Stretch dependence of the electrical breakdown strength and dielectric constant of dielectric elastomers
Smart materials and structures (Print)
The dielectric reliability of low k materials during mechanical deformation attracts tremendous attention owing to the increasing demand for thin electronics to meet the ever-shrinking form factor of consumer products. However, the strong coupling between dielectric/electric and mechanical properties limits the use of low-k dielectrics in industrial applications. We report the leakage current and dielectric properties of a nanolattice capacitor during compressive stress cycling. Measuring
... ng. Measuring electrical breakdowns during the stress cycling, combined with a theoretical model and in-situ mechanical experiments, provide insights to key breakdown mechanisms. Electrical breakdown occurs at nearly 50% strain featuring a switch-like binary character, correlated with a transition from beam bending and buckling to collapse. Breakdown strength appears to recover after each cycle, concomitant with nanolattice's shape recovery. The compressive displacement at breakdown decreases with cycling due to permanently buckled beams, transforming conduction mechanism from Schottky to Poole-Frankel emission. Remarkably, our capacitor with 99% porosity, k ~ 1.09 is operative up to 200 V whereas devices with 17% porous alumina films breakdown upon biasing based on a percolation model. Similarly with electrical breakdown, the dielectric constant of the capacitor is recoverable with five strain cycles, and stable under 25% compression. These outstanding capabilities of the nanolattice are essential for revolutionizing future flexible electronics.