X-ray standing waves in a heterostructure: application to a Zn1−xCoxO epilayer on ZnO(00.)-O substrate

• Published in: Acta crystallographica. Section A, Foundations of crystallography Vol. 60; no. 4; pp. 339 - 350
• Main Authors: Zheng, Y., Boulliard, J. C., Soyer, A., Pétroff, J. F.
• Format: Journal Article
• Language: English
• Published: 5 Abbey Square, Chester, Cheshire CH1 2HU, England Munksgaard International Publishers 01-07-2004; Blackwell
• Subjects: Condensed matter: electronic structure, electrical, magnetic, and optical properties; dynamical theory; Exact sciences and technology; Magnetic properties and materials; Magnetic semiconductors; Optical properties and condensed-matter spectroscopy and other interactions of matter with particles and radiation; Other solid inorganic materials; Photoluminescence; Physics; Studies of specific magnetic materials; thin epitaxic film; X-ray standing waves; Inorganic compounds; Epitaxial layers; Dynamic theory; Ternary compounds; Transition element compounds; Fluorescence; Cobalt oxides; Crystal growth from vapors; Experimental study; Pulsed lasers; Magnetic semiconductors; Defects; Thin films; Interfaces; Standing waves; Zinc oxides; Reflection spectrum; Laser ablation technique; Heterostructures
• ISSN: 0108-7673; 1600-5724
• DOI: 10.1107/S0108767304014473

X‐ray standing waves (XSW) in a thin epitaxic film are treated in the framework of the dynamical theory. It is demonstrated that the fluorescence yield around the main peak of the rocking curve has essentially the same characteristics as that of the usual XSW on a bulk crystal surface. Thus, XSW provide a direct method to probe the atom position in a thin film. The method was applied to an epilayer of the diluted magnetic semiconductor Zn0.94Co0.06O, in order to determine the Co‐atom position. The XSW established that Co atoms occupy the substitutional Zn site in the ZnO matrix, although their coherent fraction, which measures the degree of order, is rather low. Moreover, the measurement of the Zn fluorescence in the film gives approximately the same value for the coherent fraction of the Zn atoms. Besides, by using the substrate rocking curve, it is shown that the XSW signal of the Zn atoms in the substrate can be detected through the film. This interesting approach allows the coherent fraction of an element of a substrate below an interface to be probed in situ. For the Zn fluorescence, the coherent fraction is lower near the interface than in the bulk. These results should relate to strains and defects on both sides of the interface.