Name: growth and electrostatic/chemical properties of metal/laalo3/srtio3 heterostructures
Uploaded: 2018-02-08T14:00:00.000+00:00
Duration: 11 min 54 s
Description: Watch this Scientific Journal Video about Growth and Electrostatic/chemical Properties of Metal/LaAlO3/SrTiO3 Heterostructures at JoVE.com

这项工作得到了来自紧急救济协调员赠款 #615759 "薄荷", 区域 le-de 法国昏暗的 "Oxymore" (项目 "NEIMO") 和美国抵抗组织项目 "NOMILOPS" 的支持。h.n 的部分支持 EPSRC--jsp 核心核心计划, 即 jsp 的科研资助 (B) (#15H03548)。问得到德意志 Forschungsgemeinschaft (HO 53461-1; 博士后奖学金, 问)。D.C.V. 感谢法国高等教育和研究部和 CNRS 为他的博士论文融资。感谢巴黎大学 Saclay (达朗伯计划) 和 CNRS 为他在 CNRS/泰雷兹的逗留提供资金。

注意:本协议中描述的所有5步骤都可以在任何时候暂停和重新启动, 唯一的条件是, 该示例在步骤3.4 到5的高真空下保持不中断。
1. 停止 (001) 基板的终止:
<ol><li>填充超声波清洗剂 (用40赫变换器) 与水和热它到60° c。用丙酮填充硼硅酸盐玻璃烧杯。独立的烧杯大小, 一定要填补至少20% 的最大体积, 以确保基板是很好地淹没。<ol>
<li>放置一个出箱混合终止单面抛光 (001) 定向停止单晶衬底 (55 毫米2在横向尺寸, 0.5 毫米的厚度, miscut 角之间的0.01°和 0.02°) 内硼硅酸盐玻璃烧杯。</li>
		<li>在丙酮中几种基材, 用氮气吹枪将基体干燥3分钟左右, 操作压力约 5 bar。</li>
	</ol>
</li>
	<li>重复步骤 1.1, 但使用异丙醇, 然后去离子水。</li>
	<li>将清洁的衬底放在由聚偏氟乙烯 (PVDF) 制成的样品架上, 带有 "北斗" 形状 (图 1a)。用运行的去离子水填充第二个硼硅酸盐玻璃烧杯 (图 1b)。 注意:烧杯应足够大, 使样品持有人适合它。</li>
	<li>将基板放置在样品夹中。</li>
	<li>穿戴适当的保护, 填满烧杯 (图 1b), 通常由聚四氟乙烯、PTFE 制成, 其最大体积约 20%, 具有缓冲氢氟酸 (hf) 解决方案 (hf: NH4F = 1:7)。与步骤1.3 中使用的大小烧杯大致相同。</li>
	<li>将样品持有人淹没在 HF 中整整三十年代, 并立即将其移动到去离子自来水中, 以阻止随后的化学反应。轻轻地搅动它。</li>
	<li>2分钟后, 从去离子水中取出样品夹。取出衬底, 用氮气吹枪擦干。 注意:更多的细节可以在川崎的食谱11中找到。 警告:使用的 HF 溶液具有极强的腐蚀性和毒性。在适当的工作环境中, 始终对已使用的 HF 解决方案进行操作和处理。与身体部位接触后中毒的症状可能在接触后一天内开始可见, 在最初的几个小时可能不会造成任何疼痛。还可以使用基于 HCl-硝酸3酸性溶液12或无酸性终止配方13的替代终止过程。</li>
	<li>将衬底插入管式炉 (图 1c) 在20° c。将炉膛部分压力设置为约1的氧气自动取款机。将温度提高到1000° c, 以20° c/分钟的速度退火基板, 在1000° c 下3小时。3小时后, 让样品冷却到20° c。卸下纸张。关闭氧气源</li>
	<li>重复步骤 1.1, 去除退火过程中促进的后续表面污染物。</li>
</ol>2. 单晶老挝目标的制备:
<ol><li>机械抛光一个单晶老挝目标 (1 英寸直径) 轻轻使用砂纸和异丙醇溶液作为润滑剂。用氮气吹枪擦干</li>
	<li>在传送带上安装目标。 注意:确保旋转木马允许目标轮换。</li>
	<li>在 loadlock 腔中插入旋转木马 (图 2)。让目标在真空中加气, 同时不断泵腔 (直到它达到 10-8毫巴范围内的压力)。将传送带传送到 PLD 室 (图 3a和3b)。等待基本压力在 10-9毫巴范围内。 注意:在无 loadlock 室和真空传输系统中, 典型的等待时间和基本压力会受到严重影响。</li>
	<li>使用准分子激光能量计检查激光能量。为此, 使用矩形狭缝 (6 毫米 x 16 mm) 和外部衰减器的权利后, 激光源调节的形状和能量的光束 (图 4a和4b)。将能量计放置在激光束的路径中, 在第二会聚透镜和石英窗之间。然后, 以任意频率拍摄激光器, 并使用电能表读取能量。</li>
