# Epitaxial 2D HfSe2 Semiconductor/TaSe2 Metal van der Waals Heterostructure

C. Sthioul, Y. Chernukha, H. Koussir, Christophe Coinon, G. Patriarche, L.

Thomas, P. Roussel, B. Grandidier, Pascale Diener, X. Wallart

► To cite this version:

C. Sthioul, Y. Chernukha, H. Koussir, Christophe Coinon, G. Patriarche, et al., Epitaxial 2D HfSe2 Semiconductor/TaSe2 Metal van der Waals Heterostructure. 23rd European Workshop on Molecular Beam Epitaxy (EuroMBE 2025), Mar 2025, Auron, France. [hal-05039146](https://hal.science/hal-05039146v1)

HAL Id: hal-05039146

https://hal.science/hal-05039146v1

Submitted on 18 Apr 2025

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Distributed under a Creative Commons Attribution 4.0 International License
Epitaxial 2D HfSe₂ Semiconductor/TaSe₂ Metal van der Waals
Heterostructure

C. Sthioul,¹*, Y. Chernukha,¹ H. Koussir,¹ C. Coinon,¹ G. Patriarche,² L. Thomas,¹
P. Roussel,² B. Grandidier,¹ P. Diener,¹ and X. Wallart¹

¹Univ. Lille, CNRS, Centrale Lille, Univ. Polytechnique Hauts-de-France, Junia-ISEN,
UMR 8520 - IEMN, F-59000 Lille, France

² Université Paris-Saclay, CNRS, Centre de Nanosciences et de Nanotechnologies, 91120,
Palaiseau, Paris, France

² Unité de Catalyse et de Chimie du Solide (UCCS), Université de Lille, CNRS, Centrale
Lille, Université d'Artois, UMR 8181 - UCCS, F-59000 Lille, France

*E-mail: coretin.sthioul@univ-lille.fr

The formation of low resistance electrical contacts on 2D semiconductors remains a challenge and is
one of the bottlenecks for their application in devices. Although some successful attempts have been
reported [1], the standard contact fabrication by metal deposition often induces defects and damages to
the 2D materials, which degrade their intrinsic properties. One way to circumvent that relies on the use
of a metallic 2D material allowing a van der Waals interface with the 2D semiconductor. In this work,
we focus on such a system involving a metallic (TaSe₂) and a semiconducting (HfSe₂) transition metal
dichalcogenide (TMD). HfSe₂ seems promising due to its predicted high carrier mobility [2] whereas
TaSe₂ clearly exhibits a metallic character in its 2H phase [3]. Interestingly, a high work function has
been reported for both materials and make their association appealing for contact realization [4].

We first optimize the growth of TaSe₂ and HfSe₂ layers on Se-terminated GaP(111)B substrates. The layers are prepared by MBE under excess Se with a typical growth rate in the 3-4 ML/h range. HfSe₂ crystallizes in the 1T phase whose structural quality is rather independent on the growth temperature within the explored range (250-500°C). By contrast, multilayers TaSe₂ mostly exhibit the 3R and 2H polytypes with an improvement of the film crystallinity with increasing growth temperature and the layers grown between 250°C and 500°C have a resistivity comparable to those reported for bulk TaSe₂. In both cases, diffraction techniques clearly evidence the epitaxial relationships between the GaP substrate and the TMD layer. These latter are preserved during the growth of the HfSe₂/TaSe₂ heterostructure (Fig. 1) and the respective polytypes of each material are clearly identified in the stacking using scanning transmission electron microscopy (Fig. 2). Finally, photoelectron spectroscopy measurements show a n-type doping in HfSe₂ and a small work-function mismatch with TaSe₂ (Fig. 3).

The authors acknowledge the financial support from the Tunne2D (ANR-21-CE24-0030) and ADICT (ANR-22-
PEEL-0011) projects, as well as the French technological network RENATECH.

[1] Y. Wang et al., Nature 610, 61 (2022)

[2] W. Zhang et al., Nano Research 7, 1731 (2014)

[3] F. J. Di Salvo et al., Physical Review B 14(4), 1543 (1976).

[4] D. Tsoutsou et al., ACS Appl. Mater. Interfaces 8, 1836-1841 (2016)
<figure><img src="image_2.png" /><figcaption>Fig. 1: In-plane grazing incidence X-ray diffraction pattern of a TaSe<sub>2</sub>/HfSe<sub>2</sub>/GaP heterostructure. The HfSe<sub>2</sub> [1 0 0] // TaSe<sub>2</sub> [1 0 0] // [2-1-1] GaP epitaxial relationship is verified.</figcaption></figure>

<figure><img src="image_3.png" /><figcaption>Fig. 3: Band alignments in a TaSe<sub>2</sub>/HfSe<sub>2</sub> heterostructure grown on n-type GaP substrates, as derived from X-ray and ultra-violet electron spectroscopy measurements. The GaP electron affinity and band gap energies are from the literature [5,6].</figcaption></figure>

<footnote>[5] Levinshtein M. et al. (Ed.), *Handbook Series on Semiconductor Parameters*, vol.1, World Scientific, 104-124 (1996)</footnote>

<footnote>[6] Greenaway D. L. et al., *Journal of Physics and Chemistry of Solids* 26(9), 1445-1458 (1965)</footnote>