This work is supported by the National Institute of Standards and Technology of the United States Department of Commerce.

1.准备底物<ol><li>得到的4英寸的硅（Si）晶片重掺杂p掺杂Si构成覆盖约300nm 的 SiO 2。该基板结构将允许衬底以用作背栅。 </li><li>使用制图/设计软件，设计出1厘米×具有均匀间隔的功能，如列举的杂交1厘米图案，在x和y方向上作为位置定位器使用在基板上用于传输样品薄片和对准标记电子束光刻（ 图1）。 <ol><li>打开在起草程序的新文件，如AutoCAD。 </li><li>使用折线得出如下标记:相交的2.25微米×12.00微米矩形标注8.25微米×14.25微米数字字符组成I）十字间隔150微米的一处。二）一角形成的全球位置标识符连接30微米的正方形标有16.50×28.50微米数字恰拉cters;三）小15微米×15微米的杂交等距离任何授予了四种位置标识间隔150微米分开。 </li><li>确保所有位置标识符在1cm以内×1厘米极限适合。 </li><li>该文件保存为.GDS文件或保存为另一个文件（如为.dxf）并将其转换为一个.GDS文件。 </li></ol></li><li>开发或顺序从商业来源与上述1厘米×1厘米花纹横过4英寸×4英寸的空间排列的光掩模，以允许一个4英寸Si晶片上的图案的副本的全覆盖。 </li><li>在Si晶片光刻图案化的光刻胶掩模。 <ol><li>附加4英寸晶片卡盘光刻胶微调。确保它有足够的固定。 </li><li>用干净的镊子，将一个硅晶片上的微调夹头。确保在晶片的中心位于卡盘。 </li><li>用塑料吸管，覆盖polydimethylglutarimide为基础的剥离整个晶圆光刻胶（LOR）。 </li><li>旋转的LOR包覆片以4000rpm进行45秒。 </li><li>烘烤LOR中涂覆的晶片在170℃下5分钟。 </li><li>让LOR涂覆晶片凉爽1-2分钟。 </li><li>用干净的镊子，将LOR涂层的硅晶片上的微调夹头。确保在晶片的中心位于卡盘。 </li><li>使用塑料移液管，包括在传统的酚醛正光刻胶设计为60秒烘烤，在115℃，以产生12.3 KA涂覆整个晶片。 </li><li>旋转晶片以5,000rpm进行60秒。 </li><li>烤晶圆在90-110℃下60秒。 </li><li>让晶圆酷1-2分钟。 </li><li>通过将光掩模的掩模对准朝下（朝向晶片）的掩模的图案化的铬和装载双层-光刻胶涂覆的晶片掩模之下准备接触光刻使光致抗蚀剂朝上（朝向掩模）。 </li><li>晶片对准掩模，使得晶片的整体将与排列1厘米构图15; 1厘米模式。 </li><li>暴露在紫外线宽带（350纳米至450纳米）使用I-线（365nm带通滤波器），在100毫焦/厘米2，或20毫瓦/ cm 2的4.8秒的光。 </li><li>曝光后，发展光致抗蚀剂通过浸渍以常规酚醛正性光刻胶兼容显影剂在RT溶液40-60秒轻度和一致的搅动涂覆晶片。 </li><li>以下浸没在显影剂溶液中的浴，冲洗在去离子水中的晶片。 </li><li>使用氮气枪，吹干显影的光刻胶掩模涂覆晶片。 </li></ol></li><li>存款铬/金金属上使用电​​子束蒸发器的光致抗蚀剂掩模涂覆晶片。 <ol><li>发泄电子束蒸发器室。 </li><li>将晶圆面朝下放在样品支架板。 </li><li>打开电子束蒸发器室门。 </li><li>将样品支架板到衬底支架与晶片朝下。 </li><li>检查Cr和Au都属于淀积源。 </li><li>关闭电子束蒸发器腔门和泵室中以至少4×10 -5帕（3×10 -7托）。 </li><li>存50埃的Cr在0.5埃/秒。 </li><li>存750埃Au中的1埃/秒。 </li><li>沉积之后，允许腔室冷却大约20分钟。 </li><li>发泄电子束蒸发器室。 </li><li>除去样品支架板和从板取下晶片。 </li><li>关闭电子束蒸发器室门和泵的腔。 </li></ol></li><li>执行金属升空。 <ol><li>制备丙酮或 N的浴-甲基-2-吡咯烷酮系溶剂足以浸没4英寸晶片。加热溶剂浴至75℃的热板上并保持在此温度。 </li><li>浸入溶剂浴的4英寸晶圆。覆盖浴使得溶剂不蒸发过。 </li><li>让晶片在75坐在溶剂浴°下进行6-24小时。要小心，不要让所​​有的溶剂蒸发掉。 </li><li>持样品只是用一对镊子的溶剂的表面下方和微妙喷洒丙酮从整个晶片以除去解除断金属的表面上的喷射瓶。 </li><li>冲洗的异丙醇浴晶片1-2分钟。 </li><li>冲洗中的去离子水的浴晶片1-2分钟。 </li><li>使用氮气枪，吹干晶片。 </li></ol></li><li>切块的晶片切割成用金刚石划线或切割锯个体样品片。如果一个切割锯时，保护在晶片表面用聚甲基丙烯酸甲酯掩模。 <ol><li>附加4英寸晶片卡盘光刻胶微调。确保它有足够的固定。 </li><li>使用清洁的镊子，将晶片上的离心器卡盘。确保在晶片的中心位于卡盘。 </li><li>使用塑料移液管，覆盖在聚甲基丙烯酸甲酯（PMMA）在整个晶片。 </li><li>旋PMMA包覆晶片在5,000rpm下120秒。 </li><li>烘烤，在180℃下120秒的PMMA包覆晶片。 </li><li>让PMMA包覆晶片凉爽1-2分钟。 </li><li>切块的样品成单独的样品片约为1厘米×1厘米大小。 </li></ol></li><li>从晶片表面去除有机残留物。 <ol><li>制备浴缸的硫酸和过氧化氢为基础的汽提器/有机清洁剂，丙酮的浴，异丙醇浴，和去离子水2浴。 </li><li>让基板片浸泡在丙酮浴中15分钟，搅拌下通过高频超声处理。 </li><li>移动衬底片的异丙醇浴中，让它浸泡由高频超声处理，搅拌15分钟。 </li><li>移动衬底片到一个去离子水浴中，并让其浸泡由高频超声处理，搅拌15分钟。 </li><li>移动衬底片的其他的去离子水浴中，让它浸泡用于通过高频超声处理，搅拌15分钟。 </LI&gt; <li>移动衬底片的硫酸和过氧化氢为基础的汽提器/有机清洗液和让它浸泡60分钟无搅动。 </li><li>同时衬底片是在有机清洗液，适当处理的其他浴的内容并清洗玻璃器皿。准备两个新的去离子水浴场。 </li><li>以下的有机剥离，将基板件中的去离子水浴中，并让它浸泡5分钟，同时搅拌由高频超声处理。 </li><li>移动衬底片的其他的去离子水浴中，让它浸泡5分钟，同时搅拌由高频超声处理。 </li><li>使用氮气枪，吹干衬底片。 </li></ol></li></ol> 2.样品转移到片状基材<ol><li>合成或从合作者或商业源获得高品质的大样。 </li><li>去角质样片。 <ol><li>切几片标准晶片切割的TaPE略微-较大超过1厘米×3厘米，留下剥离纸覆盖粘合剂。 </li><li>用一把锋利的剃刀，小心地取出离型纸的一部分，使略超过1厘米×1cm的胶粘剂是对每件磁带暴露。 </li><li>用力按下一个准备一块胶布对大样的粘接部分。如果大样是由非常小的粉末状的片，倒入少量样品的载玻片上，按磁带插入幻灯片上的积累样本。 </li><li>剥离从散装样品确保上的粘合剂样品的良好覆盖胶带。 </li><li>按样品片胶带的粘合面非常坚决地反对另一块胶带的粘合面。 </li><li>剥离两片带分开，目视检查样本覆盖的两片胶带。 </li><li>重复这个过程，2.2.5和2.2.6，直到样品片出现几乎是透明的。 </li><li>用力将胶带机智的粘合面对一块制备的基板的从第1步剥离胶带远h进样薄片离开附着于基材样品薄片。 </li></ol></li><li>目视搜索使用光学显微镜（图2）适合样品薄片，并注意其在基板利用构图步骤1.2-1.4所述位置标记的位置。 </li><li>用原子力显微镜（AFM）测量样品片的厚度。样品薄片应当在厚度10小于100纳米。 </li><li>存款溅射二氧化硅（可选）。 注意:此步骤是仅必要的，如果范德华力附着的样品与基板不足以足够的附着力。这样做不允许样品的制造成霍尔棒通过在本文中（步骤3.3）所概述的程序。 <ol><li>排气溅镀系统负载锁。 </li><li>打开负载锁的门。 </li><li>将样品容纳件样品转移到片样品架和地点样本支架上的传送臂。 </li><li>关闭负载锁定装置的门和抽气装载锁定。 </li><li>启动序列与样品架传送到溅射室。 </li><li>等待的2.7×10 -5帕（2×10 -7）基地真空。 </li><li>使用DC电源，溅射的 SiO 2的100-200纳米到样品片收容转移样品薄片。 </li><li>沉积之后，启动序列与样品架返回到负载锁定。 </li><li>泄负载锁定并取出样品架。 </li><li>除去从样品保持器的碎片。 </li><li>抽空溅射系统负载锁定。 </li></ol></li><li>准备一摞层状材料的薄片 注意:如果研究人员希望产生脱落，并确定在步骤2.1-2.4多个片组成的异质这一步才是必需的。 <ol><li>通过将一小滴的P创建一个透明的机械邮票olydimethylsiloxane（PDMS）在真空载玻片和固化。 </li><li>旋PDMS上的顶部聚丙烯碳酸酯（PPC）作为印模和层状材料之间的直接接触。 </li><li>定位机械邮票上的异质结构栈中使用的层状材料的第一薄片。 </li><li>按邮票向下样品片。 </li><li>该系统加热到约40℃，以增加PPC和样品片之间的吸引力。 </li><li>慢慢抬起印模与附着到PPC中样品薄片。 </li><li>定位在异质结构堆叠要使用超过层状材料的下一薄片附有样品薄片的机械邮票。 </li><li>确保保持排列的两个样品薄片，缓慢降低戳，使得附连到PPC中薄片进入与层状材料的下一薄片在异质结构栈中使用的接触。 </li><li>轻轻按下印记向下SAMPLË片。 </li><li>该系统加热到约40℃，增加样本片之间的吸引力。 </li><li>慢慢抬起印模与附着在堆叠中的样品薄片。 </li><li>重复步骤2.6.7-2.6.11直至所需结构完成。 </li><li>通过轻轻按压含有层状材料的堆叠到衬底片的邮票的异质结构栈转移到一个新的衬底。 </li><li>加热该体系至100℃。 </li><li>慢慢抬起邮票上，留下连接到衬底片层状材料的薄片的堆叠。 </li></ol></li></ol>器件结构3.电子束曝光<ol><li>使用光学显微镜，采取公聚焦图像在20X放大倍数的样本薄片/片栈将用于设备构图和100X。包括在电子束模式D中的至少一个位置标记图案化步骤1.2-1.4用于对准目的的图像中ESIGN。 </li><li>使用制图/设计软件，设计准备的电子束光刻。 <ol><li>在步骤1.2产生开放式设计文件。 </li><li>进口20X图像从步骤3.1，并相应地调整图像大小与设计适当规模。 </li><li>图像对准在设计的位置标记对应于其中样品薄片位于所述图案化衬底片上。 </li><li>使用100X图像重复步骤3.2.2和3.2.3。 </li><li>创建一个新层的设计方案，绘制出6端子霍尔棒模式在样本图像，使得暴露的区域将被腐蚀掉，留下厅酒吧。 </li><li>创建一个新层的设计方案，电气金属触点从终端领先的样品接触垫。 </li><li>文件保存到一个.GDS文件或将其保存在另一种格式，并转换成一个.GDS文件。 </li></ol></li><li>模式6端子霍尔棒PMMA面罩（跳过这一步，如果SiO 2的</suB&gt;被覆​​层沉积在步骤2.5）。 <ol><li>旋的层聚甲基丙烯酸甲酯具有95万的分子量根据在步骤1.7.1至1.7.6概述的程序配制样品上。 </li><li>装载样品放入电子束光刻系统。 </li><li>利用扫描电子显微镜（SEM），从样品11定位对准标记在衬底上为止。 </li><li>根据具体所使用的电子束光刻系统中的过程校准系统进行适当的阶段转动和长度尺度。 </li><li>关掉电子束，以防止PMMA的无用曝光和中心光束位置在在步骤3.2中制备的图案的中心。 </li><li>加载.GDS文件拖到电子束光刻系统计算机和对系统编程，以从步骤3.2.5具有希望的分辨率，根据特定于所使用的电子束平版印刷系统的打印过程霍尔图案层。 </li><li>执行T他电子束系统的图案化方案，以根据系统的用户手册所述的PMMA暴露于电子束。 </li><li>除去从电子束系统的样品。 </li></ol></li><li>蚀刻样品分成6端子霍尔棒（跳过这一步如果二氧化硅涂层沉积在步骤2.5）。 <ol><li>泄反应离子蚀刻系统。 </li><li>装载样品放入蚀刻室。 </li><li>泵系统，以约1.3×10 -3帕（1×10 -5乇）。 </li><li>利用特有的样品材料以蚀刻样品蚀刻配方。注意:对于的hBN /石墨烯/的hBN栈，从4标准立方厘米（sccm）的O 2和40sccm的CHF 3在60瓦射频产生等离子体（RF）功率具有约30纳米/分钟的蚀刻速率;一个1-2分钟的蚀刻通常是足够的。 </li><li>在蚀刻工艺完成后，泄蚀刻室。 </li><li>卸载样品和泵腐蚀室。 </li><li>冲洗样品在丙酮中为1-2分钟的浴。 </li><li>冲洗的异丙醇浴样品1-2分钟。 </li><li>冲洗中的去离子水的浴样品1-2分钟。 </li></ol></li><li>模式PMMA掩码的金属触点沉积。 <ol><li>旋的层聚甲基丙烯酸甲酯具有495,000的分子量根据在步骤1.7.1至1.7.6概述的程序配制样品上。 </li><li>旋的PMMA配制的950000分子量的第二层到样品上，根据在步骤1.7.1至1.7.6概述的程序。 </li><li>重复步骤3.3.2-3.3.8，这一次从步骤3.2.6利用接触图案层。 </li></ol></li><li>如果SiO 2的覆盖层沉积在步骤2.5中，蚀刻掉的 SiO 2在由掩模露出的区域，以允许电触点直接与样品薄片连接。 <ol><li>硬烤掩模在180℃5分钟。 </li><li>让1-2分钟样品凉爽。 </li><li>蚀刻暴露的 SiO 2，2％的HF浴中足够长的时间，以暴露样品薄片而不损坏PMMA掩模-约1-2分钟为100纳米的 SiO 2，目视确认该蚀刻每10-20秒到进度确保PMMA仍然完好无损。 </li><li>如果PMMA的掩模损坏，除去PMMA通过漂洗丙酮的样品60秒，然后异丙醇60秒，然后用去离子水60秒，吹干使用氮气枪，然后重复步骤3.5的样品。 </li></ol></li><li>存款铬/金金属上使用电​​子束蒸发器，通过重复步骤1.5的样品。 </li><li>重复步骤1.6执行金属升空。 </li></ol> 4.执行磁输运实验<ol><li>坚持样本电气运输系统包被装载到运输系统探头端部与银浆，让干燥的电器准备运输包装已制成的样品。使用线键合机精读NECT薄金线从该装置的接触焊盘到封装接触垫。 </li><li>装载样品放入磁输运系统。 <ol><li>附加包到探针尖端被插入到所述磁输运系统，并确保它被牢固地附着。连接电测量设备（源表，锁定放大器等 ）来探测，并连接到所有三个温度控制通道和电气测量通道。 </li><li>放空气闸，插入探头尖端插入气闸，并锁定到位钳和O形圈。 注意:步骤4.2.3和4.2.4-4.2.6和4.2.8对应必要进行使用氦3探头传输测量步骤。 </li><li>设置minisorb温度在插入到330 K至除去水蒸汽和打开气体交换阀和使用真空泵进行30分钟泵送系统，直到压力低于0.67帕（5×10 -3乇）。 </li><li>关闭交换阀和锁气阀并打开阀门分离从测量空间中的气闸的空间。 </li><li>简要地开放（不超过2秒），并关闭交换阀引入少量氦4气体到探头的空间。 </li><li>设置minisorb温度到25 K和mainsorb温度到40 K。 </li><li>慢慢放下探头插入测量空间，直至样品是场中心。 </li><li>一旦系统已达到200 K，按下控制器软件氦3冷凝序列按钮来实现温度低至0.300 K. </li></ol></li><li>取传输测量在一定温度范围内，磁场，栅极电压等的<ol><li>对于所有的测量，同时保存到数据文件中，由电流源，所述电压纵向（平行于所提供的电流）由电压表测量提供的电流/锁定放大器专用于该测量中，样品的温度由一个温度传感器位于样品附近，和由磁体产生的磁场进行测量。 </li><li>如果霍尔测量需要，节省霍尔电压（横向于所提供的电流）提供到数据文件，并且如果栅极电压被提供给调谐在信道的载流子密度，保存由相应的电压源提供的栅电压，因为好，每个测量在期望的采样率。 注意:采样速率为测量依赖于改变实验参数（温度，场， 电压等）是否被扫（从1开始重视并在设定值与变化的恒定速率结束）或阶梯形（稳定在预定的值）。在前者的情况下，采样率高达基础上，他们希望生成的数据文件的大小的研究者的判断。在后一种情况下，测量是在不断变化的实验参数的稳定。生成和保存DAT一个文件是通过数据采集软件进行处理。 </li></ol></li></ol>