	<li>将能量设置为相同 (或稍高), 就像在成长过程中使用的那样 (步骤 3.12)。 注意:激光能量的绝对值可能会因设置的几何形状而异。然而, 对于老靶消融, 使用激光注量约 1 J/厘米2 (注: 能量/光斑面积)。此外, 使用脉冲 KrF 准分子激光器的波长λ = 248 nm, 具有特征脉冲持续时间为 25 ns 和操作在最低限度的 21 kV (为改善脉冲-脉冲再现性)。</li>
	<li>旋转老挝目标约 10 rpm (使用卡鲁塞尔的旋转平台, 在那里的目标是安装)。<ol>
<li>将目标转速调整到光斑大小和激光重复率, 避免两个连续重叠的镜头, 可能导致局部过热或熔化的目标和随后的非化学计量。图 4c中提供了一个可视化描述。</li>
	</ol>
</li>
	<li>在燃烧室内插入氧气, 直到达到 2x10-4毫巴的氧分压。卸下电能表。前蚀3或4赫兹的老挝目标为20000脉冲。 注意:应设置激光器, 使光束和目标之间的夹角为45° (图 4d)。这一相对较长的老单靶消融被发现在老/停样重现性中具有决定性的作用。</li>
</ol>3. PLD 的成长:
<ol><li>对先前终止的基板表面进行原子力显微镜 (AFM) 扫描, 以验证终止、形貌和清洁 (图 5)。</li>
	<li>使用银浆, 胶水的基板, 与终止表面指向向上, 样品持有人。虽然基板的方向不相关, 但请确保它放在刀柄的中心 (图 6a)。</li>
	<li>加热到大约100° c 为10分钟, 以便溶剂蒸发和浆糊变硬 (为优选的热量传导)。让样品架冷却下来。</li>
	<li>在 loadlock 中插入样品夹。使用在集群内的手臂, 转移样品持有人到 XPS 室分析氧, 碳和钛峰 (参考步骤5的详细信息)。</li>
	<li>将样品架转移到 PLD 室, 基板朝向老挝目标 (图 6b)。</li>
	<li>在腔室内插入氧气以达到 2x10-4毫巴的氧分压。将样品架的温度提高到730° c (在25° c/分钟)。</li>
	<li>利用反射高能电子衍射 (高能), 使电子束在掠角 (°和3之间) 与基体表面对齐, 从而在荧光屏上观察到衍射斑点。使用 CCD 摄像机和图像分析软件实时监控每个点的强度。使用 30 kV 和40µA 电流的源电压。</li>
	<li>将样品架放在离目标63毫米远的地方。 注意:根据所使用的 PLD 设置的几何形状, 目标到基板距离可能需要某种程度的优化。</li>
	<li>拍摄激光, 以校准的能量, 使其匹配约 1 J/cm2 (与步骤2.4 相同的方式)。再次, 使用矩形狭缝 (6 毫米 x 16 mm) 和外部衰减器的权利后, 激光出口调节的形状和能量的光束 (图 4a和4b)。</li>
	<li>将激光频率设置为1赫兹. 停止拍摄激光和删除能量表。</li>
	<li>启动老挝目标的旋转 (与步骤2.6 相同的方式)。启动高能振荡读数。等待它稳定。</li>
	<li>开始拍摄激光。观察羽流 (图 6c) 和高能振荡 (图 6d)。根据所需的厚度, 停止激光在一个振荡的峰值。 注意:请记住, 每个振荡表示一个单元格 (uc) 的增长。为了本实验的目的, 分别生长1和 2 uc 进行运输和光谱实验。</li>
	<li>增长完成后, 关闭高能枪并进行后退火步骤。 注意:后退火步骤是在生长完成后进行的。<ol>
<li>开始后退火, 增加氧气分压在会议厅从 2x10-4毫巴 (增长压力), 以 1x10-1毫巴和降低样品持有人的温度从730° c (生长温度) 到500° c。</li>
		<li>在温度和压力稳定后, 引入一个静态氧分压约300毫巴, 同时保持样品持有人的温度在500° c。将样品留在这些条件下60分钟。</li>
	</ol>
</li>
	<li>冷却样品在25° c/分钟, 同时保持它在相同的氧分压, 直到它达到室温。</li>
	<li>将样品转移到 XPS 室, 以研究钛峰值或相对镧/铝浓度可能发生的价态变化 (有关详细信息, 请参阅步骤 5)。</li>
	<li>为确保老挝表面保持原始, 请将示例在真空中传输到溅射室 (图 7a), 该样本在 10-8毫巴范围内的压力下始终保持不移。 注意:执行这些实验时,原位将导致碳和水在表面的积聚, 最终导致改变结果。</li>
</ol>4. 金属 Overlayers 磁控溅射:
注意:根据所需的金属, 诸如 Ar 压力、沉积电流和靶向衬底距离的参数可能稍有不同。根据所用溅射装置的几何形状, 建议对每个沉积过程进行优化。下面的过程描述了沉积 3 nm 的 Co。
<ol><li>将样品表面朝下朝向目标。</li>
	<li>在溅射腔内插入纯 Ar, 以达到 4.5x10-4毫巴 (约 100 sccm) 的气氛。</li>
