Name: plasma-assisted molecular beam epitaxy of n-polar inaln-barrier high-electron-mobility transistors
Uploaded: 2016-11-24T13:00:00.000+00:00
Duration: 10 min 31 s
Description: Watch this Scientific Journal Video about Plasma-assisted Molecular Beam Epitaxy of N-polar InAlN-barrier High-electron-mobility Transistors at JoVE.com

The authors thank Mr. Neil Green for assistance with sample preparation. This work was supported by the Office of Naval Research under funding from Dr. P. Maki. MTH was supported by a National Research Council Postdoctoral Fellowship.

1.积液细胞斜坡和流量校准<ol><li>确认液态氮的流向低温板和生长室已达到基本压力。 </li><li>斜坡上升的喷射室到其光束通量测量（BFM）温度以1℃/秒的升温速率为Ga和在细胞中，并为铝10℃/分钟。等待细胞1小时，热稳定。 </li><li>打开每个单元的快门为30-60秒，然后关闭快门1-2分钟。重复三次每个小区。丢弃第一束流离子规测量和平均后两种。调整电池温度根据先前通量/温度校准以获得所需的磁通。 </li></ol> 2.基板制备和加载<ol><li> 易地基板清洗 <ol><li>负载开盒即用的N-极性GaN衬底直接，没有任何易地清洗。如果晶片被暴露在空气中更超过几个小时，冲洗下丙酮（30秒），异丙醇（30秒）和去离子（DI）水（60秒）。漂洗优选浸没在可能的，因为它往往留在晶片表面上更小的颗粒。 注:有关嘎极性GaN衬底建议更严格的表面的清洁23 </li></ol></li><li> 装载晶圆 <ol><li>关闭负载锁隔离闸阀，并用N 2通气。 </li><li>装载在支架晶片和盒返回到负载锁定。打开负载锁定低真空泵，打开低真空泵阀和岐管阀。 </li><li>当歧管压力已降至低于0.1乇，关闭歧管和低真空泵阀。关掉低真空泵和打开装载锁定涡轮泵隔离阀。 </li><li>允许负载锁定抽空30-60分钟。理想情况下，使用10 -6 -10 -7托的负载锁定压力转移到准备室前。 </li><li>打开负载锁定到制备腔室，并且使用摆动棒晶片传送到手推车。然后用台车到晶片在制备腔室传送到除气站。手动移动台车沿着上使用该准备容室的旋转穿通线的轨道。 </li></ol></li><li> 脱气晶圆 <ol><li>斜坡除气站加热器温度到700℃历时10分钟。 </li><li> 30分钟后，递减的温度回落到100℃。当温度≤250℃，使用该摆动棒在除气站传送晶片返回到手推车。 </li></ol></li><li> 负载晶片到生长室 <ol><li>降低基板操纵到装载位置，打开准备/生长室闸阀和晶片保持器传送到操纵器。 </li><li>抬起手来生长部位，基底加热器附近。 </li><li>取出小车和ClOSE闸阀。 </li><li>打开N 2瓶头阀，调节阀和隔离针形阀。设置质量流量控制器（MFC）以1.5标准立方厘米（或根据需要以得到3-4×10 -5乇的室压力）。对于等离子点火的最佳压力是强烈依赖于系统。注意，N 2必须是超高纯度（大于6N优选更好）和一个附加滤波在线路用于进一步降低杂质。 </li><li>与N *和主百叶窗关闭时，打开等离子体RF电源和自动匹配网络控制器。加大射频功率，直到血浆点燃。 </li><li>设置RF功率和N 2流量为所需的工艺条件，在这种情况下，350瓦和2.0标准立方厘米。从给定的等离子体条件所产生的N *通量系统相关，但在这里，这些条件屈服的5.0纳米/分钟的GaN生长速度，或1.8纳米-2秒的N *通量-1。监控与连接到一台光谱仪的血浆稳定性等离子体室的后窗。 </li></ol></li><li> 原位表面处理:嘎沉积和解吸 <ol><li>衬底加热器斜坡上升至10℃，高于所需的GaN生长温度与≤1℃/秒的升温速率。在这种情况下使用的730℃的估计晶片温度。 </li><li>打开RHEED系统上观看的晶片表面的劣化和监测镓覆盖。手动打开基板转动。设置了触发RHEED采集软件每衬底旋转一次收集的RHEED图案同时衬底生长过程中旋转，以提供一个静态图像。 </li><li>打开衬底快门和Ga快门1分钟。确保RHEED强度减小那么作为嘎积累达到平稳。 Ga束流的应类似于用于GaN生长。在此，Ga束流为大约3.7纳米-2秒-1。 </li><li>关闭快门2分钟，并确保RHEED强度增加并达到2分钟结束前一个平台，表明嘎解吸。 </li><li>重复步骤2.5.2-2.5.4三次，24然后斜衬底的GaN生长的温度。 </li></ol></li></ol> 3. HEMT增长<ol><li> 缓冲区增长 <ol><li>通过打开N *快门对于1分钟氮化开始生长。 </li><li>通过打开铝快门长出薄薄的1-3纳米丰富的N- AlN成核层。此AlN层可以帮助防止穿透位错的产生，25然而，在AlN层复杂的X射线衍射（XRD）测量，不推荐基于XRD-校准样品。使用相同的Al磁通作为InAlN层，或约0.36纳米-2秒-1，给予大约为1纳米/分钟的生长速率。 </li><li>关闭Al和N *快门和立即打开嘎快门10秒，让嘎饱和从表面上看，RHEED强度应减少RApidly。打开N *快门（以尕快门仍然打开），并增加5分钟的GaN。使用成为或C掺杂，特别是对独立GaN衬底，防止在缓冲漏电电流。 </li><li>关闭Ga和N *百叶窗1分钟生长中断。监测RHEED强度。如果RHEED强度立即增大，则Ga束流不够高。如果RHEED强度&gt; 30秒之后增加或没有达到1分钟内的高原则Ga束流的过高。参见图3。 </li><li>增加几度基板温度（或减少镓喷射室温度），以补偿在3.1.4看到高镓通量。如果Ga的流量为过低，降低基板温度（或者增加Ga的喷射室温度）进行补偿。 <ol><li>重复步骤3.1.3-3.1.5，直到有一个15-30秒的延迟RHEED强度增加并且RHEED强度达到前1分钟的高原之前。 </li></ol></LI&gt; <li>继续重复步骤3.1.4-3.1.5直到达到所需的GaN的厚度。由校准增长率乘以总的生长时间确定的厚度。对于富Ga生长，确定由N *通量，其可以反过来采用XRD测量为一个单独生长校准样品以已知的生长时间的厚度来计算的增长率。 </li></ol></li><li> InAlN屏障增长 <ol><li>再等待1分钟，最后GaN生长步骤后，以确保所有嘎蒸发。 </li><li>急剧下降到InAlN生长温度约为630℃。允许将基板温度稳定约2分钟。 </li><li>打开In，Al和N *百叶窗。该RHEED强度应该减少与前3分钟内到达平台期。 RHEED强度的持续下降可以指示在积累，这是不利的InAlN增长。 RHEED图应保持条纹，表明表面光滑。我的n和铝通量约为0.31和0.36纳米-2秒-1，给予的1.25纳米/分钟III族有限的增长速度。 </li><li>关闭在，Al和N *所需的阻挡层厚度后百叶窗已经达到。对于富的N-增长，确定由总III族流量的增长速度。测量使用一个单独生长InAlN校准样品的XRD的增长速度。对于使用这里给出的条件15nm的InAlN屏障，打开百叶窗12分30秒。 </li></ol></li><li> 夹层和渠道增长 <ol><li>首先打开嘎快门5秒，然后打开N *快门和生长的GaN中间层。基板温度应该仍然在InAlN生长温度。 </li><li>打开铝快门，无需关闭或Ga N *百叶窗成长的AlN的中间层。用于中间层的的Al通量应大于N *磁通相同或稍高，最好使用不同的Al渗出细胞然后与用于InAlN阻挡层，叔o避免不必更改电池温度。请参阅步骤3.2.4。 </li><li>关闭N *和Al百叶窗，但离开嘎快门打开。坡道衬底温度达到GaN沟道温度。 </li><li> 30秒后关闭嘎快门。等待30秒（或者只要RHEED强度开始增加），并重新打开嘎快门。继续循环镓快门直到基板已达到GaN沟道生长温度。这将同时防止过度积累嘎保护表面。 </li><li>打开嘎快门5秒，然后打开N *快门和成长GaN沟道。 </li><li>关闭嘎，N *及主要百叶窗。坡道使基板温度下降到200℃，关掉N *等离子体和关闭的 N 2气流。 </li><li>斜坡细胞下降到待机温度，如果完成的一天。 </li><li>等待将衬底温度降低低于250℃，腔室压力下降到低于8×10 -7乇，然后打开生长室闸阀和晶片支架传送回手推车。 </li><li>按照步骤2.2到晶片传送回负载锁定的反向，泄用N 2和取出晶片。确保生长室闸阀被打开负载锁定之前闭合，并且该负载锁定涡轮泵闸阀放空之前关闭。 </li><li>按照步骤2.2.3-2.2.5到磁带盒和负载锁定回到高真空。 </li></ol></li></ol> 4.表征<ol><li>利用光学显微镜来检查可能的渠道增长过程中形成的凹坑，裂纹或Ga液滴，XRD检查界面和结构质量，原子力显微镜来检查表面形貌表征材料的品质。20,21 </li><li>如果Ga的液滴存在，沉浸在浓HF酸晶片5-10分钟以除去液滴而不损坏化学敏感N极性面。 </li><li>测量表水库istance使用Lehighton的接触电阻的测量。 </li><li>处理样品，让电器特性，包括大厅和CTLM测量，直流和射频晶体管特性。9,26 </li></ol>

