Interfacial control of MnTe crystalline phase via molecular beam epitaxy

MnTe is attractive for a wide range of antiferromagnetic spintronic devices due to its unique magnetic properties with transitions occurring up to room temperature. An advantage and also a challenge are that MnTe has several polymorphs that occur at similar energy scales, thus selecting and achieving phase-pure growth of a targeted polymorph is difficult. In the bulk, the NiAs-phase MnTe is stable and is the prototype material predicted to be an altermagnetic. The ZnS-phase, stabilized only in thin film form, is a wide band gap (~3eV) semiconductor that is of interest for magneto-optical applications. Thus, understanding and controlling the growth of phase-pure MnTe thin films is critical. Here, we present how to controllably grow both phase-pure ZnS and NiAs MnTe thin films by molecular beam epitaxy on lattice-matched InP (111). The central mechanism that determines the polymorph is the termination of the InP substrates. Using a combination of structural, electronic, and spectroscopic probes, we show that this is effective at producing samples of high structural, electronic, and magnetic quality, which is the first step towards understanding and utilizing MnTe for an array of future studies and applications.