这项工作得到了部分支持, 其中大部分是由 105-2221-001-011-MY3 和最多 105-2622-8-002-001 的项目资助, 由科技部, 台湾, 并部分由应用科学研究中心资助的重点项目, 中央研究院,台湾。

1. 单个2D 材料的增长 (MoS2和 WS2)
<ol><li>
用射频溅射系统进行过渡金属沉积
	<ol>
<li>一个干净的 2 x 2 cm2蓝宝石衬底放置在样品持有人与抛光的一面向溅射系统的目标的过渡金属沉积。蓝宝石基板的选择是由于蓝宝石在高温和原子平面表面的化学稳定性。</li>
		<li>泵下溅射室到 3 x 10-6乇依次使用一个机械泵, 其次是扩散泵。</li>
		<li>将 Ar 气体注入溅射系统, 并使用质量流量控制器 (MFC) 使气体流量保持在40毫升/分钟。</li>
		<li>使用手动压力控制阀将腔室压力保持在 5 x 10-2乇上, 并点燃 Ar 等离子体。将输出功率保持在 40 W。</li>
		<li>使用手动轮角锥阀将燃烧室压力降低到 5 x 10-3乇。</li>
		<li>手动打开蓝宝石衬底与2英寸金属靶之间的快门, 并开始金属沉积。在沉积过程中, 将溅射功率保持在 40 w, 用于钼和钨。背景压力保持在 5 x 10-3乇与40毫升/分钟氩气流量。</li>
		<li>控制溅射时间, 沉积不同厚度的过渡金属薄膜。由于金属厚度薄, 溅射时间将提供更好的控制膜厚度比从石英晶体谐振器的读数。 注意: 使用当前原稿所讨论的方法生长的 MoS2和 WS2的层数与 pre-deposited 钼和 W 薄膜的溅射次数成正比。溅射时间的确定获得 MoS2和 WS2与所需的层数是基于横断面高分辨率透射电子显微镜 (HRTEM) 图像的不同溅射时间的样品。然而, 如果 pre-deposited 钼和 w 薄膜太厚, mo 和 w 氧化物的分离将成为主导生长机制, 而不是平面 MoS2和 WS2胶片增长。因此, 层数与溅射时间的比例仅限于少量层 TMDs。随着 mos2在当前原稿中的生长情况, 当 mos2胶片少于10层时, 层数将与溅射时间成正比。溅射时间是三十年代为5层 MoS 的成长2。</li>
	</ol>
</li>
	<li>
过渡金属膜的硫化
	<ol>
<li>将蓝宝石衬底与 pre-deposited 过渡金属薄膜放在热熔炉的中心硫化。</li>
		<li>将硫磺粉放在气流的上游, 距离炉子加热区2厘米。在这个位置, 当基体温度增加到800° c 时, S 粉末的蒸发温度将是120° c。精确控制硫化中不同过渡金属的粉末重量。在工作中, S 粉末重量是1.5 克为 Mo 和 1.0 g 为 W。 注: 我们根据每种用不同的硫粉制备的材料的结果, 确定了用于制备 MoS2和 WS2薄膜的硫粉量。</li>
		<li>保持炉膛压力在0.7 乇。在硫化过程中, 使用130毫升/分钟氩气作为载体气体。</li>
		<li>将加热炉的温度从室温提高到800° c, 在40分钟内将温度提高到20° c/分钟. 将温度保持在800° c, 直到硫粉完全蒸发。之后, 加热器的功率被切断, 以降低炉温。炉子从800° c 到达室温需要大约30到40分钟。</li>
	</ol>
</li>
	<li>使用 488 nm 激光15,16,17执行拉曼光谱测量。获取横截面 HRTEM 图像以验证2D 晶体的层数15、16、17。</li>
</ol>2. WS2/MoS2垂直单杂结构的增长
注: 本节用于创建一个由5层 MoS2和4层 WS2组成的具有蓝宝石层的单异质结构。
<ol><li>按照与步骤1.1 相同的步骤操作。使用三十年代溅射时间的射频溅射系统将 Mo 薄膜沉积在蓝宝石衬底上。</li>
	<li>Sulfurize 的 Mo 薄膜遵循相同的硫化步骤 1.2, 为 MoS2的增长。五层 MoS2将在硫化过程之后获得。</li>
