Epitaxial Growth of Two-Dimensional Magnetic Lateral and Vertical Heterostructures

Abstract

Two-dimensional (2D) magnetic heterostructures provide ideal platforms for manipulating the spin degree of freedom, exploring interfacial coupling effects, and exploiting novel spintronic devices. However, controlled synthesis of magnetic heterostructures remains challenging, especially for magnetic lateral heterostructures. Here, we synthesize magnetic lateral and vertical heterostructures via chemical vapor deposition. The lateral and vertical antiferromagnetic−ferromagnetic non-van der Waals (vdWs) α-MnSe/Cr 2 Se 3 heterostructures can be selectively attained by tuning the vapor concentrations of precursors. The lateral heterostructures manifest sharp and contaminant-free interfaces without obvious extended defects. Moreover, a non-vdWs/non-vdWs lateral heterostructure at the 2D limit (∼1 nm) is grown. The vertical heterostructures exhibit uniform and highly ordered superlattices, indicating the high quality of the moireś uperlattices. We further apply this heteroepitaxial growth approach to synthesize non-vdWs/vdWs magnetic heterostructures, including α-MnSe/graphene and α-MnSe/MoS 2 . Our work paves the way for the scalable synthesis of two-dimensional lateral and vertical magnetic heterostructures for fundamental studies and potential device applications.

Stoichiometry-Tunable Synthesis and Magnetic Property Exploration of Two-Dimensional Chromium Selenides

“…Raman spectroscopy characterizations were first carried out to distinguish the structural information on the two types CVD-derived Cr x Se y nanosheets (Figure e,f). As for the H 2 -assisted (route-I) CVD-derived Cr x Se y nanosheets (∼20 nm thick), the characteristic Raman peaks appear at ∼123, ∼156, ∼172, ∼189, ∼205, ∼238, and ∼254 cm –1 (Figure e), matching well with that of Cr 2 Se 3 (∼152, ∼172, ∼183, ∼201, and ∼233 cm –1 ). , These minor deviations in peak positions should be ascribed to the thickness dependence of these Raman modes, as has been documented by previous reports. , In contrast, Raman peaks for non-H 2 -assisted (route-II) CVD-derived Cr x Se y nanosheets (∼17 nm thick) show seven primary Raman characteristic peaks at ∼76, ∼97, ∼148, ∼173, ∼199, ∼238, and ∼279 cm –1 (Figure f), distinct from that of previously reported CrSe (∼251 and ∼284 cm –1 ), CrSe 2 (∼169 and ∼250 cm –1 ), and Cr 2 Se 3 (∼152, ∼172, ∼183, ∼201, and ∼233 cm –1 ). , This possibly corresponds to the formation of another type Cr x Se y compound under the normal CVD route, namely Cr 3 Se 4 , as has been experimentally demonstrated in the following part of this work. Thickness-dependent Raman spectra of two types Cr x Se y are also displayed in Figure S4, and the different peak positions further confirm their diverse structures.…”