SrTiO_3-xN_x thin films synthesized using nitrogen plasma assisted hybrid molecular beam epitaxy

For perovskite oxynitrides, it has been proven challenging to maintain cation stoichiometry while incorporating nitrogen at the anion site in conventional thin film deposition approaches, such as pulsed laser deposition and sputtering. Post-synthesis nitridation routes for bulk perovskites using high temperature NH₃ anneals have been applied with limited success. Nonequilibrium thin film synthesis techniques offer an alternative strategy allowing large amounts of nitrogen into the film lattice during growth. We report the synthesis of strontium titanium oxynitride (SrTiO_3-xN_x) thin films using nitrogen plasma assisted hybrid molecular beam epitaxy. The self-regulated growth regime offered by hybrid molecular beam epitaxy can still be accessed in the presence of a nitrogen plasma. Nitrogen incorporation rates larger than 10% have been obtained, accompanied by substantial changes of the film lattice parameter. Temperature dependent impedance spectroscopy, second harmonic generation, and spectroscopic ellipsometry will be discussed to elucidate the effect of nitrogen on the ferroelectric, dielectric, and optical properties in SrTiO_3-xN_x films.