<ol>
	<li>Doty, F. P. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Properties+of+CdZnTe+crystals+grown+by+a+high+pressure+Bridgman+method.">Properties of CdZnTe crystals grown by a high pressure Bridgman method.</a> Journal of Vacuum Science &amp; Technology B. 10 (4), 1418-1422 (1992).</li><li>Ikesue, A., Kinoshita, T., Kamata, K., Yoshida, K. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Fabrication+and+optical+properties+of+high-performance+polycrystalline+Nd-YAG+Ceramics+for+Solid-State+Lasers.">Fabrication and optical properties of high-performance polycrystalline Nd-YAG Ceramics for Solid-State Lasers.</a> Journal of the American Ceramic Society. 78 (4), 1033-1040 (1995).</li><li>Elwell, D., Scheel, H. J. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=.">.</a> Crystal Growth From High-Temperature Solutions. , (2011).</li><li>Doty, F. P. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Properties+of+CdZnTe+crystals+grown+by+a+high+pressure+Bridgman+method.">Properties of CdZnTe crystals grown by a high pressure Bridgman method.</a> Journal of Vacuum Science &amp; Technology B. 10 (4), 1418-1422 (1992).</li><li>Ikesue, A., Kinoshita, T., Kamata, K., Yoshida, K. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Fabrication+and+optical+properties+of+high-performance+polycrystalline+Nd-YAG+Ceramics+for+Solid-State+Lasers.">Fabrication and optical properties of high-performance polycrystalline Nd-YAG Ceramics for Solid-State Lasers.</a> Journal of the American Ceramic Society. 78 (4), 1033-1040 (1995).</li><li>Elwell, D., Scheel, H. J. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=.">.</a> Crystal Growth From High-Temperature Solutions. , (2011).</li><li>Therese, G. H. A., Kamath, P. V. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Electrochemical+Synthesis+of+Metal+Oxides+and+Hydroxides.">Electrochemical Synthesis of Metal Oxides and Hydroxides.</a> Chemistry of Materials. 12, 1195-1294 (2000).</li><li>Capper, P. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Bulk+Crystal+Growth+-+Methods+and+Materials.">Bulk Crystal Growth - Methods and Materials.</a> Handbook of Electronic and Photonic Materials. , 231-254 (2007).</li><li>Seiler, D. G., Becker, W. M., Roth, L. M. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Inversion-Asymmetry+Splitting+of+the+Conduction+Band+in+GaSb+from+Shubnikov-de+Haas+Measurements.">Inversion-Asymmetry Splitting of the Conduction Band in GaSb from Shubnikov-de Haas Measurements.</a> Physical Review B. 1, 764-775 (1970).</li><li>Greenblatt, M. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Molybdenum+Oxide+Bronzes+with+Quasi-Low-Dimensional+Properties.">Molybdenum Oxide Bronzes with Quasi-Low-Dimensional Properties.</a> Chemical Reviews. 88, 31-53 (1988).</li><li>Novoselov, K. S., 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=Two-dimensional+gas+of+massless+Dirac+fermions+in+graphene.">Two-dimensional gas of massless Dirac fermions in graphene.</a> Nature. 438, 197-200 (2005).</li><li>Wang, L., 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-Dimensional+Electrical+Contact+to+a+Two-Dimensional+Metal.">One-Dimensional Electrical Contact to a Two-Dimensional Metal.</a> Science. 342, 614-617 (2013).</li><li>Giessibl, F. J. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Advances+in+Atomic+Force+Microscopy.">Advances in Atomic Force Microscopy.</a> Reviews of Modern Physics. 75, 949-983 (2003).</li><li>Smith, K. C. A., Oatley, C. W. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=The+Scanning+Electron+Microscope+and+its+Fields+of+Applications.">The Scanning Electron Microscope and its Fields of Applications.</a> British Journal of Applied Physics. 6, 391-399 (1955).</li><li>Geim, A. K., Grigorieva, I. V. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Van+der+Waals+heterostructures.">Van der Waals heterostructures.</a> Nature. 499, 419-425 (2013).</li></ol>

