Browsing by Author "Özbey, Doğukan Hazar"

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Open Access
Investigation of anisotropic mechanical, electronic, and charge carrier transport properties of germanium-pnictogen monolayers
(Institute of Physics Publishing Ltd., 2022-02-04) Abboud, Mohammad; Özbey, Doğukan Hazar; Kılıç, M. E.; Durgun, Engin
Recently, novel two-dimensional (2D) GeP and GeAs systems have been fabricated by mechanical exfoliation and utilized in various applications. These developments have brought the 2D germanium-pnictogens, C2/m-GeX (X = N, P, As, Sb, and Bi) structures into the limelight. In this study, we systematically investigate the structural, mechanical, electronic, and charge carrier transport properties of GeX monolayers by using first-principles methods. Our results show that the considered systems are dynamically stable and possess anisotropic physical properties. Examined structures are found to be flexible, and their mechanical strength and stiffness decrease down the group-V, in line with the trends of the bond strength, cohesive energy, charge transfer, and electron localization function. Additionally, the zigzag in-plane direction is mechanically superior to the armchair direction. The electronic band structure calculations based on HSE06 hybrid functional with the inclusion of spin–orbit coupling indicate that GeX monolayers are either direct or quasi-direct semiconductors with band gaps lying within the infrared and visible spectrum. The estimated charge carrier mobilities are highly anisotropic and also differ significantly depending on the structure and carrier type. These unique properties render GeX monolayers as suitable 2D materials for flexible nanoelectronic applications.
Open Access
The Janus GePas monolayer for efficient photocatalytic water splitting
(2021-08) Özbey, Doğukan Hazar
The sun is considered an inexhaustible natural energy resource compared to fos-sil fuels. Regarding the limited amount of fuels such as coal and petroleum and their eﬀect on nature, any application that has the ability to harvest the sun-light and produce energy becomes extremely important. One of the potential mechanisms that can remedy the energy demand in the future is photocatal-ysis, and two-dimensional (2D) materials with suitable electronic and optical properties oﬀer new possibilities for photocatalytic applications. Although vari-ous 2D materials have hitherto been speciﬁed as adequate candidates, materials with high photocatalytic eﬃciency for water splitting are still minimal. In this regard, a novel 2D Janus GePAs monolayer is predicted and its capability for photocatalytic water splitting is examined by performing ﬁrst-principles density functional theory. The GePAs monolayer is shown to possess robust dynamic and thermal stability. The direct electronic band gap in the visible region and band edge positions of the strain-free and strained monolayers are revealed to be convenient for redox reactions in wide pH ranges. The low recombination proba-bility of charge carriers ensured by high and anisotropic carrier mobility enhances the material’s photocatalytic potential. Optical response calculations, including many-body interactions, exhibit signiﬁcant optical absorption capacity in the UV–visible range. Furthermore, ultra-low exciton binding energy facilitates dis-sociation into free electrons and holes, promoting photocatalytic reactions. Our study suggests GePAs monolayer is an ideal and remarkably promising material to be utilized in visible-light-driven photocatalytic applications.
Embargo
Promising anisotropic mechanical, electronic, and charge transport properties of 2D InN alloys for photocatalytic water splitting
(Elsevier, 2023-11-30) Özbey, Doğukan Hazar; Kilic, M. E.; Durgun, Engin
Two-dimensional (2D) materials with unique physical properties lead to new possibilities in future nanomaterial-based devices. Among them, 2D structures suitable to be the solar-driven catalyst for water-splitting reactions have become excessively important since the demand for clean energy sources has increased. Apart from the conventional crystals with well-known symmetries, recent studies showed that materials with exotic decorations could possess superior features in these kinds of applications. In this respect, we report novel 2D tetrahexagonal (th-) InN crystal and its ordered alloys In0.33 X0.67N (X = Al, Ga) that can be utilized as effective catalysts for water splitting reactions. Proposed structures possess robust energetic, dynamical, thermal, and mechanical stability with a versatile mechanical response. After a critical tensile strain value, all monolayers exhibit strain-induced negative Poisson's ratio in a particular crystal direction, making them half-auxetic materials. The examined materials are indirect semiconductors with desired band gaps and band edge positions for water-splitting applications. Due to their structural anisotropy, they have direction-dependent mobility that can keep the photogenerated charge carriers separated by reducing their recombination probability, which boosts the photocatalytic process. High absorption capacity in the wide spectral range underlines their potential performance. The versatile mechanical, electronic, and optical properties of 2D th-InN and its alloys, together with their remarkable structural stability, indicate that they can appropriately be exploited in the future for water splitting applications.
