Substrate‐Controlled Response Coefficients in Thin Films

Abstract To obtain materials with desired properties, material compositions are primarily altered, whereas thin films offer additional unique avenues. By combining state‐of‐the‐art first‐principles calculations and experimental investigations of thin films of strontium titanate as an exemplary representative of a broad class of perovskite oxides and the extensive family of ferroelectrics, a novel approach is presented to achieving superior material responses to external stimuli. The findings reveal that substrate‐imposed deformations, or strains, significantly alter the frequencies and magnitudes of atomic vibrations in thin films. Consequently, material‐specific response‐stimulus coefficients can become strain‐dependent. The strain‐dependent Curie constant, which characterizes the dielectric response to thermal stimuli, is theoretically justified and experimentally validated. Given that atomic vibrations fundamentally govern various response coefficients in a wide range of materials, and that thin films are typically deformed by substrates, it is anticipated that unprecedented responses can be generally attained through substrate‐induced control of atomic vibrations in thin films.