Ultralow-k materials used in high voltage devices require mechanical resilience and electrical and dielectric stability even when subjected to mechanical loads. Existing devices with organic polymers suffer from low thermal and mechanical stability while those with inorganic porous structures struggle with poor mechanical integrity. Recently, three-dimensional hollow-beam nanolattices have emerged as promising candidates that satisfy these requirements. However, their properties are maintained for only five stress cycles at strains below 25%. Korean researchers at Gwangju Institute of Science and Technology (GIST) demonstrate that alumina nanolattices with different relative density distributions across their height elicit a deterministic mechanical response concomitant with a 1.5 ~ 3.3 times higher electrical breakdown strength than nanolattices with uniform density. This study appears in the journal Advanced Materials in Nov. 15th, 2022. 

These density-variant nanolattices exhibit an ultralow-k of ~ 1.2, accompanied by complete electric and dielectric stability and mechanical recoverability over 100 cyclic compressions to 62.5% strain. We explain the enhanced insulation and long-term cyclical stability by the bi-phase deformation where the lower-density region protects the higher-density region as it is compresses before the higher-density region, allowing to simultaneously possess high strength and ductility like composites. This study highlights the superior electrical performance of the bi-phase nanolattice with a single interface in providing stable conduction and maximum breakdown strength.

Professor Kim said, "We expect our results to be used in flexible electronic device systems or high voltage systems used in electric vehicles, space, and aviation in the future.

Ultralow-k capacitors and their mechanical stress-strain relationship and self-recovering dielectric breakdown strength results during compressive deformation. 

[Reference] Kim J. et al., (2022) “Enabling durable ultralow-k capacitors with enhanced breakdown strength in density-variant nanolattices.” Advanced Materials

[Main Authors] Min-Woo Kim and Bong-Joong Kim (Gwangju Institute of Science and Technology), Max Lifson and Julia Greer (Caltech)

* Contact email : Professor Bong-Joong Kim (kimbj@gist.ac.kr)