	<li>按照步骤1.1 的相同步骤操作。使用三十年代溅射时间的射频溅射系统将 W 薄膜沉积在 MoS2/蓝宝石衬底上。</li>
	<li>Sulfurize 为 WS2的增长而遵循步骤1.2 的相同硫化过程的 W 胶片。WS2的四层将在硫化过程之后的 MoS2的顶部获得。 注: 金属沉积和硫化过程与个别材料相同。Mo 和 W 薄膜的溅射时间取决于 MoS2和 WS2层所需的层数。可以通过重复相同的生长过程来建立双或 multi-hetero 结构。在垂直异质结构中, TMDs 的序列也可以根据样本结构而改变。</li>
</ol>3. 薄膜传输和器件制作程序
<ol><li>
2D 晶体薄膜的膜传递过程
	<ol>
<li>自旋外套三滴聚 (甲基丙烯酸甲酯) (PMMA) 在 TMD 薄膜上覆盖整个薄膜室温。两级旋转转速的微调是 500 rpm 为十年代和 800 rpm 为十年代。在120° c 固化5分钟后, PMMA 厚度约为3µm。</li>
		<li>将 PMMA/TMD/蓝宝石样品放在充满去离子水的培养皿中。</li>
		<li>利用在 DI 水中的镊子, 从蓝宝石基体上剥离出 PMMA/TMD 薄膜的一角。</li>
		<li>热250毫升的1米 koh 水溶液 (14 克 koh 丸混合250毫升水) 在烧杯到100° c。将样品移动到加热的 KOH 水溶液中, 继续剥离 PMMA/TMD 薄膜, 直到胶片完全从基底剥离。剥皮需要大约1分钟完成。</li>
		<li>使用一个单独的蓝宝石衬底, 从 KOH 溶液中舀出 PMMA/TMD 薄膜。将胶片移至250毫升的烧杯中, 用 DI 水冲洗膜上的残渣。在这一阶段, PMMA/TMD 薄膜与蓝宝石底材之间的附着力很弱。因此, 这部影片将 de-attach 从蓝宝石衬底浸入到 DI 水中。</li>
		<li>重复步骤 3.1.4-3.1.5 三次使用新的 DI 水, 以确保大部分的残留 KOH 是从影片中删除。 注意: 每个 TMD 层之间的附着力要比蓝宝石衬底的 TMDs 强得多。因此, 相同的传输过程可以应用于单个 MoS2/WS2材料或其异质结构。2D 晶体薄膜将被完全剥离的基板, 这是类似于剥离的 MoS2/石墨烯杂-结构在以前的出版物中讨论18。根据转移薄膜的目的, 本步骤中提到的基板可以是蓝宝石衬底或带有 pre-deposited 电极的2/Si 衬底, 如步骤3.2 所述。其他基板也可用于此目的。</li>
	</ol>
</li>
	<li>
2D 晶体晶体管的制造。
	<ol>
<li>使用标准光刻来定义的电极模式, 在2/Si 衬底15,16,17。由 10 nm 钛 (Ti) 或 100 nm 金 (Au) 制成的源和漏极电极是在 300 nm 的2/p 型 Si 衬底上制作的。</li>
		<li>将带 pre-patterned 的源/漏极的2/Si 衬底浸入装满 DI 水的烧杯中, 并将其附加到在步骤3.1 中准备的 PMMA/tmd 薄膜的 tmd 一侧。</li>
		<li>烘烤样品在100° c 为3分钟, 在影片以后附有了一层的2/Si 基体, 去除水残渣。</li>
		<li>滴三滴 pmma 的样品与 pmma/TMD 薄膜覆盖整个表面, 使薄膜更牢固地附着在基板上。</li>
		<li>在移动到下一步骤之前, 将样品放置在电子干柜中至少8小时。</li>
		<li>用丙酮填充两个不同的250毫升烧杯。将与 pmma/TMD 薄膜相连的样品依次浸入两个不同的烧杯, 分别填充丙酮50和10分钟, 除去顶部 pmma 层。</li>
		<li>使用标准的光刻和反应离子蚀刻定义晶体管通道15,16,17。后栅 MoS2和 WS2/mos2杂结构晶体管是捏造的151617。设备的通道长度和宽度分别为5和150μ m。</li>
		<li>使用双通道系统源仪器测量晶体管的电流电压特性15,16,17。</li>
	</ol>
</li>
</ol>