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C. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Oxygen+incorporation+in+homoepitaxial+N-polar+GaN+grown+by+radio+frequency-plasma+assisted+molecular+beam+epitaxy:+Mitigation+and+modeling.">Oxygen incorporation in homoepitaxial N-polar GaN grown by radio frequency-plasma assisted molecular beam epitaxy: Mitigation and modeling.</a> J. Appl. Phys. 112 (1), 013507 (2012).</li><li>Storm, D. F., 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=Effect+of+interfacial+oxygen+on+the+microstructure+of+MBE-grown+homoepitaxial+N-polar.">Effect of interfacial oxygen on the microstructure of MBE-grown homoepitaxial N-polar.</a> J. Cryst. Growth. 409, 14 (2014).</li><li>Meyer, D. 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=High+Electron+Velocity+Submicrometer+AlN/GaN+MOS-HEMTs+on+Freestanding+GaN+Substrates.">High Electron Velocity Submicrometer AlN/GaN MOS-HEMTs on Freestanding GaN Substrates.</a> IEEE Electron Device Lett. 34, 199 (2013).</li><li>Moseley, M., Billingsley, D., Henderson, W., Trybus, E., Doolittle, W. A. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Transient+atomic+behavior+and+surface+kinetics+of+GaN.">Transient atomic behavior and surface kinetics of GaN.</a> J. Appl. Phys. 106 (1), 014905 (2009).</li><li>Koblm&#252;ller, 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=Ga+Adlayer+Governed+Surface+Defect+Evolution+of+(0001)GaN+Films+Grown+by+Plasma-Assisted+Molecular+Beam+Epitaxy.">Ga Adlayer Governed Surface Defect Evolution of (0001)GaN Films Grown by Plasma-Assisted Molecular Beam Epitaxy.</a> Jpn. J. Appl. Phys. 44 (28), L906-L908 (2005).</li><li>Poblenz, C., Waltereit, P., Speck, J. S. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Uniformity+and+control+of+surface+morphology+during+growth+of+GaN+by+molecular+beam+epitaxy.">Uniformity and control of surface morphology during growth of GaN by molecular beam epitaxy.</a> J. Vac. Sci. Technol., B. 23 (4), 1379-1385 (2005).</li></ol>

The authors have nothing to disclose.

高品质的GaN缓冲层的生长是在任何III族氮化物HEMT实现高电子迁移率的关键。在N极性InAlN HEMT的情况下，缓冲层生长是由所有镓从InAlN生长之前的表面去除的要求变得复杂。有各种技术，除了程序来完成此这里描述的，例如金属调制外延，27使用的生长条件在中间镓覆盖率和Ga液滴积累制度，28的边缘或允许连续N * -磁通掺入过量嘎当嘎快门被周期性关闭。24 <p class=...

