By using first-principles calculations, we have studied the atomic and electronic structures of FeSe monolayer and bilayer thin films on SrTiO${}_3$ (001) with SrO or TiO${}_2$ termination. We find that both FeSe monolayer and bilayer on either termination behave like a slightly doped semiconductor with a collinear antiferromagnetic order on Fe ions. FeSe is adhered to the SrTiO${}_3$ surface by a dipole-dipole interaction. The Fermi surface is mainly of the contribution of Fe-$3d$ orbitals. The valence band contributed mainly by the O-$2p$ orbitals in the TiO${}_2$ layer is located slightly below the Fermi level, which can become conducting upon a small doping of holes. For electron-doped SrTiO${}_3$ (001) with TiO${}_2$ termination, the Fermi level and the energy bands of the FeSe monolayer shift into the energy band gap of the substrate.

• Received 29 February 2012

DOI:https://doi.org/10.1103/PhysRevB.85.235123