我们非常感谢帮助罗尔夫·Follat​​h，罗兰·胡贝尔，K.莫勒，Inosov德米特罗，约尔格·芬克，安德烈亚斯Koitzsch，贝恩德·毕希纳，安德烈Varykhalov，埃米尔Rienks，奥利弗·雷德，Setti Thirupathaiah，丹尼斯Vyalikh，Molodtsov谢尔盖·克莱门斯Laubschat，拉莫纳韦伯，沃尔夫冈·赫尔曼·杜尔埃贝哈特，基督教荣，托马斯·布鲁姆，格尔德赖卡特，大卫巴彻勒，启Godehusen，马丁Knupfer，斯特凡Leßny，德克Lindackers的斯特凡·莱热，拉尔夫·福伦达，汤家骅Schönfelder，谁构思的"1立方"项目，设计，建造和调试的光束线和终端站以及组织和用户提供支持。 该项目"1立方角分辨光电子能谱"已经由BMBF金"的最高分辨率ARPES"，以及直接由BESSYII和IFW - 德累斯顿。这种特殊的工作得到了DFG优先方案SPP1458，授予:ZA 654/1-1，BO1912/3-1的和BO1912/2-2。 EC和BPD日ANK在约翰内斯堡大学理学院差旅费。 AV，RF和MC承认从欧盟-FP7/2007-2013的支持下赠款协议N. 264098 - MAMA。

1。安装示例<ol><li>本实验采用亥姆霍兹 - Zentrum柏林BESSY储存环同步加速器辐射。光子束线旅游，我们的最终站，其中一个样品安装。 </li><li>从单晶材料以进行调查，钌酸锶在这里开始。使用银环氧树脂胶样品的样品架。银基的环氧树脂，可确保良好的热接触和电接触。 </li><li>胶的铝顶部后的单晶表面。的顶部后，将被用于切割样品在超高真空中，以暴露一个原子的干净的表面。 </li><li>装载在装载锁定装置的样本保持器。 </li></ol> 2。 ，实现超高真空和热隔离<ol><li>开始抽空负载锁定的超高真空室的污染降到最低。 </li><li>监视的压力。一旦压力约10 -8毫巴一直取得，转让装配的准备室，随后的主要chamber.The冰冷的手指和样品支架经过特殊设计，以保证最好的氦锅热接触。 </li><li>这些示范版本显示通过使用锥形表面的接触面积增加，这是如何实现的。锥形表面被压靠在彼此的样本保持器和冷的手指被牢牢地固定在的地方使用的钛螺母和螺栓。 </li></ol> 3。定位和冷却样品<ol><li>下一个步骤是使用输送臂的方位角内的冷手指沿定向样品。修复的位置的样品，通过拧紧螺母与支承臂连接到该室的相反侧，同时施加反作用力。 </li><li>劈开的样本通过移动操纵器向上，使柱的顶部除去与支撑臂的相互作用。 </li><li>束快门关闭后，将样品在光束线使用机械手的位置。一旦样品是在地方，使确保正确关闭cryoshields。 </li><li>开始抽上1-K锅和流通中的氦-3气体冷却样品到基准温度。测量温度接近样品，并在实验过程中不会改变。 </li><li>打开光束的光束快门。使用千分尺装置上的螺丝来调整位置的样品，所以，它是在分析仪的透镜的焦点。这种调整是非常重要的。 </li></ol> 4。收集数据<ol><li>一旦安装准备就绪后，切换到角分辨模式的分析仪和记录的频谱扫描模式。这将产生用于二维能量角曲线的数据。 </li><li>构造一个的费米面地图使用的数据。选择极角对应的费米能级口岸的苏佩的研究钌酸锶rconducting差距。 </li><li>记录高分辨率的光谱在所选定的极角的上方和下方的超导转变温度的锶钌调查超导能隙的行为。 </li></ol>