分子束外延（MBE）是一种多功能的外延薄膜生长技术，其用碱的压力低至10 -11乇采用的超高真空环境，以确保在生长膜低杂质掺入。外延生长层的组成和生长速率是通过控制每一个喷射室的温度，并且因此各种源物质的蒸发通量测定。在III族氮化物外延，Ⅲ族元素（在，铝，镓），而活性氮（N *）磁通由任一的N 2等离子体1,2-（RF等离子体提供通常由喷射室中提供的基的情况下-assisted MBE:PAMBE或RFMBE）或氨（NH 3 -MBE）3,4- MBE生长的5特征在于较低的生长温度和更清晰的界面陡峭比其他的外延生长技术，如金属有机化学气相沉积的示意图被示出。在图1中。 <p类="jove_content"&gt; <img alt="图1" src="/files/ftp_upload/54775/54775fig1.jpg" /> 图1:。MBE系统原理示意图，显示加载锁定，传送系统，除气站和生长室<a href="http://ecsource.jove.com/files/ftp_upload/54775/54775fig1large.jpg" target="_blank">请点击此处查看该图的放大版本。</a> III族氮化物可以在具有各种晶体取向衬底上生长。最常用的取向是镓极性的c面，它允许的二维电子气的形成而不掺杂通过利用阻挡层，通常AlGaN和GaN沟道之间偏振差。氮化镓的各种非极性和半极性方向已收到光电子显著注意由于在量子阱，这也使得这些取向不太希望为HEMT应用A 6,7-减小极化效应纳秒。 N极性导向设备是用于下一代高频HEMT操作有吸引力，由于比常规镓极性设备几个固有的优点。8在N极性装置的阻挡层生长在GaN沟道下方， 如图2，所得在自然回屏障有助于该信道的静电控制和减少短沟道效应，同时允许容易当前接入到GaN沟道和减少接触电阻。阻挡也可以从通道分别控制，这样，当信道厚度按比例缩小的用于高频器件的屏障设计可以被修改，以补偿失去的费米能级钉扎效应信道的费用。 <img alt="图2" src="/files/ftp_upload/54775/54775fig2.jpg" /> 图2:（a）一种N极性HEMT和（b）一种镓极性HEMT为COMPAR的外延层概略层结构ISON。 <a href="http://ecsource.jove.com/files/ftp_upload/54775/54775fig2large.jpg" target="_blank">请点击此处查看该图的放大版本。</a> 在高速使用HEMT器件，高功率放大器通常生长在SiC衬底采取SiC的高热导率的优点。低的穿透位错密度的独立式GaN衬底可以被用来提高电子迁移率，9从而改善高频性能。以下的AlN成核层的生长，一个厚的GaN缓冲生长到空间中的杂质在离HEMT信道的再生长界面分离并改善电隔离。不像其他的III-V材料，氮化镓由PAMBE生长通常需要的生长条件与一组-III / V比大于1， 即 ，富金属的条件下，10,11，以达到平滑的表面形态更大。 x中铝1×N的是一个ALTER天然阻挡材料为III族氮化物HEMT器件，并已收到显著关注最近，因为它可以生长晶格匹配的GaN对于x≈0.18，并可以在相对的AlGaN障碍两次沟道电荷由于其高自发极化产生12-15不同于的AlGaN障碍，镓将优先结合到在InAlN层，16因而必须小心，以确保富Ga GaN缓冲层的生长和InAlN生长之前后的表面是自由过量的Ga。 镓的表面上控制可以通过suppling Ga的磁通比Ga的液滴形成所需的磁通稍小来完成。然而，这种增长窗口小，并且不足镓表面覆盖将导致表面形态降解成高原/沟槽的形态，而过量的Ga束流会导致镓积累和宏观液滴形成。17反射高能电子衍射（RHEED）INTENS<html>性可用于监测镓积累和解吸。ガ表面覆盖率是通过RHEED强度降低，和关闭ガ之间任何滞后指示（和N *）百叶窗和在RHEED强度的初始增加表明镓累积， 如图3。 <img alt="图3" src="/files/ftp_upload/54775/54775fig3.jpg" /> 图3:监控嘎覆盖，使用触发采集下旋转收购RHEED模式计量的RHEED强度 RHEED强度信号。 （未示出）不足Ga束流通过关闭快门之后立即增加强度指示。饱和/理想嘎覆盖率由快门关闭和突然的RHEED增白和多余嘎覆盖率视为初始RHEED增亮两个延迟以及导致全强度恢复较为缓慢强度增加的时间超过60秒之间的延迟表示。COM /文件/ ftp_upload / 54775 / 54775fig3large.jpg"目标="_空白"&gt;点击此处查看该图的放大版本。 实现高品质通过PAMBE InAlN由横向成分波动的存在复杂的，导致由以富以界包围富铝域的"蜂窝"的微观结构。此微结构18消除是通过使用基板温度约50取得℃下在解吸，15,19,20或约630℃，N极性InAlN发作以上。在这种高温下生长机制，则在具有In x Al 1-×N个组合物是衬底温度的强函数，以导致较低的掺入更高的温度。该通量可以增加以补偿蒸发掉，但实际上最大的在流量由掺入效率的降低与增加流量限制21除了降低衬底温度或增加在通量，增加生长速度也可以增加在组合物由于"以掩埋效应"，其中，进入的铝原子陷阱以及防止其蒸发。21,22高等生长速率可以通过按比例增加的In和Al通量来实现。为了保持生长条件Ñ富中，N *将需要以及增加，这可以通过增加RF等离子体功率来实现，增加的 N 2流量，改善了等离子体室设计，或者增加光圈板孔密度。 在基于InAlN类HEMT额外外延层包括GaN和AlN中间层（离子液体）和GaN沟道。 AlN的IL插入的屏障和渠道之间能增加流动性μ以及沟道薄层电荷密度N s 个 。在移动性的增加归因于减少与InAlN B电子波函数重叠arrier和随后的合金散射。9为确保在AlN的IL高质量的增长，过量的Ga束流的生长过程中供给到充当表面活性剂。的GaN的IL可以在AlN IL和屏障之间使用，以进一步改善流动性，同时减少信道的费用。 GaN沟道可以在相同的温度下InAlN屏障来生长，允许从阻挡尽管离子液体和信道持续增长。改进的流动性已经被中断的AlN IL后生长和生长所述GaN沟道之前增加的生长温度下得到。在这种情况下的保护镓表面覆盖有中断，以防止流动性降解过程中被保持。 下面的协议特别适用于生长在N极性GaN衬底InAlN屏障HEMT器件。它可以通过包括一个50纳米厚的n富AlN层可以直接延伸到第C-极性4H-或6H-SiC衬底的生长。

<table><tbody><tr><td>Freestanding N-polar GaN wafer</td><td>Kyma</td><td></td><td>10 mm x 10 mm</td></tr><tr><td>C-polar SiC wafer</td><td>Cree</td><td>W4TRE0R-L600</td><td>3 inch diameter</td></tr><tr><td>Microelectronics grade acetone</td><td>Fischer Scientific</td><td>A18-4</td><td></td></tr><tr><td>Microelectronics grade isoproponal</td><td>J.T. Baker</td><td>9079-05/JT9079-5</td><td></td></tr><tr><td>Al source material (6N5 pure)</td><td>UMC</td><td>ALR62060I</td><td></td></tr><tr><td>Ga source material (7N pure)</td><td>UMC</td><td>GA701</td><td></td></tr><tr><td>In source material (7N pure)</td><td>UMC</td><td>IN750</td><td></td></tr><tr><td>ULSI N&lt;sub&gt;2&lt;/sub&gt; source gas (6N pure)</td><td>Matheson Tri-gas</td><td>G2659906D</td><td></td></tr><tr><td>PRO-75 MBE system</td><td>OmicronScientia</td><td></td><td></td></tr></tbody></table>

plasma-assisted molecular beam epitaxy of n-polar inaln-barrier high-electron-mobility transistors

