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Heterostructures

It is made of two or more different materials, divided into vertical and transverse heterojunctions, and the lattice mismatch between different materials is required to be<< 5%.

  • Take GaAs/AlAs as (Lattice constants are similar):

    1. Import GaAs and AlAs crystal structures from the database respectively: click File→ Load From Online Database in the menu, select Ga and As elements and click search, select the structure which space group is F-43m then click load; Open it again, select Al and As elements and click search, select the structure which space group is F-43m then click load
    2. Build heterostructure: Click Build→ Build Heterostructure in the menu. Add the GaAs and AlAs structures, select the new lattice constant in the detailed settings.
DrawingBuild heterojunctions
DrawingParameter settings

  • Take the Fe/TiC colattice interface as an example (Lattice constants differ greatly):

    1. Import Fe and TiC body material structures from the database respectively: click File→ Load From Online Database in the menu, select Fe element and click search, select the structure which space group is Im-3m then click load; Open it again, select Ti and C elements and click search, select the structure which space group is Fm-3m then click load
    2. Calculate the lattice mismatch: read the lattice constant of the structure separately, in the example, Fe is a=b=c=2.840, TiC is a=b=c=4.336, and the lattice mismatch is (4.336-2.840)/4.336 ≈ 35%;
    3. Build supercell: Due to the large difference in lattice constants, higher mismatch can be treated by cell expansion to find the smallest common multiple of the lattice constant. Click Modify→ Build Supercell, and set the supercell size in the pop-up window;
    supercell sizeFe supercell lattice constantTiC supercell lattice constant
    1×1×12.8404.336
    2×2×25.6808.671
    3×3×38.52013.008
    4×4×411.36017.344
    5×5×514.20021.680
    1. Calculate the lattice mismatch: the cell expansion found that the lattice constant of 3×3×3 supercells of Fe and 2×2×2 supercells of TiC were similar, and the lattice mismatch was (8.671-8.520)/8.671 ≈ 1.7%;
    2. Build heterostructure: Click Build→ Build Heterostructure in the menu. Add the Fe and TiC supercell structures, select C for stacking direction, select the new lattice constant in the detailed settings.
DrawingBuild heterojunctions
DrawingParameter settings

  • Take the example of a two-dimensional heterojunction between MoS2/graphene layers (Large difference in lattice constants):

    1. Import single-layer graphene and MoS2 structures respectively: you can import from the online database, and perform Two-dimensional materials modeling
    2. Calculate the lattice mismatch: read the lattice constant of the structure separately, in the example, graphene is a=b=2.468, MoS2 is a=b=3.19, and the lattice mismatch is (3.19-2.468)/3.19 ≈ 23%;
    3. Build supercell: Due to the large difference in lattice constants, higher mismatch can be treated by cell expansion to find the smallest common multiple of the lattice constant. Click Modify→ Build Supercell, and set the supercell size in the pop-up window;
    supercell sizeGraphene supercell lattice constantMoS2 supercell lattice constant
    1×1×12.4683.19
    2×2×14.9366.38
    3×3×17.4049.57
    4×4×19.87212.76
    5×5×112.34015.95
    1. Calculate the lattice mismatch: the 4×4×1 supercell of graphene and the 3×3×1 supercell of MoS2 were similar, and the lattice mismatch was (9.872-9.57)/9.872 ≈ 3%;
    2. Build heterostructure: Click Build→ Build Heterostructure in the menu. Add the graphene and MoS2 monolayer supercell structures, select C for stacking direction, select Keep thickness constant for lattice matching method. To separate the layers of the heterostructure from each other, you need to set the buffer thickness in the detailed settings.
DrawingBuild heterojunctions
DrawingParameter settings