The authors declare no competing financial interests. Commercial materials, instruments and equipment are identified in this paper to specify the experimental procedure as completely as possible. In no case does such identification imply a recommendation or endorsement by the National Institute of Standards.

采集高质量大块样品，其特征在于，以确保适当的组成和结构的后，将样品经图案化成为通过剥离样品的薄片中描绘的几何上1厘米×1厘米的片基片的。基板重p掺杂Si构成覆盖约300nm 的 SiO 2是优选的，因为它们增加了实验参数空间通过使背栅的应用。样品必须足够薄 - 少于10纳米 - 以产生足够的场效应调谐在霍尔棒装置的导电沟道的整体的化学势。样品厚度由适当使用标准的晶片切割用胶带从散装材料剥离薄片和重复按磁带薄片粘附到它到新鲜磁带直到薄片是足够的厚度为所计划的实验的目的的控制。转移到衬底片样品太小，看用肉眼，所以在光学显微镜必须用来识别传送块适于制造成霍尔棒。样品薄片厚度是利用原子力显微镜（AFM）精确测量，但是研究人员提供足够的经验可以是能够识别所希望的厚度的基础上，薄片的颜色样本。 一个显着的挑战，在这个手稿中描述的技术程序，当出现样本片不充分坚持通过范德华力单片基板。在这种情况下，在任何数目的步骤的制造步骤的（特别是在浸在溶剂）将样品薄片将被撞或洗掉衬底片表面的。这是通过在该手稿所述的新颖技术，其中将样品薄片通过涂覆溅射的 SiO 2的片在固定到衬底片处理。一旦这样做，将样品薄片的部件必须暴露，以允许所述直接一个dherence的金属触点。用于这些联系人的沉积的掩模，可以使用由作为对于在SiO 2的蚀刻的掩模，以适应这种目的，如在此将蚀刻的 SiO 2的确切位置的金属接触将沉积，从而允许电接触到样品片，同时仍保持固定用溅射的 SiO 2在其大部分区域的薄片。执行此步骤允许的新型散装材料已经合成为大小不足的散料运输的常规测量的晶体，从而为许多新材料为追求探索性材料科学研究的一部分，运输研究的传输测量。 在本文中描述的实验技术提供了深厚的技术进步来自堆叠多层材料到异质结构的能力。这具有许多优点。六方氮化硼（的hBN）可用于夹层其他2D的材料，如石墨，以产品从与空气相互作用而产生的缺陷​​的表面上，允许载体状态的更准确的，无缺陷的运输测量。此外，有趣的突发行为可以观察到从栈不同材料12形成异质结构。去角质之后，转移到衬底片，并确定合适的样品片，一个过程可以遵循生产涉及的谨慎使用的聚合物，聚二甲基硅氧烷（PDMA）和聚丙烯碳酸酯（PPC）样品传输的多层材料的异质堆栈。此方法允许这样的堆叠，而不会引入这些聚合物的小球作为相邻材料之间的污染物，如堆叠发生按层状材料的清洁表面在一起。已完成的异质结构堆叠可以被转移到一个新的单片基板的器件制造。 设备栎阳离子是一个涉及许多步骤，严格的流程。一旦合适的样品片已经转移，确定，和，如果需要的话，堆积成包括几个单独的薄片的一个异质结构中，聚合物掩模应用和图案化和涉及在制造过程中的蚀刻和金属沉积几个迭代的步骤可能需要几个天以产生单一高质量样品。由于这种方法，由此所希望的大小，厚度和质量的薄片可以在任何地方发现单片基板和霍尔棒尺寸上的一块已被确定后，必须确定的查找和探针的性质，光刻必须做通过电子束光刻。电子束光刻是一种先进的光刻技术，其允许结构的直接写至通过使用电子聚焦光束的扫描的近5纳米的尺寸。具体器件结构对于每个样品制备。利用等离子体基因各向同性蚀刻完成时额定在反应性离子蚀刻（RIE）系统。为六方氮化硼/石墨烯/六方氮化硼叠层的蚀刻，用于该等离子体蚀刻的气体为O 2和CHF 3的混合物。沉积的金属接点由一薄层的Cr，旨在用作粘附层和第二层的Au中750纳米，选择了它的高导电率，淀积顺序地在高真空中的电子束蒸发室。该装置的制造是成功的金属剥离下列金属沉积之后完成，之后该点，设备可以被结合到封装并装入磁输运低温恒温器用于实验测量。 进步这个手稿中描述的制造和实验技术的将涉及改善由个别薄片可以被堆叠成异质结构的过程。此外，个别薄片和分层材料的层叠剥离s转换异质结构通过在该手稿描述的技术不限于那些没有暴露于空气中实现的材料。额外的考虑，如进行多步骤的在惰性环境中，必须采取用于由氧化破坏，如过渡金属二硫属化物和铋硫族化物拓扑绝缘体材料。磁输运系统将继续看到改善作为强磁体和较低的温度下低温恒温器被工程，导致功能更强大的实验测量能力。

先进的电子技术的追求材料的平台要求的高通量材料的合成和随后的表征方法。在这种追求兴趣的新型材料，可以产生散装直接反应合成1,2-，电化学生长3,4-，和其他方法5以更快速的方式相比，如分子束外延或更多参与单晶薄膜沉积技术化学气相沉积。测量块状晶体样品的输运性质的常规方法是切割的矩形棱柱形的片段约为1毫米×1毫米×6毫米的尺寸和连接线导致在一个霍尔棒构6的样品。 某些材料构成挑战，其中传统的散装霍尔棒装置的制造方法是不足以产生一个可测量的装置，用于传输样品测量。这可以是导致产生的结晶太小附加引线到，即使是一个功能强大的光学显微镜下，因为所需的样品厚度是1的量级，以只有几个单层，或因为一个目的是衡量一叠层状二维材料与近或亚纳米厚度。第一类包括，例如纳米线和氧化钼的某些制剂铜器7。第二类包括单对极少数的二维材料，例如石墨烯8层 ，TMDS（ 二硫化钼，WTE 2等），和拓扑绝缘体（ 的 Bi 2硒3，铋锑x 1-X 3碲等 ）。第三类包括制备由经由层转移，的hBN-石墨烯的hBN 9的最显着的一个三层堆积层叠的二维材料的各层通过手工装配异质结构。 新型Ë的探索性研究lectronic原材料的需求，足够制造方法上难以测量的样品设备。通常情况下，第一批直接反应或电化学生长合成新材料的产量非常小的单晶微米尺寸级的尺寸。这种样品在历史上被证明极为困难附加金属接触到，因此有必要改善样品生长参数以实现较大的晶体，以方便运输装置制造，呈现的障碍物的新材料的高通量研究。为了使材料的快速表征，器件制造为非常小的样品的方法，已被设计成只要初步批次已经产生允许新材料的表征。这种方法的细微变化是适用于制造使用二维材料，例如石墨烯，的hBN，和TMDS剥离样品，设备以及这种毫安的多层异质结构terials。设备被附着和引线键合到一个包，用于插入一个商业超导磁体，干燥氦气靠近循环低温恒温器磁输运系统。传输测量是在温度下降到0.300 K和磁场高达12吨