	<li>将基板放置在离 Co 目标大约7厘米的位置。</li>
	<li>随着快门关闭, 坡道的电流高达约100毫安 (36 W), 使等离子体被点燃。</li>
	<li>与稳定的血浆 (图 7b), 降低电流到80毫安 (沉积电流) 以及 Ar 到 5.2 sccm 的流入。确保等离子体保持稳定。</li>
	<li>预溅射 Co 靶约5分钟, 除去任何可能在其表面形成的氧化层。</li>
	<li>与样品在室温下, 打开快门和存款二十五年代. 关闭快门结束沉积。<ol>
<li>在运输实验中, 沉积一个随后的上限层约 3 nm Al (其表面钝化, 形成一个 AlOx 保护层后, 暴露在空气), 以防止氧化的基础金属层。 注意:生长率不直接地在会议厅内测量。为了做到这一点, 在使用相同的参数时, 用不同的沉积时间生长各种样品。然后, 用 x 射线反射测量每个样品的厚度。对所使用的每个金属靶进行一次此过程。</li>
	</ol>
</li>
	<li>将电流向下斜向零, 关闭 Ar 源并泵入腔室。</li>
	<li>再一次将样品持有者转移到 XPS 室 (图 8a), 以检查在 Ti 2p 水平上可能的价态变化以及在金属/老挝界面上可能发生的氧化反应 (有关详细信息, 请参阅步骤 5)。</li>
</ol>5. 原位 X 射线光电子能谱:
<ol><li>将示例与与电子分析器轴 (图 8b) 平行的曲面法线对齐。</li>
	<li>接近 X 射线枪尽可能靠近样品 (避免机械接触之间的枪端和样品持有人, 以防止损坏), 并打开它。<ol>
<li>在这个实验中, 使用一个 1253.6 eV 的激发能量的 Mg Kα源。将灯丝设置为在15伏的阳极电压下达到20毫安的发射电流。关于分析仪的电子光学, 选择一个2毫米直径的入口狭缝和一个5x11 毫米的长方形形状的出口狭缝。 注意:有关最大发射电流和阳极电压的信息, 请参阅 XPS 设置手册。另外, 对于其他特定设置, 进出卡瓦的大小可能会有所不同。如果分析仪有不同的规格, 选择的狭缝, 以避免过高的强度在电子计数单位。</li>
	</ol>
</li>
	<li>打开 X 射线枪后, 确保该腔室处于超高真空状态 (10-10毫巴范围)。收集测量光谱 (在0和 1200 ev 结合能之间) 与一个选择的步 0.05 ev, 居住时间 0.5 s, 通行证能量在30和 60 ev 之间和一个适当的透镜方式达到最小的斑点大小可能。根据预期的分辨率调整值。<ol>
<li>找到相关峰值的位置 (图 8c)。对于改进的统计, 测量每个峰值数倍和平均收集的光谱。</li>
	</ol>
</li>
	<li>使用适当的 XPS 处理软件分析频谱。<ol>
<li>为了从给定的跃迁中识别电子, 定义一个包括峰值分析的能量范围。</li>
		<li>创建适当的背景曲线 (通常为雪莉背景14) 并将其从原始数据中减去。</li>
		<li>使用书目参考文献15, 找到构成测量峰值的可能峰值。特别注意不同峰值的表距和相对强度。 注意:更深入地了解所收集的 XPS 数据是在 "代表性结果" 部分以及 Ref.7中提供的。</li>
	</ol>
</li>
</ol>6. 磁实验:
<ol><li>使用超声波楔焊机, 金属/老挝/样品与铝或 Au 线联系, 以接触埋接口 (图 9a)。 注意:根据所使用的设置和运输测量支架的类型, 选择合适的楔形-采样距离、力和时间。</li>
	<li>使用8线几何 (4 在 van der 范德堡-渠道 1-和4在霍尔几何-渠道 2-)。要做到这一点, 首先通过接触的一个通道的运输测量持有人的四个角落的样品在 van der 范德堡几何。然后, 与示例中以前完成的联系人联系第二个通道 (图 9b)。</li>
	<li>通过万用表测量电阻, 检查触点是否良好。为了确保样品是均匀的, 验证不同方向测量的电阻是大致相同的, 这样 van der 范德堡 R100≈R010条件得到满足。 注意:如果 r100和 r010明显不同, 则应在两个方向上执行 van der 范德堡测量 (如下 Ref.16)。先前的研究报告了在老挝/在17中强各向异性的电气传输特性。</li>
	<li>在传输设置中装载持有者。<ol>
<li>测量电阻 (通道 1) 下至 2 K。</li>
		<li>在低温下, 通过扫掠外部和垂直磁场 (从-9 到 9 T) 依次测量磁电阻 (通道 1) 和霍尔效应 (通道 2), 为金属/老挝/µA 样品寻找通常10到100的电流。</li>
		<li>重复步骤6.4.2。为 5 k, 10 k, 50 k, 100 k, 200 k 和 300 k, 为了观察磁电阻演化与温度。</li>
	</ol>
</li>
</ol>

