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在以前工作的基础上，进一步研究了SrTiO3（001）（STO）衬底上单层FeSe超导薄膜的分子束外延生长. 首先，通过去离子水刻蚀、盐酸溶液腐蚀和纯氧气氛中退火等步骤，获得台阶有序、具有单一TiO2终止的原子级平整表面的STO衬底，这是前提条件. 这个过程中酸的选择和退火过程中氧的流量是最为关键的因素. 其次，在FeSe薄膜的分子束外延生长中，选择适当的Fe源和Se 源束流以及衬底温度是关键因素. 如选择适当，生长模式为step-flow生长，这时得到的FeSe薄膜将是原子级平整的. 最后一步为退火，这个过程会增强FeSe薄膜结晶性以及它与SrTiO3衬底间的结合强度.
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关键词:
- SrTiO3(001) /
- 单层FeSe薄膜 /
- 高温超导 /
- 分子束外延
Based on our previous work, we have systematically investigated the molecular beam epitaxy growth of single unit-cell FeSe films on SrTiO3(001) substrates and studied the surface morphology by scanning tunneling microscopy. We found that there are three key steps to obtain large-scale uniform one unit-cell superconducting FeSe films. First, the STO(001) substrates should be treated by HCl etching and thermal annealing under oxygen flux so that a specific TiO2-terminated STO(001) surface with well-defined step-terrace structure could be obtained. Second, the Fe and Se fluxes and substrate temperature have to be controlled delicately. At last, post-growth annealing is also critical, which can remove extra Se adatoms, and more importantly facilitate the necessary electron transfer for superconductivity transition.-
Keywords:
- SrTiO3(001) /
- single unit-cell FeSe films /
- high temperature superconductivity /
- molecular beam epitaxy
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[2] He S L, He J F, Zhang W H, Zhao L, Liu D F, Liu X, Mou D X, Ou Y B, Wang Q Y, Li Z, Wang L L, Peng J P, Liu Y, Chen C Y, Yu L, Liu G D, Dong X L, Zhang J, Chen C T, Xu Z Y, Chen X, Ma X C, Xue Q K, Zhou X J 2013 Nat. Mater. 12 605
[3] Saint-James D, de Gennes P G 1963 Phys. Lett. 7 306
[4] Ginzburg V L 1964 Phys. Lett. 13 101
[5] Wang L L, Ma X C, Chen X, Xue Q K 2013 Chin. Phys. B 22 086801
[6] Unoki H, Sakudo T 1967 J. Phys. Soc. Jpn. 23 546
[7] Muller K A, Berlinger W, Waldner F 1968 Phys. Rev. Lett. 21 814
[8] Kawasaki M, Takahashi K, Maeda T, Tsuchiya R, Shinohara M, Ishiyama O, Yonezawa T, Yoshimoto M, Koinuma H 1994 Science 266 1540
[9] Koster G, Kropman B L, Rijnders G J H M, Blank D H A, Rogalla H 1998 Appl. Phys. Lett. 73 2920
[10] Biswas A, Rossen P B, Yang C H, Yang C H, Siemons W, Jung M H, Yang I K, Ramesh R, Jeong Y H 2011 Appl. Phys. Lett. 98 051904
[11] Wang X, Fei Y Y, L H B, Jin K J, Zhu X D, Chen Z H, Zhou Y L, Yang G Z 2005 Sci. China Ser. G-Phys. Mech. Astron. 35 158 (in Chinese) [王旭, 费义艳, 吕惠宾, 金奎娟, 朱湘东, 陈正豪, 周岳亮, 杨国桢 2005 中国科学 G 辑 物理学 力学·天文学 35 158]
[12] Chambers S A, Droubay T C, Capan C, Sun G Y 2012 Surf. Sci. 606 554
[13] Zhang W H, Sun Y, Zhang J S, Li F S, Guo M H, Zhao Y F, Zhang H M, Peng J P, Xing Y, Wang H C, Fujita T, Hirata A, Li Z, Ding H, Tang C J, Wang M, Wang Q Y, He K, Ji S H, Chen X, Wang J F, Xia Z C, Li L, Wang Y Y, Wang J, Wang L L, Chen M W, Xue Q K, Ma X C 2014 Chin. Phys. Lett. 31 017401
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