这项工作得到了美国海军研究实验室的核心项目的支持。

注意: 使用前请查阅所有相关的材料安全数据表 (MSDS), 并遵循所有适当的安全操作规程和程序。二氧化钒的原子层沉积生长使用一个限期反应器。用于限期增长的前体为四 (ethylmethylamido) 钒 (IV) (TEMAV) 和臭氧 (由超高纯度, 高压, 99.999% 氧气体, 0.3 流动和 5 psi 支持压力产生)。此外, 超高压 (99.999%) 氮气用于净化反应堆室。对于随后的真空退火, 超高压氧气体用于退火和超高压氮气的排气。TEMAV 是易燃的, 应仅用于适当的工程控制。压缩氧气体是一种危险, 只应用于适当的工程控制。压缩氮气是一种危险, 只应用于适当的工程控制。所有气体 (TEMAV、氧气、臭氧和氮气) 都使用适当的工程安全控制与限期反应反应器连接。不锈钢管连接臭氧发生器到限期反应堆, 因为它是清洁和更可靠的然后塑料管材。分离的超高压氧和氮气源在开始过程前使用适当的工程安全控制连接到真空退火室。丙酮和2丙醇是刺激物, 只应用于适当的个人防护设备和安全程序 (例如, 手套, 油烟机,等)。
1. 蓝宝石基底上二氧化钒的原子层沉积
<ol><li>清洁 c Al2O3 (蓝宝石) 衬底, 如下所示: 溶剂清洁基体在丙酮在40°c 在 sonicator 为5分钟, 然后直接地转移它 (没有漂洗) 到2丙醇在40°c 和油脂实验为5分钟. 冲洗基体在跑去离子用水2分钟, 用氮气烘干。</li>
	<li>确保限期反应釜室为150摄氏度, 并用氮气排出限期反应釜。</li>
	<li>将蓝宝石基板加载到反应器中, 关闭反应堆, 泵至 < 17 Pa 真空。至少等待 300s, 以确保样品达到150摄氏度。</li>
	<li>将 20 sccm 超高压氮气注入室内 (基本压力不应超过 36 Pa), 然后将臭氧脉冲用于15个饱和循环, 其中一个周期为0.05 秒的脉冲, 随后是十五年代的清除。</li>
	<li>为了增加二氧化钒, 脉冲 TEMAV 为 0.03 s 跟随了三十年代清除, 然后脉冲臭氧为 0.075 s 跟随三十年代清除。重复这个脉冲和清除周期, 直到达到预期的增长。 注意: 这个过程几乎是线性的, 每周期的增长率为 0.7-0.9 Å。</li>
	<li>先用超高压氮气排出限期反应堆室, 从限期反应堆中取出样品。将样品放在金属板上 (散热片), 使其冷却到室温。关闭限期反应堆和泵至 < 17 Pa 真空。样品现在包含蓝宝石基体上的无定形钒氧化物膜。 注意: 仔细取出样品, 因为样品加热到150摄氏度。</li>
</ol>2. 退火
注意: 在步骤1中由 "限期" 技术生长的2胶片产生无定形的 vo2。要创建面向多晶硅的2薄膜, 样品在一个具有六路十字的自定义超高真空退火室中退火。为了保持退火室的清洁, 将创建一个负载锁来插入和移除样品。3英寸直径的耐氧加热器由自定义铂丝加热器组成。该加热器提供了一个氧化镍雪橇的辐射加热, 样品安装在其中。该雪橇具有较高的发射率, 良好的传热从加热器到样品。
<ol><li>确保雪橇处于负载锁定状态, 然后用超高压氮气排气, 并打开负载锁。把样品放在雪橇上的装载锁和关闭负载锁室。</li>
	<li>使用粗泵将负载锁泵入 ~ 0.1 Pa。接下来, 切换到涡轮泵和泵负载锁定 < 10-4宾夕法尼亚州打开闸阀, 把雪橇转到退火室, 并将退火室泵到 < 10-5宾夕法尼亚州。</li>
	<li>流 1.5 sccm 超高纯度 (高压, 99.999%) 氧气进入退火室。 注: 运行氧气通过 5 sccm 质量流量控制器, 以确保低流量。压力必须介于 1x10-4和 7x10-4宾夕法尼亚州之间。这种压力必须在样品达到150摄氏度之前达到。</li>
	<li>加热雪橇到560°c (测量与高温计和热电偶) 使用热化舷梯率 ~ 20 °c/分钟. 在560°c 举行雪橇为 2 h (为300Å影片)。 注: 退火时间与厚度相关。经验数据表明退火 1 h 为样品 < 250 Å厚, 2 h 为样品 > 250 Å但 < 500 Å厚, 3 h 为样品 > 500 Å厚。</li>
	<li>关闭加热器并从加热器组件中取下雪橇 (朝向负载锁), 使样品淬火。</li>
	<li>将样品保持在氧气环境中, 直到样品温度小于150摄氏度 (例如, 在负载锁中使用高温计来测量样品温度)。 注意: 更好的样品通过等待, 直到更低的温度。一旦样品 < 150 摄氏度, 关闭氧气流和关闭闸阀。</li>
	<li>排气与超高压氮气。去除样品在 < 50 °c 并且放置样品在金属板材 (散热器) 冷却到室温。使用粗泵, 用空雪橇和泵向 0.1 Pa 关闭负载锁。切换到涡轮泵和泵负载锁定 < 10-4宾夕法尼亚州</li>
</ol>3. 表征
<ol><li>用拉曼光谱与532纳米激光激发源检验样品。
	<ol>
<li>将样品装入显微镜并将其聚焦。验证软件中照相机图像的样本焦点。将扫描激光功率设置为4兆瓦, 曝光时间为0.125 秒, 扫描次数为 10, 预览大小为40µm。</li>
		<li>单击 "实时频谱" 以观察拉曼光谱。优化对焦、激光功率、曝光时间和扫描次数, 最大限度地提高信噪比。单击 "保存频谱" 以保存数据。 开放光谱在 OMNIC。单击 "查找 Pks" 按钮以识别峰值。确定结晶度、相位 (VO2 vs vo、V2O3、v2O5、等) 和应变通过比较峰值到参考数据的钒氧化物12,13。 注: 窄峰表示高结晶质量, 而拉曼声子模式193、222和612厘米-1和/或软化389厘米-1模式的硬化是在 VO2晶体中的拉伸应变指示器。</li>
	</ol></li>
	<li>用 X 射线衍射 (XRD) 确定方向、结晶度和相位。 注: XRD 谱中峰的出现表明了晶体结构的性质, 特别是晶体结构和取向。通过将 XRD 数据峰值的2Θ角与 ICSD 的不同平面上的无机晶体结构数据库 (2) 卡相匹配, 确定 vo2的方向。通过将数据峰值与不同的钒氧化物相卡相匹配来确定相位。在这项工作中进行了实验峰与标准数据库的手工比较。单个 vo2峰值以39.9 度为单位验证了 vo2晶体质量, 并说明了型单斜 (020) 方向。</li>
	<li>X 射线光电子能谱 (XPS) 测定化学计量学和杂质含量
	<ol>
<li>将样品装载到样品架上。打开软件并单击 "排气负荷锁定"。将样品夹插入到负载锁中, 然后单击 "向下泵"。等待压力 < 4x10-5宾夕法尼亚州单击 "转移" 按钮将样品持有者移动到会议厅中。验证室压力为 < 7x10-6宾夕法尼亚州</li>
