Jules Fraunié

For the past few years, 2D ferroelectric materials have attracted strong interest for their potential in future nanoelectronics devices. The recent discovery of 2D ferroelectricity in twisted layers of insulating hexagonal boron nitride [1-3], one of the most used 2D materials, opened the route to its integration into complex van der Waals heterostructures combining hybrid properties. Indeed, when two hBN flakes are stacked with a twist angle close to 0°, spontaneous out-of-plane electric polarization occurs on large reconstructed triangular domains with AB and BA arrangements [4].  Here we show that opposite polarizations in ferroelectric domains of a folded hBN layer can imprint local n and p doping in a semiconducting transition metal dichalcogenide WSe2 monolayer. We demonstrate that WSe2 can be used as an optical probe of ferroelectricity in hBN and show that the doping density and type can be controlled with the position of the semiconductor with respect to the ferroelectric interface. Our results establish the ferroelectric hBN/WSe2 van der Waals stacking as a promising optoelectronic structure.

[1] C. R. Woods, P. Ares, H. Nevison-Andrews, M. J. Holwill, R. Fabregas, F. Guinea, A. K. Geim, K.S. Novoselov, N. R. Walet, and L. Fumagalli, Charge-Polarized Interfacial Superlattices in Marginally Twisted Hexagonal Boron Nitride, Nat Commun 12, 1 (2021).

[2] M. Vizner Stern, Y. Waschitz, W. Cao, I. Nevo, K. Watanabe, T. Taniguchi, E. Sela, M. Urbakh, O. Hod, and M. Ben Shalom, Interfacial Ferroelectricity by van Der Waals Sliding, Science 372, 1462 (2021).

[3] K. Yasuda, X. Wang, K. Watanabe, T. Taniguchi, and P. Jarillo-Herrero, Stacking-Engineered Ferroelectricity in Bilayer Boron Nitride, Science 372, 1458 (2021).

[4] L. Li and M. Wu, Binary Compound Bilayer and Multilayer with Vertical Polarizations: TwoDimensional Ferroelectrics, Multiferroics, and Nanogenerators, ACS Nano 11, 6382 (2017)