In situ preparation of superconducting infinite-layer nickelate thin films with atomically flat surface
arxiv(2024)
摘要
Since their discovery, the infinite-layer nickelates have been regarded as an
appealing system for gaining deeper insights into high temperature
superconductivity (HTSC). However, the synthesis of superconducting samples has
been proved to be challenging. Here, we develop an ultrahigh vacuum (UHV)
in situ reduction method using atomic hydrogen as
reducing agent and apply it in lanthanum nickelate system. The reduction
parameters, including the reduction temperature (T_R)
and hydrogen pressure (P_H), are systematically
explored. We found that the reduction window for achieving superconducting
transition is quite wide, reaching nearly 80^∘C in
T_R and 3 orders of magnitude in
P_H when the reduction time is set to 30 mins. And
there exists an optimal P_H for achieving the highest
T_c if both T_R and reduction
time are fixed. More prominently, as confirmed by atomic force microscopy and
scanning transmission electron microscopy, the atomically flat surface can be
preserved during the in situ reduction process, providing
advantages over the ex situ CaH_2 method for
surface-sensitive experiments.
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