Epitaxial Growth of Molecular Semiconductors Crystals on the Single-crystal Surfaces Driven by the van der Waals Interactions

Yasuo Nakayama^1,2,3*

¹Department of Pure and Applied Chemistry, Tokyo University of Science, Noda, Japan
²Division of Colloid and Interface Science, Tokyo University of Science, Noda, Japan
³Research Group for Advanced Energy Conversion, Tokyo University of Science, Noda, Japan

* Presenter:Yasuo Nakayama, email:nkym@rs.tus.ac.jp

Heteroepitaxy is one of the most fundamental technologies forming the basis of modern semiconductor electronics. Atomically-controlled design of elemental materials of the semiconductors by “molecular beam epitaxy (MBE)” techniques has enabled new classes of low-dimensional materials of peculiar electronic properties as well as high-quality semiconductor heterostructures. In the field of organic molecular electronics, where molecular solids exhibiting semiconductor-like electric behaviors are used for emerging electronic applications of light-weight, flexible, and so on, heteroepitaxy is driven by the van der Waals interactions between the physisorbed molecules and the substrates. The weakness of the van der Waals forces greatly ease the necessary condition for the occurrence of epitaxial crystalline growth of the adsorbates, and thus physisorbed molecules had been reported to undergo epitaxial growth on various substrates such as transition-metal dichalcogenides (TMDCs) and molecular single-crystals [1]. Our group is engaged in MBE of n-type semiconductor molecules on the single-crystal surfaces of p-type molecules and has revealed epitaxial growth and the crystal structures for assorted combinations of molecular species [2]. In this contribution, we will discuss the formation mechanisms of the molecular epitaxial heterojunctions driven by the van der Waals interaction by reviewing especially the C₆₀ adsorbing systems [3]. Additionally, the very recent progress in C₆₀ epitaxial growth on the atomic layer PtTe₂ surfaces [4], as one of TMDCs, will also be introduced.

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[2] Y. Nakayama, et al., Materials (Basel) 15 (2022) 7119.
[3] Y. Nakayama, et al., ACS Appl. Mater. Interf. 8 (2016) 13499; idem, Adv. Mater. Interf. 5 (2018) 1800084; idem, Appl. Phys. Express, 16 (2023) 101001.
[4] M.-K. Lin, et al., Phys. Rev. Lett. 124 (2020) 036402; idem. ACS Nano, 16 (2022) 14918.

Keywords: van der Waals epitaxy, organic semiconductor, p-n junction, transition-metal dichalcogenides