Open Access
Structural, electronic, vibrational, and thermoelectric properties of Janus Ge2⁢P⁢𝑋⁡(𝑋=N,As,Sb, and Bi) monolayers
(American Physical Society, 2024-07-08) Özbey, Doğukan Hazar; Varjovi, Mirali Jahangirzadeh; Sargın, Gözde Özbal; Sevinçli, Hâldun; Durgun, Engin
Two-dimensional (2D) Janus systems have garnered significant scientific interest owing to their novel properties and potential applications. The growing interest in these materials is driven by the idea that their structural asymmetry offers unprecedented opportunities for enhancing thermoelectric performance and unlocking groundbreaking advancements in energy conversion and waste heat utilization. In this context, we present a comprehensive study on the structural, vibrational, electronic, thermal, and thermoelectric properties of Janus Ge2PX(X = N, As, Sb, and Bi) monolayers, using first-principles calculations combined with the Landauer formalism. The suggested configurations exhibit dynamical stability and retain structural integrity even at elevated temperatures. Electronic structure calculations employing hybrid functionals (HSE06) with spin-orbit coupling reveal that Ge2PAs and Ge2PSb monolayers exhibit anisotropic characteristics as indirect semiconductors, while Ge2PN and Ge2PBi exhibit metallic behavior. We also compare the thermal, electronic, and thermoelectric transport properties of these proposed monolayers to binary 2D GeP in the ballistic limit. Notably, both Ge2PAs and Ge2PSb exhibit n-type figure of merit (ZT ) values exceeding 1 at 800 K, with their n-type ZT values surpassing that of GeP at room temperature. Our analysis underscores the distinctive structural and electronic properties of Ge2PAs and Ge2PSb monolayers, accompanied by their highly promising thermoelectric performance. These findings position them as strong candidates for energy harvesting and conversion applications.
Open Access
Two-dimensional Janus GePAs monolayer: A direct-band-gap semiconductor with high and anisotropic mobility for efficient photocatalytic water splitting
(American Physical Society, 2022-03-15) Özbey, Doğukan Hazar; Kılıç, M. E.; Durgun, Engin
Two-dimensional (2D) materials with suitable electronic and optical properties offer various possibilities for photocatalytic applications. Although various 2D materials have hitherto been specified as adequate candidates, materials with high photocatalytic efficiency for water splitting are still minimal. In this study, we predict a 2D Janus GePAs monolayer and examine its capability for photocatalytic water splitting by performing first-principles calculations. The GePAs monolayer is shown to possess robust dynamic and thermal stability. The direct electronic band gap in the visible region and band-edge positions of the strain-free and strained monolayers are revealed to be convenient for redox reactions in wide pH ranges. The low recombination probability of charge carriers ensured by high and anisotropic carrier mobility enhances the material’s photocatalytic potential. Optical response calculations, including many-body interactions, indicate significant optical absorption capacity in the UV-visible range. Furthermore, low exciton binding energy facilitates dissociation into free electrons and holes, promoting photocatalytic reactions. Our study suggests that the GePAs monolayer is an ideal and remarkably promising material to be utilized in visible-light-driven photocatalytic applications.