“…On the other hand, the non-shifting behavior of (~ 56 cm −1 ) in-plane vibration mode is well consistent with another report, where the Ga-Ga bond length is hard to vary in case of isotropic expansion initiated by a small biaxial strain (Fig. S1 ) 40 . Thus, this result reinforces our assumption about the existence of only biaxial strain in the samples.…”
Section: Resultssupporting
confidence: 93%
“…Basically, the strain induced by mechanical deformation could be categorized into four kinds: biaxial, armchair, zigzag, and shear strain. In the case of the unintentional strain generation during the 2D layered material growth, we assume that only biaxial strain contributes to the 2D GaSe strained-layers 40 . The strain-induced Raman frequency shift at the frequency of the m Raman active mode under a biaxial strain ( ε bxy ) could be derived through the mode-Grüineisen parameter as: 40 – 42 Figure 5 ( a ) Raman scattering spectra of GaSe bulk and GaSe films grown on various substrates, ( b ) An enlarged Raman spectra near E 2 2g peaks, and ( c ) Biaxial in-plane lattice strain of these GaSe layers extracted from the red-shift of Raman active mode.…”
Two-dimensional (2D) layered GaSe films were grown on GaAs (001), GaN/Sapphire, and Mica substrates by molecular beam epitaxy (MBE). The in situ reflective high-energy electron diffraction monitoring reveals randomly in-plane orientations of nucleated GaSe layers grown on hexagonal GaN/Sapphire and Mica substrates, whereas single-orientation GaSe domain is predominant in the GaSe/GaAs (001) sample. Strong red-shifts in the frequency of in-plane
vibration modes and bound exciton emissions observed from Raman scattering and photoluminescence spectra in all samples are attributed to the unintentionally biaxial in-plane tensile strains, induced by the dissimilarity of symmetrical surface structure between the 2D-GaSe layers and the substrates during the epitaxial growth. The results in this study provide an important understanding of the MBE-growth process of 2D-GaSe on 2D/3D hybrid-heterostructures and pave the way in strain engineering and optical manipulation of 2D layered GaSe materials for novel optoelectronic integrated technologies.
“…On the other hand, the non-shifting behavior of (~ 56 cm −1 ) in-plane vibration mode is well consistent with another report, where the Ga-Ga bond length is hard to vary in case of isotropic expansion initiated by a small biaxial strain (Fig. S1 ) 40 . Thus, this result reinforces our assumption about the existence of only biaxial strain in the samples.…”
Section: Resultssupporting
confidence: 93%
“…Basically, the strain induced by mechanical deformation could be categorized into four kinds: biaxial, armchair, zigzag, and shear strain. In the case of the unintentional strain generation during the 2D layered material growth, we assume that only biaxial strain contributes to the 2D GaSe strained-layers 40 . The strain-induced Raman frequency shift at the frequency of the m Raman active mode under a biaxial strain ( ε bxy ) could be derived through the mode-Grüineisen parameter as: 40 – 42 Figure 5 ( a ) Raman scattering spectra of GaSe bulk and GaSe films grown on various substrates, ( b ) An enlarged Raman spectra near E 2 2g peaks, and ( c ) Biaxial in-plane lattice strain of these GaSe layers extracted from the red-shift of Raman active mode.…”
Two-dimensional (2D) layered GaSe films were grown on GaAs (001), GaN/Sapphire, and Mica substrates by molecular beam epitaxy (MBE). The in situ reflective high-energy electron diffraction monitoring reveals randomly in-plane orientations of nucleated GaSe layers grown on hexagonal GaN/Sapphire and Mica substrates, whereas single-orientation GaSe domain is predominant in the GaSe/GaAs (001) sample. Strong red-shifts in the frequency of in-plane
vibration modes and bound exciton emissions observed from Raman scattering and photoluminescence spectra in all samples are attributed to the unintentionally biaxial in-plane tensile strains, induced by the dissimilarity of symmetrical surface structure between the 2D-GaSe layers and the substrates during the epitaxial growth. The results in this study provide an important understanding of the MBE-growth process of 2D-GaSe on 2D/3D hybrid-heterostructures and pave the way in strain engineering and optical manipulation of 2D layered GaSe materials for novel optoelectronic integrated technologies.
