以脈衝雷射沈積法研究生長溫度對成長於雲母與鈦酸鍶(100)基板上的FeSe薄膜物理特性影響之比較研究

Abstract

利用脈衝雷射沈積法準備FeSe薄膜在不同生長溫度下成長。選擇了絕緣的鈦酸鍶(100) 與雲母基板作為研究生長溫度對FeSe薄膜成長在基版上的物理特性影響之比較研究。生長溫度範圍包括低溫[LT]至高溫[HT]。從X光繞射與掃描式電子顯微鏡中的能量色散譜觀察到某些四方型FeSe (PbO型) 與六角型FeSe (NiAs型) 樣品依其生長溫度的不同有高c軸取向。利用布里奇曼法在300℃真空石英管中退火三小時以提高FeSe膜的質量。於FeSe-STO系統中，四方相FeSe佔多數，而相對地於FeSe-mica系統則以六角相FeSe為多。利用超導量子干涉儀及傳輸測量的PPMS及LCR錶度量其磁特性後觀察到即使在2K的溫度下亦未有發現任何證據顯示超導體產生轉變。

FeSe thin films were prepared at various growth temperatures by pulsed laser deposition. Insulating STO (100) substrate and mica substrate were chosen to investigate the growth temperature dependence on FeSe properties as comparative study. The growth temperature range include very low temperature[LT] to high temperature[HT] regime. X-ray diffraction and scanning electron microscopic-energy dispersive spectroscopy showed that highly c-axis oriented for both tetragonal FeSe (PbO type) and hexagonal FeSe (NiAs type) which appeared in some samples based on their growth temperature. To enhance the FeSe films quality, annealing process was conducted by Bridgman method using vacuum quartz tube at 3000C for 3hr. The tetragonal phase of FeSe was more dominant to appear in FeSe-STO system and oppositely the hexagonal FeSe phase was observed on FeSe-mica system. Magnetic behavior been measured by SQUID and transport measurement brought by PPMS and LCR meter. No clear evidence for a superconducting transition was found even down to 2 K.