<ol>
	<li>Moldt, T., 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=High-Yield+Production+and+Transfer+of+Graphene+Flakes+Obtained+by+Anodic+Bonding.">High-Yield Production and Transfer of Graphene Flakes Obtained by Anodic Bonding.</a> ACS Nano. 5, 7700-7706 (2011).</li><li>Choi, W., 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=High-Detectivity+Multilayer+MoS2+Phototransistors+with+Spectral+Response+from+Ultraviolet+to+Infrared.">High-Detectivity Multilayer MoS2 Phototransistors with Spectral Response from Ultraviolet to Infrared.</a> Adv. Mater. 24, 5832-5836 (2012).</li><li>Liu, H., Neal, A. T., Ye, P. D. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Channel+Length+Scaling+of+MoS2+MOSFETs.">Channel Length Scaling of MoS2 MOSFETs.</a> ACS Nano. 6, 8563-8569 (2012).</li><li>Wang, Q. H., Kalantar-Zadeh, K., Kis, A., Coleman, J. N., Strano, M. S. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Electronics+and+optoelectronics+of+two-dimensional+transition+metal+dichalcogenides.">Electronics and optoelectronics of two-dimensional transition metal dichalcogenides.</a> Nat. Nanotechnol. 7, 699-712 (2012).</li><li>Radisavljevic, B., Radenovic, A., Brivio, J., Giacometti, V., Kis, A. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Single-layer+MoS2+transistors.">Single-layer MoS2 transistors.</a> Nat. Nanotechnol. 6, 147-150 (2011).</li><li>Lee, Y. 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=Synthesis+of+Large-Area+MoS2+Atomic+Layers+with+Chemical+Vapor+Deposition.">Synthesis of Large-Area MoS2 Atomic Layers with Chemical Vapor Deposition.</a> Adv. Mater. 24, 2320-2325 (2012).</li><li>Yu, Y., Li, C., Liu, Y., Su, L., Zhang, Y., Cao, L. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Controlled+Scalable+Synthesis+of+Uniform,+High-Quality+Monolayer+and+Few-layer+MoS2+Films.">Controlled Scalable Synthesis of Uniform, High-Quality Monolayer and Few-layer MoS2 Films.</a> Sci. Rep. 3, 1866 (2013).</li><li>Ling, 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=Role+of+the+Seeding+Promoter+in+MoS2+Growth+by+Chemical+Vapor+Deposition.">Role of the Seeding Promoter in MoS2 Growth by Chemical Vapor Deposition.</a> Nano Lett. 14, 464-472 (2014).</li><li>Lee, Y., 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=Synthesis+of+wafer-scale+uniform+molybdenum+disulfide+films+with+control+over+the+layer+number+using+a+gas+phase+sulfur+precursor.">Synthesis of wafer-scale uniform molybdenum disulfide films with control over the layer number using a gas phase sulfur precursor.</a> Nanoscale. 6, 2821-2826 (2014).</li><li>Lin, M. Y., Su, C. F., Lee, S. C., Lin, S. Y. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=The+Growth+Mechanisms+of+Graphene+Directly+on+Sapphire+Substrates+using+the+Chemical+Vapor+Deposition.">The Growth Mechanisms of Graphene Directly on Sapphire Substrates using the Chemical Vapor Deposition.</a> J. Appl. Phys. 115, 223510 (2014).</li><li>Wu, C. R., Chang, X. R., Chang, S. W., Chang, C. E., Wu, C. H., Lin, S. Y. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Multilayer+MoS2+prepared+by+one-time+and+repeated+chemical+vapor+depositions:+anomalous+Raman+shifts+and+transistors+with+high+ON/OFF+ratio.">Multilayer MoS2 prepared by one-time and repeated chemical vapor depositions: anomalous Raman shifts and transistors with high ON/OFF ratio.</a> J. Phys. D Appl. Phys. 48, 435101 (2015).</li><li>Li, M. Y., 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=Epitaxial+growth+of+a+monolayer+WSe2-MoS2+lateral+p-n+junction+with+an+atomically+sharp+interface.">Epitaxial growth of a monolayer WSe2-MoS2 lateral p-n junction with an atomically sharp interface.</a> Science. 349, 524-528 (2015).</li><li>Zhan, Y., Liu, Z., Najmaei, S., Ajayan, M. P., Lou, J. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Large-area+vapor-phase+growth+and+characterization+of+MoS2+atomic+layers+on+a+SiO2+substrate.">Large-area vapor-phase growth and characterization of MoS2 atomic layers on a SiO2 substrate.</a> Small. 8, 966 (2012).</li><li>Woods, 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=One-Step+Synthesis+of+MoS2/WS2+Layered+Heterostructures+and+Catalytic+Activity+of+Defective+Transition+Metal+Dichalcogenide+Films.">One-Step Synthesis of MoS2/WS2 Layered Heterostructures and Catalytic Activity of Defective Transition Metal Dichalcogenide Films.</a> ACS Nano. 10, 2004-2009 (2016).</li><li>Wu, C. R., Chang, X. R., Wu, C. H., Lin, S. Y. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=The+Growth+Mechanism+of+Transition+Metal+Dichalcogenides+using+Sulfurization+of+Pre-deposited+Transition+Metals+and+the+2D+Crystal+Hetero-structure+Establishment.">The Growth Mechanism of Transition Metal Dichalcogenides using Sulfurization of Pre-deposited Transition Metals and the 2D Crystal Hetero-structure Establishment.</a> Sci. Rep. 7, 42146 (2017).</li><li>Chen, K. C., Chu, T. W., Wu, C. R., Lee, S. C., Lin, S. Y. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Layer+Number+Controllability+of+Transition-metal+Dichalcogenides+and+The+Establishment+of+Hetero-structures+using+Sulfurization+of+Thin+Transition+Metal+Films.">Layer Number Controllability of Transition-metal Dichalcogenides and The Establishment of Hetero-structures using Sulfurization of Thin Transition Metal Films.</a> J. of Phys. D: Appl. Phy. 50, 064001 (2017).</li><li>Wu, C. R., Chang, X. R., Chu, T. W., Chen, H. A., Wu, C. H., Lin, S. Y. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Establishment+of+2D+Crystal+Heterostructures+by+Sulfurization+of+Sequential+Transition+Metal+Depositions:+Preparation,+Characterization,+and+Selective+Growth.">Establishment of 2D Crystal Heterostructures by Sulfurization of Sequential Transition Metal Depositions: Preparation, Characterization, and Selective Growth.</a> Nano Lett. 16, 7093-7097 (2016).</li><li>Lin, M. Y., 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=Toward+epitaxially+grown+two-dimensional+crystal+hetero-structures:+Single+and+double+MoS2/graphene+hetero-structures+by+chemical+vapor+depositions.">Toward epitaxially grown two-dimensional crystal hetero-structures: Single and double MoS2/graphene hetero-structures by chemical vapor depositions.</a> Appl. Phys. Lett. 105, 073501 (2014).</li><li>Lee, C., Yan, H., Brus, L. E., Heinz, T. F., Hone, J., Ryu, S. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Anomalous+Lattice+Vibrations+of+Single+and+Few-Layer+MoS2.">Anomalous Lattice Vibrations of Single and Few-Layer MoS2.</a> ACS Nano. 4, 2695-2700 (2010).</li><li>Chen, K. C., Chu, T. W., Wu, C. R., Lee, S. C., Lin, S. Y. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Atomic+Layer+Etchings+of+Transition+Metal+Dichalcogenides+with+Post+Healing+Procedures:+Equivalent+Selective+Etching+of+2D+Crystal+Hetero-structures.">Atomic Layer Etchings of Transition Metal Dichalcogenides with Post Healing Procedures: Equivalent Selective Etching of 2D Crystal Hetero-structures.</a> 2D Mater. 4, 034001 (2017).</li></ol>

