薄膜系統之X光三光共振繞射研究

X-Ray Three-Beam Resonance Diffraction Study on Thin Film Systems

吳雪鴻(Hsueh-Hung Wu)

指導教授 ： 張石麟

國立清華大學/理學院/物理學系/博士(2006年)

https://doi.org/10.6843/NTHU.2006.00624

摘要

在多層膜系統中，因介面效應而產生的有趣機制一直是物理研究中重要的課題之一。欲深入探討發生這些現象的背後機制，相信瞭解介面結構是一個最基本且重要的出發點。但因多層膜的複雜幾何結構
，使得不易透過一般的繞射方法得知介面結構資訊。在本研究中，我們成功地利用三光共振繞射方法來獲取介面的結構資訊。
選擇經過Cd $L_{III}$吸收邊的不同入射光能量，測量一系列的$(200/ar{3}ar{1}1)$及$(200/1ar{3}1)$
ISR三光繞射強度。除三光不變相位外，利用 ISR反射面可給出在共振條件下的三光共振相位。進而選擇八組
介於CdTe(002)與InSb(002)間的介面繞射為主級繞射 (primary reflection) 來測量一系列與能量有關的
ISR 三光繞射強度。實驗結果發現，當主級繞射愈接近CdTe (002)繞射光，其測量到的共振相位變化越大;
相反地，愈靠近InSb (002)繞射光，變化則相對減小。配合理論計算，擬合在不同主級繞射下，
共振相位隨入射光能量變化的實驗結果，利用此實驗方法，我們成功得到在介面，其結構沿垂直晶面方向的參雜組成變化。

關鍵字

薄膜 ； X光 ； 共振 ； 介面結構

並列摘要

The investigation of the interfacial strusture of multi-layered thin film systems has been regarded as an important issue due to its high relevance to some particular properties of these systems.
Owing to its complex structural geometry, obtaining the
information on the interfacial characterization has proved to be a difficult task.
In recent times, although numerous efforts have been dedicated to solve this problem
through the development of practical experimental techniques, most of them still have some liminations.
In this thesis, we address the concept that the structural characterization of the interface
can be possibly achieved by utilizing the experimental method of x-ray multiple diffraction under resonance condition.
By using the peculiar emph{Zincblende} structure that makes
possible the measurement of the inversion symmetry-related cases of three-wave diffraction, we have
successfully extracted the crystallographic phase of a thin film system for the first time.

A series of x-ray three-beam diffraction $(200/ar{3}ar{1}1)/(200/1ar{3}1)$
were conducted under resonant conditions to measure the concentrations of the constitunt
elements of the interface between a (100) CdTe thin film and a (100) InSb substrate. The
three-beam diffraction profiles versus the azimuthal angle of rotation around [200] reveal
a wide variety of change in phase shift due to resonance for photon energies in the
vicinity of the Cd $L_{III}$ absorption edge. At different
momentum transfers $q_{r}$ along $[200]$, sensitive to the
interfacial structure, the phase shift in the resonant state also
provides sufficient information about the distributions of the Cd and
Te concentrations. This information, combined with a theoretical analysis
of the crystallographic phase of the structural-factor triplets, allows us
to determine the composition of Cd and Te as a function of depth normal to the interface.
In addition, via the propagation of the
secondary $(ar{3}ar{1}1)$ and $(1ar{3}1)$ reflected beams
along the interface, possible interface structures parallel to the
surface can also be deduced.

The hybridization of the x-ray three-beam intensity profiles has appeared distinctly
in the diffraction process, especally at some momentum transfers that have a higher
sensitivity to the interfacial structure. The anomalous disharmony of these diffracion profiles,
influenced by the almost perfect lattice mismatch of 0.04\% in the interface,
manifests the complexity of the interfacial structure. However, the severe hybridation of the intensity
has imposed a considerable limitation on the analysis of the structural composition
of the interface. Nevertheless, these data
might still validate that along the interfacial momentum transfer the variation of the resonance phase in
different degree indeed come from the effect of the interfacial structure.

並列關鍵字

thin film ； X ray ； resonance ； interface structure

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