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Citation - WoS: 1
Citation - Scopus: 2
Scalable Growth of Optically Uniform Mows2 Alloys by Sulfurization of Ultrathin Mo/W Stacks
(Elsevier Sci Ltd, 2025) Panasci, Salvatore Ethan; Schiliro, Emanuela; Koos, Antal; Kutlu, Tayfun; Sahin, Hasan; Roccaforte, Fabrizio; Giannazzo, Filippo
Two-dimensional (2D) transition metal dichalcogenides (TMDs) ternary alloys, such as MoxW1-xS2, are very appealing for the possibility of continuously tuning their excitonic bandgap by the composition. However, the deposition of ultra-thin (monolayers or few-layers) alloys with laterally uniform composition on large area represents a main challenge of currently adopted synthesis methods. In this work, we demonstrated the growth of highly uniform Mo0.5W0.5S2 bi-layers on cm2 size SiO2/Si substrates by employing a simple and scalable approach, i.e. the sulfurization of a pre-deposited ultra-thin Mo/W stack at a temperature of 700 degrees C. Comparison of Mo(1.2 nm)/SiO2, W(1.2 nm)/SiO2, and Mo(1.2 nm)/W(1.2 nm)/SiO2 samples after identical sulfurization conditions revealed very different results, i.e. (i) a uniform monolayer (1L) MoS2 film, (ii) separated multilayer WS2 islands, and (iii) a uniform bilayer (2L) Mo0.5W0.5S2 film. This indicates how W surface diffusion and coalescence on SiO2 surface plays a main role in WS2 islands formation, whereas the reaction between S vapour with Mo films or Mo/W stacks represents the dominant mechanism for the formation of MoS2 and the MoWS2 alloy. Micro-photoluminescence (PL) mapping of the obtained 2L-Mo0.5W0.5S2 film showed an excellent uniformity of light emission on large area with an exciton peak at 1.97 eV, significantly blue-shifted with respect to PL emission of 1L-MoS2 at 1.86 eV. Such highly uniform optical properties make the grown MoWS2 alloy very promising for optoelectronic applications.
Novel Single Layers of Holey Crystalline Strcutures of Hf8s12 With Diverse Magnetic States
(Elsevier, 2025) Kutlu, Tayfun; Ercem, Onur; Yagmurcukardes, Mehmet; Sahin, Hasan
Motivated by recent experiments revealing the synthesizability of novel M 8 X 12 (where M=transition metal and X=S, Se, or Te) type holey structure transition metal chalcogenide crystals such as W8Se12, the structural, electronic and vibrational properties of the single layer Hf8S12 are investigated. Density functional theory (DFT) based total energy optimizations and dynamic stability analysis show that hafnium disulfide crystals with the known 1T phase are stabilized in the holey crystal structure represented by the chemical formula Hf8S12. While 1T-HfS2 crystals are nonmagnetic, holey Hf8S12 material exhibits 4 different magnetic states along with the ferromagnetic ground state. All these magnetic states display indirect or quasi-indirect narrow bandgap semiconducting behavior. Moreover, it is shown that the in-plane stiffness and Poisson ratio values of each possible magnetic phase of Hf8S12 has a distinctive angle dependency against applied strain. Its stable crystal structure and the magnetic diversity show that Hf8S12 can bean important candidate for magneto-mechanical applications.
Anisotropic Tunability of Vibrational Modes in Black Phosphorus Under Uniaxial Compressive/Tensile Strain
(Wiley, 2023) Li, Hao; Kutlu, Tayfun; Carrascoso, Felix; Şahin, Hasan; Munuera, Carmen; Castellanos Gomez, Andres
Strain engineering is a powerful strategy for tuning the optical, electrical, vibrational properties of 2D nanomaterials. In this work, a four-point bending apparatus is constructed to apply both compressive and tensile strain on 2D anisotropic black phosphorus flake. Further polarized Raman spectroscopy is used to study the vibrational modes of black phosphorus flakes under uniaxial strain applied along various crystalline orientations. Here, a strong anisotropic blue/redshift of A1g, B2g, and A2g modes is found under compressive/tensile strain, respectively. Interestingly, mode A1g exhibits the maximum/minimum shift while mode B2g and mode A2g present the minimum/maximum shift when the strain is applied along armchair/zigzag direction. Density functional theory calculations are carried out to investigate the anisotropic strain response mechanism, finding that the strain-induced regulation of the PP bond angle, bond length, and especially interlayer interaction has a giant influence on the Raman shift. A four-point bending apparatus is constructed to study the effect of uniaxial strain on the vibrational property of anisotropic black phosphorus. Particularly, strong anisotropy on the Raman blueshift/redshift rate upon compressive/tensile strain can be observed, which results from the strain-induced regulation of the bond angle, bond length, and interlayer interactions according to density functional theory calculation analysis.image

Scopus İndeksli Yayınlar Koleksiyonu / Scopus Indexed Publications Collection

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