等离子体辅助分子束外延非常适合于III族氮化物薄膜和异质的具有高品质的高电子迁移率晶体管（HEMT器件）需要平滑，突变接口外延生长。的过程提出了N极性InAlN HEMT器件的生长，包括晶圆制备和缓冲层，所述InAlN阻挡层的AlN和GaN中间层和GaN沟道的生长。在该过程的每个步骤中的关键问题被识别，如避免在GaN缓冲嘎积累，温度对InAlN组成均一性的作用，以及在AlN层间期间使用Ga束流的和中断的GaN之前信道的增长。组成均匀N极性InAlN薄膜，证明用低至0.19纳米和表面根均方粗糙度InAlN基于被报告的HEMT结构具有带片电荷密度迁移率高达1750厘米2 / V∙秒为设备为1.7×1013厘米-2。

X射线衍射（XRD）上生长图4中N极性GaN衬底所示InAlN薄膜的扫描（a）的单峰值都为50和200纳米厚的薄膜。 50纳米厚的薄膜InAlN的XRD扫描表现Pendellösung条纹高达15 阶 ，显示非常高的界面质量。 图4中的非对称倒易空间映射（b）示出了200nm厚InAlN层具有相同q‖，因此在同一平面内晶格常数为GaN衬底，指示用于一?...

Watch this Scientific Journal Video about Plasma-assisted Molecular Beam Epitaxy of N-polar InAlN-barrier High-electron-mobility Transistors at JoVE.com

Plasma-assisted Molecular Beam Epitaxy of N-polar InAlN-barrier High-electron-mobility Transistors

分子束外延用来生长N极性InAlN阻高电子迁移率晶体管（HEMT器件）。在光滑，组成均匀InAlN层和HEMT的晶圆准备控制层生长条件和外延结构的结果与流动性高达1750厘米2 / V∙秒。

N极性InAlN阻高电子迁移率晶体管的等离子体辅助分子束外延

Plasma-assisted molecular beam epitaxy is well suited for the epitaxial growth of III-nitride thin films and heterostructures with smooth, abrupt ...

plasma-assisted-molecular-beam-epitaxy-n-polar-inaln-barrier-high

Research

JoVE Journal

Engineering

8.5K 次观看.  Naval Research Laboratory. 分子束外延用来生长N极性InAlN阻高电子迁移率晶体管（HEMT器件）。在光滑，组成均匀InAlN层和HEMT的晶圆准备控制层生长条件和外延结构的结果与流动性高达1750厘米2 / V∙秒。 

视频: Plasma-assisted Molecular Beam Epitaxy of N-polar InAlN-barrier High-electron-mobility Transistors

Molecular Beam Mass Spectrometry With Tunable Vacuum Ultraviolet (VUV) Synchrotron Radiation

Tunable soft ionization coupled to mass spectroscopy is a powerful method to investigate isolated molecules, complexes and clusters and their spectroscopy and dynamics1-4. Fundamental studies of photoionization processes of biomolecules provide information about the electronic structure of these systems. Furthermore determinations of ionization energies and other properties of biomolecules in the gas phase are not trivial, and these experiments provide a platform to generate these data. We have developed a thermal vaporization technique coupled with supersonic molecular beams that provides a gentle way to transport these species into the gas phase. Judicious combination of source gas and temperature allows for formation of dimers and higher clusters of the DNA bases. The focus of this particular work is on the effects of non-covalent interactions, i.e., hydrogen bonding, stacking, and electrostatic interactions, on the ionization energies and proton transfer of individual biomolecules, their complexes and upon micro-hydration by water1, 5-9.
We have performed experimental and theoretical characterization of the photoionization dynamics of gas-phase uracil and 1,3-dimethyluracil dimers using molecular beams coupled with synchrotron radiation at the Chemical Dynamics Beamline10 located at the Advanced Light Source and the experimental details are visualized here. This allowed us to observe the proton transfer in 1,3-dimethyluracil dimers, a system with pi stacking geometry and with no hydrogen bonds1. Molecular beams provide a very convenient and efficient way to isolate the sample of interest from environmental perturbations which in return allows accurate comparison with electronic structure calculations11, 12. By tuning the photon energy from the synchrotron, a photoionization efficiency (PIE) curve can be plotted which informs us about the cationic electronic states. These values can then be compared to theoretical models and calculations and in turn, explain in detail the electronic structure and dynamics of the investigated species 1, 3.

Molecular Beam Mass Spectrometry With Tunable Vacuum Ultraviolet VUV Synchrotron Radiation

A molecular beam coupled to tunable vacuum ultraviolet photoionization mass spectrometer at a synchrotron provides a convenient tool to explore the electronic structure of isolated gas phase molecules and clusters. Proton transfer mechanisms in DNA base dimers were elucidated with this technique.

可调式真空紫外（VUV）同步辐射分子束质谱分析

Tunable soft ionization coupled to mass spectroscopy is a powerful method to investigate isolated molecules, complexes and clusters and their spectroscopy ...