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Lett. 98 (24), 242904 (2011).</li><li>Lesne, E. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=.">.</a> Non-Equilibrium Spin Accumulation Phenomenon at the LaAlO3/SrTiO3(001) Quasi-Two-Dimensional Electron System. , (2015).</li><li>Sato, H. K., Bell, C., Hikita, Y., Hwang, H. Y. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Stoichiometry+control+of+the+electronic+properties+of+the+LaAlO3/SrTiO3+heterointerface.">Stoichiometry control of the electronic properties of the LaAlO3/SrTiO3 heterointerface.</a> Appl. Phys. Lett. 102 (25), 251602 (2013).</li><li>Warusawithana, M. P., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=LaAlO3+stoichiometry+is+key+to+electron+liquid+formation+at+LaAlO3/SrTiO3+interfaces.">LaAlO3 stoichiometry is key to electron liquid formation at LaAlO3/SrTiO3 interfaces.</a> Nat. Commun. 4, (2013).</li><li>Arras, R., Ruiz, V. G., Pickett, W. E., Pentcheva, R. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Tuning+the+two-dimensional+electron+gas+at+the+LaAlO3/SrTiO3(001)+interface+by+metallic+contacts.">Tuning the two-dimensional electron gas at the LaAlO3/SrTiO3(001) interface by metallic contacts.</a> Phys. Rev. B. 85 (12), (2012).</li><li>Fu, Q., Wagner, T. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Interaction+of+nanostructured+metal+overlayers+with+oxide+surfaces.">Interaction of nanostructured metal overlayers with oxide surfaces.</a> Surf. Sci. Rep. 62 (11), 431-498 (2007).</li><li>Chen, 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=Metallic+and+Insulating+Interfaces+of+Amorphous+SrTiO3-based+Oxide+Heterostructures.">Metallic and Insulating Interfaces of Amorphous SrTiO3-based Oxide Heterostructures.</a> Nano Lett. 11 (9), 3774-3778 (2011).</li><li>Posadas, A. B., 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=Scavenging+of+oxygen+from+SrTiO3+during+oxide+thin+film+deposition+and+the+formation+of+interfacial+2DEGs.">Scavenging of oxygen from SrTiO3 during oxide thin film deposition and the formation of interfacial 2DEGs.</a> J. Appl. Phys. 121 (10), (2017).</li><li>Sing, 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=Profiling+the+interface+electron+gas+of+LaAlO3/SrTiO3+heterostructures+with+hard+x-ray+photoelectron+spectroscopy.">Profiling the interface electron gas of LaAlO3/SrTiO3 heterostructures with hard x-ray photoelectron spectroscopy.</a> Phys. Rev. Lett. 102 (17), (2009).</li><li>Hasegawa, S. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Reflection+High-Energy+Electron.">Reflection High-Energy Electron.</a> Charact. Mater. , 1925-1938 (2012).</li><li>Wrobel, 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=Comparative+study+of+LaNiO3/LaAlO3+heterostructures+grown+by+pulsed+laser+deposition+and+oxide+molecular+beam+epitaxy.">Comparative study of LaNiO3/LaAlO3 heterostructures grown by pulsed laser deposition and oxide molecular beam epitaxy.</a> Appl. Phys. Lett. 110 (4), 0 (2017).</li><li>Blank, D. H. A., Dekkers, M., Rijnders, G. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Pulsed+laser+deposition+in+Twente:+from+research+tool+towards+industrial+deposition.">Pulsed laser deposition in Twente: from research tool towards industrial deposition.</a> J. Phys. D. Appl. Phys. 47 (3), 34006 (2014).</li><li>Preziosi, D., Sander, A., Barth&#233;l&#233;my, A., Bibes, M. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Reproducibility+and+off-stoichiometry+issues+in+nickelate+thin+films+grown+by+pulsed+laser+deposition.">Reproducibility and off-stoichiometry issues in nickelate thin films grown by pulsed laser deposition.</a> AIP Adv. 7 (1), (2017).</li><li>Hensling, F. V. E., Xu, C., Gunkel, F., Dittmann, R. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Unraveling+the+enhanced+Oxygen+Vacancy+Formation+in+Complex+Oxides+during+Annealing+and+Growth.">Unraveling the enhanced Oxygen Vacancy Formation in Complex Oxides during Annealing and Growth.</a> Sci. Rep. 7, 39953 (2017).</li><li>Xu, C., B&#228;umer, C., Heinen, R. A., Hoffmann-Eifert, S., Gunkel, F., Dittmann, R. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Disentanglement+of+growth+dynamic+and+thermodynamic+effects+in+LaAlO3/SrTiO3+heterostructures.">Disentanglement of growth dynamic and thermodynamic effects in LaAlO3/SrTiO3 heterostructures.</a> Sci. Rep. 6, 22410 (2016).</li><li>Breckenfeld, E., 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+growth+induced+(non)stoichiometry+on+interfacial+conductance+in+LaAlO3/SrTiO3.">Effect of growth induced (non)stoichiometry on interfacial conductance in LaAlO3/SrTiO3.</a> Phys. Rev. Lett. 110 (19), (2013).</li></ol>

