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首页> 外文会议>Intl Symp on Optical Fabrication, Testing, and Surface Evaluation >Structure and x-ray optical properties of MBE-grown multilayers (Invited Paper)
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Structure and x-ray optical properties of MBE-grown multilayers (Invited Paper)

机译：MBE生长的多层膜的结构和X射线光学性质（邀请论文）

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Abstract: The structure, and therefore the performance, of multilayer x-ray mirrors is directly related to the growth mode of the constituent materials. We review some of our recent results from using molecular beam epitaxy (MBE) for the growth and study of materials for x-ray optics. This work involves the study of surfaces and interfaces important to improving conventional multilayer mirrors and development of superlattice mirrors. Recently, we have successfully grown hcp (0001) Be epitaxially on (0001) $alpha@-Al$-2$/O$-3$/ substrates. We find the orientation and morphology are strongly influenced by the substrate temperature during deposition. The discovery of a technique to grow Be epitaxially, coupled with the favorable optical constants of this material, gives Be-based multilayers great potential for the development of superlattice x-ray optics. In our preliminary studies of Be/Ge multilayers we found them to have a layered structure, making Be/Ge a potentially useful combination for soft x-ray mirrors. In another series of studies, we performed investigations of film growth and interface formation using a variety of surface analysis techniques for Mo on Si and for X on B (where X $EQ Pd, Ag, Si). These studies were carried out by depositing onto clean surfaces in ultra high vacuum, followed by characterization with in situ reflection high-energy electron diffraction (RHEED), low-energy electron diffraction (LEED), Auger electron spectroscopy (AES), x-ray photoelectron spectroscopy (XPS), and ex situ by scanning tunneling microscopy (STM) and x-ray diffraction. Continuous growth of multiple coverages on a single substrate was accomplished with a technique involving a moveable sample shutter. For Mo-Si, our data are consistent with a composition profile that has an atomically abrupt transition between Si and amorphous MoSi$-x$/, where x $EQ 2 for the first 4 angstroms. The fraction of Si then decreases, with the composition approaching pure Mo after 15 - 20 angstroms depending upon the growth temperature. This silicide interlayer causes only a small reduction in the reflectivity of Mo/Si soft x- ray mirrors with $Lambda $GRT 60 angstroms, but has severe effects for smaller period structures. For Ag-B, the XPS, AES, and STM data are all characteristic of an island (three-dimensional) growth mode. At an Ag coverage 15 angstroms, the islands range in height from 100 to 200 angstroms and are 2000 to 3000 angstroms across. Although the interface between Ag and B may be sharp, the island growth mode causes too much roughness for the multilayers to be useful for short-wavelength optics. For Pd-B, the Pd reacts with the B to form an amorphous, Pd-rich boride. Although the absorber layer is an alloy, our calculations indicate that the ideal normal-incidence reflectivity of the reacted multilayers could be as high as 51% at 80 angstroms. For Si on B, the interface is quite sharp and the amorphous Si forms a smooth continuous layer. Si/B multilayers are useful as narrow bandpass mirrors for $lambda $GRT 125 angstroms. !24
机译：摘要：多层X射线反射镜的结构及其性能直接关系到组成材料的生长方式。我们回顾了使用分子束外延（MBE）来生长和研究X射线光学材料的最新结果。这项工作涉及对改善传统多层反射镜和开发超晶格反射镜非常重要的表面和界面的研究。最近，我们已经成功地在（0001）$ alpha @ -Al $ -2 $ / O $ -3 $ /基板上外延生长hcp（0001）。我们发现在沉积过程中衬底的温度强烈影响取向和形态。外延生长Be的技术的发现，再加上这种材料的良好光学常数，为Be基多层膜提供了发展超晶格X射线光学器件的巨大潜力。在我们对Be / Ge多层膜的初步研究中，我们发现它们具有分层结构，使Be / Ge成为软X射线镜的潜在有用组合。在另一系列研究中，我们使用多种表面分析技术对Si上的Mo和B上的X（其中X $ EQ Pd，Ag，Si）进行了膜生长和界面形成的研究。这些研究是通过在超高真空下沉积在干净的表面上，然后通过原位反射进行表征的：高能电子衍射（RHEED），低能电子衍射（LEED），俄歇电子能谱（AES），x射线光电子能谱（XPS），并通过扫描隧道显微镜（STM）和X射线衍射进行非原位测量。使用涉及可移动样品百叶窗的技术可以在单个基板上连续生长多个覆盖物。对于Mo-Si，我们的数据与在Si和非晶MoSi $ -x $ /之间具有原子突变的成分分布一致，其中前4埃x $ EQ 2。然后，Si的含量降低，根据生长温度，组成在15-20埃后接近纯Mo。这种硅化物夹层只会使Mo / Si软X射线反射镜的反射率小幅降低，而λ/ GRT为60埃，但是对于较小的周期结构会产生严重影响。对于Ag-B，XPS，AES和STM数据都是孤岛（三维）生长模式的特征。在Ag覆盖15埃时，这些岛的高度范围为100至200埃，跨度为2000至3000埃。尽管Ag和B之间的界面可能很锐利，但是岛生长模式导致多层的粗糙度过大，无法用于短波长光学器件。对于Pd-B，Pd与B反应形成无定形，富含Pd的硼化物。尽管吸收层是合金，但我们的计算表明，反应后的多层的理想法向入射反射率在80埃时可能高达51％。对于B上的Si，界面非常锋利，非晶硅形成光滑的连续层。 Si / B多层膜可用作λ$ GRT 125埃的窄带通镜。 ！24

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