Large Spin Diffusion Length in an Amorphous Organic Semiconductor

Abstract

We directly measured a spin diffusion length (lambdas) of 13.3 nm in amorphous organic semiconductor (OS) rubrene (C42H28) by spin polarized tunneling. In comparison, no spin-conserved transport has been reported in amorphous Si or Ge. Absence of dangling bond defects can explain the spin transport behavior in amorphous OS. Furthermore, when rubrene barriers were grown on a seed layer, the elastic tunneling characteristics were greatly enhanced. Based on our findings, lambdas in single-crystalline rubrene can be expected to reach even millimeters, showing the potential for organic spintronics development.

Observation of a large spin-dependent transport length in organic spin valves at room temperature

“…The R p value was obtained at a magnetic field of 3,000 Oe. The calculation shows an MR ratio of 5.3% at 300 K, which is one of the highest MR ratios that have been reported at room temperature 7,8,[10][11][12][13] . Note that both the MR ratios and device resistance increased with decreasing measurement temperatures.…”

“…C 60 is stable and easily forms a high-quality molecular film via thermal evaporation. In particular, the hyperfine interaction in C 60 is considerably weak because of the absence of polarized hydrogen nuclei and the low natural abundance of 13 C nuclear spins in the C 60 molecule 11,12,14,15 . The weak hyperfine interaction has been predicted to increase the SDT length 28 , which has been demonstrated at low temperatures using a deuterated polymer as a spacer in organic spin valve devices 29 .…”

“…The observation of SDT in OSs in the hopping process has also been reported 2,3 in such materials as tris (8-hydroxyquinolinato) aluminium (Alq 3 ) and rubrene. However, most studies have only been carried out at low temperatures because of the evident reduction in the SDT length with increasing measurement temperatures until the MR effect finally disappears at room temperature 2,[13][14][15][16][17][18][19] . Thus, whether a large SDT length can be realized in OSs at room temperature remains unclear.…”

“…An MR ratio greater than 5% was observed at room temperature, which is one of the highest MR ratios reported to date 7,8,[10][11][12][13] . Most importantly, a large SDT length of approximately 110 nm was experimentally observed in the C 60 layer at room temperature.…”

“…Most importantly, a large SDT length of approximately 110 nm was experimentally observed in the C 60 layer at room temperature. This research may strongly motivate the development of spin-based organic devices, such as organic spin valves [1][2][3][4][5][6][7][8][9][10][11][12][13][14][15] and spin-based organic light-emitting diodes 20 .…”