A self-assembly driven process to synthesize island-structured dielectric films is presented. An intermetallic reaction in platinized silicon substrates provides preferential growth sites for the complex oxide dielectric layer. Microscopy and spectroscopy analyses have been used to propose a mechanism for this structuring process. This provides a simple and scalable process to synthesize films with increased surface area for sensors, especially those materials with a complex chemistry. The ability of these island-structured dielectric films to improve sensitivity by a factor of 100 compared to continuous films in applications as substrates for surfaceenhanced Raman scattering (SERS) is demonstrated.