		<li>将测量参数输入到实验树中。打开 X 光枪与400µm 的斑点大小, 然后打开洪水枪。为测量量添加一个点, 然后为前体元素 (C 和 N) 以及薄膜元素 (V 和 O) 的高分辨率扫描添加点。对于每一个测量, 增加通行证能量 (200 ev 为勘测和 20 ev 为高分辨率扫描) 和扫描次数 (2 或更多为调查和15为高分辨率)。</li>
		<li>在样品的所需位置放置十字叉以进行点测量。单击并突出显示实验树标题, 然后单击菜单栏上的 "实验运行" 以执行所有测量扫描。</li>
		<li>执行调查 ID 程序以识别和分析影片中的元素。选择手动峰值添加后跟峰值匹配按钮, 分析高分辨率数据扫描中的键合。根据 XPS 手册14, 以综合峰值强度的比值来确定化学计量。</li>
		<li>完成后, 关闭枪, 然后单击转移按钮, 将样本持有人移动到负载锁。在加载锁中的示例后, 单击 "排气负载锁定" 并卸载该示例。 注意: 这标识了调查中所有元素的存在, 从而识别出杂质。XPS 峰值在特定的结合能显示钒氧化物的价, 如图 1所示。例如, 这些结果显示了两个代表 XPS 测量获得的深度分析与簇离子枪蚀刻的 as 沉积样品。xps 测量的表面显示的峰值在 518 eV 表明存在的 V2O5, 而 xps 测量的蚀刻样品 (在影片的散装) 显示了一个峰值在 516 eV 证明存在的 VO2。全宽半 max 表示钒在薄膜中的粘结均匀性 (换言之, 相纯度)。另外, 对其他能量峰值的分析可以识别污染物 (> 1%)。</li>
	</ol></li>
	<li>用原子力显微镜测定形态学 (AFM)
	<ol>
<li>打开计算机和 AFM 电子。启动 Nanoscope 程序, 选择攻丝模式, 然后选择负载实验。初始化阶段。</li>
		<li>按照屏幕左侧的实验顺序, 然后单击 "设置" 菜单。使用焦点控件将光学聚焦在悬臂上。单击 "优化激光位置" 将激光对准探头。单击 "Autoalign 检测器" 按钮, 然后单击 Autotune 悬臂。</li>
		<li>加载样品并打开真空。</li>
		<li>单击 "导航" 按钮, 使用轨迹球将样本置于头部下方。单击 "笔尖反射", 并使用轨迹球将头部降低到样品表面, 同时按住焦点按钮直到笔尖处于焦点。单击 "示例" 按钮并关闭 AFM 引擎盖。</li>
		<li>单击 "检查参数" 菜单。确保扫描大小为 < 1 µm, 并将样品/线设置为512。单击 "参与" 菜单按钮。等待二十年代。</li>
		<li>设置扫描大小为3µm, 并保持扫描速度在3.92 赫兹. 如果需要, 通过改变参数来优化图像: 驱动器振幅、振幅设定点、积分和比例增益。</li>
		<li>通过单击 "捕获" 按钮后面的 "下拉" 按钮来捕获所需的图像。在扫描之后, 单击 "提取" 按钮。</li>
		<li>双击所需的图像以在分析软件中打开它。要确定形态学, 请单击 "拼合" 按钮, 然后单击 "执行"。通过点击粗糙度计算表面粗糙度来提取统计参数, 然后单击粒子分析, 计算深度直方图和平均晶粒尺寸。</li>
		<li>单击 "导航" 菜单, 然后单击 "示例加载位置"。关闭真空并卸载样品。 注意: 为了从样品到样品的一致性, 保持相同的 AFM 扫描参数。</li>
	</ol></li>
	<li>确定光学透射率和反射率。
	<ol>
<li>使用可调谐光源, 测量近红外区域 (或接近) 正常入射时的光学透射率和反射率。校准系统无样品100% 透射率, 并与金镜近100% 的反射率。</li>
		<li>将 VO2示例加载到温度控制阶段。在所需温度下稳定试样。测量透射率和反射率在所需的光谱范围, 例如, 在整个近红外区域。 注: 为获得最佳结果, 温度应在20摄氏度以上和低于2 (通常为68摄氏度) 的过渡温度以下变化。</li>
	</ol></li>
</ol>4. 模拟光学常数 (介电常数和折射率)
<ol><li>将复介电常数 ( ε) 模型作为光子能量的函数, E, 使用以下等式 (其中ε∞ 是高频介电常数, 后跟n振荡器的总和, n是振荡器振幅, En 振荡器能量, 和Bn 振荡器阻尼): <img alt="Equation 1" src="/files/ftp_upload/57103/57103eq1.jpg"> 注意: 自定义 Matlab 程序对数据进行分析和建模。</li>
	<li>在步骤4.1 中输入蓝宝石衬底的已知参数, 并使用它们计算介质介电常数作为光波长的函数。然后计算折射率 (n = √ε), 并用折射率计算基体的反射率和透射率。</li>
	<li>将步骤4.2 的结果与实测数据进行比较, 然后使用优化技术 (如并用单纯形米德15) 来更新步骤4.2 的输入参数, 以减少测量结果和计算所得值之间的误差, 从而优化蓝宝石衬底的参数。</li>
	<li>在步骤4.1 中的等式中估计2的参数, 并使用它们计算介电介电常数。然后计算折射率 (n = √ε) 并使用该值, 连同 VO2厚度、衬底厚度、折射率 (从步骤 4.3)、光波长、光学极化和入射角度作为向传输16的输入, 以获得2涂层基底的反射率和透射率。使用优化技术 (如并用单纯形米德15) 来更新vo 2 输入参数, 并减少测量结果和计算所得值之间的误差, 从而优化了vo2 的参数。</li>
	<li>在若干温度下执行步骤4.2 至 4.4, 横跨二氧化钒的绝缘和金属状态 (温度从30到90°c)。对 VO2的折射率的温度依赖性进行建模, 如下所示: <img alt="Equation 3" src="/files/ftp_upload/57103/57103eq3.jpg"> 其中εVO2(t)是作为温度函数的 VO2的折射率, εins 和ε金属是绝缘和金属相的介电介电常数, f (t)是一种与温度相关的功能, 用于控制绝缘和金属光学特性的分布。对f (T)使用费米-狄拉克类似函数来控制绝缘和金属状态之间的过渡, 类似于有效中近似17、18、19, 所给出的: <img alt="Equation 4" src="/files/ftp_upload/57103/57103eq4.jpg"> 其中tt 是转换温度, W控制转换的宽度。</li>
	<li>采用优化技术对f (T)方程中的参数 (W 和 Tt) 进行更新, 以减少测量结果与计算所得值之间的误差, 从而优化过渡温度和宽度。这导致了温度和波长依赖模型的介电介电常数和折射率的 VO2。</li>
</ol>