科研

工程学

Nanofabrication of Gate-defined GaAs/AlGaAs Lateral Quantum Dots

A quantum computer is a computer composed of quantum bits (qubits) that takes advantage of quantum effects, such as superposition of states and entanglement, to solve certain problems exponentially faster than with the best known algorithms on a classical computer. Gate-defined lateral quantum dots on GaAs/AlGaAs are one of many avenues explored for the implementation of a qubit. When properly fabricated, such a device is able to trap a small number of electrons in a certain region of space. The spin states of these electrons can then be used to implement the logical 0 and 1 of the quantum bit. Given the nanometer scale of these quantum dots, cleanroom facilities offering specialized equipment- such as scanning electron microscopes and e-beam evaporators- are required for their fabrication. Great care must be taken throughout the fabrication process to maintain cleanliness of the sample surface and to avoid damaging the fragile gates of the structure. This paper presents the detailed fabrication protocol of gate-defined lateral quantum dots from the wafer to a working device. Characterization methods and representative results are also briefly discussed. Although this paper concentrates on double quantum dots, the fabrication process remains the same for single or triple dots or even arrays of quantum dots. Moreover, the protocol can be adapted to fabricate lateral quantum dots on other substrates, such as Si/SiGe.

This paper presents a detailed fabrication protocol for gate-defined semiconductor lateral quantum dots on gallium arsenide heterostructures. These nanoscale devices are used to trap few electrons for use as quantum bits in quantum information processing or for other mesoscopic experiments such as coherent conductance measurements.

纳米加工门定义的GaAs / AlGaAs多量子点横向

A quantum computer is a computer composed of quantum bits (qubits) that takes advantage of quantum effects, such as superposition of states and ...

Electron Channeling Contrast Imaging for Rapid III-V Heteroepitaxial Characterization

Misfit dislocations in heteroepitaxial layers of GaP grown on Si(001) substrates are characterized through use of electron channeling contrast imaging (ECCI) in a scanning electron microscope (SEM). ECCI allows for imaging of defects and crystallographic features under specific diffraction conditions, similar to that possible via plan-view transmission electron microscopy (PV-TEM). A particular advantage of the ECCI technique is that it requires little to no sample preparation, and indeed can use large area, as-produced samples, making it a considerably higher throughput characterization method than TEM. Similar to TEM, different diffraction conditions can be obtained with ECCI by tilting and rotating the sample in the SEM. This capability enables the selective imaging of specific defects, such as misfit dislocations at the GaP/Si interface, with high contrast levels, which are determined by the standard invisibility criteria. An example application of this technique is described wherein ECCI imaging is used to determine the critical thickness for dislocation nucleation for GaP-on-Si by imaging a range of samples with various GaP epilayer thicknesses. Examples of ECCI micrographs of additional defect types, including threading dislocations and a stacking fault, are provided as demonstration of its broad, TEM-like applicability. Ultimately, the combination of TEM-like capabilities &#8211; high spatial resolution and richness of microstructural data &#8211; with the convenience and speed of SEM, position ECCI as a powerful tool for the rapid characterization of crystalline materials.

The use of electron channeling contrast imaging in a scanning electron microscope to characterize defects in III-V/Si heteroexpitaxial thin films is described. This method yields similar results to plan-view transmission electron microscopy, but in significantly less time due to lack of required sample preparation.

电子通道造影的快速III-V异质特征

Misfit dislocations in heteroepitaxial layers of GaP grown on Si(001) substrates are characterized through use of electron channeling contrast imaging ...

Silicon Metal-oxide-semiconductor Quantum Dots for Single-electron Pumping

As mass-produced silicon transistors have reached the nano-scale, their behavior and performances are increasingly affected, and often deteriorated, by quantum mechanical effects such as tunneling through single dopants, scattering via interface defects, and discrete trap charge states. However, progress in silicon technology has shown that these phenomena can be harnessed and exploited for a new class of quantum-based electronics. Among others, multi-layer-gated silicon metal-oxide-semiconductor (MOS) technology can be used to control single charge or spin confined in electrostatically-defined quantum dots (QD). These QD-based devices are an excellent platform for quantum computing applications and, recently, it has been demonstrated that they can also be used as single-electron pumps, which are accurate sources of quantized current for metrological purposes. Here, we discuss in detail the fabrication protocol for silicon MOS QDs which is relevant to both quantum computing and quantum metrology applications. Moreover, we describe characterization methods to test the integrity of the devices after fabrication. Finally, we give a brief description of the measurement set-up used for charge pumping experiments and show representative results of electric current quantization.

The fabrication process and experimental characterization techniques relevant to single-electron pumps based on silicon metal-oxide-semiconductor quantum dots are discussed.

硅金属 - 氧化物 - 半导体量子点单电子泵

As mass-produced silicon transistors have reached the nano-scale, their behavior and performances are increasingly affected, and often deteriorated, by ...

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 ...

