这项工作是由英国工程和物理科学研究理事会下的授权号EP/G065640/1和由美国国家科学基金会的支持下，授权号DMR-0908767 [ML和LHL]和授权号DMR-0907007 [DH]。

在这个协议中，薄膜的有序化的FeRh合金都是用在MgO（001）基片直流磁控溅射。样品都生长在约200奥斯特的磁场由永磁体阵列，它是用来设置在面内磁各向异性的。的目标直径为50毫米，而目标和衬底之间的距离大约为10厘米。成长的FeRh，适用于磁性材料直流磁性圆环磁控枪使用。该加热器是电灯泡位于上方2厘米的基板和由一个金属圆柱体所包围，以保持加热的体积小。最高温度可能在这个系统〜1,050 K。该系统能容纳24个不同的底物，但是，我们通常制作，由于时间限制外延样品时长少于10个。这里介绍的这种样品制备方案的细节是已知的在我们的真空系统工作良好。由于是在不同的许多细节相当于真空系统秒，为定量参数，如温度，时间等的要求。在其它系统可能采取不同的最佳值。然而，下面的描述将被证明是有用的指南给读者。 在下面的详细协议，它假定读者熟悉良好的真空实践的基础，例如使用手套的处理，将进入真空室[参见，例如，参考文献26]的所有组件。 1。基板和目标准备本节描述了制备该溅射沉积室中的和单晶的MgO衬底。 <ol><li>冲洗（001）的MgO基片在异丙醇和它们安装在基片支架。载入这些进入真空室。 </li><li>安装目标的FeRh在磁控管枪和重新组装枪。对于具有等原子组成的样品，我们已经发现，与铁47的目标相对湿度53是最合适的，产生最清晰的magnetostructural相变。测试，有磁控管和周围屏蔽之间没有短路。同样，准备以用于覆盖层的任何目标（s）。 </li><li>关闭真空室和泵下来。 </li><li>一旦真空度比1×10 -6乇更好，加热衬底至870 K。显示器的真空度和升温速度，以确保该压力不上升高于这个水平。保持在该温度下过夜。 </li><li>增长开始前一小时，开始通过迈斯纳陷阱流液氮。真空应提高到优于4×10-7乇。 </li><li>质量流量控制器设定为65sccm的工作气流。溅射气体为Ar，用4％的氢，以避免在生长过程中样品氧化。打开燃气流量阀。在腔室中的压力应该上升到低毫乇范围内。 </li><li>生长之前，预溅射靶的FeRh为1,200秒，30 W。 </li></ol> 2。外延沉积本节描述了层的FeRh通过直流磁控溅射沉积。 <ol><li>调节质量流量控制器的设定点，得到4×10 -3托的室压。允许定居到一个稳定值的压力。 </li><li>检查该衬底温度保持在870 K和稳定。 </li><li>接通电源到磁控管产生的0.4埃/秒的总沉积速率。在装有石英晶体监控室中，这可以通过使用该显示器，如果适当地校准。如果该腔室不具有石英晶体监测，生长后的厚度测量可以是有益的，以及运行之间的再现性高的水平。 </li><li>打开快门和沉积的FeRh加热的衬底上的时间适当，得到所需厚度的长度。例如，一个500秒的沉积会产生一个样本20nm厚。&lt;/ LI&gt; <li>关闭快门。 </li><li>切断电源磁控管。 </li><li>关闭气体阀门。 </li><li>提高样品温度至970 K。拿住样品在该温度一小时。压力应在整个保持大于1×10 -6乇更好。改变这种退火温度的影响可以在德弗里斯等[20]发现</li><li>切断加热器电源和冷却样品至室温。在这个系统中，这至少需要三个小时。 </li><li>交押金，使用类似的步骤2.1-2.7步骤的任何覆盖层。在低于〜370 K A温度沉积盖层是必不可少的，以防止相互扩散入的FeRh层27。 </li><li>发泄室用干燥的氮气，打开它，并取出样本。他们应该显得明亮而有光泽。 </li></ol> 3。常规后成长表征本节提供了基本characterizati的概述关于开展对我国大多数样品的FeRh的步骤。因为有许多可能的等效方法来进行这些测量，这里的描述的性质不太详细，规定，和相当集中的任何这样的测量的基本特征。 <ol><li>进行低角度Χ射线反射扫描，以确定样品的厚度。装载样品中的衍射，并与检测器角2θ≈1°对齐在ω。如果有的话，χ还应对齐。运行一个标准的θ-2θ扫描，θ从0°运行，直到仪器的本底噪声达到，通常一旦θ≥11°为一个质量好的样品。明确Kiessig（薄膜干涉）条纹应该是可见的，从该外延层的厚度可以被确定。 </li><li>进行高角度Χ-射线衍射扫描，以确定的化学有序度。这可以是车里德用仍安装在从步骤3.1衍射仪的样品。在MgO衬底峰应该被发现（在2θ= 42.9°，如果铜的Kα辐射被使用）和样品中的ω再次对齐。再次，运行θ-2θ，至少覆盖范围12.5°&lt;θ&lt;62.5°（再次假设铜的Kα辐射），以使两者的FeRh（001）和（002）峰，以及在衬底的峰值，被捕获。 </li><li>进行的温度的样品的电阻率的依存性的测量来确定转变温度。使电接触件的样品，例如，一个标准的4点测量可制成以避免接触电阻的问题。如果正在使用一个直流方法，使测量正向和反向电流的方向和平均，以空关在高温下产生的任何热电动势的电阻。然后将样品在温度续轧热台（在该设置中的阶段是在一个小的涡轮泵的高真空腔室，以确保避免任何氧化的），并测量其电阻随着温度的两个加热的功能和冷却的扫描，以便在任何滞后第一阶magnetostructural相变可以被确定。 </li></ol>