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没有利益冲突的声明。

正如上面所示，实现的方法是非常有效的，在研究的低能量的电子结构的单晶。最近的仪器的改进，从一个单纯的表征和带映射工具已经把角分辨光电子能谱成一个复杂的多体光谱。一个现代化的实验提供了坚实的电子结构或纳米对象，一个新的水平精度的信息。访问的费米表面的金属的情况下，能隙半导体和绝缘体，它们的表面状态，能带结构和动量依赖的费米速度允许在一般水平的电子结构的特征。从头计算计算收益率的带宽和费米速度renormalizations和比较确定的复杂性，材料强度的相关性。的费米能级附近的精细结构常电检测的指纹之间的相互作用提供了可能性NS和自由度，如声子，等离激元，旋波动等系统的动量相关研究，可以找出最主要的相互作用和单出，例如，超导体的配对调解员或密度波系统。更彻底的调查，涉及到确定的序参量的对称性，从而提供了一个根本的层面上现有的理论或刺激新的方法的关键测试。 在每一个实验的方法，也有某些缺点。它是已知的光电子在晶体内强烈的散射，从而具有相对短的非弹性纤维的平均自由程。作为一个结果，逸出深度可以是非常小的，下降到几个晶格常数。这定义了该方法的灵敏度的表面，并在某些情况下，表面的电子结构的确是不同的体积6。但是，ARPES提供许多工具来监测这种情况。其中的第em是各种激发光子能量的使用。正如前面所提到的，对于一个给定的光子能量，它是可能的，也估计的组件的表面相垂直的动量。 ARPES谱观察到的周期性结构，允许一个确定的绝对K Z和相应的动量分辨率提供这个数量的不确定性。在这样一种方式中的实验值的逸出深度可估计的不确定性原理δk z的 *δZ〜1。的下一个工具来控制的表面灵敏度的方法是可变的光的偏振。据证明，使用圆偏振光，它是能够区分的光电子信号7的表面和本体的贡献。使用各种偏振和交付同步加速器光源的光子能量的另一个优点，就是可以把解开矩阵元素的影响，从真正的谱函数的功能。矩阵元素的转移概率，它可以抑制光电子信号在动量空间和特定的区域，ARPES谱8-10误解的结果。 显然，该方法不是很适合强烈的3D材料，这是难以切割原位，并获得原子级清洁，平整的表面。最后，在绝缘体的ARPES复杂得多，因为它是必要的，以补偿充电发生的，因为不能够得到补偿出射电子的磁通通过样本保持器11的电接触。

如今ARPES被广泛用于确定固体的电子结构。一般，不同的变化，此方法是由所需的辐射激发的电子源定义。我们使用同步加速器辐射，因为它提供了一个独特的机会来调整的偏振和在很宽的能量范围内的激发光子能量和由高强度，小的带宽（能源HN的不确定性）的特征在于，它可以被聚焦到一个狭窄的光束收集光电子从几十微米的光斑。同步加速器辐射产生在电子储存环迫使电子在环中循环的顺序的2电子伏特的能量**通过周期性强磁铁（波荡）的安排。磁场偏转电子和如此快速的电子改变其方向时，他们发出的辐射。正是这种辐射，然后引导到所谓的束线，在其中进一步单色由衍射光栅集中由几个镜的表面上的样品。有很多这样的设施在世界各地。我们的最终站位于BESSY储存环的Helmholtz-Zentrum酒店柏林的光束线之一。 本ARPES设施的心脏是电子能量分析仪（ 图1）。由于我们感兴趣的动能和角度在电子离开表面，它是很方便的，在一次测量中检测到它们。一个非常简单的原则，使这种方法成为现实。至于在一个基本的实验用的光学透镜，其重点中的点的平面波转换成的后焦平面上，从而进行空间的傅里叶变换，电子光学透镜项目离开表面的电子在特定的角度中的一个点的焦平面（ 图1）。在这种方式中，我们获得的倒数， 即动量，空间。在远程控制策从在焦平面的前进方向相对应的角度和从而光电子的势头。现在的电子有能源方面加以分析。为了这个目的，半球形分析仪的入射狭缝正好被放置在电子光学透镜的焦平面。两个半球上的电压是这样选择的，只与特定的动能（为了能量）的电子将被引导在中间的两个半球和土地上的二维检测器的中央线完全相同。那些更快将击中探测器接近的外半球;那些慢将朝着内半球偏转。在这样一种方式中，我们可以得到同时作为一个功能的角度和动能的光电子强度分布。 与现有方法相比，我们的方法的主要优点是使用的他3 cryomanipulator的。至少有两个原因，进行OUt是在低温下的测量。的材料的温度越高，越涂抹满分成为电子态的能量和动量。要确定精度高的电子结构，该温度下要避免扩大。此外，许多物理特性和温度有关，一些订货现象，在低温和知识系统的基态的电子结构， 即 T = 0，是极为重要的。降温的样品下降到十分之一秒的开尔文的最有效的方法之一是，以液化他3气。在许多实验中达到子·开尔文的温度是没有问题的，因为热辐射，超低温下的主要敌人，可以有效地屏蔽。不幸的是，这是不是的情况下，光电子的实验。我们需要的入射光与出射电子免费提供。这是通过专门设计的狭缝在三个岭diation盾牌，具有不同的温度。为了补偿的光子束和室温辐射引起的热负荷，低温恒温器的冷却功率应该是非常高的。这是通过非常大的两个泵的抽气速度减少的液态He 3以上的蒸气压，从而冷却的冷的手指和样品。我们3系统的设计规范，使其成为全球最强大的。这也许是唯一的地方，在这个星球上，人们可以看到一个1 K冰冷的表面上通过一个房间的温度窗口，"最冷可见"。 现代光电子实验是在图1中所示的草图。 （绿色虚线）的同步辐射光束照亮样本并激发光电子1 K的冷表面。电子被投射到半球形分析仪的入口狭缝，排序条件方面的角度（黄色，洋红和青色的痕迹对应different的倾斜角），然后，分析在动能方面， 图2示出了作为的函数的典型的强度分布的倾斜角和动能。预期确实是这样的强度分布，作为比较，与该材料的能带结构的计算显示（右面板）。这是我们的互惠空间的窗口。 通过扫描电压上的透镜和半球和绕垂直轴的旋转样品（极角），我们可以探索广泛的结合能范围内，以及宽区域的往复空间以前所未有的详细。绘制在费米能级的函数的两个组成部分，在平面内的动量，计算从倾斜和极性的角度强度，特别是，我们有至费米表面（FS）的直接访问。 *在"不确定性"，我们理解实验者的最佳估计多远的实验数量可能是从"真实的的价值。" *低能量环的〜0.8 GeV时，高能量的1 - 8 GeV的能量。