<table border="0" cellpadding="0" cellspacing="0" width="840">
	<tbody>
		<tr height="42">
			<td height="42" style="height:42px;width:200px;">Cryogenic Limited 12T CFMS</td>
			<td style="width:89px;">Cryogen Limited</td>
			<td style="width:135px;">CFM-12T-H3- IVTI-25</td>
			<td style="width:417px;">Magnetotransport system customized with modulated field magnet (step 4)</td>
		</tr>
		<tr height="42">
			<td height="42" style="height:42px;width:200px;">7270 DSP Lock-in amplifier</td>
			<td style="width:89px;">Signal Recovery</td>
			<td style="width:135px;">7270</td>
			<td style="width:417px;">lock-in amplifier for source/drain and voltage measurements (step 4)</td>
		</tr>
		<tr height="42">
			<td height="42" style="height:42px;width:200px;">GS200 DC Voltage/Current Source</td>
			<td style="width:89px;">Yokogawa</td>
			<td style="width:135px;">GS200</td>
			<td style="width:417px;">Voltage source for gate voltage application (step 4)</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:200px;">2636B System Sourcemeter</td>
			<td style="width:89px;">Keithley</td>
			<td style="width:135px;">2636B</td>
			<td style="width:417px;">Sourcemeter for source/drain and voltage measurements</td>
		</tr>
		<tr height="42">
			<td height="42" style="height:42px;width:200px;">DWL 2000 Laser Pattern Generator</td>
			<td style="width:89px;">Heidelberg Instruments</td>
			<td style="width:135px;">DWL 2000</td>
			<td style="width:417px;">Generate chrome mask for lithography of substrate location/alignment feature pattern (step 1.3)</td>
		</tr>
		<tr height="42">
			<td height="42" style="height:42px;width:200px;">Suss MicroTec MA6/BA6 Contact Aligner</td>
			<td style="width:89px;">Suss</td>
			<td style="width:135px;">MA6</td>
			<td style="width:417px;">Used for the lithography of substrate location/alignment feature pattern (step 1.4.12)</td>
		</tr>
		<tr height="42">
			<td height="42" style="height:42px;width:200px;">JEOL Direct Write Electron Beam Lithography System</td>
			<td style="width:89px;">JEOL</td>
			<td style="width:135px;">JBX 6300-FS&#160;</td>
			<td style="width:417px;">Perform high-resolution lithography of devices</td>
		</tr>
		<tr height="42">
			<td height="42" style="height:42px;width:200px;">Discovery 550 Sputtering System</td>
			<td style="width:89px;">Denton Vacuum</td>
			<td style="width:135px;">Discovery 550</td>
			<td style="width:417px;">Perform SiO2 sputtering (step 2.5)</td>
		</tr>
		<tr height="42">
			<td height="42" style="height:42px;width:200px;">Infinity 22 Electron Beam Evaporator</td>
			<td style="width:89px;">Denton Vacuum</td>
			<td style="width:135px;">Infinty 22</td>
			<td style="width:417px;">Perform Cr/Au deposition (steps 1.5 and 3.7)</td>
		</tr>
		<tr height="42">
			<td height="42" style="height:42px;width:200px;">Unaxis 790 Reactive Ion Etcher</td>
			<td style="width:89px;">Unaxis</td>
			<td style="width:135px;">Unaxis 790</td>
			<td style="width:417px;">Etch sample into Hall bar structure (step 3.4)</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:200px;">Name</td>
			<td style="width:89px;">Company</td>
			<td style="width:135px;">Catalog Number</td>
			<td style="width:417px;">Comments</td>
		</tr>
		<tr height="42">
			<td height="42" style="height:42px;width:200px;">PMMA 495 A4</td>
			<td style="width:89px;">MicroChem</td>
			<td style="width:135px;">PMMA 495 A4</td>
			<td style="width:417px;">Polymer coating/electron beam mask for lithography (step 3.5.1)</td>
		</tr>
		<tr height="42">
			<td height="42" style="height:42px;width:200px;">PMMA 950 A4</td>
			<td style="width:89px;">MicroChem</td>
			<td style="width:135px;">PMMA 950 A4</td>
			<td style="width:417px;">Polymer coating/electron beam mask for sample dicing and lithography (steps 1.7.3, 3.3.1, and 3.5.2)</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:200px;">S1813 positive photoresist</td>
			<td style="width:89px;">MicroChem</td>
			<td style="width:135px;">S1813 G2</td>
			<td style="width:417px;">Positive photoresist (step 1.4.8)</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:200px;">LOR resist</td>
			<td style="width:89px;">MicroChem</td>
			<td style="width:135px;">LOR 3A</td>
			<td style="width:417px;">Lift off resist (step 1.4.3)</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">1:3 MIBK:IPA PMMA developer</td>
			<td style="width:89px;">MicroChem</td>
			<td style="width:135px;">1:3 MIBK:IPA</td>
			<td style="width:417px;">PMMA developer</td>
		</tr>
		<tr height="42">
			<td height="42" style="height:42px;width:200px;">MF-321 Developer</td>
			<td style="width:89px;">MicroChem</td>
			<td style="width:135px;">MF-321</td>
			<td style="width:417px;">Novolac positive photoresist-compatible developer solution (step 1.4.15)</td>
		</tr>
		<tr height="42">
			<td height="42" style="height:42px;width:200px;">Diglycidiyl ether-terminated polydimethylsiloxane</td>
			<td style="width:89px;">Sigma Aldrich</td>
			<td style="width:135px;">SA 480282</td>
			<td style="width:417px;">For layered material stacking (step 2.6.1)</td>
		</tr>
		<tr height="42">
			<td height="42" style="height:42px;width:200px;">Polypropylene carbonate</td>
			<td style="width:89px;">Sigma Aldrich</td>
			<td style="width:135px;">SA 389021</td>
			<td style="width:417px;">For layered material stacking (step 2.6.2)</td>
		</tr>
	</tbody>
</table>

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.