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L. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Exchange+inversion+in+ternary+modifications+of+iron+rhodium.">Exchange inversion in ternary modifications of iron rhodium.</a> Journal of Applied Physics. 35 (3), 938 (1964).</li><li>Yuasa, 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=First-order+magnetic+phase+transition+in+bcc+FeRh-Ir+alloy+under+high+pressures+up+to+6.2+GPa.">First-order magnetic phase transition in bcc FeRh-Ir alloy under high pressures up to 6.2 GPa.</a> Journal of the Physical Society of Japan. 63 (3), 855 (1994).</li><li>Lu, W., Nam, N. T., Suzuki, T. <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+Pt+doping+on+the+structure,+magnetic,+and+magneto-optical+properties+of+ordered+FeRh-Pt+thin+films.">Effect of Pt doping on the structure, magnetic, and magneto-optical properties of ordered FeRh-Pt thin films.</a> IEEE Transactions on Magnetics. 45 (6), 2716 (2009).</li><li>Kushwaha, P., Lakhani, A., Rawat, R., Chaddah, P. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Low-temperature+study+of+field-induced+antiferromagnetic-ferromagnetic+transition+in+Pd-doped+FeRh.">Low-temperature study of field-induced antiferromagnetic-ferromagnetic transition in Pd-doped FeRh.</a> Phys Rev. 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作者宣称，他们有没有竞争的财务权益。

在这里，我们已经证明，该方法可以用来制备的FeRh的外延层样品的良好的晶体质量和B2的化学有序度很高。该方法适用于各种各样的外延金属层，包括有序合金的制备。虽然我们已经使用了B2有序化的FeRh的合金，例如，在这里，因为它显示了显着的相变时，该化学计量是正确的，化学订货存在，也可用于其它材料的这种方法。例如，既FePd和的FePt具有L1 0相，这导致了非常强单轴磁各向异性。我们已经成功地生长这种材料在过去，显示的FePt 8畴壁阻力，并在这两个FePd和铁铂10大反常霍尔效应。随着生长温度和速率，并适当选择基板的适当调整，这种方法应该是用于制备多种DIF有用ferent磁性和非磁性金属外延层显示化学顺序。 然而，这种方法的一个限制是需要的单晶衬底，实现外延。这意味着困难将进行实验，如平面图透射电子或X射线显微术或融合成建了衬底晶片等近无处不在硅上的技术会遇到。要解决这个问题的一个可能的方法是长出薄薄MgO层在其上的FeRh然后可以沉积。这可以产生出的平面纹理成核局部外延生长每个氧化镁颗粒37的上方。值得注意的是，有可能使用一种方法，用离子束以生长薄的MgO层，同时具有（001）织构和面内上形成非晶表面的晶体取向协助被定向在45°到衬底法线38枪。这可能会允许B2有序化的FeRh对如电子或X射线吨增长ransparent的Si 3 N 4膜，其能够存活在我们的协议所需的高生长温度下进行，或者在Si晶片的原生氧化层上。 该方法的进一步的改进包括采用B2有序的底层，如NiAl金属39，以促进B2排序中的FeRh外延层当它被极薄，或者其用途建立涉及多个化学有序层37的异质结构。由于可以的FeRh掺杂在Rh现场调整转变温度T T了（例如使用铱40，41或Pt 40，42）或向下（ 例如使用金40，27或Pd 40，43），创造中的FeRh层的掺杂分布可导致设计，在磁访问作为样品被加热和冷却。这开辟了在生成外延层的纯磁分层在一个可控的方式44的路由。