<ol>
	<li>Park, J. H., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Measurement+of+a+solid-state+triple+point+at+the+metal-insulator+transition+in+VO2.">Measurement of a solid-state triple point at the metal-insulator transition in VO2.</a> Nature. 500 (7463), 431-434 (2013).</li><li>Yang, Z., Ko, C., Ramanathan, S. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Oxide+Electronics+Utilizing+Ultrafast+Metal-Insulator+Transitions.">Oxide Electronics Utilizing Ultrafast Metal-Insulator Transitions.</a> Annu. Rev. Mater. Res. 41 (1), 337-367 (2011).</li><li>Tan, X., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Unraveling+Metal-insulator+Transition+Mechanism+of+VO2+Triggered+by+Tungsten+Doping.">Unraveling Metal-insulator Transition Mechanism of VO2 Triggered by Tungsten Doping.</a> Sci. Rep. 2, 466 (2012).</li><li>Verleur, H. W., Barker, A. S., Berglund, C. N. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Optical+Properties+of+VO2+between+0.25+and+5+eV.">Optical Properties of VO2 between 0.25 and 5 eV.</a> Phys. Rev. 172 (3), 788-798 (1968).</li><li>Kiria, P., Hyett, G., Binions, R. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Solid+State+Thermochromic+Materials.">Solid State Thermochromic Materials.</a> Adv. Mater. Lett. 1 (2), 86-105 (2010).</li><li>Konovalova, O. P., Sidorov, A. I., Shaganov, I. I. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Interference+systems+of+controllable+mirrors+based+on+vanadium+dioxide+for+the+spectral+range+06-106+micrometer.">Interference systems of controllable mirrors based on vanadium dioxide for the spectral range 06-106 micrometer.</a> J. Opt. Technol. 66 (5), 391 (1999).</li><li>Premkumar, P. A., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Process+Study+and+Characterization+of+VO2+Thin+Films+Synthesized+by+ALD+Using+TEMAV+and+O3+Precursors.">Process Study and Characterization of VO2 Thin Films Synthesized by ALD Using TEMAV and O3 Precursors.</a> ECS J. Solid State Sci. Technol. 1 (4), P169-P174 (2012).</li><li>Rampelberg, G., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Crystallization+and+semiconductor-metal+switching+behavior+of+thin+VO2+layers+grown+by+atomic+layer+deposition.">Crystallization and semiconductor-metal switching behavior of thin VO2 layers grown by atomic layer deposition.</a> Thin Solid Films. 550, 59-64 (2014).</li><li>Peter, A. P., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Metal-Insulator+Transition+in+ALD+VO2++Ultrathin+Films+and+Nanoparticles:+Morphological+Control.">Metal-Insulator Transition in ALD VO2 Ultrathin Films and Nanoparticles: Morphological Control.</a> Adv. Funct. Mater. 25 (5), 679-686 (2015).</li><li>Rampelberg, G. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=.">.</a> Thin film synthesis of VO2 and VN by gas-solid reactions and atomic layer deposition. , (2016).</li><li>Kats, M. A., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Vanadium+Dioxide+as+a+Natural+Disordered+Metamaterial:+Perfect+Thermal+Emission+and+Large+Broadband+Negative+Differential+Thermal+Emittance.">Vanadium Dioxide as a Natural Disordered Metamaterial: Perfect Thermal Emission and Large Broadband Negative Differential Thermal Emittance.</a> Phys. Rev. X. 3 (4), 041004 (2013).</li><li>Atkin, J. M., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Strain+and+temperature+dependence+of+the+insulating+phases+of+VO2+near+the+metal-insulator+transition.">Strain and temperature dependence of the insulating phases of VO2 near the metal-insulator transition.</a> Phys. Rev. B. 85 (2), 020101 (2012).</li><li>Petrov, G. I., Yakovlev, V. V., Squier, J. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Raman+microscopy+analysis+of+phase+transformation+mechanisms+in+vanadium+dioxide.">Raman microscopy analysis of phase transformation mechanisms in vanadium dioxide.</a> Appl. Phys. Lett. 81 (6), 1023-1025 (2002).</li><li>Moulder, J. F. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=.">.</a> Handbook of X-ray Photoelectron Spectroscopy: A Reference Book of Standard Spectra for Identification and Interpretation of XPS Data. , (1992).</li><li>Nelder, J. A., Mead, R. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=A+Simplex+Method+for+Function+Minimization.">A Simplex Method for Function Minimization.</a> Comput. J. 7 (4), 308-313 (1965).</li><li>Born, M., Wolf, E. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=.">.</a> Principles of Optics: Electromagnetic Theory of Propagation, Interference and Diffraction of Light. , (1999).</li><li>Choi, H. S., Ahn, J. S., Jung, J. H., Noh, T. W., Kim, D. H. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Mid-infrared+properties+of+a+VO2+film+near+the+metal-insulator+transition.">Mid-infrared properties of a VO2 film near the metal-insulator transition.</a> Phys. Rev. B. 54 (7), 4621-4628 (1996).</li><li>Jepsen, P. U., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Metal-insulator+phase+transition+in+a+VO2+thin+film+observed+with+terahertz+spectroscopy.">Metal-insulator phase transition in a VO2 thin film observed with terahertz spectroscopy.</a> Phys. Rev. B. 74 (20), 205103 (2006).</li><li>Rozen, J., Lopez, R., Haglund, R. F., Feldman, L. C. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Two-dimensional+current+percolation+in+nanocrystalline+vanadiumdioxide+films.">Two-dimensional current percolation in nanocrystalline vanadiumdioxide films.</a> Appl. Phys. Lett. 88 (8), 081902 (2006).</li><li>Tazawa, M., Jin, P., Tanemura, S. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Optical+constants+of+V1-xWxO2+films.">Optical constants of V1-xWxO2 films.</a> Appl. Opt. 37 (10), 1858-1861 (1998).</li><li>. Micro- and Nano-scale Optoelectronic Devices Using Vanadium Dioxide Available from: <a target="_blank" href="https://tspace.library.utoronto.ca/handle/1807/68313">https://tspace.library.utoronto.ca/handle/1807/68313</a> (2014)</li><li>Briggs, R. M., Pryce, I. M., Atwater, H. A. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Compact+silicon+photonic+waveguide+modulator+based+on+the+vanadium+dioxide+metal-insulator+phase+transition.">Compact silicon photonic waveguide modulator based on the vanadium dioxide metal-insulator phase transition.</a> Opt. Express. 18 (11), 11192-11201 (2010).</li><li>Dicken, M. J., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Frequency+tunable+near-infrared+metamaterials+based+on+VO2+phase+transition.">Frequency tunable near-infrared metamaterials based on VO2 phase transition.</a> Opt. Express. 17 (20), 18330 (2009).</li></ol>

