High-Mobility Transistors Based on Single Crystals of Isotopically Substituted Rubrene-d₂₈

We have performed a comprehensive study of chemical synthesis, crystal growth, crystal quality, and electrical transport properties of isotopically substituted rubrene- d 28 single crystals (D-rubrene, C 42 D 28 ). Using a modified synthetic route for protonated-rubrene (H-rubrene, C 42 H 28 ), we have obtained multigram quantities of rubrene with deuterium incorporation approaching 100%. We found that the vapor-grown D-rubrene single crystals, whose high qualities were confirmed by X-ray diffraction and atomic force microscopy, maintained the remarkable transport properties originally manifested by H-rubrene crystals. Specifically, field-effect hole mobility above 10 cm 2 V –1 s –1 was consistently achieved in the vacuum-gap transistor architecture at room temperature, with an intrinsic band-like transport behavior observed over a broad temperature range; maximum hole mobility reached 45 cm 2 V –1 s –1 near 100 K. Theoretical analysis provided estimates of the density and characteristic energy of shallow and deep traps presented in D-rubrene crystals. Overall, the successful synthesis and characterization of rubrene- d 28 paves an important pathway for future spin-transport experiments in which the H/D isotope effect on spin lifetime can be examined in the testbed of rubrene.