Tuning Surface Spin Polarization of CoFeB by Boron Diffusion Detected by Spin Resolved Photoemission  

作　　者：Qi Liu Xianyang Lu Chengrui Fu Jiarui Chen Zhe Zhang Yuting Gong Xinyue Wang Yu Yan Qinwu Gao Hui Li Xuezhong Ruan Yao Li Jun Du Jing Wu Liang He Bo Liu Rong Zhang Yongbing Xu 

机构地区：[1]Jiangsu Provincial Key Laboratory of Advanced Photonic and Electronic Materials,School of Electronic Science and Engineering,Nanjing University,Nanjing 210093,China [2]Key Laboratory for Liquid-Solid Structural Evolution and Processing of Materials(Ministry of Education),Shandong University,Jinan 250061,China [3]Department of Physics,Nanjing University,Nanjing 210093,China [4]York-Nanjing Joint Center(YNJC)for Spintronics and Nano-engineering,Department of Electronics and Physics,University of York,York YO105DD,UK [5]Key Laboratory of Spintronics Materials,Devices and Systems of Zhejiang Province,Hangzhou 311300,China

出　　处：《Chinese Physics Letters》2023年第8期86-91,共6页中国物理快报（英文版）

基　　金：supported by the National Key Research and Development Program of China(Grant No.2021YFB3601600);the National Natural Science Foundation of China(Grant Nos.12104216,61427812,11774160,51971109,51871236,51771053,U1806219);the Natural Science Foundation of Jiangsu Province of China(Grant Nos.BK20200307,BK20192006,BK20180056);the Fundamental Research Funds for the Central Universities(Grant No.21014380113)。

摘　　要：Research of spin polarization of magnetic CoFeB thin films is of practical importance in spintronic applications.Here,using a direct characterization technique of spin-resolved photoemission spectroscopy,we obtain the surface spin polarization of amorphous Co_(40)Fe_(40)B_(20)thin films with different annealing temperatures from 100℃to 500℃prepared by magnetron sputtering.After high annealing temperature,a quasi-semiconductor state is gradually formed at the CoFeB surface due to the boron diffusion.While the global magnetization remains almost constant,the secondary electrons’spin polarization,average valence band spin polarization and the spin polarization at Fermi level from spin-resolved photoemission spectroscopy show a general trend of decreasing with the increasing annealing temperature above 100℃.These distinct surface properties are attributed to the enhanced Fe-B bonding due to the boron segregation upon surface after annealing as confirmed by x-ray photoelectron spectroscopy and scanning transmission electron microscopy with energy dispersive spectroscopy.Our findings provide insight into the surface spin-resolved electronic structure of the CoFeB thin films,which should be important for development of high-performance magnetic random-access memories.

关 键 词：SPECTROSCOPY ANNEALING BORON 

分 类 号：TB383.2[一般工业技术—材料科学与工程] O469[理学—凝聚态物理]