作者没有什么可透露的。

与传统的半导体材料如 Si 和 GaAs 相比, 2D 材料在器件应用中的优势在于有可能将极薄的物体分解成几个原子层。当 si 产业进入 < 10 纳米技术节点时, si 散热 FET 的高长宽比将使器件结构不适合实际应用。因此, 2D 的材料已经出现, 因为它们有可能取代 Si 的电子器件应用。
虽然最研究的2D 材料, 石墨烯, 预计将表现出高的流动性值, 其零带隙性质已导致没有关闭状态的石墨烯晶体?...

获取2D 晶体薄膜的最常见方法之一是使用散装材料的机械剥离1,2,3,4,5。虽然采用这种方法可以很容易地获得高结晶质量的2D 晶体薄膜, 但这一方法不能获得可伸缩的2D 晶体薄膜, 这对实际应用是不利的。在以前的出版物中已经表明, 使用化学气相沉积 (CVD), 大面积和均匀的2D 晶体薄膜可以准备6,7,8,9。利用 CVD 生长技术10、11, 还演示了通过重复相同的生长周期制备的石墨烯基底和层数可控 MoS2薄膜的直接生长。在最近的一份出版物中, 在平面 WSe2/MoS2杂化结构薄片中也使用 CVD 生长技术12进行制作。尽管 CVD 生长技术有望提供可伸缩的2D 晶体薄膜, 但这种生长技术的主要缺点是不同的前体必须位于不同的2D 晶体中。不同的2D 晶体的生长条件也不尽相同。在这种情况下, 当需求增长2D 晶体异质结构时, 生长过程将变得更加复杂。
与 CVD 生长技术相比, pre-deposited 过渡金属薄膜的硫化为 TMDs1314提供了类似但更简单的增长方法。由于生长过程只涉及金属沉积和以下硫化程序, 有可能通过相同的生长过程生长不同的 TMDs。另一方面, 2D 晶体的层数可控性也可以通过改变 pre-deposited 过渡金属厚度来实现。在这种情况下, 对于不同的 TMDs, 需要将增长优化和层数控制降低到单个层. 利用这种方法, 了解生长机制对复杂 TMD 杂化结构的建立也非常重要。
在本文中, MoS2和 WS2薄膜是在类似的金属沉积生长过程中制备的, 其次是硫化程序。在硫充分和缺陷条件下, 通过硫化钼薄膜的研究得到的结果, 在硫化过程中观察到两种生长机制15。在硫充分条件下, 可在硫化过程后获得均匀、层数可控的 MoS2膜。当样品在硫亏缺条件下硫化时, 背景硫不足以形成完整的 MoS2膜, 从而使钼氧化物的分离和聚结成为早期生长阶段的主要机制。在硫化过程15之后, 将获得由少量 MoS2层覆盖的 Mo 氧化物簇的样品。通过顺序金属沉积和以下硫化程序, WS2/MoS2垂直异质结构的层数可控性下到一个单一的层可以准备15,16。利用该技术, 在四区域的蓝宝石衬底上获得了样品: (I) 空白蓝宝石衬底, (II) 独立 MoS2, (III) ws2/mos2异质结构, (IV) 独立 ws217.结果表明, 生长技术有利于垂直2D 晶体杂化结构的建立, 具有选择性生长能力。2D 晶体异质结构的增强装置性能将标志着2D 晶体实际应用的第一步。