作者没有什么可透露的。

在基板的终止, 你应该非常小心与淹没时间在 HF 解答。我们观察到, 在蚀刻的表面上, 只改变了5秒的原始配方。另外, 我们观察了基片步长和淹没时间的依赖性。对于较小的步长 (小于 100 nm) 淹没三十年代可能导致过度蚀刻, 即使事后退火程序可能足以适当地重建表面。由于使用 HF 基酸的风险, 我们还建议优化的 HCl-硝酸3酸性解决方案终止12或无酸终止技术13</...

准2D 电子系统 (q2DES) 被广泛用作研究大量的低维和量子现象的操场。从 LaAlO3/SrTiO3系统的开创性论文 (老挝语/停用)1开始, 创建了一个不同系统的新界面电子阶段的爆发。结合不同的材料导致发现的 q2DESs 与其他性质, 如电场可调谐自旋极化2, 极高的电子迁移3或铁耦合现象4。虽然大量的工作已经致力于解开这些系统的创造和操纵, 但一些实验和技术却显示出矛盾的结果, 即使是在相当相似的条件下。此外, 在静电和化学相互作用之间的平衡被发现是必不可少的正确理解的物理在玩5,6,7。
在本文中, 我们详细描述了不同的金属/老挝/异的增长, 使用脉冲激光沉积 (PLD) 和原位磁控溅射的组合。然后, 通过传输和电子光谱实验, 了解在老挝/q2DES 界面上不同表面条件对埋地的影响, 进行了电子和化学研究。
由于以前使用过多种方法来生长结晶型老挝, 因此选择合适的沉积技术是制备高质量氧化物异 (除了可能的成本和时间限制) 的关键步骤。在 PLD 中, 强烈的和短的激光脉冲命中所需材料的目标, 然后消融, 并获得沉积在基底上作为一个薄膜。这项技术的主要优点之一是能够可靠地将目标的化学计量性转移到胶片上, 这是一个关键因素, 以达到所需的相形成。此外, 通过大量复杂氧化物的反射高能电子衍射-高能进行层状生长 (实时监测) 的能力, 同时在腔室内有多个目标的可能性 (允许不同材料的生长, 而不打破真空) 和简单的设置使这项技术是最有效的和多才多艺的。
然而, 其他技术, 如分子束外延 (外延), 允许生长更高质量的外延生长。而不是有一个特定的材料的目标, 在外延, 每个特定的元素是升华对基板, 在那里他们相互反应, 形成良好的定义原子层。此外, 缺乏高能量的物种和更均匀的能量分布, 使得极尖锐的界面的制作成为8。然而, 在氧化物的生长过程中, 这一技术比 PLD 要复杂得多, 因为它必须在超高真空条件下执行 (这样, 长的平均自由路径就不会被破坏), 而且一般需要更大的投资、成本和时间。尽管在第一批老挝/其他出版物中使用的增长过程是 PLD, 但具有相似特性的样品却是由 "9" 的外延生长的。还值得注意的是, 老挝/异已经使用溅射10来增长。虽然在高温 (920 ° c) 和高氧压力 (0.8 毫巴) 上实现了原子性尖锐的界面, 但没有达到界面电导率。
对于金属盖层的生长, 我们使用磁控溅射, 因为它在质量和柔韧性之间提供了良好的平衡。然而, 其他化学气相沉积技术也可用于获得类似的结果。
最后, 运输和光谱学技术结合在这篇文章中展示了一个系统的方法来探测电子和化学的相互作用, 强调对照不同的方法的重要性, 以充分理解这些类型的系统的许多功能。

<table><tbody><tr><td>Pulsed Laser Deposition</td><td>SURFACE</td><td>PLD Workstation + UHV Cluster System</td><td></td></tr><tr><td>KrF Excimer Laser</td><td>Coherent</td><td>Compex Pro 201F</td><td></td></tr><tr><td>Reflection High-Energy Electron Diffraction (electron gun)</td><td>R-Dec Co., Ltd.</td><td>RDA-003G</td><td>Distributed in Europe by SURFACE.</td></tr><tr><td>Reflection High-Energy Electron Diffraction (CCD camera)</td><td>k-Space Associates, Inc.</td><td>kSA 400</td><td></td></tr><tr><td>Variable Laser Beam Attenuator</td><td>Metrolux</td><td>ML 2100</td><td></td></tr><tr><td>Excimer Laser Sensor</td><td>Coherent</td><td>J-50MUV-248</td><td></td></tr><tr><td>LaAlO&lt;sub&gt;3&lt;/sub&gt; target</td><td>CrysTec</td><td></td><td>Single-crystal target</td></tr><tr><td>SrTiO&lt;sub&gt;3&lt;/sub&gt; subtrates</td><td>CrysTec</td><td></td><td>Several different sizes. Possibility to order TiO&lt;sub&gt;2&lt;/sub&gt; terminated.</td></tr><tr><td>Buffered HF Acid</td><td>Technic</td><td>BOE 7:1</td><td>buffered hydrofluoric acid = BOE 7:1 (HF : NH4F = 12.5 : 87.5%) in&amp;nbsp;VLSI-quality.</td></tr><tr><td>Silver Paste</td><td>DuPont</td><td>4929N</td><td>Conductive Silver Composite.</td></tr><tr><td>Ultrasonic Cleaner</td><td>Bransonic</td><td>12</td><td>Ultrasonic Cleaning Bath</td></tr><tr><td>Tube Furnace</td><td>AET Technologies</td><td>Heat Treatment Furnace</td><td></td></tr><tr><td>Borosilicate Glass Beaker</td><td>VWR</td><td>213-1128</td><td>Iow form</td></tr><tr><td>PTFE Beaker</td><td>Dynalon</td><td>PTFE Beaker</td><td></td></tr><tr><td>Substrate holder &quot;dipper&quot;</td><td>Eberl&amp;eacute;</td><td></td><td>Custom made dipper</td></tr><tr><td>Magnetron Sputtering</td><td>PLASSYS</td><td>Sputtering system</td><td>5 chambers for targets.</td></tr><tr><td>Metal targets</td><td>Neyco S.A.</td><td></td><td>Purity &gt; 99.9%</td></tr><tr><td>X-Ray Photoelectron Spectroscopy System</td><td>Omicron</td><td>Custom XPS System</td><td></td></tr><tr><td>X-Ray Source</td><td>Omicron</td><td>DAR 400</td><td>Twin Anode X-Ray Source.</td></tr><tr><td>Energy Analyser</td><td>Omicron</td><td>EA 125</td><td></td></tr><tr><td>Atomic Force Microscopy</td><td>Bruker</td><td>Innova AFM</td><td></td></tr><tr><td>Atomic Force Microscopy Probes</td><td>Olympus</td><td>OMCL-AC160TS-R3</td><td>Micro Cantilevers</td></tr><tr><td>Wire bonding</td><td>Kulicke &amp;amp; Soffa</td><td>4523AD</td><td></td></tr><tr><td>PPMS</td><td>Quantum Design</td><td>PPMS Dynacool</td><td>9T magnet.</td></tr></tbody></table>

growth and electrostatic/chemical properties of metal/laalo3/srtio3 heterostructures