<table border="1"><tbody><tr><td> 的试剂/材料名称 </td><td> 公司 </td><td> 目录编号 </td><td> 评论 </td></tr><tr><td> ZrTe 3 2 TISE的单晶</td><td></td><td></td><td>赫尔穆特·伯杰博士，洛桑联邦理工学院，洛桑增长</td></tr><tr><td>单结晶的Sr 2 RuO 4的 </td><td></td><td></td><td>组的博士安东尼奥·韦基奥增长</td></tr><tr><td></td><td></td><td></td><td> SAMPLES ZrTe 3，TISE 2，高级2 RuO 4的 </td></tr></tbody></table>

angle-resolved photoemission spectroscopy at ultra-low temperatures

其电子结构所定义的材料的物理性质。其特征在于在固体中的电子能量（ω）和动量（k）和找到他们在一个特定的状态，与给定的ω 和 k的概率由频谱函数描述一个（k，ω）。这个功能可以直接测量，在实验的基础上著名的光电效应，阿尔伯特·爱因斯坦获得了诺贝尔文学奖，早在1921年的解释。在光电效应的光照射的表面上喷出从材料的电子。根据爱因斯坦，节约能源允许一个，以确定样品内的电子的能量，提供的能量的光的光子的出射光电子的动能是已知的。动量守恒，它也有可能估算，K表有关的瞬的光电子通过测量在该光电子离开表面的角度中的量子。这种技术被称为现代版角分辨光电子能谱（ARPES），以确定的电子结构，并利用两个守恒定律， 即固体内部的电子能量和动量。为了解决细节问题，了解局部问题，凝聚态物理的关键，需要最小化:三个量的不确定性*能量的光子，光电子的动能和温度的样品中的不确定性。 在我们的方法中，我们结合三个领域的同步辐射，表面科学和低温的最新成就。我们使用同步加速器辐射与可调的光子能量贡献的不确定性的顺序的1毫电子伏特，具有精度的顺序的1毫电子伏特的电子能量分析仪，其检测动能和他3低温恒温器的wh脑出血允许我们的样品的温度保持在低于1 K，我们讨论的示例性的单晶的Sr 2 RuO 4的和其他一些材料上获得的结果。这种材料的电子结构，可确定一个前所未有的清晰度。