作者没有什么可透露的。

这里描述的生长方法为均匀性、化学、结构和形态学提供了可重现的结果。钒前驱体对制备沉积的限期膜的正确化学计量是至关重要的。这个特殊的前驱体促进了 +4 钒价态, 不像其他许多在文献中列出的促进更普遍的 +5 价态。此外, 这个特殊的前驱体有相当低的蒸气压, 需要加热, 以提供足够的剂量在给定条件下饱和。由于这一前驱体开始下降约175摄氏度, 这对两种加热的前驱体和限期增长的温度上限。另一个关键方面, 以实现正确的化学计量是臭氧浓度 (125 毫克/升在这里) 在剂量。通常, 发电机在特定条件下产生的臭氧浓度会随着时间的推移而降低或漂移。如果发生这种情况, 则必须调整臭氧脉冲和清除时间, 以保持化学计量学、形貌和硅片的均匀性。这里所描述的是如何在 c 平面蓝宝石基底上生长2的限期, 其中包括原位臭氧预处理。清洁和成核的生长之前的步骤依赖于基体;但是, 此处描述的过程适用于大多数基板 (惰性、氧化物、金属、等)。为了确定最佳的终止清洗和对 VO2生长的准备, 应考虑物种终止与钒前驱体之间的反应性, 同时尽量减少基体上的任何本底氧化物。最后, 在高长宽比衬底上展示了这一过程 (高达 100), 但对于极端情况, 人们应该考虑暴露或静态的 conformality 方法, 以进一步提高。
实现高品质, 晶限期的能力,2薄膜是相当依赖于后沉积退火参数。最关键的方面是压力, 特别是氧气的分压。高氧压力导致小面和谷物的生长, 最终导致纳米线的形成, 以及结果在 V2O5阶段。如果氧气压力过低, 氧气会从薄膜中退火, 导致 V2O3阶段。因此, 为了保持正确的相位并尽量减少薄膜的粗糙度, 应在 1x10-4到 7x10-4宾夕法尼亚州的范围内保持氧气压力。同样, 温度对于能够结晶薄膜、保持化学计量和最小化薄膜的粗糙是至关重要的。虽然2胶片的温度难以测量, 但经验结果表明, 结晶要求温度大于500摄氏度。在较高的温度下, 很难保持正确的化学计量和相, 并产生针孔自由膜。在温度和退火时间之间也有权衡, 特别是较高的温度可以减少退火时间。此外, 退火持续时间直接与薄膜的厚度有关。较厚的薄膜需要较长的时间才能达到最大结晶。因此, 对上述方法中所描述的氧压力、退火温度和退火时间进行了优化, 以产生高品质的2薄膜, 在近理想的过渡温度下表现出最大的光学性能变化。最后, 在氧退火过程中的升温和冷却速率对粗糙度和形貌有影响;这些越慢, 电影越平滑。
2的限期沉积和随后的退火, 产生具有大面积均匀性的定向多晶薄膜。在几乎任何基质的三维纳米形貌上, 共形都提供了生长薄膜。这使 VO2集成成为新的应用程序, 尤其适合于光学设备。
在增长和光学测量之后, 建立了一个模型, 它为在近红外光谱区域 (R2 = 0.96-0. 99) 中, 在其金属和绝缘相位中的 VO2的透射率和反射率提供了一个良好的匹配数据。红外绝缘相的反射率是创建该模型最具挑战性的过程。增加了振荡条件, 但这增加了模型的复杂性, 只是略微改善了适合在这个地区。应该指出的是, 在这个模型中, 洛仑兹振荡器的叠加是一个共同的光学模型, 不一定对应于特定的电子转换。最初, 模型包括一个德鲁德术语, 但是, 在数学优化之后, 德鲁德术语基本上被消除了。因此, 对几种最小化技术进行了研究。然而, 这些不同的技术融合在不涉及德鲁德术语的类似解决方案上。在限期任用的2中缺少一个德鲁德术语可能是由于许多因素, 如 1) 掺杂半导体样电阻率, 或 2) 等离子体频率移到较低的能量和/或大碰撞率 (阻尼项), 与金属协议这些电影的性质。
在绝缘相、T < 60 °c 中, 限期的介电常数和折射率2与其他制造方法 (溅射4、20、21和脉冲激光沉积22 ) 很好地吻合.、23)。在金属状态, T > 70 °c, 这些限期的影片比其他方法制造的 VO2表现出更低的损失。值得注意的是, 虽然不同的制造方法对2的介电常数和折射率产生一些不同的值, 但所有的胶片都显示出相似的趋势。
本文的模型对光学介电常数和折射率的温度和波长依赖性与实验测量数据吻合较好。该模型能够产生良好的质量符合测量的光学数据表明, 它可以可靠地预测的光学性质的 VO2作为相变从绝缘体到金属。使用这些模型, 可以根据温度、厚度和波长, 可预见地调整 VO2的光学特性, 以设计实现静态和动态目标的光学系统。这些模型通过修改胶片的厚度和温度, 使光学系统能够在被动和主动系统中使用 VO2来设计和开发。

二氧化钒在68摄氏度附近进行结晶相变。这就产生了从型单斜到四方的结构晶体变化。此转换的起源仍然是有争议的1, 但是最近的研究帮助开发了对生成此转换的进程的理解2,3,4 。无论起源如何, 相变的光学特性, 从绝缘体 (透射光) 在室温到一个更金属材料 (反射和吸收光) 在过渡温度2上的2 。.
在过去 (溅射、物理气相沉积、化学气相沉积、分子束外延、溶液、等) 中, 已经使用了各种方法来制造2的 VO。5. VO2的属性在很大程度上取决于用于制造薄膜6的技术, 这在不同的生长技术和随后的退火之间产生了显著的变异性, 并导致不同的结晶度和薄膜性能。本文研究了原子层沉积 (限期) 生长薄膜的光学性质, 但该方法适用于各种类型的 VO2薄膜的建模。
最近, 小组正在构造光学器件, 将2的薄膜加入到光学基底上。作为一种快速增长的新的沉积方法, 埃可以帮助制造这些光学器件, 并具有比替代技术更大的优势, 如大型区域均匀性、级厚度控制和保角膜覆盖范围 7 ,8,9。对于要求采用自限逐层沉积方法的应用而言, "限期" 是一种首选技术, 它制造了各种基材 (e. g), 用于异构集成, 或3D 结构的保形涂层10.最后, 对3D 结构的适形涂层在光学应用中特别有用。
本文的实验结果表明, 在低温条件下, 用双侧抛光的 c 型蓝宝石基板, 在氧环境中退火, 制备出高质量的结晶膜, 可获得超薄、无定形的定型膜。使用实验测量, 为在 VO2中的温度和波长相关的光学变化创建一个模型, 以使其用作可调谐折射率材料11。

<table border="0" cellpadding="0" cellspacing="0" width="731">
	<tbody>
		<tr height="21">
			<td height="21" style="height:21px;width:343px;">c-Al2O3</td>
			<td style="width:111px;"></td>
			<td style="width:111px;"></td>
			<td style="width:167px;"></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:343px;">UHP Oxygen</td>
			<td style="width:111px;">Air Products</td>
			<td style="width:111px;"></td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:343px;">UHP Nitrogen</td>
			<td style="width:111px;">Air Products</td>
			<td style="width:111px;"></td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">Tetrakis(ethylmethylamido)vanadium(IV) (TEMAV)&#160;</td>
			<td style="width:111px;">Air Liquide</td>
			<td style="width:111px;"></td>
			<td></td>
		</tr>
		<tr height="42">
			<td height="42" style="height:42px;width:343px;">Acetone</td>
			<td style="width:111px;">Fischer Scientific&#160;</td>
			<td style="width:111px;">A18-4</td>
			<td></td>
		</tr>
		<tr height="42">
			<td height="42" style="height:42px;width:343px;">2-propanol</td>
			<td style="width:111px;">Fischer Scientific&#160;</td>
			<td style="width:111px;">A416P-4</td>
			<td></td>
		</tr>
		<tr height="42">
			<td height="42" style="height:42px;">Savannah S200-G2&#160;</td>
			<td>Veeco - CNT</td>
			<td style="width:111px;">Savannah S200-G2&#160;</td>
			<td></td>
		</tr>
		<tr height="42">
			<td height="42" style="height:42px;width:343px;">ozone generator&#160;</td>
			<td style="width:111px;">Veeco - CNT</td>
			<td style="width:111px;">&#160;ozone generator&#160;</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:343px;">Platinum wire heater</td>
			<td style="width:111px;">HeatWave Labs</td>
			<td style="width:111px;">custom</td>
			<td></td>
		</tr>
	</tbody>
</table>

atomic layer deposition of vanadium dioxide and a temperature-dependent optical model