在 LaAlO3 (老挝) 和 SrTiO3 (q2DES) 之间的接口上形成的准2D 电子系统引起了氧化物电子学界的广泛关注。其特征之一是存在一个关键的老挝厚度4单元细胞 (uc) 的界面电导率出现。虽然过去已经提出了静电机制来描述这种临界厚度的存在, 但化学缺陷的重要性最近得到了加强。在这里, 我们描述了金属/老挝/异的增长, 在一个超高真空 (特高压) 集群系统结合脉冲激光沉积 (增长老挝), 磁控溅射 (增长金属) 和 X 射线光电子能谱 (XPS)。我们逐步研究了金属和 q2DES 之间的化学相互作用的形成和演化。此外, 磁实验阐明了 q2DES 的传输和电子性质。这一系统的工作不仅证明了一种研究 q2DES 及其环境之间的静电和化学相互作用的方法, 而且也解开了在二维电子系统, 允许制造新类型的设备。

用于增长和特性描述的完整实验系统显示在图 2中。强烈建议通过配电室在特高压中连接不同的设置, 以确保每个生长过程后样品的表面保持原始状态。还详细描述了 PLD 室 (图 3)、磁控溅射 (图 7) 和 XPS 室 (图 8)。有关 PLD 设置中的光学路径的其他信息, 将显示在图 4</st...

Watch this Scientific Journal Video about Growth and Electrostatic/chemical Properties of Metal/LaAlO3/SrTiO3 Heterostructures at JoVE.com

Growth and Electrostatic/chemical Properties of Metal/LaAlO3/SrTiO3 Heterostructures

我们制造金属/LaAlO3/SrTiO3异使用脉冲激光沉积和原位磁控溅射组合。通过磁和原位X 射线光电子能谱实验, 研究了该系统中所形成的准二维电子气体的静电与化学现象之间的相互作用。

金属/LaAlO 的生长和静电/化学性质3/SrTiO3异

The quasi 2D electron system (q2DES) that forms at the interface between LaAlO3 (LAO) and SrTiO3 (STO) has attracted much attention from the oxide ...

growth-electrostaticchemical-properties-metallaalo3srtio3

Research

JoVE Journal

Engineering

Growth and Electrostatic/chemical Properties of Metal/LaAlO3/SrTiO3 Heterostructures

10.2K 次观看.  Université Paris-Saclay. 我们制造金属/LaAlO3/SrTiO3异使用脉冲激光沉积和原位磁控溅射组合。通过磁和原位X 射线光电子能谱实验, 研究了该系统中所形成的准二维电子气体的静电与化学现象之间的相互作用。

视频: Growth and Electrostatic/chemical Properties of Metal/LaAlO3/SrTiO3 Heterostructures

Atomically Defined Templates for Epitaxial Growth of Complex Oxide Thin Films

Atomically defined substrate surfaces are prerequisite for the epitaxial growth of complex oxide thin films. In this protocol, two approaches to obtain such surfaces are described. The first approach is the preparation of single terminated perovskite SrTiO3 (001) and DyScO3 (110) substrates. Wet etching was used to selectively remove one of the two possible surface terminations, while an annealing step was used to increase the smoothness of the surface. The resulting single terminated surfaces allow for the heteroepitaxial growth of perovskite oxide thin films with high crystalline quality and well-defined interfaces between substrate and film. In the second approach, seed layers for epitaxial film growth on arbitrary substrates were created by Langmuir-Blodgett (LB) deposition of nanosheets. As model system Ca2Nb3O10- nanosheets were used, prepared by delamination of their layered parent compound HCa2Nb3O10. A key advantage of creating seed layers with nanosheets is that relatively expensive and size-limited single crystalline substrates can be replaced by virtually any substrate material.

Various procedures are outlined to prepare atomically defined templates for epitaxial growth of complex oxide thin films. Chemical treatments of single crystalline SrTiO3 (001) and DyScO3 (110) substrates were performed to obtain atomically smooth, single terminated surfaces. Ca2 Nb3 O10- nanosheets were used to create atomically defined templates on arbitrary substrates.

原子定义模板复合氧化物薄膜的外延生长

Atomically defined substrate surfaces are prerequisite for the epitaxial growth of complex oxide thin films. In this protocol, two approaches to obtain ...

科研

化学

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 ...

工程学

Synthesis of Non-uniformly Pr-doped SrTiO3 Ceramics and Their Thermoelectric Properties

We demonstrate a novel synthesis strategy for the preparation of Pr-doped SrTiO3 ceramics via a combination of solid state reaction and spark plasma sintering techniques. Polycrystalline ceramics possessing a unique morphology can be achieved by optimizing the process parameters, particularly spark plasma sintering heating rate. The phase and morphology of the synthesized ceramics were investigated in detail using X-ray diffraction, scanning electron microcopy and energy-dispersive X-ray spectroscopy. It was observed that the grains of these bulk Pr-doped SrTiO3 ceramics were enhanced with Pr-rich grain boundaries. Electronic and thermal transport properties were also investigated as a function of temperature and doping concentration. Such a microstructure was found to give rise to improved thermoelectric properties. Specifically, it resulted in a significant improvement in carrier mobility and the thermoelectric power factor. Simultaneously, it also led to a marked reduction in the thermal conductivity. As a result, a significant improvement (> 30%) in the thermoelectric figure of merit was achieved for the whole temperature range over all previously reported maximum values for SrTiO3-based ceramics. This synthesis demonstrates the steps for the preparation of bulk polycrystalline ceramics of non-uniformly Pr-doped SrTiO3.

Synthesis of Non-uniformly Pr-doped SrTiO3 Ceramics and Their Thermoelectric Properties

A protocol for the synthesis and processing of polycrystalline SrTiO3 ceramics doped non-uniformly with Pr is presented along with the investigation of their thermoelectric properties.