微电子工业的中心范式是平面加工的方法：在连续沉积和薄膜基片材料的晶片的表面上的图案形成。很多时候，衬底是单晶，并且膜需要是外延 ，即在晶体寄存器说与下层衬底。与半导体材料，这通常是实现无论是在实验室设置1或金属有机气相外延（MOVPE）在制造2使用分子束外延（MBE）。 而金属通过MBE外延生长是可能的，所以很容易通过溅射沉积，这是对在研究和工业设置薄磁膜的沉积的最常用方法。在某些条件下，而此方法通常用多晶膜，外延生长的单晶衬底上生长相关联是可能的<s了&gt; 3。这些通常包括一个凸起的基板温度（至少对于初始层），缓慢的沉积速率，以及低真空室基本压力。这种方法已被用于，制备巨磁阻多层材料4，5为实例。 在我们自己的实验室中，我们使用外延溅射制备的单晶衬底各种磁性材料。它一直未能生长由CoFe合金外延在GaAs（001），例如，通过选择晶格匹配的钴70铁30的组合物6。这种材料是一种固溶体，其中Co和Fe原子随机填充体心立方晶格位置。我们也增加了化学有序磁性合金，其中不同的原子种类需要占用特定的晶格位置。生长协议，我们将在这里描述最初是为L1 0有序FePd和铁铂合金，这是权益S的成长发展因斯它们具有非常高的磁晶各向异性7。我们已经研究了弹道导弹扩散和自旋极化输运8,9和反常霍尔效应10在这些材料，这是可比的质量由11 MBE生长层之间的关系。 在这里，我们将使用B2有序化的FeRh外延层的例子说明我们的外延生长方法。 Fe和铑会形成合金的任何组合物中，但是一个B2有序的化合物是在近等原子比范围49-53％原子的Fe 12为化学计量的平衡状态。这个所谓的α“ -相是反铁磁（AF），展品加热一阶相变，变成的α&#39;相铁磁（FM）周围T T = 350→400K 13，14，15。两种不同的，但两者完全有序的磁场状态（II型自动对焦16和FM）之间的这种变磁转变伴随各向同性1％的体积膨胀在B2格17，18，一个大的熵释放19时，大颗粒的电阻14，和一个大的增加，载流子浓度20。中子衍射21，16和最近XMCD测量22表示3.3μ 乙磁矩在AF相位中心的铁被转移到的Rh在FM相的那一部分，与μ 铁 〜2.2μB和μRH〜0.6μ乙 。居里温度为FMα&#39;相是〜670ķ14，比得上合金的居里温度，其中x&gt; 0.53 23。的磁转变温度T T是该组合物×高度敏感的铁铑×1 - ×23，24，并 ​​且通过施加磁网络连接的〜8 K / T抑制高龄25，15。这种丰富的物理行为阵列关键取决于实现适当B2有序结构，因此允许多种测量技术进行部署，以检测适当的化学有序的标本，使其成为一个方便的例子来说明越来越多的方法高质量有序合金外延层。

<table border="1">
	<tbody>
		<tr>
			<td>Name of Reagent/Material</td>
			<td>Company</td>
			<td>Catalog Number</td>
			<td>Comments</td>
		</tr>
		<tr>
			<td>Sputter Deposition System</td>
			<td>Kurt J. Lesker Company</td>
			<td>Bespoke</td>
			<td></td>
		</tr>
		<tr>
			<td>MgO Single Crystal Substrate</td>
			<td>Pi-Kem</td>
			<td>Single-sided epi-polished</td>
			<td>(001) orientation</td>
		</tr>
		<tr>
			<td>FeRh sputtering target</td>
			<td>Pi-Kem</td>
			<td>Bespoke</td>
			<td>50 mm diameter</td>
		</tr>
		<tr>
			<td>Transmission Electron Microscope</td>
			<td>FEI</td>
			<td>Tecnai TF20</td>
			<td></td>
		</tr>
		<tr>
			<td>X-ray Diffractometer</td>
			<td>Br&#252;ker</td>
			<td>D8 Discover</td>
			<td></td>
		</tr>
		<tr>
			<td>SQUID Magnetometer</td>
			<td>Quantum Design</td>
			<td>MPMS-XL 5</td>
			<td></td>
		</tr>
	</tbody>
</table>

sputter growth and characterization of metamagnetic b2-ordered ferh epilayers

化学有序合金是在各种磁性纳米技术是有用的。他们正在使用溅射技术，最方便地制备以工业规模。在这里，我们描述了通过溅射沉积制备外延薄膜B2有序化的FeRh的到单晶氧化镁基片的方法。沉积速率较慢到加热的衬底使得时间的吸附原子既解决成晶格与衬底良好定义的外延关系，同时也发现其位在B2结构的铁和Rh亚晶格。该结构被方便地采用X射线反射和衍射，并直接使用透射电子显微照片的横截面可以被可视化。 B2有序化的FeRh表现出不同寻常的变磁相变：基态是反铁磁但合金转变成一个铁磁体加热约380 K的典型转变温度这是伴随着1％体积膨胀的单元电池：各向同性的散装的，但横向夹紧在一个外延层。反铁磁性基态和相应的第一阶相变的存在，是正确的等原子的化学计量和正确B2订货非常敏感，并因此是一种方便的手段，以证明可被沉积，这种方法的层的质量。我们还给出了它的相位变化可以被检测的各种技术的一些例子。

