Unveiling the Mechanical and Electrical Properties of Organic Single Crystals using the Wrinkling Instability
Marcos Reyes-Martinez (University of Massachusetts), Ashwin Ramasubramaniam (University of Massachusetts Amherst), Alejandro Briseno (University of Massachusetts Amherst), Alfred Crosby (University of Massachusetts Amherst)
Mechanics of Thin Films and Multilayered Structures
Tue 4:20 - 5:40
Salomon 203
The successful utilization of organic single crystals (OSCs) in semiconductor devices has allowed for the advent of a new generation of high-performance organic electronics. However, very little progress has been made towards their application in flexible and conformable devices. The aim of this presentation is to bring new understanding of the intrinsic mechanical properties of organic semiconductors and the effect of mechanical strains in charge transport phenomena. We utilize single crystals of the conjugated material rubrene as model systems. The long-range order in OSCs makes possible the study of the intrinsic physical properties without having to account for imperfections, grain boundaries, or impurities. The wrinkling instability is chosen as a metrology tool for the in-plane elastic constants due to the limited dimensions of crystals and the associated handling difficulty. In addition, Density Functional Theory with state-of-the-art van der Waals exchange-correlation functional is employed to obtain the nine independent elastic constants corresponding to orthorhombic rubrene. Good agreement between experiment and theoretical calculations is shown. Our results indicate a dependence of wrinkling wavelength on crystallographic direction resembling the well-known anisotropic electrical properties of rubrene. To elucidate the effects of mechanical strain on charge transport, single-crystal-field-effect transistors undergoing the wrinkling instability are demonstrated and investigated. This work is the first contribution quantitatively correlating crystal structure and the mechanical properties of rubrene and is the first to study electro-mechanical behavior in OSCs.