非均匀掺Pr的SrTiO的合成<sub&gt; 3</sub&gt;陶瓷及其热电性能

We demonstrate a novel synthesis strategy for the preparation of Pr-doped SrTiO3 ceramics via a combination of solid state reaction and spark plasma ...

Epitaxial Growth of Perovskite Strontium Titanate on Germanium via Atomic Layer Deposition

Atomic layer deposition (ALD) is a commercially utilized deposition method for electronic materials. ALD growth of thin films offers thickness control and conformality by taking advantage of self-limiting reactions between vapor-phase precursors and the growing film. Perovskite oxides present potential for next-generation electronic materials, but to-date have mostly been deposited by physical methods. This work outlines a method for depositing SrTiO3 (STO) on germanium using ALD. Germanium has higher carrier mobilities than silicon and therefore offers an alternative semiconductor material with faster device operation. This method takes advantage of the instability of germanium's native oxide by using thermal deoxidation to clean and reconstruct the Ge (001) surface to the 2&#215;1 structure. 2-nm thick, amorphous STO is then deposited by ALD. The STO film is annealed under ultra-high vacuum and crystallizes on the reconstructed Ge surface. Reflection high-energy electron diffraction (RHEED) is used during this annealing step to monitor the STO crystallization. The thin, crystalline layer of STO acts as a template for subsequent growth of STO that is crystalline as-grown, as confirmed by RHEED. In situ X-ray photoelectron spectroscopy is used to verify film stoichiometry before and after the annealing step, as well as after subsequent STO growth. This procedure provides framework for additional perovskite oxides to be deposited on semiconductors via chemical methods in addition to the integration of more sophisticated heterostructures already achievable by physical methods.

This work details the procedures for the growth and characterization of crystalline SrTiO3 directly on germanium substrates by atomic layer deposition. The procedure illustrates the ability of an all-chemical growth method to integrate oxides monolithically onto semiconductors for metal-oxide semiconductor devices.

锗通过原子层沉积钙钛矿型钛酸锶的外延生长

Atomic layer deposition (ALD) is a commercially utilized deposition method for electronic materials. ALD growth of thin films offers thickness control and ...

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 ...

Chemical Synthesis of Porous Barium Titanate Thin Film and Thermal Stabilization of Ferroelectric Phase by Porosity-Induced Strain

Barium titanate (BaTiO3, hereafter BT) is an established ferroelectric material first discovered in the 1940s and still widely used because of its well-balanced ferroelectricity, piezoelectricity, and dielectric constant. In addition, BT does not contain any toxic elements. Therefore, it is considered to be an eco-friendly material, which has attracted considerable interest as a replacement for lead zirconate titanate (PZT). However, bulk BT loses its ferroelectricity at approximately 130 &#176;C, thus, it cannot be used at high temperatures. Because of the growing demand for high-temperature ferroelectric materials, it is important to enhance the thermal stability of ferroelectricity in BT. In previous studies, strain originating from the lattice mismatch at hetero-interfaces has been used. However, the sample preparation in this approach requires complicated and expensive physical processes, which are undesirable for practical applications.
In this study, we propose a chemical synthesis of a porous material as an alternative means of introducing strain. We synthesized a porous BT thin film using a surfactant-assisted sol-gel method, in which self-assembled amphipathic surfactant micelles were used as an organic template. Through a series of studies, we clarified that the introduction of pores had a similar effect on distorting the BT crystal lattice, to that of a hetero-interface, leading to the enhancement and stabilization of ferroelectricity. Owing to its simplicity and cost effectiveness, this fabrication process has considerable advantages over conventional methods.

Here, we present a protocol for the synthesis of porous barium titanate (BaTiO3) thin film by a surfactant-assisted sol-gel method, in which self-assembled amphipathic surfactant micelles are used as an organic template.

孔隙诱导应变法合成多孔钛酸钡薄膜及铁电相热稳定性

Barium titanate (BaTiO3, hereafter BT) is an established ferroelectric material first discovered in the 1940s and still widely used because of its ...

Bulk and Thin Film Synthesis of Compositionally Variant Entropy-stabilized Oxides

Here, we present a procedure for the synthesis of bulk and thin film multicomponent (Mg0.25(1-x)CoxNi0.25(1-x)Cu0.25(1-x)Zn0.25(1-x))O (Co variant) and (Mg0.25(1-x)Co0.25(1-x)Ni0.25(1-x)CuxZn0.25(1-x))O (Cu variant) entropy-stabilized oxides. Phase pure and chemically homogeneous (Mg0.25(1-x)CoxNi0.25(1-x)Cu0.25(1-x)Zn0.25(1-x))O (x = 0.20, 0.27, 0.33) and (Mg0.25(1-x)Co0.25(1-x)Ni0.25(1-x)CuxZn0.25(1-x))O (x = 0.11, 0.27) ceramic pellets are synthesized and used in the deposition of ultra-high quality, phase pure, single crystalline thin films of the target stoichiometry. A detailed methodology for the deposition of smooth, chemically homogeneous, entropy-stabilized oxide thin films by pulsed laser deposition on (001)-oriented MgO substrates is described. The phase and crystallinity of bulk and thin film materials are confirmed using X-ray diffraction. Composition and chemical homogeneity are confirmed by X-ray photoelectron spectroscopy and energy dispersive X-ray spectroscopy. The surface topography of thin films is measured with scanning probe microscopy. The synthesis of high quality, single crystalline, entropy-stabilized oxide thin films enables the study of interface, size, strain, and disorder effects on the properties in this new class of highly disordered oxide materials.

