Quantitative characterization of interface stress using a nanoindentation technique for high performance flexible electronics

Abstract

Future electronics would be conformal, bendable and wearable, which requires the flexible devices possess exceptional electronic properties and mechanical stability during mechanical deformation. However, in flexible electronic systems, the quantitative characterization of interface stress between layers, which significantly impacts the mechanical properties and electronic performance of flexible devices, is still not available, which limits the optimization of device performance and deep understanding of the relevant mechanism in flexible electronic devices. Here, for the first time, a nanoindentation technique is introduced to precisely characterize the interface stress of flexible organic field effect transistors (OFETs), which are also broadly applicable for other flexible electronic devices. Moreover, the effect of interface stress on the mechanical stability of flexible OFETs is investigated. Noticeably, the results first illustrated that interface stress could be tuned by controlling the interface adhesion energy between layers. The improved interface stress would directly decrease the mechanical damage to the insulator/semiconductor interface charge transfer during bending deformation and eventually improve the mechanical stability and electrical performance of flexible devices. This study clearly demonstrates that the nanoindentation technique is a promising tool to precisely characterize the interface stress of flexible electronic systems and provides guidelines for the fabrication of high performance flexible electronics.