的超低温条件下，我们共同的设置与高分辨率的光束线和分析，使我们能够记录具有非常高的整体分辨率光谱。这在图3中示出。的能量分辨率是通常的测试来测量的宽度的费米的金属边缘。在这种情况下，它是一个新鲜蒸发的铟膜。半最大值处的全宽度（FWHM）的高斯，与阶梯函数进行卷积时的精确描述的边缘，是2毫电子伏特的顺序。详细研究的低能量的电子结构的固体是更为重要的角度分解光谱的分散功能。这样的一个例子示出在图3的中间面板。一个很尖锐的超导峰中观察到铁基的超导体LiFeAs 1表示检测ARPES有史以来最锋利的功能之一。面临着同样的势头分辨率。 0.23°的半高宽是rECORD值的电子能量分析仪的宽角度模式。该系统已被​​设计为结合三个成就，1毫电子伏特的束线的带宽，1毫电子伏特分辨率的分析仪的样品的温度和1 K。这个目标给我们的系统"1立方角分辨光电子能谱"的名称。如果所有的三个组成部分最小化，人们可能会期望FWHM〜1.4毫电子伏特。我们目前的测量结果表明，2毫电子伏特的顺序可以实现全面的解决。 另一位代表结果是我们调查的超导体SR 2 RuO 4的电子结构与临界温度1.35 K.这种材料是一种众所周知的氧化物，具有广泛的有趣的物理性能。这是第一个被发现的超导氧化后的铜酸盐2。其超导状态是不寻常的:在对耦合的电子有它们的自旋，在相同的方向上取向。这是所谓的三重峰超导。它STILL仍然没有得到很好的理解和存在的主要问题是确定的超导序参量的对称性。为了做到这一点，应该确定为超导能隙函数的势头 - 确切的任务ARPES。由于如此低的温度所需的超导不能访问在光电子实验之前，这是不可能的，以解决这个问题。在这里，我们试图做到这一点。首先，需要确定的费米面。为此，我们已在不同极性的角度记录了许多削减。其中有些是用于说明在图4中所示。现在，如果我们考虑强度仅在费米能级附近，并绘制它作为一个功能的两个角度，我们会得到费米动量， 即费米表面地图的轨迹。这种费米表面的地图显示在图5一起与所计算出的费米表面3。该协议是很好的，但实验数据显示，有更多的功能。其中有些是意外的和不寻常的4。现在，我们可以尝试来衡量的超导能隙。对于这一点，我们必须记录的光谱的上方和下方的临界温度， 即 1.35 K.在图6中，我们显示等对光谱。我们确实观察到一些变化，兼容开放的能隙，但即使是目前的能源分辨率（或者是在样品表面的温度，这可能是最高的权力）不使我们得出一个明确的结论，在Sr 2 RuO 4的能隙。 <img alt="图1" src="/files/ftp_upload/50129/50129fig1.jpg" /> 图1的实验装置的示意图。 <img alt="图2" src="/files/ftp_upload/50129/50129fig2.jpg" /> 图2。左侧面板中。考试PLE的光电子强度分布作为动能和角度的函数。直接看到固体的能带结构的右面板的材料相同的材料的能带结构的计算结果。理论数据均取自5。 <img alt="图3" fo:content-width="4.5in" fo:src="/files/ftp_upload/50129/50129fig3highres.jpg" src="/files/ftp_upload/50129/50129fig3.jpg" /> 图3。性能的实验终端站。 左面板。费米边的新鲜蒸发铟薄膜面板中的能量分布曲线（EDC）在超导的LiFeAs样本。数据取自1。 右侧面板中。动量分布曲线（MDC）的费米能级ZrTe 3。预期的总的能量系统的分辨率表示由式（1K = 0.0862毫电子伏特）。实际射孔rmance的系统是非常接近我们最初的目的是为。 <a href="https://www.jove.com/files/ftp_upload/50129/50129fig3large.jpg" target="_blank">点击此处查看大图</a> 。 <img alt="图4" fo:content-width="5in" fo:src="/files/ftp_upload/50129/50129fig4highres.jpg" src="/files/ftp_upload/50129/50129fig4.jpg" /> 图的能量动量削减4。的Sr 2 RuO 4的记录在不同的极角（步骤10）。 <a href="https://www.jove.com/files/ftp_upload/50129/50129fig4large.jpg" target="_blank">点击此处查看大图</a> 。 <img alt="图5" fo:content-width="5in" fo:src="/files/ftp_upload/50129/50129fig5highres.jpg" src="/files/ftp_upload/50129/50129fig5.jpg" /> 图5。的Sr 2 RuO 4的费米面地图，用80 eV的线性极化光〜1K。 <a href="https://www.jove.com/files/ftp_upload/50129/50129fig15large.jpg" target="_blank">点击此处查看大图</a> 。 <img alt="图6" src="/files/ftp_upload/50129/50129fig6.jpg" /> 图6。 A，B的典型光谱研究的Sr 2 RuO 4的超导能隙。红色箭头表示对应于一个单一的能量分布曲线（EDC）的动量。 T = 970 mK的C，D移位的综合EDC的领先优势。动量窗口红色箭头所表示的宽度。该间隙对应的频带附近的BZ对角线。E移位的量KF EDC作为温度的函数，从另一点上的FS的FS点，F的典型的温度特性的结合能的前缘附近的交叉两种FSS。

