Micro-spacing in-air sublimation of submillimeter-scaled rubrene nanoribbons and nanosheets for efficient optical waveguides

Abstract

Convenient and low-cost fabrication of large-scaled 1-dimensional (1D) and 2-dimensional (2D) organic crystals is vital for potential optoelectronic applications such as light-emitting diodes, transistors, lasers and optical waveguides. In this work, we report a feasible approach to fabricate submillimeter-scaled rubrene nano-ribbon (1D) and nano-sheet (2D), conducted in a micrometer-confined space and in air condition. It was found that the 1D nano-ribbons and 2D nano sheets can be selectively fabricated by tuning the heating rate of the source holder on which rubrene powder was placed. A vapor-to-solid mechanism is established for the growth of rubrene crystals. It was revealed that the growth of 1D ribbons was determined by the diffusion of rubrene on substrate surface while the growth of 2D sheets was governed by the homogeneous nucleation. Selected area electron diffraction and x-ray diffraction analysis revealed that the rubrene nano-ribbons and nano-sheets share the same single-crystalline structure with an orthorhombic cell of a = 14.49 Å, b = 7.21 Å and c = 26.92 Å. Luminescence and optical transportation measurement revealed the quite low loss optical-loss coefficient at ~590 nm for both rubrene nano-ribbons and nano-sheets, indicating their promising applications as efficient optical waveguides.