我们根据这个协议准备了很多样品的FeRh。在本节中，我们显示了使用中最常见的表征程序部分有代表性的样本获得的典型结果。结果如这些预期为在厚度范围20-50 nm的样品。我们已经习惯了我们的材料表征更深入其他方法包括X射线磁性圆二色28，掠入射X射线散射29，和极化中子反射30。我们还研究了用Au 27掺杂的合金的效果。对可以由这种材料可望性能进一步的数据可以在这些报告中可以发现，和其中包含的参考。 我们的外延层1的结构被详细地示于图1所示的透射型电子显微镜照片。该样品横截面的制备是常规的造凹坑和离子研磨技术NIQUE-标准样品制备方法（参见，例如Williams和卡特31） -和使用200千伏的电子束观察。整体层结构在图1中可以看出（a）所示 。在这种情况下，30纳米的FeRh薄膜上外延生长在MgO衬底，随后〜4 nm的Cr层和一个〜1nm厚的Al层。 （已列入该Cr层此处为一个特定的实验，并不需要在普通）。本化的FeRh / MgO和的FeRh /铬界面的粗糙度是0.6纳米和2.8纳米，分别作为从图像中测定。在图1（b）所示的氧化镁/接口的FeRh的高分辨率显微照片。从选区电子衍射证实了外延关系是化的FeRh [100]（001）| |氧化镁[110]（001）。穿过界面的晶格匹配示范外延生长的高品质。我们不显示此数据，但是已经用能量色散X射线光谱中的透射电子显微镜检查在选择样品的组成：它一直等原子比的测量不确定度范围内。 Χ射线反射数据示于图2为一个标称25nm厚的FeRh外延层上铺铝薄，多晶层。在一个标准的两圆衍射仪进行测量中的布拉格-Brentano几何，用铜的Kα射线（λ= 0.1541 nm）的，与Ni滤波器来衰减对Kα辐射。的发音Kiessig条纹，从X射线束从在层堆叠的各种接口，反映的干涉而产生，表明这些接口是光滑和良好的相关性。红色实线显示了一个适合已使用的GEnx发动机软件32执行的数据。最佳拟合参数为多层结构示于表1中 。该铝层的一部分，将已被氧化和自钝化一旦样品暴露吨的事实Ø空气在模型中考虑。 Χ-射线衍射数据为同一样品都显示在图3中 ，收集在相同的仪器。在MgO衬底的（002）反光性强和足够的锐利，只是解决了铜的Kα1和Kα则2线。该层的FeRh同时显示（001）和（002）衍射。还有，由于外延层和应变梯度的有限厚度有些展宽。 （002）的FeRh B2峰的中心在2θ= 61.3°±0.02，得到的平均外的平面的3.02±0.05埃的晶格常数。这是可能的，以确定由这两个峰的相对积分强度的的FeRh B2结构的化学顺序参数S。这个量被定义为S = R 的Fe + R 铑 -1，其中是由铁（RH）占用铁（RH）网站的部分原子33。该公式的简单检查显示吨帽子当 r 铁 = R RH = 1 和结构是完美的，S = 1，而当 r 的Fe = R 的Rh = 0.5，以使所有晶格点是随机占用，S = 0。其原因是，当S = 0的位点平均结构是体心立方，对于其结构因素不允许的（001）反射，而当S = 1的结构是简单立方的，对于其中（001）反射是允许的。这意味着在实践中， <img alt="式（1）" fo:content-width="2.5in" src="/files/ftp_upload/50603/50603eq1.jpg" width="230px" /> ，其中<img alt="公式2" fo:content-width=".2in" src="/files/ftp_upload/50603/50603eq2.jpg" width="20px" />和<img alt="式（3）" fo:content-width=".2in" src="/files/ftp_upload/50603/50603eq3.jpg" width="20px" />是（00Ⅰ）Bragg反射，分别为33的试验和理论强度。对于calcu理论强度的德拜-沃勒因素，从化的FeRh EXAFS测量的相关特征研中使用34。在这种情况下，S = 0.855±0.001，典型的这种材料的溅射薄膜。 该变磁相变可以通过多种方式来检测。它的存在表示了正确等原子的化学计量和晶格B2排序。的晶格膨胀，伴随着磁转变可能由移在布喇格的位置来检测的峰值27，但是，这需要用加热器阶段的衍射仪。 或许最明显的方法是检测的铁磁时刻的外观，因为样品是通过T T进行加热。这可以通过使用任何温度依赖性磁力仪具有足够的灵敏度，例如使用磁光克尔效应或振动样品磁强计。在图4中，我们显示了温度的磁化强度M的依赖，使用超导量子干涉仪（SQUID）磁力计测得。测量是在275-400 K范围内作出为2 K / min的温度扫描速率。所示的曲线显示了预期的自动对焦→FM相变（加热）和FM→自动对焦转换（冷却）与15 K热滞后。此测量是在高电场（50千奥斯特），并且得到的转变温度T T≈365 K的转变温度是字段依赖性，因为更高的磁场降低了调频相的自由能相对于该AF相位。通常情况下DT T / DH≈0.8 mK的/大江14,15，27。注意，磁矩在AF阶段是不太为零，但是几十鸸/厘米3时，平均在整个样品的体积。这个时刻驻留在外延层的FeRh的近界面区域，其中保持ferromagnetic（尽管以降低的磁化）时，大量的样品转变成AF相28，30。 一种方法来检测，使用简单的设备，并经常在我们的实验室中使用的过渡是使电子传输测量。最简单的测量膜的电阻率ρ的，因为ρ在FM相位比在AF阶段35，36，20少得多。 