图3示出了图案化的低温磁输运实验的目的典型霍尔棒装置。在上图的光学图像显示了一个成功制造的石墨烯/的hBN馆吧;下部图显示的过程中出现的Landau能级（LLS）的兰道尔-Büttiker边缘状态的装置的原理图，其可用于计算量化的霍尔电阻的值的传输机制，实验调查，其中将作为要讨论一个典型应用实验方法在本文中详细介绍的。通常情况下，霍尔棒结构的制造构成了整个制造过程中一个巨大的挑战。所涉及的样品蚀刻到该形状的步骤可以被跳过，并且引线可以直接附接，因为它们是以下转让给单片基板来样薄片。然而，不完全的几何将不允许车传输性的eful测量，所以跳过涉及蚀刻样品放入霍尔棒结构的步骤应被限制为初始测量。 实验参数包括磁场高达12 T，温度低至0.300 K和栅极电压高达30伏特交流电可能由振荡器从一个锁定放大器与相关的锁式AC电压测量供给而直流电流可以由具有相关联的DC电压测量一个源表来提供。交变电流与直流电流和电流的幅值是被研究必须仔细选择基于所述性能，包括耐击穿特性参数的材料构成，。霍尔电阻定义为间的电位差，或测量两端的电压， 在图3中通过所施加的电流除以引线6和2。再纵向电阻是否定义为间的电位差，或测量两端的电压，引线2和3除以所施加的电流。石墨烯霍尔棒与顶面用的hBN片完全封装石墨保护测量在1.7钾养分的磁场范围从-6 T至+6 T和背栅电压范围为-30 V至+30 V.图4显示了霍尔电阻这个参数空间中是如何变化的。在石墨烯/的hBN厅酒吧，特别是在相应的朗道能级填充霍尔电阻可观察到的高原测得的霍尔电阻的行为，是量子霍尔效应的典范，一个量子力学现象，只有通过这种应用可观察如本文所描述先进的磁输运技术。 图5显示了在B = 6吨示于图4中的数据的切片，与霍尔电阻（R XY）作为背栅电压的函数和相应的纵向电阻（R XX），为背栅极电压的函数。测量清楚地表明，石墨烯显示出量子霍尔效应与与整数值朗道能级数 n，普朗克常数 h，和电子电荷 e化霍尔电阻值。该化霍尔平台与消失的纵向电阻一致。 <img alt="图1" src="/files/ftp_upload/53506/53506fig1.jpg" /> 图1.基板图案。 （一）为样本衬底的光刻图案的位置/对准标记的设计配置的区域。该图案的金位置/对准标记（B）电脑渲染。 <a href="https://www-jove-com.remotexs.ntu.edu.sg/files/ftp_upload/53506/53506fig1large.jpg" target="_blank">请点击此处查看大图</a><html>这个数字。 <img alt="图2" src="/files/ftp_upload/53506/53506fig2.jpg" /> 图2.石墨烯薄片。毗邻通过光学显微镜观察铬/金位置标记单层石墨烯片的形象。 <a href="https://www-jove-com.remotexs.ntu.edu.sg/files/ftp_upload/53506/53506fig2large.jpg" target="_blank">请点击此处查看该图的放大版本。</a> <img alt="图3" src="/files/ftp_upload/53506/53506fig3.jpg" /> 图3.霍尔棒的设备。上图中，石墨烯/的hBN霍尔棒装置用金属光学图像引线接触到终端。下图中，与编号为对应于在该装置的光学像数字标记的端子接触引线设备示意图。箭头表明流动电流所产生的兰道尔 - Büttiker边缘状态。ES / ftp_upload / 53506 / 53506fig3large.jpg"目标="_空白"&gt;点击此处查看该图的放大版本。 <img alt="图4" src="/files/ftp_upload/53506/53506fig4.jpg" /> 霍尔电阻作为磁场和全球背栅的函数的图4的3D绘图。在量子霍尔政权作为磁场和全球背栅的功能石墨烯大厅杆的霍尔电阻的在1.7ķ证明量子传输行为3D绘图。 <a href="https://www-jove-com.remotexs.ntu.edu.sg/files/ftp_upload/53506/53506fig4large.jpg" target="_blank">请点击此处查看该图的放大版本。</a> <img alt="图5" src="/files/ftp_upload/53506/53506fig5.jpg" /> 图5. Hall和纵向磁阻。霍尔（R XY）和纵向（R XX）阻力在修复全球后门功能ED磁场│B│= 6吨展示量子霍尔效应与量子化霍尔电阻值与消失的纵向电阻相吻合。 <a href="https://www-jove-com.remotexs.ntu.edu.sg/files/ftp_upload/53506/53506fig5large.jpg" target="_blank">请点击此处查看该图的放大版本。</a>

Watch this Scientific Journal Video about Advanced Experimental Methods for Low-temperature Magnetotransport Measurement of Novel Materials at JoVE.com

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

对于新材料的低温磁输运测量先进的实验方法

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.

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

advanced-experimental-methods-for-low-temperature-magnetotransport

Nanyang Technological University

Research

JoVE Journal

Engineering

10.5K 次观看.  National Institute of Standards and Technology. 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.

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

Novel 3D/VR Interactive Environment for MD Simulations, Visualization and Analysis

The increasing development of computing (hardware and software) in the last decades has impacted scientific research in many fields including materials science, biology, chemistry and physics among many others. A new computational system for the accurate and fast simulation and 3D/VR visualization of nanostructures is presented here, using the open-source molecular dynamics (MD) computer program LAMMPS. This alternative computational method uses modern graphics processors, NVIDIA CUDA technology and specialized scientific codes to overcome processing speed barriers common to traditional computing methods. In conjunction with a virtual reality system used to model materials, this enhancement allows the addition of accelerated MD simulation capability. The motivation is to provide a novel research environment which simultaneously allows visualization, simulation, modeling and analysis. The research goal is to investigate the structure and properties of inorganic nanostructures (e.g., silica glass nanosprings) under different conditions using this innovative computational system. The work presented outlines a description of the 3D/VR Visualization System and basic components, an overview of important considerations such as the physical environment, details on the setup and use of the novel system, a general procedure for the accelerated MD enhancement, technical information, and relevant remarks. The impact of this work is the creation of a unique computational system combining nanoscale materials simulation, visualization and interactivity in a virtual environment, which is both a research and teaching instrument at UC Merced.

A new computational system featuring GPU-accelerated molecular dynamics simulation and 3D/VR visualization, analysis and manipulation of nanostructures has been implemented, representing a novel approach to advance materials research and promote innovative investigation and alternative methods to learn about material structures with dimensions invisible to the human eye.

新颖的3D / VR互动环境MD模拟，可视化和分析

The increasing development of computing (hardware and software) in the last decades has impacted scientific research in many fields including materials ...

