We perform $\mathit{in} \mathit{situ}$ angle-resolved photoemission spectroscopy to investigate the effect of surface termination conversion on two-dimensional electron gas (2DEG) at the ${\mathrm{EuTiO}}_3$(001) surface. We successfully engineered ${\mathrm{EuTiO}}_3$ with nearly single ${\mathrm{TiO}}_2$ termination via epitaxial growth on ${\mathrm{TiO}}_2$-terminated ${\mathrm{SrTiO}}_3$, and ${\mathrm{EuTiO}}_3$ with nearly complete EuO termination by inserting a ${\mathrm{SrRuO}}_3$ buffer layer into the heterostructure. The orbital configuration of the 2DEG exhibits a strong dependence on the ${\mathrm{EuTiO}}_3$ termination, and this experimental observation matches our first-principles calculation results very well. Furthermore, we observe the termination dependence of a kink feature in $d_{xy}$ band. This finding implies that many-body interactions, and possibly magnetism, are influenced by the surface termination. Our study not only introduces a method to fabricate surface or interfacial 2DEG system, but also highlights the effect of termination conversion on magnetic 2DEG.

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• Density of states
• Electronic structure
• Orbital order
• Surfaces
• Thin films
• Two-dimensional electron gas
• Angle-resolved photoemission spectroscopy
• DFT+U
• Film deposition
• Scanning transmission electron microscopy