PHYSICAL REVIEW B 106, 165301 (2022) Thickness-dependent electronic band structure in MBE-grown hexagonal InTe films A. V. Matetskiy , 1, 2 , * V. V. Mararov , 1 A. N. Mihalyuk , 1, 3, † N. V. Denisov , 1 S. V. Eremeev, 4 A. V. Zotov , 1 and A. A. Saranin 1 1 Institute of Automation and Control Processes, Far Eastern Branch of the RAS, Vladivostok 690041, Russian Federation 2 Istituto di Struttura della Materia, Consiglio Nazionale delle Ricerche, Trieste I-34149, Italy 3 Institute of High Technologies and Advanced Materials, Far Eastern Federal University, 690950 Vladivostok, Russia 4 Institute of Strength Physics and Materials Science SB RAS, 634021 Tomsk, Russia (Received 12 May 2022; accepted 19 September 2022; published 3 October 2022) Films of the hexagonal InTe with thicknesses from one to three tetralayers (TLs) were synthesized on the bilayer graphene/SiC by molecular beam epitaxy. Valence bands of the one- and two-TL-thick films were found to be flat-like near ¯ Ŵ point, but become parabolic for the three-TL-thick film and beyond. The band gap of the InTe was found to be equal to 2.1 eV for the single tetralayer and tends to reduce its size with thickness. The band structure calculations revealed a large spin splitting of the InTe single tetralayer lower conduction band with exclusive out-of-plane spin polarization. Bearing in mind inaccessibility of the hexagonal InTe in a bulk form, all above-mentioned findings open up a way for the further study of this perspective material. DOI: 10.1103/PhysRevB.106.165301 I. INTRODUCTION Layered chalcogenides provide a rich playground for a variety of condensed matter topics [1], such as semiconductor technologies [2], topological insulators [3], and superconduc- tors [4]. Recent interest to the two-dimensional (2D) materials in a context of green technologies, spintronics, and valleytron- ics pushes these materials even higher, as their quasi-2D nature provides an opportunity to isolate or grow individual layers that will remain stable. Absence of dangling bonds on the surface of these materials not only makes them relatively stable towards ambient conditions but also opens up a way for stacking of various functional layers in a controlled manner in order to construct artificial heterostructure with desired properties [5]. While electron band structure of the layered chalcogenides has an almost 2D character, it still depends on thickness, especially in an ultrathin region. Thus the III-VI materials (e.g., InSe, InS, and GaSe) were found to exhibit valence band shape transition from the bulk-like parabolic one to a Mexican-hat-like shape [6–9]. The III-VI materials were found to be perspective for use in solar energy conversion [10,11], field-effect transis- tors [12], broadband photodetection [11,13], photocatalysis [14,15], and thermoelectricity [16]. The band gap of these materials was found to strongly vary under applied field [17,18] that can be used in electronics and optoelectronics. The peculiar Mexican-hat-like dispersion of the ultrathin films provides 1D-like electronic density of states at the valence band edge [7]. In turn, a corresponding large number of conducting modes can enhance the thermoelectric properties [16,19]. Moreover, such sharp van Hove singularity near the * mateckij@iacp.dvo.ru † mih-alexey@yandex.ru Fermi level could lead to an exchange splitting of the elec- tronic states and associated tunable magnetism [20]. From the spintronic point of view, the III-VI materials were found to be promising in the tasks of the optical spin pumping [21], spin transfer [22], and spin-current generation [23]. While the ultrathin layers of hexagonal InSe and GaSe were successively synthesized and corresponding valence band shape transition was observed directly [24,25], the hexagonal phase of the InTe and GaTe appears to be less favorable than the monoclinic one. However, it was found that the hexagonal phase of GaTe can be realized in the thin films and flakes [26,27]. In the present paper, we report on the synthesis of the ultrathin hexagonal InTe film on bilayer graphene substrate by a molecular beam epitaxy (MBE) ap- proach. We explored the changes in the electronic structure as a function of film thickness starting from a single tetralayer, using angle-resolved photoemission spectroscopy (ARPES), scanning tunneling spectroscopy (STS), and ab initio calcu- lations. We found that similar to InSe, the hexagonal InTe exhibits transition from the almost flat Mexican-hat-like shape of the valence band at one- and two-layer-thick samples to the parabolic shape at the higher thicknesses. We also pre- sented detailed spin-resolved analysis of the InTe single TL electronic structure, in particular, peculiar spin texture of a conduction band valley in ¯ M point. II. EXPERIMENTAL AND CALCULATION DETAILS MBE growth of InTe films was conducted in the ultrahigh vacuum (UHV) chamber with a base pressure less than 5.0 × 10 −10 Torr, equipped with a reflection-high-energy electron diffraction (RHEED) facility. The bilayer graphene (BLG) was used as a substrate. It was formed by direct-current annealing at 1300 ◦ C of the 6H-SiC wafer. The BLG sub- strate was chosen instead of a monolayer graphene due to 2469-9950/2022/106(16)/165301(6) 165301-1 ©2022 American Physical Society