二氧化钒是一种材料, 具有可逆的金属绝缘子相变近68摄氏度。为了在广泛的基板上生长2 , 用硅片的均匀度和埃水平控制厚度, 选择了原子层沉积方法。这一限期的过程, 使高品质, 低温 (≤150°c) 增长的超薄薄膜 (100-1000 Å) 的 VO2。在此演示中, 在蓝宝石衬底上生长了2的 VO。这种低温生长技术主要产生无定形的2薄膜。随后的退火在超高真空室与压力的 7x10-4 Pa 的超高纯度 (99.999%) 氧气生产定向, 多晶 VO2薄膜。用拉曼光谱和 x-射线衍射法测定了2的结晶度、相和应变, 并用 x 射线光电子能谱法测定了化学计量学和杂质含量, 最后由原子力显微镜。这些数据证明了这种技术所生长的薄膜的高质量。创建了一个模型, 以适应在近红外光谱区域中的金属和绝缘相位的 VO2的数据。该方法的介电常数和折射率为2在其绝缘相中与其他制造方式很好地一致, 但在其金属状态上表现出不同。最后, 对薄膜光学特性的分析, 使得建立了一个波长和温度相关的复杂光学折射率模型, 用于开发2作为可调谐折射率材料。

为了鉴别生长的氧化钒的质量, x 射线光电子能谱 (XPS) 是在沉积的, 主要是无定形的 vo2薄膜 (图 1), 以及退火的水晶 vo2电影 (不显示)。X 射线衍射 (XRD) 是在退火的 VO2薄膜 (图 2) 上进行的。此外, 为了帮助量化薄膜内部化学的垂直剖面, 用聚类离子源进行深度剖面分析, 以尽量减少阳离子/负离子种类的优先蚀刻。两个典型的跟踪显示在图 1中, 一个在曲面上, 一个在大容量中。深度剖面和随后的 XPS 测量结果表明, 由于过量的环境 (不定) 氧和碳, 而沉积膜的前 1 nm 不为2 , 但在低压氧更受控制的退火过程中, 甚至表面稳定到 VO2。x 射线衍射测量是用铜 K α x 射线能量源进行的, 并显示在图 2中, 在39.9˚的单个 VO2峰值。这一峰值的签名验证了符合限期增长的 VO2的质量, 以及 (020) 晶体方向与蓝宝石基底的峰值对齐。
为了分析结晶度、相和应变, 采用 532 nm 激光器进行了拉曼光谱的激发。图 3显示了 VO2胶片的拉曼光谱, 显示了具有高结晶质量的窄峰。此外, 在钒钒低频率声子 (193 和222厘米-1) 和612厘米-1模式下增加的能量, 以及 389 cm-1模式的能量减少, 建议在这些影片中的拉伸应变12, 13。
用原子力显微镜 (AFM) 观察形态学。图 4显示的是 20-40 nm 的晶粒尺寸和 1.4 nm 的根均方根 (RMS) 粗糙度 (图 4A) 和退火胶片的 2.6 nm 的 RMS 粗糙度 (图 4B)。
利用具有扫描单色仪和光电探测器的白光光源, 在可见光和近红外区域提供覆盖, 获得光学透射率和反射率数据。图 5显示了胶片从绝缘体过渡到金属的温度依赖性, 表明过渡温度为61摄氏度。通过对实验数据的分析, 可以对2的温度和波长依赖性介电常数进行建模, 因为它从绝缘体过渡到金属。图 5显示了在使用表 1中的参数时, 模型如何准确地预测光学行为。
<img alt="Figure 1" class="xfigimg" src="/files/ftp_upload/57103/57103fig1.jpg"> 图 1: 在 c-Al2O3上, 35 nm 厚的 VO2的代表性 XPS 测量.XPS 显示, 该胶片的大部分为2 , 而表面 (包含 C 和 O 污染) 则被更转向 V2O5。化学计量建议2。<a href="/files/ftp_upload/57103/57103fig1large.jpg" target="_blank">请单击此处查看此图的较大版本.</a>
<img alt="Figure 2" class="xfigimg" src="/files/ftp_upload/57103/57103fig2v3.jpg"> 图 2: 在 c Al2O3上, 35 nm 厚的 VO2的 XRD 测量。此 XRD 测量显示单个 VO2 39.9˚中的峰值, 独立验证晶体质量并说明型单斜 (020) 方向与底层蓝宝石峰值对齐。<a href="/files/ftp_upload/57103/57103fig2v3large.jpg" target="_blank">请单击此处查看此图的较大版本.</a>
<img alt="Figure 3" class="xfigimg" src="/files/ftp_upload/57103/57103fig3.jpg"> 图 3: VO 的拉曼光谱2在 c-Al2O3.这种拉曼光谱有很窄的峰值, 表明高结晶质量, 并显示轻微的拉伸应变。<a href="/files/ftp_upload/57103/57103fig3large.jpg" target="_blank">请单击此处查看此图的较大版本.</a>
<img alt="Figure 4" class="xfigimg" src="/files/ftp_upload/57103/57103fig4.jpg"> 图 4: c-Al2O3上的 VO2的形态学。AFM 图像显示一致, 连续影片以五谷大小在20-40 毫微米的顺序和 RMS roughnesses (A) 1.4 毫微米为生长的影片和 (B) 2.6 毫微米为退火的影片。<a href="/files/ftp_upload/57103/57103fig4large.jpg" target="_blank">请单击此处查看此图的较大版本.</a>
<img alt="Figure 5" class="xfigimg" src="/files/ftp_upload/57103/57103fig5.jpg"> 图 5: 在 c-Al2O3上, 35 nm 厚的 VO2的近红外光学透射率和反射率。二氧化钒薄膜的光透射率和反射率的温度依赖性表现为40、60、70和90°c。图中的开放圆圈是在不同温度下, 在蓝宝石结构上测量的透射率、反射率和计算出的吸收, 而实线是二维温度的预测值, 而2的波长依赖性模型。<a href="/files/ftp_upload/57103/57103fig5large.jpg" target="_blank">请单击此处查看此图的较大版本.</a>
<table border="1" fo:keep-together.within-page="1" fo:keep-with-next.within-page="always"><tbody>
<tr>
<td></td>
			<td>ε∞</td>
			<td></td>
			<td>osc.1</td>
			<td>osc.2</td>
		</tr>
<tr>
<td>绝缘 子</td>
			<td colspan="4"></td>
		</tr>
<tr>
<td rowspan="3"></td>
			<td rowspan="3">3。4</td>
			<td>En
</td>
			<td>3。8</td>
			<td>1。2</td>
		</tr>
<tr>
<td>n
</td>
			<td>33</td>
			<td>2。1</td>
		</tr>
<tr>
<td>Bn
</td>
			<td>1。4</td>
			<td>1。3</td>
		</tr>
<tr>
<td>金属</td>
			<td colspan="4"></td>
		</tr>
<tr>
<td rowspan="3"></td>
			<td rowspan="3">4。5</td>
			<td>En
</td>
			<td>3。2</td>
			<td>0。6</td>
		</tr>
<tr>
<td>n
</td>
			<td>13</td>
			<td>5。3</td>
		</tr>
<tr>
<td>Bn
</td>
			<td>1。1</td>
			<td>1</td>
		</tr>
</tbody></table>表 1: 用于 VO 的典型模型参数2. 这些参数代表了振荡器模型中用于估计在其金属和绝缘相中的 VO2的介电常数。