<table><tbody><tr><td>RF sputtering system</td><td>Kao Duen Technology</td><td>N/A</td><td></td></tr><tr><td>Furnace for sulfurization</td><td>Creating Nano Technologies</td><td>N/A</td><td></td></tr><tr><td>Polymethyl methacrylate (PMMA)</td><td>Microchem</td><td>8110788</td><td>Flammable</td></tr><tr><td>KOH, &gt; 85%</td><td>Sigma-Aldrich</td><td>30603</td><td></td></tr><tr><td>Acetone, 99.5%</td><td>Echo Chemical</td><td>CMOS110</td><td></td></tr><tr><td>Sulfur (S), 99.5%</td><td>Sigma-Aldrich</td><td>13803</td><td></td></tr><tr><td>Molybdenum (Mo), 99.95%</td><td>Summit-Tech</td><td>N/A</td><td></td></tr><tr><td>Tungsten (W), 99.95%</td><td>Summit-Tech</td><td>N/A</td><td></td></tr><tr><td>C-plane Sapphire substrate</td><td>Summit-Tech</td><td>X171999</td><td>(0001) &amp;plusmn; 0.2 &amp;deg; one side polished</td></tr><tr><td>300 nm SiO&lt;sub&gt;2&lt;/sub&gt;/Si substrate</td><td>Summit-Tech</td><td>2YCDDM</td><td>P-type Si substrate, resistivity: 1-10 &amp;Omega; &amp;middot; cm.</td></tr><tr><td>Sample holder (sputtering system)</td><td>Kao Duen Technology</td><td>N/A</td><td>Ceramic material</td></tr><tr><td>Mechanical pump (sputtering system)</td><td>Ulvac</td><td>D-330DK</td><td></td></tr><tr><td>Diffusion pump (sputtering system)</td><td>Ulvac</td><td>ULK-06A</td><td></td></tr><tr><td>Mass flow controller</td><td>Brooks</td><td>5850E</td><td>The maximum Argon flow is 400 mL/min</td></tr><tr><td>Manual wheel Angle poppet valve</td><td>King Lai</td><td>N/A</td><td>Vacuum range from 2500 ~1 &amp;times; 10&lt;sup&gt;-8&lt;/sup&gt; torr</td></tr><tr><td>Raman measurement system</td><td>Horiba</td><td>Jobin Yvon LabRAM HR800</td><td></td></tr><tr><td>Transmission electron microscopy</td><td>Fei</td><td>Tecnai G2 F20</td><td></td></tr><tr><td>Petri dish</td><td>Kwo Yi</td><td>N/A</td><td></td></tr><tr><td>Tweezer</td><td>Venus</td><td>2A</td><td></td></tr><tr><td>Digital dry cabinet</td><td>Jwo Ruey Technical</td><td>DRY-60</td><td></td></tr><tr><td>Dual-channel system sourcemeter</td><td>Keithley</td><td>2636B</td><td></td></tr></tbody></table>

preparation of large-area vertical 2d crystal hetero-structures through the sulfurization of transition metal films for device fabrication

我们已经证明, 通过硫化过渡金属薄膜, 如钼 (钼) 和钨 (W), 大面积和均匀过渡金属 dichalcogenides (TMDs) MoS2和 WS2可以在蓝宝石衬底上制备。通过控制金属膜厚度, 可以利用这种生长技术获得良好的层数可控性, 降低到单层 TMDs。根据在硫缺乏条件下钼膜硫化的结果, 在硫化过程中, (a) 平面 MoS2生长和 (b) 钼氧化物的分离有两种机制。当背景硫充足时, 平面 TMD 的生长是主要的生长机制, 在硫化过程后会产生均匀的 MoS2膜。如果背景硫缺乏, 在硫化过程的初始阶段, 钼氧化物的分离将成为主要的生长机制。在这种情况下, 将获得覆盖有少量层 MoS2的 Mo 氧化物簇的样品。在连续 Mo 沉积/硫化和 W 沉积/硫化过程之后, 使用这种生长技术建立了垂直 WS2/MoS2杂化结构。分别对应于 WS2和 MoS2的拉曼峰值, 以及与单个2D 材料求和的异质结构的相同层数, 证实了垂直2D 晶体的成功建立异质结构。在将 WS2/MoS2胶片传输到带 pre-patterned 源/漏极的微晶2/Si 衬底上后, 制作了底栅极晶体管。与仅 mos2通道的晶体管相比, 具有 WS2/mos2异质结构的设备的更高的漏电流显示出, 随着2D 晶体异质结构的引入, 高级器件可以获得性能。研究结果揭示了这种生长技术在2D 晶体实际应用中的潜力。

分别在图 1ab17中显示了使用 pre-deposited 过渡金属硫化制作的单个 MoS2和 WS2的拉曼光谱和横截面 HRTEM 图像。对 MoS2和 WS2的两个特征拉曼峰值分别进行了观测, 它对应于平面内的和2D 晶体中的一个<img alt="Equation 1" src="/files/ftp_upload/56494/56494eq1.jpg"> 1g声子振动模式。mos2样本的?...

Watch this Scientific Journal Video about Preparation of Large-area Vertical 2D Crystal Hetero-structures Through the Sulfurization of Transition Metal Films for Device Fabrication at JoVE.com

Preparation of Large-area Vertical 2D Crystal Hetero-structures Through the Sulfurization of Transition Metal Films for Device Fabrication

通过 pre-deposited 过渡金属的硫化, 可以制备大面积和垂直2D 晶体杂化结构。本报告还演示了薄膜传输和器件制作程序。

硫化过渡金属膜制备大面积垂直2D 晶体杂化结构

We have demonstrated that through the sulfurization of transition metal films such as molybdenum (Mo) and tungsten (W), large-area and uniform transition ...

preparation-large-area-vertical-2d-crystal-hetero-structures-through

Universidad San Sebastian

Research

JoVE Journal

Engineering

9.1K 次观看.  National Taiwan University. 通过 pre-deposited 过渡金属的硫化, 可以制备大面积和垂直2D 晶体杂化结构。本报告还演示了薄膜传输和器件制作程序。

视频: Preparation of Large-area Vertical 2D Crystal Hetero-structures Through the Sulfurization of Transition Metal Films for Device Fabrication

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 ...

