管的I-V量测曲线与在20mA输入电流下的照片

 

 
 
 

— 数据提供:影像显示科技知识平台 (DTKP, Display Technology Knowledge Platform) —

— 整理:林晃岩教授、陈圣灏 —

奈米塑形的新方法

在过去的几十年内,奈米线特殊的光学、电子与机械性质在科学与技术上皆引起研究人员的强烈兴趣。奈米线的特性可透过后处理(post-processing)技术调整,例如:弯曲、形变、切割以及改变形状,藉此提供我们可控制如:应变工程、电子传输、机械特性、能带结构与量子特性等功能。然而现今塑形奈米线的技术受限于其可缩放比例,例如:虽然可藉由原子力显微镜尖端,以抓住与弯曲奈米线,但必须一个区段接着一个区段做处理,因此较难以制作出复杂的形状。

Ji Li与美国普渡大学(Purdue University)的同事发展出基于激光冲击(laser-shock-based)的技术作为具有可缩放比例与可控制的奈米线塑形方法(Nano Lett. 12, 3224–3230; 2012)。此研究的架构是由玻璃局限层(confinement layer)、石墨腐蚀涂层(graphite ablative coating layer) 、超薄金属箔层、弹性材料层、对准之银奈米线与硅奈米铸模块合而成(见图 1 (a))。他们使用「气-液-固」制程合成直径约100奈米之单晶奈米线。并使用强度0.07–0.2 GW cm−2 的5奈秒激光脉冲照射目标物使腐蚀涂层汽化成电浆。这些扩大的电浆由局限层弹回产生600–1000百万帕(MPa)的强大冲击压力,足以塑形金属箔层,也因此可将下方的奈米线压至模具上(见图 1 (b))。

藉由调整制程的条件,如:激光强度、基材材质与模具形状。研究人员成功地展示保形塑形(conformal shaping)、均匀弯曲与切割的银奈米线(见图 1 (d)-(h))。以保形塑形来说,常见的特征尺寸为80奈米而深度为60奈米。根据研究人员表示,横向压缩的银奈米线的方式可藉由在平坦表面的模具上达成(见图 1 (j)-(k))。

Ji Li 等人也使用穿透式电子显微镜研究侧向压缩的银奈米线微观结构的变化。他们发现在开始压缩时,奈米线的表面会有高密度的成对形变(deformation twins) ,且在压缩之后移动到内部。而这个「契合边界」(coherent boundary)对电阻率有微小的影响;成对形变的发现支持在激光冲击形成前后银奈米线可忽略电子特性变化的说法。

研究人员指出,这个新的奈米塑形技术可控制在常温常压下,同时也可使用于不同的材质,包含半导体如硅与锗等。

 

图 1、以激光冲击控制奈米线之形成:(a)不同层的组合组件图。(b)激光冲击形成的过程。(c)原始银奈米线的SEM图与硅模子的数组信道。(d)保形(conformal)奈米线的过程图。(e) 保形银奈米线的SEM图。(f)有一致弯曲之奈米线的过程图。(g)弯曲之锗奈米线的SEM图。(h)奈米线切割过程图。(i)银奈米线切割的SEM图。(j)横向压缩奈米线的过程图。(k)压缩的银奈米线SEM图。

 

资料来源: Nature Photonics 6,508 (2012), Published Date(Online): 31 July 2012,
DOI:10.1038/nphoton.2012.186
  http://www.nature.com/nphoton/journal/v6/n8/full/nphoton.2012.186.html
参考数据 Ji Li, Yiliang Liao, Sergey Suslov, and Gary J. Cheng, “Laser Shock-Based Platform for Controllable Forming of Nanowires,” pp 3224–3230 Publication Date (Web): May 17, 2012 (Letter) DOI: 10.1021/nl3012209
http://pubs.acs.org/doi/abs/10.1021/nl3012209
   
 
 
 
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