Watch this Scientific Journal Video about Angle-resolved Photoemission Spectroscopy At Ultra-low Temperatures at JoVE.com

Angle-resolved Photoemission Spectroscopy At Ultra-low Temperatures

这种方法的总体目标是，以确定低能量的电子在超低温下利用同步辐射角分辨光电子能谱结构的固体。

在极低的温度下角分辨光电子能谱

The physical properties of a material are defined by its  electronic structure. Electrons in solids are characterized by energy (&omega;)  and momentum ...

angle-resolved-photoemission-spectroscopy-at-ultra-low-temperatures

Nanyang Technological University

Research

JoVE Journal

Engineering

17.5K 次观看.  IFW-Dresden. 这种方法的总体目标是，以确定低能量的电子在超低温下利用同步辐射角分辨光电子能谱结构的固体。

视频: Angle-resolved Photoemission Spectroscopy At Ultra-low Temperatures

Synthesis and Microdiffraction at Extreme Pressures and Temperatures

High pressure compounds and polymorphs are investigated for a broad range of purposes such as determine structures and processes of deep planetary interiors, design materials with novel properties, understand the mechanical behavior of materials exposed to very high stresses as in explosions or impacts. Synthesis and structural analysis of materials at extreme conditions of pressure and temperature entails remarkable technical challenges. In the laser heated diamond anvil cell (LH-DAC), very high pressure is generated between the tips of two opposing diamond anvils forced against each other; focused infrared laser beams, shined through the diamonds, allow to reach very high temperatures on samples absorbing the laser radiation. When the LH-DAC is installed in a synchrotron beamline that provides extremely brilliant x-ray radiation, the structure of materials under extreme conditions can be probed in situ. LH-DAC samples, although very small, can show highly variable grain size, phase and chemical composition. In order to obtain the high resolution structural analysis and the most comprehensive characterization of a sample, we collect diffraction data in 2D grids and combine powder, single crystal and multigrain diffraction techniques. Representative results obtained in the synthesis of a new iron oxide, Fe4O5 1 will be shown.

The laser heated diamond anvil cell combined with synchrotron micro-diffraction techniques allows researchers to explore the nature and properties of new phases of matter at extreme pressure and temperature (PT) conditions. Heterogeneous samples can be characterized in situ under high pressure by 2D mapping and combined powder, single-crystal and multigrain diffraction approaches.

在极端的压力和温度的合成和Microdiffraction

High pressure compounds and polymorphs are investigated for a broad range of purposes such as determine structures and processes of deep planetary ...

科研

工程学

Scanning-probe Single-electron Capacitance Spectroscopy

The integration of low-temperature scanning-probe techniques and single-electron capacitance spectroscopy represents a powerful tool to study the electronic quantum structure of small systems - including individual atomic dopants in semiconductors. Here we present a capacitance-based method, known as Subsurface Charge Accumulation (SCA) imaging, which is capable of resolving single-electron charging while achieving sufficient spatial resolution to image individual atomic dopants. The use of a capacitance technique enables observation of subsurface features, such as dopants buried many nanometers beneath the surface of a semiconductor material1,2,3. In principle, this technique can be applied to any system to resolve electron motion below an insulating surface.
As in other electric-field-sensitive scanned-probe techniques4, the lateral spatial resolution of the measurement depends in part on the radius of curvature of the probe tip. Using tips with a small radius of curvature can enable spatial resolution of a few tens of nanometers. This fine spatial resolution allows investigations of small numbers (down to one) of subsurface dopants1,2. The charge resolution depends greatly on the sensitivity of the charge detection circuitry; using high electron mobility transistors (HEMT) in such circuits at cryogenic temperatures enables a sensitivity of approximately 0.01 electrons/Hz&frac12; at 0.3 K 5.

