Radio-frequency (RF) particle accelerator cavities are one of the industrial and research applications in which superconductivity, still an underexplored phenomenon, has been broadly adopted. Niobium (Nb) cavities are ubiquitous in accelerator facilities, and research to improve their reliability and quality are ongoing. However, Nb technology is reaching fundamental material limitations, and new systems must be explored to continue improvement. In this thesis, we investigate a thin film structure that has been proposed to dramatically increase both the efficiency and maximum accelerating gradient achievable in these applications. First, we discuss the reasoning behind our choice of Nb3Sn/Al2O3 for the exploration of these properties and the challenges involved in growing these materials. We show that the challenges of processing Nb3Sn can be overcome with a high-temperature growth method and that there is a growth window where the stoichiometry of the Nb3Sn films is self-regulating. Second, we scale growth up to wafer-scale films and heterostructures, and confirm the structure and quality using cross-sectional TEM. RF measurements were conducted in cavity geometry at low RF fields on wafers of Nb3Sn and Nb3Sn/Al2O3. The results of these measurements are encouraging, showing that the Nb3Sn has very low surface resistance, and compares well to a bulk Nb sample measured in the same cavity. The multilayer sample had a higher quality factor than the single-layer film, confirming that the Al2O3 layer contributes very little to surface resistance. The development of this system makes it possible to explore the effects of film morphology and heterostructure geometry on the quench field, and to study the physics of the superconductor-insulator-superconductor structure under high frequencies and magnetic fields.