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Kimya Bilim Dalı

Permanent URI for this communityhttps://hdl.handle.net/20.500.12416/4838

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Browsing Kimya Bilim Dalı by Department "Çankaya Üniversitesi, Ortak Dersler, Kimya Bilim Dalı"

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    Development of a selective wet-chemical etchant for precise 3D sculpting of silicon enabled by infrared non-linear laser modification
    (2024) Zolfaghari Borra, Mona; Radfar, Behrad; Nasser, Hisham; Çolakoğlu, Tahir; Tokel, Onur; Turnalı, Ahmet; Demirtaş, Merve; Işık Taşgın, Dilek; Üstünel, Hande; Toffoli, Daniele; İlday, Fatih Ömer; Turan, Raşit; 169107
    Recently-demonstrated high-quality three-dimensional (3D) subsurface laser processing inside crystalline silicon (c-Si) wafers opens a door to a wide range of novel applications in multidisciplinary research areas. Using this technique, novel maskless micro-pillars with precise control on the surface reflection and coverage are successfully fabricated by etching the laser-processed region of the c-Si wafer. To achieve this, a particular selective wet chemical etching is developed to follow subsurface laser processing of c-Si to reveal the desired 3D structures with smooth surfaces. Here, we report the development of a novel chromium-free chemical etching recipe based on copper nitrate, which yields substantially smooth surfaces at a high etch rate and selectivity on the both laser-processed Si surface and subsurface, i.e., without significant etching of the unmodified Si. Our results show that the etch rate and surface morphology are interrelated and strongly influenced by the composition of the adopted etching solution. After an extensive compositional study performed at room temperature, we identify an etchant with a selectivity of over 1600 times for laser-modified Si with respect to unmodified Si. We also support our findings using density functional theory calculations of HF and Cu adsorption energies, indicating significant diversity on the c-Si and laser-modified surfaces.
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    Pyrrolizine-3-ones: Synthesis and evaluation of photophysical properties
    (2024) Isik Tasgin, Dilek; Bayraktar, Irem; 169107
    We describe a synthetic approach for pyrrolizine-3-one derivatives and their photophysical properties. These compounds are prepared by a series of reactions employing the substituted pyrroles in one-pot, two-step oxidation, and intramolecular cyclization processes. The photophysical properties of the synthesized compounds were studied by using UV–Vis and fluorescence spectroscopy in different solvents. Maximum absorbance peaks were observed around 306–416 nm and maximum fluorescence emission around 603–614 nm and 465–498 nm for pyrrolyl and N-methyl pyrrolyl substituents, respectively. The introduction of a pyrrolyl substituent had a significant impact on the Stokes shifts (192–206 nm) and quantum yield values ranged from 0.002 to 0.046.