Watch this Scientific Journal Video about Atomic Layer Deposition of Vanadium Dioxide and a Temperature-dependent Optical Model at JoVE.com

Atomic Layer Deposition of Vanadium Dioxide and a Temperature-dependent Optical Model

利用蓝宝石基底上的原子层沉积 (Å) 制备了二氧化钒薄膜 (100-1000) (2)。在此之后, 光学性能的特点是通过2的 VO 的金属绝缘子转换。通过测量的光学特性, 建立了一个模型来描述2的可调谐折射率。

二氧化钒原子层沉积与温度依赖性光学模型

Vanadium dioxide is a material that has a reversible metal-insulator phase change near 68 &#176;C. To grow VO2 on a wide variety of substrates, with ...

atomic-layer-deposition-vanadium-dioxide-temperature-dependent

Research

JoVE Journal

Engineering

11.8K 次观看.  Naval Research Laboratory. 利用蓝宝石基底上的原子层沉积 (Å) 制备了二氧化钒薄膜 (100-1000) (2)。在此之后, 光学性能的特点是通过2的 VO 的金属绝缘子转换。通过测量的光学特性, 建立了一个模型来描述2的可调谐折射率。

视频: Atomic Layer Deposition of Vanadium Dioxide and a Temperature-dependent Optical Model

Construction and Testing of Coin Cells of Lithium Ion Batteries

Rechargeable lithium ion batteries have wide applications in electronics, where customers always demand more capacity and longer lifetime. Lithium ion batteries have also been considered to be used in electric and hybrid vehicles1 or even electrical grid stabilization systems2. All these applications simulate a dramatic increase in the research and development of battery materials3-7, including new materials3,8, doping9, nanostructuring10-13, coatings or surface modifications14-17 and novel binders18. Consequently, an increasing number of physicists, chemists and materials scientists have recently ventured into this area. Coin cells are widely used in research laboratories to test new battery materials; even for the research and development that target large-scale and high-power applications, small coin cells are often used to test the capacities and rate capabilities of new materials in the initial stage. 
 In 2010, we started a National Science Foundation (NSF) sponsored research project to investigate the surface adsorption and disordering in battery materials (grant no. DMR-1006515). In the initial stage of this project, we have struggled to learn the techniques of assembling and testing coin cells, which cannot be achieved without numerous help of other researchers in other universities (through frequent calls, email exchanges and two site visits). Thus, we feel that it is beneficial to document, by both text and video, a protocol of assembling and testing a coin cell, which will help other new researchers in this field. This effort represents the "Broader Impact" activities of our NSF project, and it will also help to educate and inspire students.
In this video article, we document a protocol to assemble a CR2032 coin cell with a LiCoO2 working electrode, a Li counter electrode, and (the mostly commonly used) polyvinylidene fluoride (PVDF) binder. To ensure new learners to readily repeat the protocol, we keep the protocol as specific and explicit as we can. However, it is important to note that in specific research and development work, many parameters adopted here can be varied. First, one can make coin cells of different sizes and test the working electrode against a counter electrode other than Li. Second, the amounts of C black and binder added into the working electrodes are often varied to suit the particular purpose of research; for example, large amounts of C black or even inert powder were added to the working electrode to test the "intrinsic" performance of cathode materials14. Third, better binders (other than PVDF) have also developed and used18. Finally, other types of electrolytes (instead of LiPF6) can also be used; in fact, certain high-voltage electrode materials will require the uses of special electrolytes7.

A protocol to construct and test coin cells of lithium ion batteries is described. The specific procedures of making a working electrode, preparing a counter electrode, assembling a cell inside a glovebox and testing the cell are presented.

钮扣电池锂离子电池的建设和测试

Rechargeable lithium ion batteries have wide applications in electronics, where customers always demand more capacity and longer lifetime.  Lithium ion ...

科研

工程学

Fabricating Metamaterials Using the Fiber Drawing Method

Metamaterials are man-made composite materials, fabricated by assembling components much smaller than the wavelength at which they operate 1. They owe their electromagnetic properties to the structure of their constituents, instead of the atoms that compose them. For example, sub-wavelength metal wires can be arranged to possess an effective electric permittivity that is either positive or negative at a given frequency, in contrast to the metals themselves 2. This unprecedented control over the behaviour of light can potentially lead to a number of novel devices, such as invisibility cloaks 3, negative refractive index materials 4, and lenses that resolve objects below the diffraction limit 5. However, metamaterials operating at optical, mid-infrared and terahertz frequencies are conventionally made using nano- and micro-fabrication techniques that are expensive and produce samples that are at most a few centimetres in size 6-7. Here we present a fabrication method to produce hundreds of meters of metal wire metamaterials in fiber form, which exhibit a terahertz plasmonic response 8. We combine the stack-and-draw technique used to produce microstructured polymer optical fiber 9 with the Taylor-wire process 10, using indium wires inside polymethylmethacrylate (PMMA) tubes. PMMA is chosen because it is an easy to handle, drawable dielectric with suitable optical properties in the terahertz region; indium because it has a melting temperature of 156.6 &deg;C which is appropriate for codrawing with PMMA. We include an indium wire of 1 mm diameter and 99.99% purity in a PMMA tube with 1 mm inner diameter (ID) and 12 mm outside diameter (OD) which is sealed at one end. The tube is evacuated and drawn down to an outer diameter of 1.2 mm. The resulting fiber is then cut into smaller pieces, and stacked into a larger PMMA tube. This stack is sealed at one end and fed into a furnace while being rapidly drawn, reducing the diameter of the structure by a factor of 10, and increasing the length by a factor of 100. Such fibers possess features on the micro- and nano- scale, are inherently flexible, mass-producible, and can be woven to exhibit electromagnetic properties that are not found in nature. They represent a promising platform for a number of novel devices from terahertz to optical frequencies, such as invisible fibers, woven negative refractive index cloths, and super-resolving lenses.

Metamaterials at terahertz frequencies offer unique opportunities, but are challenging to fabricate in bulk. We adapt the fabrication procedure for microstructured polymer optical fibers to inexpensively fabricate metamaterials potentially on an industrial scale. We produce polymethylmethacrylate fibers containing ~10 &mu;m diameter indium wires separated by ~100 &mu;m, which exhibit a terahertz plasmonic response.

制造超材料使用光纤拉丝法

Metamaterials are man-made composite materials, fabricated by assembling components much smaller than the wavelength at which they operate 1. They owe ...

