Browsing by Author "Karabulut, Nahide"

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Fabrication and Characterization of Al/Ca2Nb3O10 and Al/ Ca2Nb3-xTaO10/P-Si Layered Perovskite Oxide-Based Heterojunction Diodes
(Elsevier Science SA, 2026) Karabulut, Nahide; Duman, Caglar; Bolen, Meltem Gor
Two-dimensional (2D) materials have garnered considerable interest for next-generation semiconductor device development due to their atomic-scale thickness and distinctive electronic, optical, and surface properties. Their high surface-to-volume ratio, low defect density, and tunable band structure render them particularly suitable for fundamental electronic components, such as p-n junction and semiconductor-based diodes. The ability of 2D materials to form vertical heterostructures confers advantages over conventional semiconductor diodes, including lower operating voltages and enhanced photosensitivity. In this study, Schottky type heterojunction diodes based on n-CNO/p-Si and n-CNTO/p-Si heterostructures were fabricated using the layered perovskite oxides KCa2Nb3O10 (CNO) and its tantalum-doped derivative KCa2Nb3-xTaxO10 (x = 1.5; CNTO). CNO and CNTO nanosheets were synthesized via solid-state reaction, proton exchange, and exfoliation, and were subsequently deposited onto p-type silicon substrates by spin coating. Current-voltage (I-V) characteristics of the fabricated diodes exhibited rectification ratios of 3,06 x 106 (CNO) and 4.77 x 106 (CNTO), with corresponding ideality factors of 1.91 and 1.78, respectively. The devices exhibited favorable performance characteristics, including low leakage current and high rectification ratios. In particular, CNTO-based structures demonstrated better electrical performance compared to CNO due to defect engineering facilitated by Ta doping. These findings underscore the promise of CNO and CNTO nanosheets as semiconductor materials for future optoelectronic applications.
Fundamentals of Two-Dimensional Ca2nb3o10 (Cno)
(Springer, 2025) Karabulut, Nahide; Demir, Busra Aydin; Karacam, Safiye; Duman, Caglar; Bolen, Meltem Gor
The two-dimensional material that emerged with the discovery of graphene has attracted great attention due to its interesting optical, electrical and mechanical properties. In recent years, especially two-dimensional (2D) perovskite oxides have attracted attention due to their ability to exhibit insulating, semiconducting or conducting properties. Dion-Jacobson perovskite oxides from the 2D perovskite oxide family have been intensively investigated due to their remarkable chemical and physical properties such as giant magnetoresistance, high-temperature superconductivity, ferroelectricity and photocatalytic activity. In this review, the properties, synthesis methods and device applications of calcium niobate nanosheets (KCa2Nb3O10 commonly referred to as CNO), one of the Dion-Jacobson perovskite oxides, are discussed. Promising results have been obtained in Ultraviolet (UV) detection and photocatalytic applications with CNO structures. However, when the literature was examined, no review article was found that examined CNO nanosheets in detail. It is thought that; this study will fill this gap in the literature.
Numerical Simulation of a Graphene/N-ws2 Hit Solar Cell
(IOP Publishing Ltd, 2025) Karabulut, Nahide; Aydin, Busra; Duman, Caglar
In this study, the WS2/a-Si:H/p-cSi heterojunction with intrinsic thin layer (HIT) solar cell structure was designed and simulated using the AFORS-HET software (version 2.5). Tungsten disulfide (WS2) stands out among two-dimensional materials due to its superior electrical and optical properties in photonic device applications. The optical and electronic properties of WS2 change as the thickness varies from bulk to monolayer. In this study, unlike other simulation studies on solar cells based on transition metal dichalcogenides in the literature, variation of the parameters such as the band gap, electron affinity, and refractive index with variation of the number of WS2 layers were taken into account. HIT solar cells are preferred among silicon-based solar cells due to their very high cell efficiencies. For this purpose, amorphous silicon (a-Si) was used as an interlayer. Additionally, graphene was used as the contact material due to its superior properties, and its performance was compared with ITO contacts. By optimizing the thicknesses and carrier concentrations of WS2, p-cSi, and the thickness of a-Si, a very high photovoltaic conversion efficiency of 29.64% was achieved. To the best of our knowledge, there is no study in the existing literature that investigates the integration of a WS2 layer in HIT solar cells. However, the findings of this study demonstrate that both the proposed device architecture and the WS2 material exhibit promising potential for future applications in optoelectronic technologies.