科研

工程学

Writing and Low-Temperature Characterization of Oxide Nanostructures

Oxide nanoelectronics is a rapidly growing field which seeks to develop novel materials with multifunctional behavior at nanoscale dimensions. Oxide interfaces exhibit a wide range of properties that can be controlled include conduction, piezoelectric behavior, ferromagnetism, superconductivity and nonlinear optical properties. Recently, methods for controlling these properties at extreme nanoscale dimensions have been discovered and developed. Here are described explicit step-by-step procedures for creating LaAlO3/SrTiO3 nanostructures using a reversible conductive atomic force microscopy technique. The processing steps for creating electrical contacts to the LaAlO3/SrTiO3 interface are first described. Conductive nanostructures are created by applying voltages to a conductive atomic force microscope tip and locally switching the LaAlO3/SrTiO3 interface to a conductive state. A versatile nanolithography toolkit has been developed expressly for the purpose of controlling the atomic force microscope (AFM) tip path and voltage. Then, these nanostructures are placed in a cryostat and transport measurements are performed. The procedures described here should be useful to others wishing to conduct research in oxide nanoelectronics.

Oxide nanostructures provide new opportunities for science and technology. The interfacial conductivity between LaAlO3 and SrTiO3 can be controlled with near-atomic precision using a conductive atomic force microscopy technique. The protocol for creating and measuring conductive nanostructures at LaAlO3/SrTiO3 interfaces is demonstrated.

写作和氧化物纳米结构的低温特性

Oxide nanoelectronics is a rapidly growing field which seeks to develop novel materials with multifunctional behavior at nanoscale dimensions.  Oxide ...

Detection and Recovery of Palladium, Gold and Cobalt Metals from the Urban Mine Using Novel Sensors/Adsorbents Designated with Nanoscale Wagon-wheel-shaped Pores

Developing low-cost, efficient processes for recovering and recycling palladium, gold and cobalt metals from urban mine remains a significant challenge in industrialized countries. Here, the development of optical mesosensors/adsorbents (MSAs) for efficient recognition and selective recovery of Pd(II), Au(III), and Co(II) from urban mine was achieved. A simple, general method for preparing MSAs based on using high-order mesoporous monolithic scaffolds was described. Hierarchical cubic Ia3d wagon-wheel-shaped MSAs were fabricated by anchoring chelating agents (colorants) into three-dimensional pores and micrometric particle surfaces of the mesoporous monolithic scaffolds. Findings show, for the first time, evidence of controlled optical recognition of Pd(II), Au(III), and Co(II) ions and a highly selective system for recovery of Pd(II) ions (up to ~95%) in ores and industrial wastes. Furthermore, the controlled assessment processes described herein involve evaluation of intrinsic properties (e.g., visual signal change, long-term stability, adsorption efficiency, extraordinary sensitivity, selectivity, and reusability); thus, expensive, sophisticated instruments are not required. Results show evidence that MSAs will attract worldwide attention as a promising technological means of recovering and recycling palladium, gold and cobalt metals.

Because of the importance and extensive use of palladium, gold and cobalt metals in high-technology equipment, their recovery and recycling constitute an important industrial challenge. The metal recovery system described herein is a simple, low-cost means for the effective detection, removal, and recovery of these metals from the urban mine.

检测和钯的回收，从城市矿山黄金和钴金属使用标有纳米货车车轮形的孔隙新型传感器/吸附剂

Developing low-cost, efficient processes for recovering and recycling palladium, gold and cobalt metals from urban mine remains a significant challenge in ...

Fabrication of Low Temperature Carbon Nanotube Vertical Interconnects Compatible with Semiconductor Technology

We demonstrate a method for the low temperature growth (350 &#176;C) of vertically-aligned carbon nanotubes (CNT) bundles on electrically conductive thin-films. Due to the low growth temperature, the process allows integration with modern low-&#954; dielectrics and some flexible substrates. The process is compatible with standard semiconductor fabrication, and a method for the fabrication of electrical 4-point probe test structures for vertical interconnect test structures is presented. Using scanning electron microscopy the morphology of the CNT bundles is investigated, which demonstrates vertical alignment of the CNT and can be used to tune the CNT growth time. With Raman spectroscopy the crystallinity of the CNT is investigated. It was found that the CNT have many defects, due to the low growth temperature. The electrical current-voltage measurements of the test vertical interconnects displays a linear response, indicating good ohmic contact was achieved between the CNT bundle and the top and bottom metal electrodes. The obtained resistivities of the CNT bundle are among the average values in the literature, while a record-low CNT growth temperature was used.

A method for the growth of low temperature vertically-aligned carbon nanotubes, and the subsequent fabrication of vertical interconnect electrical test structures using semiconductor fabrication is presented.

低温碳纳米管垂直互连的制作兼容半导体技术

We demonstrate a method for the low temperature growth (350 &#176;C) of vertically-aligned carbon nanotubes (CNT) bundles on electrically conductive ...

Experimental Methods for Investigation of Shape Memory Based Elastocaloric Cooling Processes and Model Validation

Shape Memory Alloys (SMA) using elastocaloric cooling processes have the potential to be an environmentally friendly alternative to the conventional vapor compression based cooling process. Nickel-Titanium (Ni-Ti) based alloy systems, especially, show large elastocaloric effects. Furthermore, exhibit large latent heats which is a necessary material property for the development of an efficient solid-state based cooling process. A scientific test rig has been designed to investigate these processes and the elastocaloric effects in SMAs. The realized test rig enables independent control of an SMA&#39;s mechanical loading and unloading cycles, as well as conductive heat transfer between SMA cooling elements and a heat source/sink. The test rig is equipped with a comprehensive monitoring system capable of synchronized measurements of mechanical and thermal parameters. In addition to determining the process-dependent mechanical work, the system also enables measurement of thermal caloric aspects of the elastocaloric cooling effect through use of a high-performance infrared camera. This combination is of particular interest, because it allows illustrations of localization and rate effects &#8212; both important for efficient heat transfer from the medium to be cooled.
The work presented describes an experimental method to identify elastocaloric material properties in different materials and sample geometries. Furthermore, the test rig is used to investigate different cooling process variations. The introduced analysis methods enable a differentiated consideration of material, process and related boundary condition influences on the process efficiency. The comparison of the experimental data with the simulation results (of a thermomechanically coupled finite element model) allows for better understanding of the underlying physics of the elastocaloric effect. In addition, the experimental results, as well as the findings based on the simulation results, are used to improve the material properties.

Experimental methods for investigation of solid state cooling processes and characterization of elastocaloric material properties of Shape Memory Alloys (SMA) are presented. A custom-built test rig has been designed for controlling and comprehensive monitoring of elastocaloric cooling processes. Furthermore, it provides a validation platform for thermomechanically coupled modeling approaches.

基于形状记忆调查Elastocaloric冷却过程和模型验证实验方法

Shape Memory Alloys (SMA) using elastocaloric cooling processes have the potential to be an environmentally friendly alternative to the conventional vapor ...

Measurement of Outgassing Rates of Steels

Steels are commonly used materials in the fabrication of vacuum systems because of their good mechanical, corrosion, and vacuum properties. A variety of steels meet the criterion of low outgassing required for high or ultrahigh vacuum applications. However, a given material can present different outgassing rates depending on its manufacturing process or the various pretreatment processes involved during the fabrication. Thus, the measurement of outgassing rates is highly desirable for a specific vacuum application. For this reason, the rate-of-pressure rise (RoR) method is often used to measure the outgassing of hydrogen after bakeout. In this article, a detailed description of the design and execution of the experimental protocol involved in the RoR method is provided. The RoR method uses a spinning rotor gauge to minimize errors that stem from outgassing or the pumping action of a vacuum gauge. The outgassing rates of two ordinary steels (stainless steel and mild steel) were measured. The measurements were made before and after the heat pretreatment of the steels. The heat pretreatment of steels was performed to reduce the outgassing. Extremely low rates of outgassing (on the order of 10&#8722;11 Pa m3 sec&#8722;1 m&#8722;2) can be routinely measured using relatively small samples.