Fabrication of Schottky Diodes on Zn-polar BeMgZnO/ZnO Heterostructure Grown by Plasma-assisted Molecular Beam Epitaxy

Heterostructure field effect transistors (HFETs) utilizing a two dimensional electron gas (2DEG) channel have a great potential for high speed device applications. Zinc oxide (ZnO), a semiconductor with a wide bandgap (3.4 eV) and high electron saturation velocity has gained a great deal of attention as an attractive material for high speed devices. Efficient gate modulation, however, requires high-quality Schottky contacts on the barrier layer. In this article, we present our Schottky diode fabrication procedure on Zn-polar BeMgZnO/ZnO heterostructure with high density 2DEG which is achieved through strain modulation and incorporation of a few percent Be into the MgZnO-based barrier during growth by molecular beam epitaxy (MBE). To achieve high crystalline quality, nearly lattice-matched high-resistivity GaN templates grown by metal-organic chemical vapor deposition (MOCVD) are used as the substrate for the subsequent MBE growth of the oxide layers. To obtain the requisite Zn-polarity, careful surface treatment of GaN templates and control over the VI/II ratio during the growth of low temperature ZnO nucleation layer are utilized. Ti/Au electrodes serve as Ohmic contacts, and Ag electrodes deposited on the O2 plasma pretreated BeMgZnO surface are used for Schottky contacts.

Attainment of high-quality Schottky contacts is imperative for achieving efficient gate modulation in heterostructure field effect transistors (HFETs). We present the fabrication methodology and characteristics of Schottky diodes on Zn-polar BeMgZnO/ZnO heterostructures with high-density two dimensional electron gas (2DEG), grown by plasma-assisted molecular beam epitaxy on GaN templates.

等离子体辅助分子束外延法制备的锌极性 BeMgZnO/氧化锌异质结构肖特基二极管的制备

Heterostructure field effect transistors (HFETs) utilizing a two dimensional electron gas (2DEG) channel have a great potential for high speed device ...

Plasma-Assisted Molecular Beam Epitaxy Growth of Mg3N2 and Zn3N2 Thin Films

This article describes a procedure for growing Mg3N2 and Zn3N2 films by plasma-assisted molecular beam epitaxy (MBE). The films are grown on 100 oriented MgO substrates with N2 gas as the nitrogen source. The method for preparing the substrates and the MBE growth process are described. The orientation and crystalline order of the substrate and film surface are monitored by the reflection high energy electron diffraction (RHEED) before and during growth. The specular reflectivity of the sample surface is measured during growth with an Ar-ion laser with a wavelength of 488 nm. By fitting the time dependence of the reflectivity to a mathematical model, the refractive index, optical extinction coefficient, and growth rate of the film are determined. The metal fluxes are measured independently as a function of the effusion cell temperatures using a quartz crystal monitor. Typical growth rates are 0.028 nm/s at growth temperatures of 150 &#176;C and 330 &#176;C for Mg3N2 and Zn3N2 films, respectively.

Plasma-Assisted Molecular Beam Epitaxy Growth of Mg3N2 and Zn3N2 Thin Films

This article describes the growth of epitaxial films of Mg3N2 and Zn3N2 on MgO substrates by plasma-assisted molecular beam epitaxy with N2 gas as the nitrogen source and optical growth monitoring.

Mg3N2和 Zn3N2薄膜的等离子辅助分子束外延生长

This article describes a procedure for growing Mg3N2 and Zn3N2 films by plasma-assisted molecular beam epitaxy (MBE). The films are grown on 100 oriented ...

Graphene-Assisted Quasi-van der Waals Epitaxy of AlN Film on Nano-Patterned Sapphire Substrate for Ultraviolet Light Emitting Diodes

This protocol demonstrates a method for graphene-assisted quick growth and coalescence of AlN on nano-pattened sapphire substrate (NPSS). Graphene layers are directly grown on NPSS using catalyst-free atmospheric-pressure chemical vapor deposition (APCVD). By applying nitrogen reactive ion etching (RIE) plasma treatment, defects are introduced into the graphene film to enhance chemical reactivity. During metal-organic chemical vapor deposition (MOCVD) growth of AlN, this N-plasma treated graphene buffer enables AlN quick growth, and coalescence on NPSS is confirmed by cross-sectional scanning electron microscopy (SEM). The high quality of AlN on graphene-NPSS is then evaluated by X-ray rocking curves (XRCs) with narrow (0002) and (10-12) full width at half-maximum (FWHM) as 267.2 arcsec and 503.4 arcsec, respectively. Compared to bare NPSS, AlN growth on graphene-NPSS shows significant reduction of residual stress from 0.87 GPa to 0.25 Gpa, based on Raman measurements. Followed by AlGaN multiple quantum wells (MQWS) growth on graphene-NPSS, AlGaN-based deep ultraviolet light-emitting-diodes (DUV LEDs) are fabricated. The fabricated DUV-LEDs also demonstrate obvious, enhanced luminescence performance. This work provides a new solution for the growth of high quality AlN and fabrication of high performance DUV-LEDs using a shorter process and less costs.

A protocol for graphene-assisted growth of high-quality AlN films on nano-patterned sapphire substrate is presented.

紫外发光二极管纳米图案蓝宝石基板的AlN薄膜的石墨烯辅助准范德瓦尔斯皮Taxy

This protocol demonstrates a method for graphene-assisted quick growth and coalescence of AlN on nano-pattened sapphire substrate (NPSS). Graphene layers ...

