Kasuya Naotaka, Tsurumi Junto, Okamoto Toshihiro, Watanabe Shun, Takeya Jun
Material Innovation Research Center (MIRC) and Department of Advanced Materials Science, Graduate School of Frontier Sciences, The University of Tokyo, Kashiwa, Japan.
AIST-UTokyo Advanced Operando-Measurement Technology Open Innovation laboratory (OPERAND-OIL), National Institute of Advanced Industrial Science and Technology (AIST), Kashiwa, Japan.
Nat Mater. 2021 Oct;20(10):1401-1406. doi: 10.1038/s41563-021-01074-4. Epub 2021 Sep 6.
A highly conductive metallic gas that is quantum mechanically confined at a solid-state interface is an ideal platform to explore non-trivial electronic states that are otherwise inaccessible in bulk materials. Although two-dimensional electron gases have been realized in conventional semiconductor interfaces, examples of two-dimensional hole gases, the counterpart to the two-dimensional electron gas, are still limited. Here we report the observation of a two-dimensional hole gas in solution-processed organic semiconductors in conjunction with an electric double layer using ionic liquids. A molecularly flat single crystal of high-mobility organic semiconductors serves as a defect-free interface that facilitates two-dimensional confinement of high-density holes. A remarkably low sheet resistance of 6 kΩ and high hole-gas density of 10 cm result in a metal-insulator transition at ambient pressure. The measured degenerate holes in the organic semiconductors provide an opportunity to tailor low-dimensional electronic states using molecularly engineered heterointerfaces.
一种在固态界面处受到量子力学限制的高导电性金属气体，是探索在块体材料中无法获得的非平凡电子态的理想平台。尽管二维电子气已在传统半导体界面中实现，但二维空穴气（二维电子气的对应物）的实例仍然有限。在此，我们报告了在溶液处理的有机半导体中结合使用离子液体的双电层观察到二维空穴气。高迁移率有机半导体的分子平面单晶作为无缺陷界面，有助于二维限制高密度空穴。6 kΩ的极低表面电阻和10 cm的高空穴气密度导致在环境压力下发生金属-绝缘体转变。在有机半导体中测得的简并空穴为利用分子工程异质界面定制低维电子态提供了机会。