Scanning-probe single-electron capacitance spectroscopy facilitates the study of single-electron motion in localized subsurface regions. A sensitive charge-detection circuit is incorporated into a cryogenic scanning probe microscope to investigate small systems of dopant atoms beneath the surface of semiconductor samples.

扫描探针单电子电容谱

The integration of low-temperature scanning-probe techniques and single-electron capacitance spectroscopy represents a powerful tool to study the ...

Quantum State Engineering of Light with Continuous-wave Optical Parametric Oscillators

Engineering non-classical states of the electromagnetic field is a central quest for quantum optics1,2. Beyond their fundamental significance, such states are indeed the resources for implementing various protocols, ranging from enhanced metrology to quantum communication and computing. A variety of devices can be used to generate non-classical states, such as single emitters, light-matter interfaces or non-linear systems3. We focus here on the use of a continuous-wave optical parametric oscillator3,4. This system is based on a non-linear &#967;2 crystal inserted inside an optical cavity and it is now well-known as a very efficient source of non-classical light, such as single-mode or two-mode squeezed vacuum depending on the crystal phase matching. 
Squeezed vacuum is a Gaussian state as its quadrature distributions follow a Gaussian statistics. However, it has been shown that number of protocols require non-Gaussian states5. Generating directly such states is a difficult task and would require strong &#967;3 non-linearities. Another procedure, probabilistic but heralded, consists in using a measurement-induced non-linearity via a conditional preparation technique operated on Gaussian states. Here, we detail this generation protocol for two non-Gaussian states, the single-photon state and a superposition of coherent states, using two differently phase-matched parametric oscillators as primary resources. This technique enables achievement of a high fidelity with the targeted state and generation of the state in a well-controlled spatiotemporal mode.

We describe the reliable generation of non-Gaussian states of traveling optical fields, including single-photon states and coherent state superpositions, using a conditional preparation method operated on the non-classical light emitted by optical parametric oscillators. Type-I and type-II phase-matched oscillators are considered and common procedures, such as the required frequency filtering or the high-efficiency quantum state characterization by homodyning, are detailed.

光与连续波光学参量振荡器的量子态工程

Engineering non-classical states of the electromagnetic field is a central quest for quantum optics1,2. Beyond their fundamental significance, such states ...

Investigating Single Molecule Adhesion by Atomic Force Spectroscopy

Atomic force spectroscopy is an ideal tool to study molecules at surfaces and interfaces. An experimental protocol to couple a large variety of single molecules covalently onto an AFM tip is presented. At the same time the AFM tip is passivated to prevent unspecific interactions between the tip and the substrate, which is a prerequisite to study single molecules attached to the AFM tip. Analyses to determine the adhesion force, the adhesion length, and the free energy of these molecules on solid surfaces and bio-interfaces are shortly presented and external references for further reading are provided. Example molecules are the poly(amino acid) polytyrosine, the graft polymer PI-g-PS and the phospholipid POPE (1-palmitoyl-2-oleoyl-sn-glycero-3-phosphoethanolamine). These molecules are desorbed from different surfaces like CH3-SAMs, hydrogen terminated diamond and supported lipid bilayers under various solvent conditions. Finally, the advantages of force spectroscopic single molecule experiments are discussed including means to decide if truly a single molecule has been studied in the experiment.

A protocol to couple a large variety of single molecules covalently onto an AFM tip is presented. Procedures and examples to determine the adhesion force and free energy of these molecules on solid supports and bio-interfaces are provided.

调查单分子粘附的原子力谱

Atomic force spectroscopy is an ideal tool to study molecules at surfaces and interfaces. An experimental protocol to couple a large variety of single ...

Resonance Raman Spectroscopy of Extreme Nanowires and Other 1D Systems

This paper briefly describes how nanowires with diameters corresponding to 1 to 5 atoms can be produced by melting a range of inorganic solids in the presence of carbon nanotubes. These nanowires are extreme in the sense that they are the limit of miniaturization of nanowires and their behavior is not always a simple extrapolation of the behavior of larger nanowires as their diameter decreases. The paper then describes the methods required to obtain Raman spectra from extreme nanowires and the fact that due to the van Hove singularities that 1D systems exhibit in their optical density of states, that determining the correct choice of photon excitation energy is critical. It describes the techniques required to determine the photon energy dependence of the resonances observed in Raman spectroscopy of 1D systems and in particular how to obtain measurements of Raman cross-sections with better than 8% noise and measure the variation in the resonance as a function of sample temperature. The paper describes the importance of ensuring that the Raman scattering is linearly proportional to the intensity of the laser excitation intensity. It also describes how to use the polarization dependence of the Raman scattering to separate Raman scattering of the encapsulated 1D systems from those of other extraneous components in any sample.

