On pinning-depinning and microkink-flow in solid state dewetting: Insights by in-situ ESEM on Al thin films

Abstract

The dynamics of solid state dewetting phenomena of a 50 nm thick, mazed bicrystalline Al film on single crystalline α-Al 2 O 3 (sapphire) substrates was studied in-situ using an environmental scanning electron microscope (ESEM). The bicrystalline Al thin films served as a model system where the influence of grain boundaries and texture effects are well determined compared to polycrystalline films. The experiments were performed in controlled oxidizing and reducing atmospheres at 773 K and 823 K, respectively, to shed light on the differences in dewetting mechanisms and dynamics. While the reducing atmosphere led to spontaneous dewetting at 823 K after an incubation time of a few minutes, a hierarchical dewetting process was observed for the sluggish dewetting under oxidizing conditions. Voids initiated at (substrate or surface) defects and expanded trying to maintain a hexagonal shape. Pinning and depinning processes led to a discontinuous void growth and irregular void shapes including finger instabilities. As a consequence, the void growth followed a variety of power law exponents between 0.10 and 0.55. A new microkink-flow mechanism was discovered at the terminating Al planes at the void.

Evaluation and application of a new scintillator‐based heat‐resistant back‐scattered electron detector during heat treatment in the scanning electron microscope

“…This technique has been used for decades and many different scientific questions have been addressed 12–18 . Using a (VP)SEM, most of the collected information comes from two electron signals, secondary electrons (SE) and backscattered electrons (BSE) being the main electron emissions used to produce images.…”