Optical Trapping of Nanoparticles

Optical trapping is a technique for immobilizing and manipulating small objects in a gentle way using light, and it has been widely applied in trapping and manipulating small biological particles. Ashkin and co-workers first demonstrated optical tweezers using a single focused beam1. The single beam trap can be described accurately using the perturbative gradient force formulation in the case of small Rayleigh regime particles1. In the perturbative regime, the optical power required for trapping a particle scales as the inverse fourth power of the particle size. High optical powers can damage dielectric particles and cause heating. For instance, trapped latex spheres of 109 nm in diameter were destroyed by a 15 mW beam in 25 sec1, which has serious implications for biological matter2,3.
A self-induced back-action (SIBA) optical trapping was proposed to trap 50 nm polystyrene spheres in the non-perturbative regime4. In a non-perturbative regime, even a small particle with little permittivity contrast to the background can influence significantly the ambient electromagnetic field and induce a large optical force. As a particle enters an illuminated aperture, light transmission increases dramatically because of dielectric loading. If the particle attempts to leave the aperture, decreased transmission causes a change in momentum outwards from the hole and, by Newton's Third Law, results in a force on the particle inwards into the hole, trapping the particle. The light transmission can be monitored; hence, the trap can become a sensor. The SIBA trapping technique can be further improved by using a double-nanohole structure.
The double-nanohole structure has been shown to give a strong local field enhancement5,6. Between the two sharp tips of the double-nanohole, a small particle can cause a large change in optical transmission, thereby inducing a large optical force. As a result, smaller nanoparticles can be trapped, such as 12 nm silicate spheres7 and 3.4 nm hydrodynamic radius bovine serum albumin proteins8. In this work, the experimental configuration used for nanoparticle trapping is outlined. First, we detail the assembly of the trapping setup which is based on a Thorlabs Optical Tweezer Kit. Next, we explain the nanofabrication procedure of the double-nanohole in a metal film, the fabrication of the microfluidic chamber and the sample preparation. Finally, we detail the data acquisition procedure and provide typical results for trapping 20 nm polystyrene nanospheres.

The following setup approach details low power optical trapping of dielectric nanoparticles using a double-nanohole in metal film.

纳米粒子的光学捕获

Optical trapping is a technique for immobilizing and manipulating small objects in a gentle way using light, and it has been widely applied in trapping ...

Fabrication of Nano-engineered Transparent Conducting Oxides by Pulsed Laser Deposition

Nanosecond Pulsed Laser Deposition (PLD) in the presence of a background gas allows the deposition of metal oxides with tunable morphology, structure, density and stoichiometry by a proper control of the plasma plume expansion dynamics. Such versatility can be exploited to produce nanostructured films from compact and dense to nanoporous characterized by a hierarchical assembly of nano-sized clusters. In particular we describe the detailed methodology to fabricate two types of Al-doped ZnO (AZO) films as transparent electrodes in photovoltaic devices: 1) at low O2 pressure, compact films with electrical conductivity and optical transparency close to the state of the art transparent conducting oxides (TCO) can be deposited at room temperature, to be compatible with thermally sensitive materials such as polymers used in organic photovoltaics (OPVs); 2) highly light scattering hierarchical structures resembling a forest of nano-trees are produced at higher pressures. Such structures show high Haze factor (&gt;80%) and may be exploited to enhance the light trapping capability. The method here described for AZO films can be applied to other metal oxides relevant for technological applications such as TiO2, Al2O3, WO3 and Ag4O4.

We describe the experimental method to deposit nanostructured oxide thin films by nanosecond Pulsed Laser Deposition (PLD) in the presence of a background gas. By using this method Al-doped ZnO (AZO) films, from compact to hierarchically structured as nano-tree forests, can be deposited.

制备纳米设计的脉冲激光沉积透明导电氧化物

Nanosecond Pulsed  Laser Deposition (PLD) in the presence of a background gas allows the deposition  of metal oxides with tunable morphology, structure, ...

Measurement and Analysis of Atomic Hydrogen and Diatomic Molecular AlO, C2, CN, and TiO Spectra Following Laser-induced Optical Breakdown

In this work, we present time-resolved measurements of atomic and diatomic spectra following laser-induced optical breakdown. A typical LIBS arrangement is used. Here we operate a Nd:YAG laser at a frequency of 10 Hz at the fundamental wavelength of 1,064 nm. The 14 nsec pulses with anenergy of 190 mJ/pulse are focused to a 50 &#181;m spot size to generate a plasma from optical breakdown or laser ablation in air. The microplasma is imaged onto the entrance slit of a 0.6 m spectrometer, and spectra are recorded using an 1,800 grooves/mm grating an intensified linear diode array and optical multichannel analyzer (OMA) or an ICCD. Of interest are Stark-broadened atomic lines of the hydrogen Balmer series to infer electron density. We also elaborate on temperature measurements from diatomic emission spectra of aluminum monoxide (AlO), carbon (C2), cyanogen (CN), and titanium monoxide (TiO).
The experimental procedures include wavelength and sensitivity calibrations. Analysis of the recorded molecular spectra is accomplished by the fitting of data with tabulated line strengths. Furthermore, Monte-Carlo type simulations are performed to estimate the error margins. Time-resolved measurements are essential for the transient plasma commonly encountered in LIBS.

Measurement and Analysis of Atomic Hydrogen and Diatomic Molecular AlO, C2, CN, and TiO Spectra Following Laser-induced Optical Breakdown

Time-resolved atomic and diatomic molecular species are measured using LIBS. The spectra are collected at various time delays following the generation of optical breakdown plasma with Nd:YAG laser radiation&#160;and are analyzed to infer electron density and temperature.

测量和原子氢和双原子分子ALO，C分析<sub&gt; 2</sub&gt;，CN和二氧化钛光谱承接激光诱导光学击穿

In this work, we present time-resolved measurements of atomic and diatomic spectra following laser-induced optical breakdown. A typical LIBS arrangement ...

Atomic Force Microscopy of Red-Light Photoreceptors Using PeakForce Quantitative Nanomechanical Property Mapping

Atomic force microscopy (AFM) uses a pyramidal tip attached to a cantilever to probe the force response of a surface. The deflections of the tip can be measured to ~10 pN by a laser and sectored detector, which can be converted to image topography. Amplitude modulation or &#8220;tapping mode&#8221; AFM involves the probe making intermittent contact with the surface while oscillating at its resonant frequency to produce an image. Used in conjunction with a fluid cell, tapping-mode AFM enables the imaging of biological macromolecules such as proteins in physiologically relevant conditions. Tapping-mode AFM requires manual tuning of the probe and frequent adjustments of a multitude of scanning parameters which can be challenging for inexperienced users. To obtain high-quality images, these adjustments are the most time consuming.
PeakForce Quantitative Nanomechanical Property Mapping (PF-QNM) produces an image by measuring a force response curve for every point of contact with the sample. With ScanAsyst software, PF-QNM can be automated. This software adjusts the set-point, drive frequency, scan rate, gains, and other important scanning parameters automatically for a given sample. Not only does this process protect both fragile probes and samples, it significantly reduces the time required to obtain high resolution images. PF-QNM is compatible for AFM imaging in fluid; therefore, it has extensive application for imaging biologically relevant materials.
The method presented in this paper describes the application of PF-QNM to obtain images of a bacterial red-light photoreceptor, RpBphP3 (P3), from photosynthetic R. palustris in its light-adapted state. Using this method, individual protein dimers of P3 and aggregates of dimers have been observed on a mica surface in the presence of an imaging buffer. With appropriate adjustments to surface and/or solution concentration, this method may be generally applied to other biologically relevant macromolecules and soft materials.