The Effect of Anodization Parameters on the Aluminum Oxide Dielectric Layer of Thin-Film Transistors

Aluminum-oxide (Al2O3) is a low cost, easily processable and high dielectric constant insulating material that is particularly appropriate for use as the dielectric layer of thin-film transistors (TFTs). Growth of aluminum-oxide layers from anodization of metallic aluminum films is greatly advantageous when compared to sophisticated processes such as atomic layer deposition (ALD) or deposition methods that demand relatively high temperatures (above 300 &#176;C) such as aqueous combustion or spray-pyrolysis. However, the electrical properties of the transistors are highly dependent on the presence of defects and localized states at the semiconductor/dielectric interface, which are strongly affected by the manufacturing parameters of the anodized dielectric layer. To determine how several fabrication parameters influence the device performance without performing all possible combination of factors, we used a reduced factorial analysis based on a Plackett-Burman design of experiments (DOE). The choice of this DOE permits the use of only 12 experimental runs of combinations of factors (instead of all 256 possibilities) to obtain the optimized device performance. The ranking of the factors by the effect on device responses such as the TFT mobility is possible by applying analysis of variance (ANOVA) to the obtained results.

Anodization parameters for growth of the aluminum-oxide dielectric layer of zinc-oxide thin-film transistors (TFTs) are varied to determine the effects on the electrical parameter responses. Analysis of variance (ANOVA) is applied to a Plackett-Burman design of experiments (DOE) to determine the manufacturing conditions that result in optimized device performance.

阳极化参数对薄膜晶体管氧化铝介电层的影响

Aluminum-oxide (Al2O3) is a low cost, easily processable and high dielectric constant insulating material that is particularly appropriate for use as the ...

化学

In Situ Transmission Electron Microscopy with Biasing and Fabrication of Asymmetric Crossbars Based on Mixed-Phased a-VOx

Resistive switching crossbar architecture is highly desired in the field of digital memories due to low cost and high-density benefits. Different materials show variability in resistive switching properties due to the intrinsic nature of the material used, leading to discrepancies in the field because of underlying operation mechanisms. This highlights a need for a reliable technique to understand mechanisms using nanostructural observations. This protocol explains a detailed process and methodology of in&#160;situ nanostructural analysis as a result of electrical biasing using transmission electron microscopy (TEM). It provides visual and reliable evidence of underlying nanostructural changes in real time memory operations. Also included is the methodology of fabrication and electrical characterizations for asymmetric crossbar structures incorporating amorphous vanadium oxide. The protocol explained here for vanadium oxide films can be easily extended to any other materials in a metal-dielectric-metal sandwiched structure. Resistive switching crossbars are predicted to serve the programmable logic and neuromorphic circuits for next-generation memory devices, given the understanding of the operation mechanisms. This protocol reveals the switching mechanism in a reliable, timely, and cost-effective way in any type of resistive switching materials, and thereby predicts the device&#39;s applicability.

In Situ Transmission Electron Microscopy with Biasing and Fabrication of Asymmetric Crossbars Based on Mixed-Phased a-VOx

Presented here is a protocol for analyzing nanostructural changes during in&#160;situ biasing with transmission electron microscopy (TEM) for a stacked metal-insulator-metal structure. It has significant applications in resistive switching crossbars for the next generation of programmable logic circuits and neuromimicking hardware, to reveal their underlying operation mechanisms and practical applicability.

N极性InAlN阻高电子迁移率晶体管的等离子体辅助分子束外延

摘要

探索更多视频

此视频中的章节

可调式真空紫外（VUV）同步辐射分子束质谱分析

纳米加工门定义的GaAs / AlGaAs多量子点横向

电子通道造影的快速III-V异质特征

硅金属 - 氧化物 - 半导体量子点单电子泵

对于新材料的低温磁输运测量先进的实验方法

等离子体辅助分子束外延法制备的锌极性 BeMgZnO/氧化锌异质结构肖特基二极管的制备

Mg₃N₂和 Zn₃N₂薄膜的等离子辅助分子束外延生长

紫外发光二极管纳米图案蓝宝石基板的AlN薄膜的石墨烯辅助准范德瓦尔斯皮Taxy

阳极化参数对薄膜晶体管氧化铝介电层的影响

基于混合相位a-VO_x的不对称横杆的偏置和制造现场传输电子显微镜

N极性InAlN阻高电子迁移率晶体管的等离子体辅助分子束外延

摘要

探索更多视频

此视频中的章节

可调式真空紫外（VUV）同步辐射分子束质谱分析

纳米加工门定义的GaAs / AlGaAs多量子点横向

电子通道造影的快速III-V异质特征

硅金属 - 氧化物 - 半导体量子点单电子泵

对于新材料的低温磁输运测量先进的实验方法

等离子体辅助分子束外延法制备的锌极性 BeMgZnO/氧化锌异质结构肖特基二极管的制备

Mg3N2和 Zn3N2薄膜的等离子辅助分子束外延生长

紫外发光二极管纳米图案蓝宝石基板的AlN薄膜的石墨烯辅助准范德瓦尔斯皮Taxy

阳极化参数对薄膜晶体管氧化铝介电层的影响

基于混合相位a-VOx的不对称横杆的偏置和制造现场传输电子显微镜

Mg₃N₂和 Zn₃N₂薄膜的等离子辅助分子束外延生长

基于混合相位a-VO_x的不对称横杆的偏置和制造现场传输电子显微镜