Two-Dimensional Palladium Diselenide with Strong In-Plane Optical Anisotropy and High Mobility Grown by Chemical Vapor Deposition

Yiyi Gu, Hui Cai, Jichen Dong, Yiling Yu, Anna N. Hoffman, Chenze Liu, Akinola D. Oyedele, Yu Chuan Lin, Zhuozhi Ge, Alexander A. Puretzky, Gerd Duscher, Matthew F. Chisholm, Philip D. Rack, Christopher M. Rouleau, Zheng Gai, Xiangmin Meng, Feng Ding, David B. Geohegan, Kai Xiao

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Abstract

Two-dimensional (2D) palladium diselenide (PdSe2) has strong interlayer coupling and a puckered pentagonal structure, leading to remarkable layer-dependent electronic structures and highly anisotropic in-plane optical and electronic properties. However, the lack of high-quality, 2D PdSe2 crystals grown by bottom-up approaches limits the study of their exotic properties and practical applications. In this work, chemical vapor deposition growth of highly crystalline few-layer (≥2 layers) PdSe2 crystals on various substrates is reported. The high quality of the PdSe2 crystals is confirmed by low-frequency Raman spectroscopy, scanning transmission electron microscopy, and electrical characterization. In addition, strong in-plane optical anisotropy is demonstrated via polarized Raman spectroscopy and second-harmonic generation maps of the PdSe2 flakes. A theoretical model based on kinetic Wulff construction theory and density functional theory calculations is developed and described the observed evolution of “square-like” shaped PdSe2 crystals into rhombus due to the higher nucleation barriers for stable attachment on the (1,1) and (1,−1) edges, which results in their slower growth rates. Few-layer PdSe2 field-effect transistors reveal tunable ambipolar charge carrier conduction with an electron mobility up to ≈294 cm2 V−1 s−1, which is comparable to that of exfoliated PdSe2, indicating the promise of this anisotropic 2D material for electronics.

Original languageEnglish
Article number1906238
JournalAdvanced Materials
Volume32
Issue number19
DOIs
StatePublished - May 1 2020

Funding

Y.G. and H.C. contributed equally to this work. The optical characterization, STM measurements, and device fabrication were conducted at the Center for Nanophase Materials Sciences, which is a DOE Office of Science User Facility. The synthesis science and STEM characterization were supported by the U.S. Department of Energy, Office of Science, Basic Energy Sciences, Materials Science and Engineering Division. Y.G. acknowledges support from China Scholarship Council (CSC) Grant #201704910555. J.C.D. and F.D. acknowledge the support from the Institute for Basic Science (IBS-R019-D1) of Korea and the usage of IBS-CMCM super computing system, Cimulator.

FundersFunder number
U.S. Department of Energy
Office of Science
Basic Energy Sciences
Division of Materials Sciences and Engineering
China Scholarship Council201704910555
Institute for Basic ScienceIBS-R019-D1

    Keywords

    • PdSe
    • bottom-up synthesis
    • chemical vapor deposition
    • electron mobility
    • optical anisotropy

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