Observation of metallic TeO2 thin film with rutile structure on FeTe surface

The discovery of high mobility p-type two-dimensional beta-tellurite (beta-TeO2) has led to an increasing interest in tellurium oxide-related polymorphs. Bulk TeO2 is known to exist in three polymorphs (alpha-, beta-, and gamma-TeO2), all of which exhibit wide bandgaps. By utilizing the interfacial interactions, we successfully synthesized a new polymorph of TeO2 with a rutile structure on a tetragonal FeTe surface via soft surface oxidation. Irrespective of the film thickness, the rutile TeO2 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 TeO2 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 TeO2, based on interface engineering and in situ tunneling spectroscopy, can help tune the electronic properties of tellurium oxide in reduced dimensions.