The paper describes a method for producing extreme nanowires by melt infiltration into carbon nanotubes and how 1D systems may be characterized and investigated using Resonance Raman Spectroscopy to determine vibrational and optical excitation energies.

至尊纳米线和其他维系统的共振拉曼光谱

This paper briefly describes how nanowires with diameters corresponding to 1 to 5 atoms can be produced by melting a range of inorganic solids in the ...

High Resolution Phonon-assisted Quasi-resonance Fluorescence Spectroscopy

High resolution optical spectroscopy methods are demanding in terms of either technology, equipment, complexity, time or a combination of these. Here we demonstrate an optical spectroscopy method that is capable of resolving spectral features beyond that of the spin fine structure and homogeneous linewidth of single quantum dots (QDs) using a standard, easy-to-use spectrometer setup. This method incorporates both laser and photoluminescence spectroscopy, combining the advantage of laser line-width limited resolution with multi-channel photoluminescence detection. Such a scheme allows for considerable improvement of resolution over that of a common single-stage spectrometer. The method uses phonons to assist in the measurement of the photoluminescence of a single quantum dot after resonant excitation of its ground state transition. The phonon&#39;s energy difference allows one to separate and filter out the laser light exciting the quantum dot. An advantageous feature of this method is its straight forward integration into standard spectroscopy setups, which are accessible to most researchers.

The manuscript describes a method of phonon-assisted quasi-resonant fluorescence spectroscopy that incorporates both laser-limited resolution and photoluminescence (PL) spectroscopy. This method utilizes optical phonons to provide linewidth-limited resolution spectra of atom-like semiconductor structures in the energy domain. The method is also easily realized with a single spectrometer optical spectroscopy setup.

高分辨率声子辅助准共振荧光光谱仪

High resolution optical spectroscopy methods are demanding in terms of either technology, equipment, complexity, time or a combination of these. Here we ...

Free-form Light Actuators &#8212; Fabrication and Control of Actuation in Microscopic Scale

Liquid crystalline elastomers (LCEs) are smart materials capable of reversible shape-change in response to external stimuli, and have attracted researchers&#39; attention in many fields. Most of the studies focused on macroscopic LCE structures (films, fibers) and their miniaturization is still in its infancy. Recently developed lithography techniques, e.g., mask exposure and replica molding, only allow for creating 2D structures on LCE thin films. Direct laser writing (DLW) opens access to truly 3D fabrication in the microscopic scale. However, controlling the actuation topology and dynamics at the same length scale remains a challenge.
In this paper we report on a method to control the liquid crystal (LC) molecular alignment in the LCE microstructures of arbitrary three-dimensional shape. This was made possible by a combination of direct laser writing for both the LCE structures as well as for micrograting patterns inducing local LC alignment. Several types of grating patterns were used to introduce different LC alignments, which can be subsequently patterned into the LCE structures. This protocol allows one to obtain LCE microstructures with engineered alignments able to perform multiple opto-mechanical actuation, thus being capable of multiple functionalities. Applications can be foreseen in the fields of tunable photonics, micro-robotics, lab-on-chip technology and others.

Here, we fabricate 3D polymeric micro/nano structures in which both the shape and the molecular alignment can be engineered with nanometer scale accuracy by the use of direct laser writing. Light induced deformation of several types of liquid crystalline elastomer microstructures can be controlled in the microscopic scale.

自由形式的光驱动器 - 制作和开动控制在微观尺度

Liquid crystalline elastomers (LCEs) are smart materials capable of reversible shape-change in response to external stimuli, and have attracted ...

Evanescent Field Based Photoacoustics: Optical Property Evaluation at Surfaces

Here, we present a protocol to estimate material and surface optical properties using the photoacoustic effect combined with total internal reflection. Optical property evaluation of thin films and the surfaces of bulk materials is an important step in understanding new optical material systems and their applications. The method presented can estimate thickness, refractive index, and use absorptive properties of materials for detection. This metrology system uses evanescent field-based photoacoustics (EFPA), a field of research based upon the interaction of an evanescent field with the photoacoustic effect. This interaction and its resulting family of techniques allow the technique to probe optical properties within a few hundred nanometers of the sample surface. This optical near field allows for the highly accurate estimation of material properties on the same scale as the field itself such as refractive index and film thickness. With the use of EFPA and its sub techniques such as total internal reflection photoacoustic spectroscopy (TIRPAS) and optical tunneling photoacoustic spectroscopy (OTPAS), it is possible to evaluate a material at the nanoscale in a consolidated instrument without the need for many instruments and experiments that may be cost prohibitive.