“…Several experimental and theoretical studies have demonstrated that 2D TMDs such as MoS 2 or WS 2 , which have an MX 2 stoichiometry, possess larger bandgaps than their bulk counterparts and certain indirect to direct bandgap transitions can occur with decreasing thickness, making them suitable candidates for optoelectronic devices. [11][12][13][14][15][16] Due to the fact that PTMCs possess a suitable bandgap for photovoltaics and transistors, [4][5][6][7][17][18][19][20][21][22] excellent thermal transport, 21,23 inherent flexibility, [24][25][26] and smaller exciton binding energies [4][5][6] make them viable substitutes for TMDs in device applications. In addition, it has been reported that applying strain, 24,26,27 creating heterostructures, [28][29][30][31] and chemical functionalization [32][33][34] can effectively tune the electronic and optical properties of monolayer GaSe, and it has been reported that GaSe can be used as a suitable substrate for other 2D materials.…”
Section: Introductionmentioning
confidence: 99%
“…[11][12][13][14][15][16] Due to the fact that PTMCs possess a suitable bandgap for photovoltaics and transistors, [4][5][6][7][17][18][19][20][21][22] excellent thermal transport, 21,23 inherent flexibility, [24][25][26] and smaller exciton binding energies [4][5][6] make them viable substitutes for TMDs in device applications. In addition, it has been reported that applying strain, 24,26,27 creating heterostructures, [28][29][30][31] and chemical functionalization [32][33][34] can effectively tune the electronic and optical properties of monolayer GaSe, and it has been reported that GaSe can be used as a suitable substrate for other 2D materials. 35,36 Although GaSe has been reliably synthesized and the lattice constant, quasiparticle gap, and optical gap have been experimentally characterized, 23,[37][38][39][40][41][42][43][44] results obtained...…”
“…These materials present a variety of electrical, mechanical, optical, and thermal properties differing according to their structure and composition, with clearly distinct Raman signatures according the number of layers, polytype, isostructural structures composed by different atoms within the family, and heterostructures . Information about bulk forms is of fundamental importance to the understanding of symmetry‐breaking perturbations at the nanoscale induced by uniaxial strain (breaking of in‐plane isotropy for materials with high lattice symmetry), exfoliation (breaking of the out‐of‐plane translational symmetry), and defects, among other procedures to be held soon in layered materials like jacutingaite. Knowledge of the effects of such procedures is important to understand how structural modifications can influence, for example, the performance of jacutingaite as a QSHI.…”
Jacutingaite (Pt2HgSe3) is a recently discovered layered platinum‐group mineral. Recent experimental studies have shown that it displays the properties of a quantum spin Hall insulator (QSHI), and theoretical studies indicate that its two‐dimensional monolayer is a QSHI with a robust topological gap of ∼0.5 eV. Jacutingaite is thus promising for potential applications to nanoelectronics and spintronics. The Raman spectrum of three‐dimensional bulk jacutingaite and the symmetries of its vibrational modes, fundamental for understanding structural modifications of this material, are still unexplored. Here, we address the zone‐center Raman optical phonons of bulk jacutingaite by experiments, symmetry, and first‐principles calculations. The improved synthesis used here provided crystals of higher purity and of micrometer size, allowing the study of single crystals. Polarized Raman spectroscopy was used to assign the symmetries of nine out of the 11 Raman‐active modes expected by group theory and their respective selection rules. The calculated wavenumbers of the Raman‐active modes, in addition to their atomic displacements, are in very good agreement with experiments. In addition, we discuss the use of different exchange correlation functionals within density functional theory, as local functionals and nonlocal functionals that best describe van der Waals interactions. The influence of the inclusion of spin–orbit coupling on calculated vibrational phonon wavenumbers and lattice parameters is commented, and it was found that the local density approximation provides a good description. Our results are of paramount importance to further exploitation of the effects of jacutingaite's structural modifications to tune its properties, as well as for its structural, optical, electronic, mechanical, and thermal applications.
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