科研

工程学

Atomically Traceable Nanostructure Fabrication

Reducing the scale of etched nanostructures below the 10 nm range eventually will require an atomic scale understanding of the entire fabrication process being used in order to maintain exquisite control over both feature size and feature density. Here, we demonstrate a method for tracking atomically resolved and controlled structures from initial template definition through final nanostructure metrology, opening up a pathway for top-down atomic control over nanofabrication. Hydrogen depassivation lithography is the first step of the nanoscale fabrication process followed by selective atomic layer deposition of up to 2.8 nm of titania to make a nanoscale etch mask. Contrast with the background is shown, indicating different mechanisms for growth on the desired patterns and on the H passivated background. The patterns are then transferred into the bulk using reactive ion etching to form 20 nm tall nanostructures with linewidths down to ~6 nm. To illustrate the limitations of this process, arrays of holes and lines are fabricated. The various nanofabrication process steps are performed at disparate locations, so process integration is discussed. Related issues are discussed including using fiducial marks for finding nanostructures on a macroscopic sample and protecting the chemically reactive patterned Si(100)-H surface against degradation due to atmospheric exposure.

We report a protocol for combining the atomic metrology of the Scanning Tunneling Microscope for surface patterning with selective Atomic Layer Deposition and Reactive Ion Etching. Using a robust process involving numerous atmospheric exposures and transport, 3D nanostructures with atomic metrology are fabricated.

原子纳米结构可追溯制造

Reducing the scale of etched nanostructures below the 10 nm range eventually will require an atomic scale understanding of the entire fabrication process ...

Ohmic Contact Fabrication Using a Focused-ion Beam Technique and Electrical Characterization for Layer Semiconductor Nanostructures

Layer semiconductors with easily processed two-dimensional (2D) structures exhibit indirect-to-direct bandgap transitions and superior transistor performance, which suggest a new direction for the development of next-generation ultrathin and flexible photonic and electronic devices. Enhanced luminescence quantum efficiency has been widely observed in these atomically thin 2D crystals. However, dimension effects beyond quantum confinement thicknesses or even at the micrometer scale are not expected and have rarely been observed. In this study, molybdenum diselenide (MoSe2) layer crystals with a thickness range of 6-2,700 nm were fabricated as two- or four-terminal devices. Ohmic contact formation was successfully achieved by the focused-ion beam (FIB) deposition method using platinum (Pt) as a contact metal. Layer crystals with various thicknesses were prepared through simple mechanical exfoliation by using dicing tape. Current-voltage curve measurements were performed to determine the conductivity value of the layer nanocrystals. In addition, high-resolution transmission electron microscopy, selected-area electron diffractometry, and energy-dispersive X-ray spectroscopy were used to characterize the interface of the metal&#8211;semiconductor contact of the FIB-fabricated MoSe2 devices. After applying the approaches, the substantial thickness-dependent electrical conductivity in a wide thickness range for the MoSe2-layer semiconductor was observed. The conductivity increased by over two orders of magnitude from 4.6 to 1,500 &#937;&#8722;1 cm&#8722;1, with a decrease in the thickness from 2,700 to 6 nm. In addition, the temperature-dependent conductivity indicated that the thin MoSe2 multilayers exhibited considerably weak semiconducting behavior with activation energies of 3.5-8.5 meV, which are considerably smaller than those (36-38 meV) of the bulk. Probable surface-dominant transport properties and the presence of a high surface electron concentration in MoSe2 are proposed. Similar results can be obtained for other layer semiconductor materials such as MoS2 and WS2.

We describe the approaches for the device fabrication and electrical characterization of molybdenum diselenide (MoSe2) layer semiconductor nanostructures with different thicknesses. In addition, the fabrication of ohmic contacts for MoSe2-layer nanocrystals by the focused-ion beam deposition method using platinum (Pt) as a contact metal is described.

欧姆接触制造用聚焦离子束技术和电气特性的半导体层的纳米结构

Layer semiconductors with easily processed two-dimensional (2D) structures exhibit indirect-to-direct bandgap transitions and superior transistor ...

Advanced Experimental Methods for Low-temperature Magnetotransport Measurement of Novel Materials

Novel electronic materials are often produced for the first time by synthesis processes that yield bulk crystals (in contrast to single crystal thin film synthesis) for the purpose of exploratory materials research. Certain materials pose a challenge wherein the traditional bulk Hall bar device fabrication method is insufficient to produce a measureable device for sample transport measurement, principally because the single crystal size is too small to attach wire leads to the sample in a Hall bar configuration. This can be, for example, because the first batch of a new material synthesized yields very small single crystals or because flakes of samples of one to very few monolayers are desired. In order to enable rapid characterization of materials that may be carried out in parallel with improvements to their growth methodology, a method of device fabrication for very small samples has been devised to permit the characterization of novel materials as soon as a preliminary batch has been produced. A slight variation of this methodology is applicable to producing devices using exfoliated samples of two-dimensional materials such as graphene, hexagonal boron nitride (hBN), and transition metal dichalcogenides (TMDs), as well as multilayer heterostructures of such materials. Here we present detailed protocols for the experimental device fabrication of fragments and flakes of novel materials with micron-sized dimensions onto substrate and subsequent measurement in a commercial superconducting magnet, dry helium close-cycle cryostat magnetotransport system at temperatures down to 0.300 K and magnetic fields up to 12 T.

