Scopus İndeksli Yayınlar Koleksiyonu / Scopus Indexed Publications Collection

Permanent URI for this collectionhttps://hdl.handle.net/11147/7148

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Department: search.filters.department.Izmir Institute of TechnologySubject: search.filters.subject.2D materials

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  • Article
    Citation - WoS: 4
    Citation - Scopus: 4
    Ultra-Thin Double-Layered Hexagonal Cui: Strain Tunable Properties and Robust Semiconducting Behavior
    (Iop Publishing Ltd, 2024) Demirok, A. C.; Sahin, H.; Yagmurcukardes, M.
    In this study, the freestanding form of ultra-thin CuI crystals, which have recently been synthesized experimentally, and their strain-dependent properties are investigated by means of density functional theory calculations. Structural optimizations show that CuI crystallizes in a double-layered hexagonal crystal (DLHC) structure. While phonon calculations predict that DLHC CuI crystals are dynamically stable, subsequent vibrational spectrum analyzes reveal that this structure has four unique Raman-active modes, allowing it to be easily distinguished from similar ultra-thin two-dimensional materials. Electronically, DLHC CuI is found to be a semiconductor with a direct band gap of 3.24 eV which is larger than that of its wurtzite and zincblende phases. Furthermore, it is found that in both armchair (AC) and zigzag (ZZ) orientations the elastic instabilities occur over the high strain strengths indicating the soft nature of CuI layer. In addition, the stress-strain curve along the AC direction reveal that DLHC CuI undergoes a structural phase transition between the 4% and 5% tensile uniaxial strains as indicated by a sudden drop of the stress in the lattice. Moreover, the phonon band dispersions show that the phononic instability occurs at much smaller strain along the ZZ direction than that of along the AC direction. Furthermore, the external strain direction can be deduced from the predicted Raman spectra through the splitting rates of the doubly degenerate in-plane vibrations. The mobility of the hole carriers display highly anisotropic characteristic as the applied strain reaches 5% along the AC direction. Due to its anomalous strain-dependent electronic features and elastically soft nature, DLHC of CuI is a potential candidate for future electro-mechanical applications.
  • Article
    Citation - WoS: 5
    Citation - Scopus: 5
    Van Der Waals Heterostructures of Alas and Inse: Stacking-Dependent Raman Spectra and Electric Field Dependence of Electronic Properties
    (Elsevier B.V., 2024) Yayak,Y.O.; Topkiran,U.C.; Yagmurcukardes,M.; Sahin,H.
    In the present work, the electronic and vibrational properties of a van der Waals type heterostructure, composed of single layers of AlAs and InSe, are investigated using density functional theory (DFT)-based first-principles calculations. Vibrational analyses reveal that dynamically stable single layers of AlAs and InSe form van der Waals type heterostructure which is shown to exhibit stacking-dependent Raman spectra by means of the frequency shifts. According to our findings, a type-II band alignment with a direct band gap of 1.84 eV is found in the ground state stacking of AlAs/InSe vertical heterostructure, in contrast to the indirect band gap behaviors of each individual layer. Moreover, the application of an external vertical electric field shows that the both band alignment type and the electronic behavior of the heterostructure can be tuned. The heterostructure is found to exhibit direct to indirect band gap transition under negative electric field as well as a transition from type-II to type-I heterojunction under negative fields up to 0.3 V/Å. The stronger fields along the same direction results in overlapping of valence states of each layer and lead to a non-linear change of the energy band gap. Overall, the predicted van der Waals type heterobilayer of InSe and AlAs with stacking-dependent vibrational features and well-controlled electronic properties under external field is shown to be potential candidate for optical and optoelectronic applications. © 2024 Elsevier B.V.