運用脈衝鐳射沉積成長新穎超導薄膜材料(Sr2RuO4, Fe1-xSe)

PLD Growth of Novel Superconducting Thin film (Sr2RuO4, Fe1-xSe)

呼延澍元(Huyan, Shuyuan)

指導教授 ： 郭瑞年 ； 吳茂昆

國立清華大學/理學院/物理學系/碩士(2014年)

https://doi.org/10.6843/NTHU.2014.00390

摘要

脈衝鐳射蒸鍍技術是適用于現代物理學基礎研究的重要材料製備工具。它通過高能鐳射轟擊特定靶材產生混合等離體羽輝並達到同質沉積的目的。相較於其他沉積技術具有快速，且適用面廣的特點。而在薄膜材料的實際成長過程中，材料中不同元素的蒸汽壓、原子品質、化學穩定性以及氧化物材料中極易損耗的O元素都會很大程度上影響到同質磊晶的效果。以上問題都需要我們通過相應的方法加以克服。
本論文介紹了我們使用鐳射分子束泵晶系統嘗試成長具有鈣鈦礦結構的鍶釕氧系列氧化物薄膜，包括鐵磁性材料SrRuO3 以及 p波超導材料Sr2RuO4，以及使用自己架設的真空脈衝鐳射沉積系統嘗試成長含有有序鐵原子空位的Fe4Se5。通過調變靶材-基板距離和腔體氣壓以及雙靶材交替成長方式，我們解決了Ru易缺少的問題並成功製備極高品質SrRuO3, Sr2RuO4薄膜。相反地，我們利用特定條件下脈衝鐳射沉積非同質磊晶的特點，通過成長過程中加設磁場以及實現成長結束後的常溫原位淬火製備出成分接近Fe：Se=4:5 四方晶體結構的Fe，Se化合物薄膜。本文同時會介紹這些材料的特性以及研究價值。

關鍵字

脈衝鐳射沉積 ； 超導 ； 薄膜 ； 鍶釕氧化合物 ； 鐵硒

並列摘要

Pulsed Laser deposition (PLD) is an important instrument for thin film growth in scientific research. It is widely applicable for a variety of materials especially for complex oxide which has high melting point and firm structure. However the PLD is sometimes not the proper homo-epitaxy because elements have different atomic mass, vapour pressure, ionization energy and chemical stability. So it is not easy to avoid non-homogeneous deposition unless getting the optimized growth parameters or finding some ways to cover the “deficit”
In this thesis, we introduce effective methods for high quality thin film growth of Ruddlesden-Popper series complex oxide by Laser Molecular Beam Epitaxy (LMBE) including ferromagnetic SrRuO3 and chiral p-wave superconductor Sr2RuO4, in which Ru, as a volatile element, is very easy to form deficiencies during the process of thin film growth. Sr2RuO4 is the potential host of Half-quantum vortex (HQV), the Majorona zero mode is predicted exist in the core of HQV. So there will be a big scientific research value to fabricate high quality superconducting thin film of Sr2RuO4. On the other hand, we make use of experience we had accumulated to fabricate Fe1-xSe thin film such as pure Fe4Se5 in order to complete the phase diagram of High Tc Fe-pnictide superconductor, which will help us to understand the mechanism of High Tc superconductivity better.

並列關鍵字

PLD ； Superconductivity ； Thin Film ； Ruthenium Oxide Series ； Iron Selenide

參考文獻

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