We describe the methodology of mechanical exfoliation and deposition of flakes of novel materials with micron-sized dimensions onto substrate, fabrication of experimental device structures for transport experimentation, and the magnetotransport measurement in a dry helium close-cycle cryostat at temperatures down to 0.300 K and magnetic fields up to 12 T.

对于新材料的低温磁输运测量先进的实验方法

Novel electronic materials are often produced for the first time by synthesis processes that yield bulk crystals (in contrast to single crystal thin film ...

Preparation of Liquid-exfoliated Transition Metal Dichalcogenide Nanosheets with Controlled Size and Thickness: A State of the Art Protocol

We summarize recent advances in the production of liquid-exfoliated transition metal dichalcogenide (TMD) nanosheets with controlled size and thickness. Layered crystals of molybdenum disulphide (MoS2) and tungsten disulphide (WS2) are exfoliated in aqueous surfactant solution by sonication. This yields highly polydisperse mixtures containing nanosheets with broad size and thickness distributions. However, for most purposes, specific sizes (in terms of both lateral dimension and thickness) are required. For example, large and thin nanosheets are desired for (opto) electronic applications, while laterally small nanosheets are interesting for catalytic applications. Therefore, post-exfoliation size selection is an important step that we address here. We provide a detailed protocol on the efficient size selection in large quantities by liquid cascade centrifugation and the size and thickness quantification by statistical microscopic analysis (atomic force microscopy and transmission electron microscopy). The comparison of MoS2 and WS2 shows that both materials are size-selected in a similar way by the same procedure. Importantly, the dispersions of size-selected nanosheets show systematic changes in their optical extinction spectra with size due to edge and confinement effects. We show how these optical changes are related quantitatively to the nanosheets dimensions and describe how mean nanosheets length and layer number can be extracted reliably from the extinction spectra. The exfoliation and size selection protocol can be applied to a broad range of layered crystals as we have previously demonstrated for graphene, gallium sulphide (GaS) and black phosphorus.

A protocol for the liquid exfoliation of layered materials to nanosheets, their size selection and size measurement by microscopic and spectroscopic techniques is presented.

与尺寸可控液体剥离的过渡金属二硫属化物纳米片和厚度的制备:艺术议定书的国家

We summarize recent advances in the production of liquid-exfoliated transition metal dichalcogenide (TMD) nanosheets with controlled size and thickness. ...

Spark Plasma Sintering Apparatus Used for the Formation of Strontium Titanate Bicrystals

A spark plasma sintering apparatus was used as a novel method for diffusion bonding of two single crystals of strontium titanate to form bicrystals with one twist grain boundary. This apparatus utilizes high uniaxial pressure and a pulsed direct current for rapid consolidation of material. Diffusion bonding of strontium titanate bicrystals without fracture, in a spark plasma sintering apparatus, is possible at high pressures due to the unusual temperature dependent plasticity behavior of strontium titanate. We demonstrate a method for the successful formation of bicrystals at accelerated time scales and lower temperatures in a spark plasma sintering apparatus compared to bicrystals formed by conventional diffusion bonding parameters. Bond quality was verified by scanning electron microscopy. A clean and atomically abrupt interface containing no secondary phases was observed using transmission electron microscopy techniques. Local changes in bonding across the boundary was characterized by simultaneous scanning transmission electron microscopy and spatially resolved electron energy-loss spectroscopy.

A viable technique for the formation of strontium titanate bicrystals at high pressure and fast heating rate via the spark plasma sintering apparatus is developed.

放电等离子烧结设备中使用的钛酸锶双晶体的形成

A spark plasma sintering apparatus was used as a novel method for diffusion bonding of two single crystals of strontium titanate to form bicrystals with ...

Aerosol-assisted Chemical Vapor Deposition of Metal Oxide Structures: Zinc Oxide Rods

Whilst columnar zinc oxide (ZnO) structures in the form of rods or wires have been synthesized previously by different liquid- or vapor-phase routes, their high cost production and/or incompatibility with microfabrication technologies, due to the use of pre-deposited catalyst-seeds and/or high processing temperatures exceeding 900 &#176;C, represent a drawback for a widespread use of these methods. Here, however, we report the synthesis of ZnO rods via a non-catalyzed vapor-solid mechanism enabled by using an aerosol-assisted chemical vapor deposition (CVD) method at 400 &#176;C with zinc chloride (ZnCl2) as the precursor and ethanol as the carrier solvent. This method provides both single-step formation of ZnO rods and the possibility of their direct integration with various substrate types, including silicon, silicon-based micromachined platforms, quartz, or high heat resistant polymers. This potentially facilitates the use of this method at a large-scale, due to its compatibility with state-of-the-art microfabrication processes for device manufacture. This report also describes the properties of these structures (e.g., morphology, crystalline phase, optical band gap, chemical composition, electrical resistance) and validates its gas sensing functionality towards carbon monoxide.