ρ为同一25nm的外延层的FeRh为其中X-射线数据示出的温度依赖关系绘于图5中 ，使用一个标准的四点探针法测定的：弹簧加载，镀金引脚被上到样品压面进行接触的样品，将其安装在加热器阶段在一个小的自定义的真空室，以防止任何样品的氧化热的时候。线性，金属ρ（T）的依赖性被认为是在这两个AF和调频阶段，但在resistivi显着下降两者之间的TY。 如图5中所示的滞后是magnetostructural相变发生的一个清晰的指纹，是一种方便的方法来测量的转变温度，这是由在Dρ/ dt的最低点给出（在图5中的插图示出）。另一个容易地测量传输特性，霍尔效应，还可以用来确认过渡的存在，因为有两相20之间的霍尔系数有很大差异。 <img alt="图1" fo:content-width="5in" src="/files/ftp_upload/50603/50603fig1highres.jpg" width="600" /> 图1。在MgO衬底上的外延层的FeRh的透射电子显微镜照片。 （a）图像表明该层的结构。该是的FeRh 30nm厚了进一步〜4 nm的Cr层和〜1 nm的铝盖沉积在上面。在第i顶端的无定形区<html>法师是在横截面样品制备中使用的环氧树脂（b）一个高分辨率的氧化镁界面的FeRh的形象。通过该接口的外延匹配是在这里看到，相关的关系，从选区电子衍射证实，是的FeRh [100]（001）| |。氧化镁[110]（001） <a href="https://www.jove.com/files/ftp_upload/50603/50603fig1highres.jpg" target="_blank">点击这里查看大图</a> <img alt="图2" fo:content-width="5in" src="/files/ftp_upload/50603/50603fig2.jpg" width="600" /> 图2。从一个25纳米厚的FeRh透视反射光谱外延层上铺多晶铝，实线是如文中所述，使用在表1中给出的参数拟合。插图显示了该组的拟合参数相关联的散射长度密度分布。g2highres.jpg“目标=”_blank“&gt;点击这里查看大图<img alt="图3" fo:content-width="5in" src="/files/ftp_upload/50603/50603fig3.jpg" width="500" /> 图3。从一个25纳米厚的FeRh的X射线衍射光谱外延层上铺多晶铝。的（001）峰的FeRh的存在表明B2顺序已经发生。化学序参量为S = 0.855±0.001，如使用在文本中描述的方法测定。 <a href="https://www.jove.com/files/ftp_upload/50603/50603fig3highres.jpg" target="_blank">点击这里查看大图</a> <img alt="图4" fo:content-width="5in" src="/files/ftp_upload/50603/50603fig4.jpg" width="500" /> 图4。一个50纳米厚的外延层的FeRh上铺多晶体的磁化强度M与温度的关系线的Al，这些数据均用在胶片平面施加一个50千奥斯特场。转变温度T T被认为是〜365 K的大约15 K的滞后宽度<a href="https://www.jove.com/files/ftp_upload/50603/50603fig4highres.jpg" target="_blank">点此查看大图</a> <img alt="图5" fo:content-width="5in" src="/files/ftp_upload/50603/50603fig5.jpg" width="500" /> 图5。上铺铝25 nm厚的一层的FeRh的电阻率ρ的温度依赖性 。插图是ρ相对于温度 T的导数。转变温度T T都被看作是447 K于冷却到自动对焦阶段升温到FM相和375 K表。 <a href="https://www.jove.com/files/ftp_upload/50603/50603fig5highres.jpg" target="_blank">点击这里查看大图</a> <table border="1"><tbody><tr><td> 层 </td><td> 密度（个/ nm 3） </td><td> 厚度（纳米） </td><td> 粗糙度（nm）的 </td></tr><tr><td>的Al 2 O 3钝化层</td><td> 25.5±0.9 </td><td> 2.18±0.08 </td><td> 1.0±0.1 </td></tr><tr><td>铝盖</td><td> 60.6±0.6 </td><td> 0.91±0.02 </td><td> 0.6±0.2 </td></tr><tr><td>外延层的FeRh </td><td> 38.7±0.3 </td><td> 25.09±0.06 </td><td> 0.400±0.002 </td></tr><tr><td>氧化镁基板</td><td> 53.4±1.3 </td><td> ∞ </td><td> 0.1761±0.0003 </td></tr></tbody></table> 表1。拟合参数为图2中所示，从而导致在该图的插图中所示的散射长度密度分布的X射线反射率光谱。

