Abstract
Regardless of the dissimilarity in the crystal symmetry, the two-dimensional GaSe materials grown on GaAs(001) substrates by molecular beam epitaxy reveal a screw-dislocation-driven growth mechanism. The spiral-pyramidal structure of GaSe multi-layers was typically observed with the majority in ε-phase. Comprehensive investigations on temperature-dependent photoluminescence, Raman scattering, and X-ray diffraction indicated that the structure has been suffered an amount of strain, resulted from the screw-dislocation-driven growth mechanism as well as the stacking disorders between monolayer at the boundaries of the GaSe nanoflakes. In addition, Raman spectra under various wavelength laser excitations explored that the common ε-phase of 2D GaSe grown directly on GaAs can be transformed into the β-phase by introducing a Se-pretreatment period at the initial growth process. This work provides an understanding of molecular beam epitaxy growth of 2D materials on three-dimensional substrates and paves the way to realize future electronic and optoelectronic heterogeneous integrated technology as well as second harmonic generation applications.
Highlights
Lack of studies on quasi-van der Waals epitaxy of GaSe grown on commercial substrates that have inequality of surface symmetry to GaSe such as Si(001) and GaAs(001) results in inflexibility in controlling crystal quality, area, especially, phase of the materials
Large-scale spiral-pyramidal structure of GaSe multilayers was observed from atomic force microscopy (AFM) images as a result of screw-dislocation-driven (SDD) growth mode
The comprehensive analyses including high-resolution X-ray diffraction (HR-XRD), Raman scattering, temperature-dependent photoluminescence (PL), and high-resolution transmission electron microscopy (HR-TEM) exposed that the ε-phase dominance and the strains of the GaSe multi-layers were originated from the SDD growth mode
Summary
Large-scale spiral-pyramidal structure of GaSe multilayers was observed from atomic force microscopy (AFM) images as a result of screw-dislocation-driven (SDD) growth mode. The comprehensive analyses including high-resolution X-ray diffraction (HR-XRD), Raman scattering, temperature-dependent photoluminescence (PL), and high-resolution transmission electron microscopy (HR-TEM) exposed that the ε-phase dominance and the strains of the GaSe multi-layers were originated from the SDD growth mode.
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