New method to reduce the optical band gap of strontium titantate thin films
With the promise of sunlight into fuel, strontium titanate (SrTiO3) is widely studied. The problem is the optical band gap or the energy needed to get electrons to do work after being hit with light. At 3.2 electron-volts, the gap requires ultraviolet light. Scientists at Pacific Northwest National Laboratory shortened the gap to 2.3 eV, putting it in the visible light regime. The shorter gap is thanks to a new technique that fabricates epitaxial strontium titanate films with equal concentrations of lanthanum and chromium additives, or dopants. An expitaxial film is created by putting a crystalline layer on a crystalline surface one atom at a time to make an ideal material. The added elements reduce the gap without creating any undesirable defects.