A method for investigating the structure of a protein photoreceptor using atomic force microscopy (AFM) is described in this paper. PeakForce Quantitative Nanomechanical Property Mapping (PF-QNM) reveals intact protein dimers on a mica surface.

冲红灯光感受器原子力显微镜使用PeakForce定量纳米机械性能映射

Atomic force microscopy (AFM) uses a pyramidal tip attached to a cantilever to probe the force response of a surface. The deflections of the tip can be ...

Making Record-efficiency SnS Solar Cells by Thermal Evaporation and Atomic Layer Deposition

Tin sulfide (SnS) is a candidate absorber material for Earth-abundant, non-toxic solar cells. SnS offers easy phase control and rapid growth by congruent thermal evaporation, and it absorbs visible light strongly. However, for a long time the record power conversion efficiency of SnS solar cells remained below 2%. Recently we demonstrated new certified record efficiencies of 4.36% using SnS deposited by atomic layer deposition, and 3.88% using thermal evaporation. Here the fabrication procedure for these record solar cells is described, and the statistical distribution of the fabrication process is reported. The standard deviation of efficiency measured on a single substrate is typically over 0.5%. All steps including substrate selection and cleaning, Mo sputtering for the rear contact (cathode), SnS deposition, annealing, surface passivation, Zn(O,S) buffer layer selection and deposition, transparent conductor (anode) deposition, and metallization are described. On each substrate we fabricate 11 individual devices, each with active area 0.25 cm2. Further, a system for high throughput measurements of current-voltage curves under simulated solar light, and external quantum efficiency measurement with variable light bias is described. With this system we are able to measure full data sets on all 11 devices in an automated manner and in minimal time. These results illustrate the value of studying large sample sets, rather than focusing narrowly on the highest performing devices. Large data sets help us to distinguish and remedy individual loss mechanisms affecting our devices.

Tin sulfide (SnS) is a candidate material for Earth-abundant, non-toxic solar cells. Here, we demonstrate the fabrication procedure of the SnS solar cells employing atomic layer deposition, which yields 4.36% certified power conversion efficiency, and thermal evaporation which yields 3.88%.

通过热蒸发和原子层沉积使记录效率的SnS太阳能电池

Tin sulfide (SnS) is a candidate absorber material for Earth-abundant, non-toxic solar cells. SnS offers easy phase control and rapid growth by congruent ...

Fabrication and Operation of a Nano-Optical Conveyor Belt

The technique of using focused laser beams to trap and exert forces on small particles has enabled many pivotal discoveries in the nanoscale biological and physical sciences over the past few decades. The progress made in this field invites further study of even smaller systems and at a larger scale, with tools that could be distributed more easily and made more widely available. Unfortunately, the fundamental laws of diffraction limit the minimum size of the focal spot of a laser beam, which makes particles smaller than a half-wavelength in diameter hard to trap and generally prevents an operator from discriminating between particles which are closer together than one half-wavelength. This precludes the optical manipulation of many closely-spaced nanoparticles and&#160;limits the&#160;resolution of optical-mechanical systems. Furthermore, manipulation using focused beams requires beam-forming or steering optics, which can be very bulky and expensive. To address these limitations in the system scalability of conventional optical trapping our lab has devised an alternative technique which utilizes near-field optics to move particles across a chip. Instead of focusing laser beams in the far-field, the optical near field of plasmonic resonators produces the necessary local optical intensity enhancement to overcome the restrictions of diffraction and manipulate particles at higher resolution. Closely-spaced resonators produce strong optical traps which can be addressed to mediate the hand-off of particles from one to the next in a conveyor-belt-like fashion. Here, we describe how to design and produce a conveyor belt using a gold surface patterned with plasmonic C-shaped resonators and how to operate it with polarized laser light to achieve super-resolution nanoparticle manipulation and transport. The nano-optical conveyor belt chip can be produced using lithography techniques and easily packaged and distributed.

The scalability and resolution of conventional optical manipulation techniques are limited by diffraction. We circumvent the diffraction limit and describe a method of optically transporting nanoparticles across a chip using a gold surface patterned with a path of closely spaced C-shaped plasmonic resonators.

一个纳米光输送带的制作和操作

The technique of using focused laser beams to trap and exert forces on small particles has enabled many pivotal discoveries in the nanoscale biological ...

Digital Printing of Titanium Dioxide for Dye Sensitized Solar Cells

Silicon solar cell manufacturing is an expensive and high energy consuming process. In contrast, dye sensitized solar cell production is less environmentally damaging with lower processing temperatures presenting a viable and low cost alternative to conventional production. This paper further enhances these environmental credentials by evaluating the digital printing and therefore additive production route for these cells. This is achieved here by investigating the formation and performance of a metal oxide photoelectrode using nanoparticle sized titanium dioxide. An ink-jettable material was formulated, characterized and printed with a piezoelectric inkjet head to produce a 2.6 &#181;m thick layer. The resultant printed layer was fabricated into a functioning cell with an active area of 0.25 cm2 and a power conversion efficiency of 3.5%. The binder-free formulation resulted in a reduced processing temperature of 250 &#176;C, compatible with flexible polyamide substrates which are stable up to temperatures of 350 &#730;C. The authors are continuing to develop this process route by investigating inkjet printing of other layers within dye sensitized solar cells.

This paper investigates the suitability of inkjet printing for the manufacturing of dye-sensitized solar cells. A binder-free TiO2 nanoparticle ink was formulated and printed onto a FTO glass substrate. The printed layer was fabricated into a cell with an active area of 0.25 cm2 and an efficiency of 3.5%.

钛白粉用于染料敏化太阳能电池的数码印刷

Silicon solar cell manufacturing is an expensive and high energy consuming process. In contrast, dye sensitized solar cell production is less ...

Electrospray Deposition of Uniform Thickness Ge23Sb7S70 and As40S60 Chalcogenide Glass Films

Solution-based electrospray film deposition, which is compatible with continuous, roll-to-roll processing, is applied to chalcogenide glasses. Two chalcogenide compositions are demonstrated: Ge23Sb7S70 and As40S60, which have both been studied extensively for planar mid-infrared (mid-IR) microphotonic devices. In this approach, uniform thickness films are fabricated through the use of computer numerical controlled (CNC) motion. Chalcogenide glass (ChG) is written over the substrate by a single nozzle along a serpentine path. Films were subjected to a series of heat treatments between 100 &#176;C and 200 &#176;C under vacuum to drive off residual solvent and densify the films. Based on transmission Fourier transform infrared (FTIR) spectroscopy and surface roughness measurements, both compositions were found to be suitable for the fabrication of planar devices operating in the mid-IR region. Residual solvent removal was found to be much quicker for the As40S60 film as compared to Ge23Sb7S70. Based on the advantages of electrospray, direct printing of a gradient refractive index (GRIN) mid-IR transparent coating is envisioned, given the difference in refractive index of the two compositions in this study.

Electrospray Deposition of Uniform Thickness Ge23Sb7S70 and As40S60 Chalcogenide Glass Films

A method of uniform thickness solution-derived chalcogenide glass film deposition is demonstrated using computer numerical controlled motion of a single-nozzle electrospray.

二氧化钒原子层沉积与温度依赖性光学模型

摘要

探索更多视频

此视频中的章节