The synthesis of high quality bulk and thin film (Mg0.25(1-x)CoxNi0.25(1-x)Cu0.25(1-x)Zn0.25(1-x))O and (Mg0.25(1-x)Co0.25(1-x)Ni0.25(1-x)CuxZn0.25(1-x))O entropy-stabilized oxides is presented.

组分变熵稳定氧化物的体积和薄膜合成

Here, we present a procedure for the synthesis of bulk and thin film multicomponent (Mg0.25(1-x)CoxNi0.25(1-x)Cu0.25(1-x)Zn0.25(1-x))O (Co variant) and ...

Radio Frequency Magnetron Sputtering of GdBa2Cu3O7&#8722;&#948;/ La0.67Sr0.33MnO3 Quasi-bilayer Films on SrTiO3 (STO) Single-crystal Substrates

Here, we demonstrate a method of coating ferromagnetic La0.67Sr0.33MnO3 (LSMO) nanoparticles on (001) SrTiO3 (STO) single-crystal substrates by radio frequency (RF) magnetron sputtering. LSMO nanoparticles were deposited with diameters from 10 to 20 nm and heights between 20 and 50 nm. At the same time, (Gd) Ba2Cu3O7&#8722;&#948; ((Gd) BCO) films were fabricated on both undecorated and LSMO nanoparticle decorated STO substrates using RF magnetron sputtering. This report also describes the properties of GdBa2Cu3O7&#8722;&#948;/ La0.67Sr0.33MnO3 quasi-bilayer films structures (e.g., crystalline phase, morphology, chemical composition); magnetization, magneto-transport, and superconducting transport properties were also evaluated.

Radio Frequency Magnetron Sputtering of GdBa2Cu3O7ÃƒÆ’Ã‚Â¢Ãƒâ€¹Ã¢â‚¬Â 'ÃƒÆ’Ã…Â½ Â´/ La0.67Sr0.33MnO3 Quasi-bilayer Films on SrTiO3 STO Single-crystal Substrates

Here, we present a protocol to grow LSMO nanoparticles and (Gd) BCO films on (001) SrTiO3 (STO) single-crystal substrates by radio frequency (RF)-sputtering.

Gdba2cu 3 o7 的射频磁控管散射-/la0.67sr 0.67 mno 3 准双层薄膜上的 srtio 3 (sto) 单晶基板上

Here, we demonstrate a method of coating ferromagnetic La0.67Sr0.33MnO3 (LSMO) nanoparticles on (001) SrTiO3 (STO) single-crystal substrates by radio ...

Metal Oxide Heterojunction for Photocatalytic Activities

There is a significant global demand for improvements in synthesis techniques and their optimal characteristics, especially for industrial-scale applications. Sol-gel-based solution combustion synthesis (SG-SCS) is a simple method to produce ordered porous materials. In this regard, Pearson&#39;s hard and soft acids and bases theory assists in selecting host-dopant reactivity to form a proper heterojunction.
The formation of a heterojunction also changes the essential properties of the materials, improving photocatalysis via charge transfer or synergistic activities. A calcination temperature of 500 &#176;C is ideal for this process based on the results of the stability assessment via a differential thermogravimetry ratio analysis (DTG).
The nanoscale dimensions of the nanoparticles (NPs) and nanocomposites (NCs) generated were validated using X-ray diffraction and high-resolution transmission electron microscopy (HRTEM). Furthermore, the scanning electron microscopy micrographs and BET analyses confirmed the porosity nature of the materials. HRTEM, X-ray photoelectron spectroscopy, and energy-dispersive X-ray investigations established the materials composition. The study found that NCs degraded the acid orange 8 (AO8) color more efficiently than bare ZnO.

The development of a heterojunction boosts the photocatalytic activities of solution combustion synthesis, which is a time-/energy-efficient process. Advanced analytical characterization techniques were used in this protocol to evaluate the materials&#39; characteristics, and nanocomposites demonstrated improved acid orange-8 dye degradation.

There is a significant global demand for improvements in synthesis techniques and their optimal characteristics, especially for industrial-scale ...

Tuning Oxide Properties by Oxygen Vacancy Control During Growth and Annealing

Electrical, optical, and magnetic properties of oxide materials can often be controlled by varying the oxygen content. Here we outline two approaches for varying the oxygen content and provide concrete examples for tuning the electrical properties of SrTiO3-based heterostructures. In the first approach, the oxygen content is controlled by varying the deposition parameters during a pulsed laser deposition. In the second approach, the oxygen content is tuned by subjecting the samples to annealing in oxygen at elevated temperatures after the film growth. The approaches can be used for a wide range of oxides and nonoxide materials where the properties are sensitive to a change in the oxidation state.
The approaches differ significantly from electrostatic gating, which is often used to change the electronic properties of confined electronic systems such as those observed in SrTiO3-based heterostructures. By controlling the oxygen vacancy concentration, we are able to control the carrier density over many orders of magnitude, even in nonconfined electronic systems. Moreover, properties can be controlled, which are not sensitive to the density of itinerant electrons.

Oxide materials show many exotic properties that can be controlled by tuning the oxygen content. Here, we demonstrate the tuning of oxygen content in oxides by varying the pulsed laser deposition parameters and by performing postannealing. As an example, electronic properties of SrTiO3-based heterostructures are tuned by growth modifications and annealing.

通过生长和退火过程中的氧空位控制来调整氧化物性能

Electrical, optical, and magnetic properties of oxide materials can often be controlled by varying the oxygen content. Here we outline two approaches for ...

金属/LaAlO 的生长和静电/化学性质₃/SrTiO₃异

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