Periodically Structured Glancing Angle Deposition Thin Films

Thin films fabricated using the glancing angle deposition technique have a porous microstructure consisting of freestanding columns. Many promising applications of such thin films require that the columns be arranged in periodic arrays using substrate topographies-so-called seed layers-that enforce controlled film nucleation. In this paper, we present the optimized design, fabrication, and characteristics of periodically structured thin films, achieving highly uniform periodic film morphologies. We derive geometrical rules for designing substrate seed layers, and explain how to fabricate large area seed patterns with submicrometer features. Using negative-resist electron-beam lithography and laser direct write lithography, we have reached extremely high pattern densities. An experimental analysis is provided of seed-enforced nucleation and thin-film growth, showing that the elimination of film growth between seeds is crucial, and that the substrate seed layer geometry must match the intended film microstructure. Finally, we discuss the enhanced properties of periodically structured oblique angle thin films and their applications.