Advanced techniques for glancing angle deposition

TLDR

In physical vapor deposition at oblique angles, the columnar growth angle and porosity of a thin film are coupled, so achieving a large columnar angle requires a very porous film, while a near‑vertical columnar film yields a dense microstructure. The authors aim to develop a glancing‑angle deposition technique that decouples columnar inclination and film density. Their method employs substrate motion during deposition to independently control the columnar growth angle and film density. Using this technique, they fabricate microstructured materials with 10‑nm three‑dimensional control suitable for optical, chemical, biological, mechanical, magnetic, and electrical applications.

Abstract

When a thin film is deposited by physical vapor deposition, with the vapor flux arriving at an oblique angle from the substrate normal, and under conditions of sufficiently limited adatom mobility to create a columnar microstructure, the resulting structure is somewhat porous and grows at an angle inclined toward the vapor source. For a given material and set of deposition conditions, there is a fixed relationship between the angle of vapor flux incident on the substrate and the inclination angle at which the columnar thin film grows. As the porosity of the film is also dependent on the incident flux angle, column growth angle and porosity cannot be chosen independently. If a large columnar angle (more parallel to the substrate) is desired, the flux must be deposited at a large oblique angle resulting in a very porous film. Conversely, if a near vertical columnar film is desired, the flux must arrive more perpendicular to the substrate and the resulting film has a tightly packed, dense microstructure. We present a technique, based on glancing angle deposition, employing substrate motion during deposition, which allows the columnar growth inclination angle and film density to be controlled independently. With this method, microstructurally controlled materials can be fabricated with three dimensional control on a 10 nm scale for use in optical, chemical, biological, mechanical, magnetic, and electrical applications.