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Although electrolyte gating has been demonstrated to enable control of electronic phase transitions in many materials, long sought-after gate-induced insulator-metal transitions in organic semiconductors remain elusive. To better understand limiting factors in this regard, here we report detailed wide-range resistance-temperature (R-T) measurements at multiple gate voltages on ionic-liquid-gated rubrene single crystals. Focusing on the previously observed high-bias regime where conductance anomalously decreases with increasing bias magnitude, we uncover two surprising (and related) features. First, distinctly cooling-rate-dependent transport is detected for the first time. Second, power law R-T is observed over a significant T window, which is highly unusual in an insulator. These features are discussed in terms of electronic disorder at the rubrene/ionic liquid interface influenced by (i) cooling-rate-dependent structural order in the ionic liquid and (ii) the intriguing possibility of a gate-induced glassy short-range charge-ordered state in rubrene. These results expose new physics at the gated rubrene surface, pointing to exciting new directions in the field.
Bibliographical noteFunding Information:
Work was supported by the MRSEC program of the National Science Foundation at the University of Minnesota under Award Number DMR-1420013. C.D.F. thanks S. Fratini and A. F. Morpurgo for stimulating discussions concerning possible charge ordering phenomena. X.R. thanks B. Tang for DSC measurements.
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Reporting period for MRSEC
- Period 5
PubMed: MeSH publication types
- Journal Article