Watch this Scientific Journal Video about Sputter Growth and Characterization of Metamagnetic B2-ordered FeRh Epilayers at JoVE.com

Sputter Growth and Characterization of Metamagnetic B2-ordered FeRh Epilayers

一个用溅射制备有序合金的外延层方法。在B2有序化的FeRh的化合物用作一个例子，因为它显示一个磁转变是敏感地依赖于化学顺序和合金的确切组成的程度。

变磁B2有序化的FeRh外延层溅射生​​长和表征

Chemically ordered alloys are useful in a variety of magnetic nanotechnologies. They are most conveniently prepared at an industrial scale using ...

sputter-growth-characterization-metamagnetic-b2-ordered-ferh

Research

JoVE Journal

Engineering

14.5K 次观看.  University of Leeds. 一个用溅射制备有序合金的外延层方法。在B2有序化的FeRh的化合物用作一个例子，因为它显示一个磁转变是敏感地依赖于化学顺序和合金的确切组成的程度。 

视频: Sputter Growth and Characterization of Metamagnetic B2-ordered FeRh Epilayers

Simulation, Fabrication and Characterization of THz Metamaterial Absorbers

Metamaterials (MM), artificial materials engineered to have properties that may not be found in nature, have been widely explored since the first theoretical1 and experimental demonstration2 of their unique properties. MMs can provide a highly controllable electromagnetic response, and to date have been demonstrated in every technologically relevant spectral range including the optical3, near IR4, mid IR5 , THz6 , mm-wave7 , microwave8 and radio9 bands. Applications include perfect lenses10, sensors11, telecommunications12, invisibility cloaks13 and filters14,15. We have recently developed single band16, dual band17 and broadband18 THz metamaterial absorber devices capable of greater than 80% absorption at the resonance peak. The concept of a MM absorber is especially important at THz frequencies where it is difficult to find strong frequency selective THz absorbers19. In our MM absorber the THz radiation is absorbed in a thickness of ~ &lambda;/20, overcoming the thickness limitation of traditional quarter wavelength absorbers. MM absorbers naturally lend themselves to THz detection applications, such as thermal sensors, and if integrated with suitable THz sources (e.g. QCLs), could lead to compact, highly sensitive, low cost, real time THz imaging systems.

This protocol outlines the simulation, fabrication and characterization of THz metamaterial absorbers. Such absorbers, when coupled with an appropriate sensor, have applications in THz imaging and spectroscopy.

模拟，太赫兹超材料吸收器的制备与表征

Metamaterials (MM),  artificial materials engineered to have properties that may not be found in  nature, have been widely explored since the first ...

科研

工程学

Fabrication And Characterization Of Photonic Crystal Slow Light Waveguides And Cavities

Slow light has been one of the hot topics in the photonics community in the past decade, generating great interest both from a fundamental point of view and for its considerable potential for practical applications. Slow light photonic crystal waveguides, in particular, have played a major part and have been successfully employed for delaying optical signals1-4 and the enhancement of both linear5-7 and nonlinear devices.8-11
Photonic crystal cavities achieve similar effects to that of slow light waveguides, but over a reduced band-width. These cavities offer high Q-factor/volume ratio, for the realization of optically12 and electrically13 pumped ultra-low threshold lasers and the enhancement of nonlinear effects.14-16 Furthermore, passive filters17 and modulators18-19 have been demonstrated, exhibiting ultra-narrow line-width, high free-spectral range and record values of low energy consumption.
To attain these exciting results, a robust repeatable fabrication protocol must be developed. In this paper we take an in-depth look at our fabrication protocol which employs electron-beam lithography for the definition of photonic crystal patterns and uses wet and dry etching techniques. Our optimised fabrication recipe results in photonic crystals that do not suffer from vertical asymmetry and exhibit very good edge-wall roughness. We discuss the results of varying the etching parameters and the detrimental effects that they can have on a device, leading to a diagnostic route that can be taken to identify and eliminate similar issues.
The key to evaluating slow light waveguides is the passive characterization of transmission and group index spectra. Various methods have been reported, most notably resolving the Fabry-Perot fringes of the transmission spectrum20-21 and interferometric techniques.22-25 Here, we describe a direct, broadband measurement technique combining spectral interferometry with Fourier transform analysis.26 Our method stands out for its simplicity and power, as we can characterise a bare photonic crystal with access waveguides, without need for on-chip interference components, and the setup only consists of a Mach-Zehnder interferometer, with no need for moving parts and delay scans.
When characterising photonic crystal cavities, techniques involving internal sources21 or external waveguides directly coupled to the cavity27 impact on the performance of the cavity itself, thereby distorting the measurement. Here, we describe a novel and non-intrusive technique that makes use of a cross-polarised probe beam and is known as resonant scattering (RS), where the probe is coupled out-of plane into the cavity through an objective. The technique was first demonstrated by McCutcheon et al.28 and further developed by Galli et al.29

Use of photonic crystal slow light waveguides and cavities has been widely adopted by the photonics community in many differing applications. Therefore fabrication and characterization of these devices are of great interest. This paper outlines our fabrication technique and two optical characterization methods, namely: interferometric (waveguides) and resonant scattering (cavities).

