Structural Transition in Epitaxial Co-Cr Multilayers as Studied by X-ray Absorption Spectroscopy

• Main Authors: Yu-Chi Liou, 劉育祈
• Other Authors: Way-Faung Pong
• Format: Others
• Language: zh-TW
• Published: 1999
• Online Access: http://ndltd.ncl.edu.tw/handle/85357115417955519680

碩士 === 淡江大學 === 物理學系 === 87 === We have performed the Co and Cr K-edge x-ray-absorption measurements to investigate the variation of local electronic and atomic structures as a function of the Cr-layer thickness in the epitaxial [Co (40A)/Cr (tCr)] (t = 2, 3, 5, 7, and 9A) multilayers. The Cr K-edge x-ray absorption near edge fine structure (XANES) spectra for Co/Cr multilayers indicate an abrupt transition of the Cr layer from a bcc structure to a hcp structure when the thcikness of the Cr layer is reduced to ~5A or three layers. Since the thermodynamically most stable structure for Cr is the cubic bcc structure, the abrupt transition to the hexagonal structure of the Co layer show that the elastic strain energy generated in the Co/Cr interface is approximaely equal to the energy difference between the bcc and hcp structures of a three-layer Cr film. Our results offer an upper limit for the ability of the strain energy in the Co/Cr interface to stablize the hcp structure in the thin Cr layer. The bond-length distortion in the Co layer observed in the extended x-ray absorption fine structure (EXAFS) measurements performed at the Co and Cr K-edge are consistent with the XANES results.