Columnar zinc oxide structures in the form of rods are synthesized via aerosol-assisted chemical vapor deposition without the use of pre-deposited catalyst-seed particles. This method is scalable and compatible with various substrates based on either silicon, quartz or polymers.

金属氧化物结构的气溶胶辅助化学气相沉积: 氧化锌棒

Whilst columnar zinc oxide (ZnO) structures in the form of rods or wires have been synthesized previously by different liquid- or vapor-phase routes, ...

化学

Synthesis of a Thiol Building Block for the Crystallization of a Semiconducting Gyroidal Metal-sulfur Framework

We present a method for preparing thioester molecules as the masked form of the thiol linkers and their utilization for accessing a semiconducting and porous metal-dithiolene network in the highly ordered single crystalline state. Unlike the highly reactive free-standing thiols, which tend to decompose and complicate the crystallization of metal-thiolate open frameworks, the thioester reacts in situ to provide the thiol species, serving to mitigate the reaction between the mercaptan units and the metal centers, and to improve crystallization consequently. Specifically, the thioester was synthesized in a one-pot procedure: an aromatic bromide (hexabromotriphenylene) reacted with excess sodium thiomethoxide under vigorous conditions to first form the thioether intermediate product. The thioether was then demethylated by the excess thiomethoxide to provide the thiolate anion that was acylated to form the thioester product. The thioester was conveniently purified by standard column chromatography, and then used directly in the framework synthesis, wherein NaOH and ethylenediamine serve to revert in situ the thioester to the thiol linker for assembling the single-crystalline Pb(II)-dithiolene network. Compared with other methods for thiol synthesis (e.g., by cleaving alkyl thioether using sodium metal and liquid ammonia), the thioester synthesis here uses simple conditions and economical reagents. Moreover, the thioester product is stable and can be conveniently handled and stored. More importantly, in contrast to the generic difficulty in accessing crystalline metal-thiolate open frameworks, we demonstrate that using the thioester for in situ formation of the thiol linker greatly improves the crystallinity of the solid-state product. We intend to encourage broader research efforts on the technologically important metal-sulfur frameworks by disclosing the synthetic protocol for the thioester as well as the crystalline framework solid.

Here, we present a one-pot, transition-metal-free synthesis of thiols and thioesters from aromatic halides and sodium thiomethoxide, followed by the preparation of single crystals of a metal-dithiolene network using thiol species generated in situ from the more stable and tractable thioester.

半导体回转金属硫框架结晶的硫醇构建块的合成

We present a method for preparing thioester molecules as the masked form of the thiol linkers and their utilization for accessing a semiconducting and ...

A Standard and Reliable Method to Fabricate Two-Dimensional Nanoelectronics

Two-dimensional (2D) materials have attracted huge attention due to their unique properties and potential applications. Since wafer scale synthesis of 2D materials is still in nascent stages, scientists cannot fully rely on traditional semiconductor techniques for related research. Delicate processes from locating the materials to electrode definition need to be well controlled. In this article, a universal fabrication protocol required in manufacturing nanoscale electronics, such as 2D quasi-heterojunction bipolar transistors (Q-HBT), and 2D back-gated transistors are demonstrated. This protocol includes the determination of material position, electron beam lithography (EBL), metal electrode definition, et al. A step by step narrative of the fabrication procedures for these devices are also presented. Furthermore, results show that each of the fabricated devices has achieved high performance with high repeatability. This work reveals a comprehensive description of process flow for preparing 2D nano-electronics, enables the research groups to access this information, and pave the way toward future electronics.

The article aims to introduce a standard and reliable fabrication procedure for the development of future low dimensional nanoelectronics.

制造二维电子学的标准可靠方法

Two-dimensional (2D) materials have attracted huge attention due to their unique properties and potential applications. Since wafer scale synthesis of 2D ...

Fabricating van der Waals Heterostructures with Precise Rotational Alignment

In this work we describe a technique for creating new crystals (van der Waals heterostructures) by stacking distinct ultrathin layered 2D materials. We demonstrate not only lateral control but, importantly, also control over the angular alignment of adjacent layers. The core of the technique is represented by a home-built transfer setup which allows the user to control the position of the individual crystals involved in the transfer. This is achieved with sub-micrometer (translational) and sub-degree (angular) precision. Prior to stacking them together, the isolated crystals are individually manipulated by custom-designed moving stages that are controlled by a programmed software interface. Moreover, since the entire transfer setup is computer controlled, the user can remotely create precise heterostructures without coming into direct contact with the transfer setup, labeling this technique as &#8220;hands-free&#8221;. In addition to presenting the transfer set-up, we also describe two techniques for preparing the crystals that are subsequently stacked.

In this work we describe a technique that is used to create new crystals (van der Waals heterostructures) by stacking ultrathin layered 2D materials with precise control over position and relative orientation.

使用精确旋转对齐来制造范德瓦尔斯异构结构

In this work we describe a technique for creating new crystals (van der Waals heterostructures) by stacking distinct ultrathin layered 2D materials. We ...