A protocol for the measurement of outgassing rates of hydrogen from ordinary steel vacuum chambers using the rate-of-pressure rise method is presented.

钢的出气率的测量

Steels are commonly used materials in the fabrication of vacuum systems because of their good mechanical, corrosion, and vacuum properties. A variety of ...

Experimental Procedure for Warm Spinning of Cast Aluminum Components

High performance, cast aluminum automotive wheels are increasingly being incrementally formed via flow forming/metal spinning at elevated temperatures to improve material properties. With a wide array of processing parameters which can affect both the shape attained and resulting material properties, this type of processing is notoriously difficult to commission. A simplified, light-duty version of the process has been designed and implemented for full-size automotive wheels. The apparatus is intended to assist in understanding the deformation mechanisms and the material response to this type of processing. An experimental protocol has been developed to prepare for, and subsequently perform forming trials and is described for as-cast A356 wheel blanks. The thermal profile attained, along with instrumentation details are provided. Similitude with full-scale forming operations which impart significantly more deformation at faster rates is discussed.

An experimental protocol for instrumented warm rotary forming of cast aluminum alloys employing a bespoke industrially scaled apparatus is presented. Experimental considerations including thermal and mechanical effects are discussed, as well as similitude with full-scale processing of automotive wheels.

铸铝零部件的暖纺纱实验程序

High performance, cast aluminum automotive wheels are increasingly being incrementally formed via flow forming/metal spinning at elevated temperatures to ...

Standardized Method for Measuring Collection Efficiency from Wipe-sampling of Trace Explosives

One of the limiting steps to detecting traces of explosives at screening venues is effective collection of the sample. Wipe-sampling is the most common procedure for collecting traces of explosives, and standardized measurements of collection efficiency are needed to evaluate and optimize sampling protocols. The approach described here is designed to provide this measurement infrastructure, and controls most of the factors known to be relevant to wipe-sampling. Three critical factors (the applied force, travel distance, and travel speed) are controlled using an automated device. Test surfaces are chosen based on similarity to the screening environment, and the wipes can be made from any material considered for use in wipe-sampling. Particle samples of the explosive 1,3,5-trinitroperhydro-1,3,5-triazine (RDX) are applied in a fixed location on the surface using a dry-transfer technique. The particle samples, recently developed to simulate residues made after handling explosives, are produced by inkjet printing of RDX solutions onto polytetrafluoroethylene (PTFE) substrates. Collection efficiency is measured by extracting collected explosive from the wipe, and then related to critical sampling factors and the selection of wipe material and test surface. These measurements are meant to guide the development of sampling protocols at screening venues, where speed and throughput are primary considerations.

Optimized sampling protocols and the development of new wipe materials can be facilitated by standardized measurements of collection efficiency from wipe-sampling. Our approach for sampling trace explosives uses an automated device to control speed, force, and distance during wipe-sampling followed by extraction of collected explosives.

从微量炸药的擦拭取样测量收集效率的标准化方法

One of the limiting steps to detecting traces of explosives at screening venues is effective collection of the sample. Wipe-sampling is the most common ...

A Novel Method for In Situ Electromechanical Characterization of Nanoscale Specimens

Electrically assisted deformation (EAD) is increasingly being used to improve the formability of metals during processes such as sheet metal rolling and forging. Adoption of this technique is proceeding despite disagreement concerning the underlying mechanism responsible for EAD. The experimental procedure described herein enables a more explicit study compared to previous EAD research by removing thermal effects, which are responsible for disagreement in interpreting previous EAD results. Furthermore, as the procedure described here enables EAD observation in situ and in real time in a transmission electron microscope (TEM), it is superior to existing post-mortem methods that observe EAD effects post-test. Test samples consist of a single crystal copper (SCC) foil having a free-standing tensile test section of nanoscale thickness, fabricated using a combination of laser and ion beam milling. The SCC is mounted to an etched silicon base that provides mechanical support and electrical isolation while serving as a heat sink. Using this geometry, even at high current density (~3,500 A/mm2), the test section experiences a negligible temperature increase (&#60;0.02 &#176;C), thus eliminating Joule heating effects. Monitoring material deformation and identifying the corresponding changes to microstructures, e.g. dislocations, are accomplished by acquiring and analyzing a series of TEM images. Our sample preparation and in situ experiment procedures are robust and versatile as they can be readily utilized to test materials with different microstructures, e.g., single and polycrystalline copper.

A Novel Method for In Situ Electromechanical Characterization of Nanoscale Specimens

Isolating electrical and thermal effects on electrically assisted deformation (EAD) is very difficult using macroscopic samples. Metallic sample micro- and nanostructures together with a custom test procedure have been developed to evaluate the impact of applied current on the formation without joule heating and evolution of dislocations on these samples.

一种新的方法<em&gt;原位</em&gt;纳米级样品的机电表征

Electrically assisted deformation (EAD) is increasingly being used to improve the formability of metals during processes such as sheet metal rolling and ...

Micro/Nano-scale Strain Distribution Measurement from Sampling Moir&#233; Fringes

This work describes the measurement procedure and principles of a sampling moir&#233; technique for full-field micro/nano-scale deformation measurements. The developed technique can be performed in two ways: using the reconstructed multiplication moir&#233; method or the spatial phase-shifting sampling moir&#233; method. When the specimen grid pitch is around 2 pixels, 2-pixel sampling moir&#233; fringes are generated to reconstruct a multiplication moir&#233; pattern for a deformation measurement. Both the displacement and strain sensitivities are twice as high as in the traditional scanning moir&#233; method in the same wide field of view. When the specimen grid pitch is around or greater than 3 pixels, multi-pixel sampling moir&#233; fringes are generated, and a spatial phase-shifting technique is combined for a full-field deformation measurement. The strain measurement accuracy is significantly improved, and automatic batch measurement is easily achievable. Both methods can measure the two-dimensional (2D) strain distributions from a single-shot grid image without rotating the specimen or scanning lines, as in traditional moir&#233; techniques. As examples, the 2D displacement and strain distributions, including the shear strains of two carbon fiber-reinforced plastic specimens, were measured in three-point bending tests. The proposed technique is expected to play an important role in the non-destructive quantitative evaluations of mechanical properties, crack occurrences, and residual stresses of a variety of materials.

A sampling moir&#233; technique featuring 2-pixel and multi-pixel sampling methods for high-accuracy strain distribution measurements at the micro/nano-scale is presented here.

微米/纳米尺度应变分布测量从采样莫尔条纹

This work describes the measurement procedure and principles of a sampling moir&#233; technique for full-field micro/nano-scale deformation measurements. ...