光子晶体慢光波导和腔体的制备与表征

Slow light has been one of the hot topics in the photonics community in the past decade, generating great interest both from a fundamental point of view ...

Design, Fabrication, and Experimental Characterization of Plasmonic Photoconductive Terahertz Emitters

In this video article we present a detailed demonstration of a highly efficient method for generating terahertz waves. Our technique is based on photoconduction, which has been one of the most commonly used techniques for terahertz generation 1-8. Terahertz generation in a photoconductive emitter is achieved by pumping an ultrafast photoconductor with a pulsed or heterodyned laser illumination. The induced photocurrent, which follows the envelope of the pump laser, is routed to a terahertz radiating antenna connected to the photoconductor contact electrodes to generate terahertz radiation. Although the quantum efficiency of a photoconductive emitter can theoretically reach 100%, the relatively long transport path lengths of photo-generated carriers to the contact electrodes of conventional photoconductors have severely limited their quantum efficiency. Additionally, the carrier screening effect and thermal breakdown strictly limit the maximum output power of conventional photoconductive terahertz sources. To address the quantum efficiency limitations of conventional photoconductive terahertz emitters, we have developed a new photoconductive emitter concept which incorporates a plasmonic contact electrode configuration to offer high quantum-efficiency and ultrafast operation simultaneously. By using nano-scale plasmonic contact electrodes, we significantly reduce the average photo-generated carrier transport path to photoconductor contact electrodes compared to conventional photoconductors 9. Our method also allows increasing photoconductor active area without a considerable increase in the capacitive loading to the antenna, boosting the maximum terahertz radiation power by preventing the carrier screening effect and thermal breakdown at high optical pump powers. By incorporating plasmonic contact electrodes, we demonstrate enhancing the optical-to-terahertz power conversion efficiency of a conventional photoconductive terahertz emitter by a factor of 50 10.

We describe methods for the design, fabrication, and experimental characterization of plasmonic photoconductive emitters, which offer two orders of magnitude higher terahertz power levels compared to conventional photoconductive emitters.

电浆光电导太赫兹发射器的设计，制造和实验表征

In this video article we present a detailed demonstration of a highly efficient method for generating terahertz waves. Our technique is based on ...

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 ...

Patterning via Optical Saturable Transitions - Fabrication and Characterization

This protocol describes the fabrication and characterization of nanostructures using a novel nanolithographic technique called Patterning via Optical Saturable Transitions (POST). In this technique the chemical properties of organic photochromic molecules that undergo single-photon reactions are exploited, enabling rapid top-down nanopatterning over large areas at low light intensities, thereby, allowing for the circumvention of the far-field diffraction barrier.4 Simple, cost-effective, high throughput and resolution alternatives to nanopatterning are being explored, such as, two-photon polymerization5,6, beam pen lithography (BPL)7, scanning electron beam lithography (SEBL), and focused ion beam (FIB) patterning. However, multi-photon approaches require high light intensities, which limit their potential for high throughput and offer low image contrast. Although, electron and ion beam lithographic processes offer increased resolution, the serial nature of the process is limited to slow writing speeds, which also prevents patterning of features over large areas. Beam-pen lithography is an approach towards parallel near-field optical lithography. However, the gap between the source of the beam and the surface of the photoresist needs to be controlled extremely precisely for good pattern uniformity and this is very challenging to accomplish for large arrays of beams. Patterning via Optical Saturable Transitions (POST) is an alternative optical nanopatterning technique for patterning sub-wavelength features1-3. Since this technique uses single photons instead of electrons, it is extremely fast and does not require high light intensities1-3, opening the door to massive parallelization.

We report that the diffraction limit of conventional optical lithography can be overcome by exploiting the transitions of organic photochromic derivatives induced by their photoisomerization at low light intensities.1-3 This paper outlines our fabrication technique and two locking mechanisms, namely: dissolution of one photoisomer and electrochemical oxidation.

通过光学吸收跃迁图案 - 制备与表征

This protocol describes the fabrication and characterization of nanostructures using a novel nanolithographic technique called Patterning via Optical ...

