Surface preparation method for investigating the three-dimensional electronic structure of perovskite nickelates

The investigation of the electronic structures on perovskite oxides using surface-sensitive spectroscopy techniques is often hindered by their “uncleavable” nature, typically requiring expensive and complex experimental setups that integrate the capabilities of sample synthesis and spectroscopy measurement under ultrahigh vacuum condition. Here, we address this challenge by developing an ozone-annealing process that yields atomically flat surfaces on perovskite oxide thin films, making them suitable for high-resolution angle-resolved photoemission spectroscopy measurements. Using this method, we present a three-dimensional electronic structure study of <a:math xmlns:a="http://www.w3.org/1998/Math/MathML"><a:mrow><a:msub><a:mi>Nd</a:mi><a:mrow><a:mn>1</a:mn><a:mo>−</a:mo><a:mi>x</a:mi></a:mrow></a:msub><a:msub><a:mi>Sr</a:mi><a:mi>x</a:mi></a:msub><a:msub><a:mi>NiO</a:mi><a:mn>3</a:mn></a:msub></a:mrow></a:math> (<b:math xmlns:b="http://www.w3.org/1998/Math/MathML"><b:mrow><b:mi>x</b:mi><b:mo>=</b:mo><b:mn>0</b:mn></b:mrow></b:math> and 0.175) thin films with unprecedented accuracy. The experimentally determined low-energy fermiology exhibits quantitative agreements with two-band tight-binding simulations, which is further validated by first-principles calculations considering the material's actual crystal structure. This work provides an accessible approach for ARPES measurements on perovskite oxides and other strongly correlated oxides, including the recently discovered high-<c:math xmlns:c="http://www.w3.org/1998/Math/MathML"><c:msub><c:mi>T</c:mi><c:mtext>c</c:mtext></c:msub></c:math> nickelates.