arXiv subjects

Mustafa Urgen

Publications and source records attributed to Mustafa Urgen.

4 recordsLinked to original sources

arXiv2023

PyNanospacing: TEM image processing tool for strain analysis and visualization

The diverse spectrum of material characteristics including band gap, mechanical moduli, color, phonon and electronic density of states, along with catalytic and surface properties are intricately intertwined with the atomic structure and the corresponding interatomic bond-lengths. This interconnection extends to the manifestation of interplanar spacings within a crystalline lattice. Analysis of these interplanar spacings and the comprehension of any deviations, whether it be lattice compression or expansion, commonly referred to as strain, hold paramount significance in unraveling various unknowns within the field. Transmission Electron Microscopy (TEM) is widely used to capture atomic-scale ordering, facilitating direct investigation of interplanar spacings. However, creating critical contour maps for visualizing and interpreting lattice stresses in TEM images remains a challenging task. Here we developed a Python code for TEM image processing that can handle a wide range of materials including nanoparticles, 2D materials, pure crystals and solid solutions. This algorithm converts local differences in interplanar spacings into contour maps allowing for a visual representation of lattice expansion and compression. The tool is very generic and can significantly aid in analyzing material properties using TEM images, allowing for a more in-depth exploration of the underlying science behind strain engineering via strain contour maps at the atomic level.

cond-mat.mtrl-sci↗

arXiv2022

Can stress-induced changes in phonon frequencies of ZrSiO4 make it a potential IR spectroscopy-based pressure sensor?

Functional materials that can serve as high-pressure transducers are limited, making such sensor material sought after. It has been reported that hydrostatic pressures highly influence Raman shifts of ZrSiO4. Therefore, zirconium silicate has been suggested as a Raman spectroscopic pressure sensor. However, mass applications of a Raman-based sensor technology poses a wide range of challenges. We demonstrate that ZrSiO4 also exhibits pressure-dependent infrared (IR) spectra. Furthermore, the IR peaks of ZrSiO4 are sensitive to shear stresses and non-hydrostatic pressures, making this material a unique sensor for determining a variety of mechanical stresses through IR spectroscopy.

cond-mat.mtrl-sci↗

arXiv2021

Ab-initio calculation of point defect equilibria during heat treatment: Nitrogen, hydrogen, and silicon doped diamond

Point defects are responsible for a wide range of optoelectronic properties in materials, making it crucial to engineer their concentrations for novel materials design. However, considering the plethora of defects in co-doped semiconducting and dielectric materials and the dependence of defect formation energies on heat treatment parameters, process design based on an experimental trial and error approach is not an efficient strategy. This makes it necessary to explore computational pathways for predicting defect equilibria during heat treatments. The accumulated experimental knowledge on defect transformations in diamond is unparalleled. Therefore, diamond is an excellent material for benchmarking computational approaches. By considering nitrogen, hydrogen, and silicon doped diamond as a model system, we have investigated the pressure dependence of defect formation energies and calculated the defect equilibria during heat treatment of diamond through ab-initio calculations. We have plotted monolithic-Kröger-Vink diagrams for various defects, representing defect concentrations based on process parameters, such as temperature and partial pressure of gases used during heat treatments of diamond. The method demonstrated predicts the majority of experimental data, such as nitrogen aggregation path leading towards the formation of the B center, annealing of the B, H3, N3, and NVHx centers at ultra high temperatures, the thermal stability of the SiV center, and temperature dependence of NV concentration. We demonstrate the possibility of designing heat treatments for a wide range of semiconducting and dielectric materials by using a relatively inexpensive yet robust first principles approach, significantly accelerating defect engineering and high-throughput novel materials design.

cond-mat.mtrl-sci↗

arXiv2017

Switching dynamics of morphology-structure in chemically deposited carbon films -a new insight

Carbon is one of the most investigated materials and shows chaotic behavior in terms of evolving structure. Synthesizing carbon materials largely depend on the deposition technique, process parameters, condition of substrate surface and ratios of the gaseous chemistry. A variety of techniques have been employed to depositing carbon films from various gaseous mixtures to different substrate materials. In this study, carbon thin and thick films are discussed for different techniques known as hot filament chemical vapor deposition and microwave plasma chemical vapor deposition where their synthesis process has been explained in a new context. Here, we discuss attained dynamics of atoms or tiny grains amalgamating into a particular phase of grain or crystallite and electron-dynamics responsible for binding atoms in the formation of all sorts of tiny grains, grains and crystallites controlling overall morphology-structure of films thickness at few nanometers to several microns. Carbon atoms when in solid state, on amalgamation at flat surface result into bind under uniform electron-dynamics and when the amalgamation is at uneven surface, they result into bind under non-uniform electron-dynamics. Substrates under appropriate surface defects or abrasion result into an improved rate of nucleation of tiny grains, hence, their increased rate of growth. This study embarks on unexplored science of carbon films where in addition to localized process parameters nature of substrate also influence dynamics of formation of tiny clusters, grains and crystallites at their initial stage of formation. Our results and discussions enlighten us to revisit the nucleation and growth mechanisms of different sorts of films deposit at any scale and at any substrate surface constituting different composition.

cond-mat.mtrl-sci↗