Protocol of Electrochemical Test and Characterization of Aprotic Li-O2 Battery

We demonstrate a method for electrochemical testing of an aprotic Li-O2 battery. An aprotic Li-O2 battery is made of a Li-metal anode, an aprotic electrolyte, and an O2-breathing cathode. The aprotic electrolyte is a solution of lithium salt with aprotic solvent; and porous carbon is commonly used as the cathode substrate. To improve the performance, an electrocatalyst is deposited onto the porous carbon substrate by certain deposition methods, such as atomic layer deposition (ALD) and wet-chemistry reaction. The as-prepared cathode materials are characterized by scanning electron microscopy (SEM), transmission electron microscopy (TEM), and X-ray absorption near edge structure (XANES). A Swagelok-type cell, sealed in a glass chamber filled with pure O2, is used for the electrochemical test on a battery test system. The cells are tested under either capacity-controlled mode or voltage controlled mode. The reaction products are investigated by electron microscopy, X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), attenuated total reflection Fourier transform infrared (ATR-FTIR) spectroscopy, and Raman spectroscopy to study the possible pathway of oxygen reduction reaction (ORR) and oxygen evolution reaction (OER). This protocol demonstrates a systematic and efficient arrangement of routine tests of the aprotic Li-O2 battery, including the electrochemical test and characterization of battery materials.

Protocol of Electrochemical Test and Characterization of Aprotic Li-O2 Battery

A protocol for the electrochemical testing of an aprotic Li-O2 battery with the preparation of electrodes and electrolytes and an introduction of the frequently used methods of characterization is presented here.

电化学测试的协议及表征非质子锂的O<sub&gt; 2</sub&gt;电池

We demonstrate a method for electrochemical testing of an aprotic Li-O2 battery. An aprotic Li-O2 battery is made of a Li-metal anode, an aprotic ...

Fabrication and Characterization of Superconducting Resonators

Superconducting microwave resonators are of interest for a wide range of applications, including for their use as microwave kinetic inductance detectors (MKIDs) for the detection of faint astrophysical signatures, as well as for quantum computing applications and materials characterization. In this paper, procedures are presented for the fabrication and characterization of thin-film superconducting microwave resonators. The fabrication methodology allows for the realization of superconducting transmission-line resonators with features on both sides of an atomically smooth single-crystal silicon dielectric. This work describes the procedure for the installation of resonator devices into a cryogenic microwave testbed and for cool-down below the superconducting transition temperature. The set-up of the cryogenic microwave testbed allows one to do careful measurements of the complex microwave transmission of these resonator devices, enabling the extraction of the properties of the superconducting lines and dielectric substrate (e.g., internal quality factors, loss and kinetic inductance fractions), which are important for device design and performance.

Superconducting microwave resonators are of interest for detection of light, quantum computing applications and materials characterization. This work presents a detailed procedure for fabrication and characterization of superconducting microwave resonator scattering parameters.

制备与表征超导谐振器的

Superconducting microwave resonators are of interest for a wide range of applications, including for their use as microwave kinetic inductance detectors ...

Production and Characterization of Vacuum Deposited Organic Light Emitting Diodes

A method for producing simple and efficient thermally-activated delayed fluorescence organic light-emitting diodes (OLEDs) based on guest-host or exciplex donor-acceptor emitters is presented. With a step-by-step procedure, readers will be able to repeat and produce OLED devices based on simple organic emitters. A patterning procedure allowing the creation of personalized indium tin oxide (ITO) shape is shown. This is followed by the evaporation of all layers, encapsulation and characterization of each individual device. The end goal is to present a procedure that will give the opportunity to repeat the information presented in cited publication but also using different compounds and structures in order to prepare efficient OLEDs.

A protocol for the production of simple structured organic light-emitting diodes (OLEDs) is presented.

真空沉积有机发光二极管的生产与表征

A method for producing simple and efficient thermally-activated delayed fluorescence organic light-emitting diodes (OLEDs) based on guest-host or exciplex ...

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

The quasi 2D electron system (q2DES) that forms at the interface between LaAlO3 (LAO) and SrTiO3 (STO) has attracted much attention from the oxide electronics community. One of its hallmark features is the existence of a critical LAO thickness of 4 unit-cells (uc) for interfacial conductivity to emerge. Although electrostatic mechanisms have been proposed in the past to describe the existence of this critical thickness, the importance of chemical defects has been recently accentuated. Here, we describe the growth of metal/LAO/STO heterostructures in an ultra-high vacuum (UHV) cluster system combining pulsed laser deposition (to grow the LAO), magnetron sputtering (to grow the metal) and X-ray photoelectron spectroscopy (XPS). We study step by step the formation and evolution of the q2DES and the chemical interactions that occur between the metal and the LAO/STO. Additionally, magnetotransport experiments elucidate on the transport and electronic properties of the q2DES. This systematic work not only demonstrates a way to study the electrostatic and chemical interplay between the q2DES and its environment, but also unlocks the possibility to couple multifunctional capping layers with the rich physics observed in two-dimensional electron systems, allowing the fabrication of new types of devices.

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

We fabricate metal/LaAlO3/SrTiO3 heterostructures using a combination of pulsed laser deposition and in situ magnetron sputtering. Through magnetotransport and in situ X-ray photoelectron spectroscopy experiments, we investigate the interplay between electrostatic and chemical phenomena of the quasi two-dimensional electron gas formed in this system.

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 ...

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 ...

变磁B2有序化的FeRh外延层溅射生​​长和表征

变磁B2有序化的FeRh外延层溅射生长和表征