Observation of metallic TeO 2 thin film with rutile structure on FeTe surface

The discovery of high mobility p -type two-dimensional beta-tellurite (β-TeO 2 ) has led to an increasing interest in tellurium oxide-related polymorphs. Bulk TeO 2 is known to exist in three polymorphs (α-, β-, and γ-TeO 2 ), all of which exhibit wide bandgaps. By utilizing the interfacial interactions, we successfully synthesized a new polymorph of TeO 2 with a rutile structure on a tetragonal FeTe surface via soft surface oxidation. Irrespective of the film thickness, the rutile TeO 2 exhibited a metallic Fermi surface, as revealed by low-temperature scanning tunneling spectroscopy and further confirmed by our theoretical calculations. Striped wrinkles with an apparent lattice shift were observed on large rutile TeO 2 monolayer islands due to lattice distortion. The density of states around the Fermi level accordingly shift from a U-shaped gap to a V-shaped feature. Our synthesis and observation of rutile TeO 2 , based on interface engineering and in situ tunneling spectroscopy, can help tune the electronic properties of tellurium oxide in reduced dimensions.