Here we present a protocol to estimate material and surface optical properties using the photoacoustic effect combined with total internal reflection. This technique evanescent field-based photoacoustics can be used to create a photoacoustic metrology system to estimate materials&#39; thicknesses, bulk and thin film refractive indices, and explore their optical properties.

基于渐逝场光声:光学性能评估在表面

Here, we present a protocol to estimate material and surface optical properties using the photoacoustic effect combined with total internal reflection. ...

A Simple Dewar/Cryostat for Thermally Equilibrating Samples at Known Temperatures for Accurate Cryogenic Luminescence Measurements

The design and operation of a simple liquid nitrogen Dewar/cryostat apparatus based upon a small fused silica optical Dewar, a thermocouple assembly, and a CCD spectrograph are described. The experiments for which this Dewar/cryostat is designed require fast sample loading, fast sample freezing, fast alignment of the sample, accurate and stable sample temperatures, and small size and portability of the Dewar/cryostat cryogenic unit. When coupled with the fast data acquisition rates of the CCD spectrograph, this Dewar/cryostat is capable of supporting cryogenic luminescence spectroscopic measurements on luminescent samples at a series of known, stable temperatures in the 77-300 K range. A temperature-dependent study of the oxygen quenching of luminescence in a rhodium(III) transition metal complex is presented as an example of the type of investigation possible with this Dewar/cryostat. In the context of this apparatus, a stable temperature for cryogenic spectroscopy means a luminescent sample that is thermally equilibrated with either liquid nitrogen or gaseous nitrogen at a known measureable temperature that does not vary (&#916;T &#60; 0.1 K) during the short time scale (~1-10 sec) of the spectroscopic measurement by the CCD. The Dewar/cryostat works by taking advantage of the positive thermal gradient dT/dh that develops above liquid nitrogen level in the Dewar where h is the height of the sample above the liquid nitrogen level. The slow evaporation of the liquid nitrogen results in a slow increase in h over several hours and a consequent slow increase in the sample temperature T over this time period. A quickly acquired luminescence spectrum effectively catches the sample at a constant, thermally equilibrated temperature.

A simple liquid nitrogen Dewar/cryostat apparatus comprised of a small fused silica optical Dewar, a thermocouple, and a charge-coupled device (CCD) spectrograph are described. The experiments for which this Dewar/cryostat is designed require fast sample loading, freezing, and alignment, accurate and stable sample temperatures, and small size/portability.

一个简单的杜瓦瓶/低温恒温器的热的样品配平在为准确低温发光测量已知温度

The design and operation of a simple liquid nitrogen Dewar/cryostat apparatus based upon a small fused silica optical Dewar, a thermocouple assembly, and ...

Measuring the Densities of Aqueous Glasses at Cryogenic Temperatures

We demonstrate a method for determining the vitreous phase cryogenic temperature densities of aqueous mixtures, and other samples that require rapid cooling, to prepare the desired cryogenic temperature phase. Microliter to picoliter size drops are cooled by projection into a liquid nitrogen-argon (N2-Ar) mixture. The cryogenic temperature phase of the drop is evaluated using a visual assay that correlates with X-ray diffraction measurements. The density of the liquid N2-Ar mixture is adjusted by adding N2 or Ar until the drop becomes neutrally buoyant. The density of this mixture and thus of the drop is determined using a test mass and Archimedes principle. With appropriate care in drop preparation, management of gas above the liquid cryogen mixture to minimize icing, and regular mixing of the cryogenic mixture to prevent density stratification and phase separation, densities accurate to &#60;0.5% of drops as small as 50 pL can readily be determined. Measurements on aqueous cryoprotectant mixtures provide insight into cryoprotectant action, and provide quantitative data to facilitate thermal contraction matching in biological cryopreservation.

A protocol for determining the vitreous phase densities of micro- to pico-liter size drops of aqueous mixtures at cryogenic temperatures is described.

在低温下测量水性玻璃的密度

We demonstrate a method for determining the vitreous phase cryogenic temperature densities of aqueous mixtures, and other samples that require rapid ...