PENGARUH STONE-WALES DEFECT TEHADAP SIFAT OPTIK MONOLAYER h-BN MENGGUNAKAN DENSITY FUNCTIONAL THEORY

Priyo Prasetyo, NIM.: 21106020001 (2025) PENGARUH STONE-WALES DEFECT TEHADAP SIFAT OPTIK MONOLAYER h-BN MENGGUNAKAN DENSITY FUNCTIONAL THEORY. Skripsi thesis, UIN SUNAN KALIJAGA YOGYAKARTA.

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Abstract

Hexagonal boron nitride (h-BN) is a two-dimensional material that possesses a range of unique properties, including mechanical stability, chemical stability, thermal stability, semiconducting behavior, ultraviolet absorption, and biocompatibility. These characteristics give h-BN potential for applications across various fields, one of which is photonic devices. Photonic devices based on h-BN can be broadened and optimized through defect engineering, such as stone–wales defects, which can significantly alter the properties of h-BN. This study investigates the influence of stone–wales defects on the properties of monolayer hexagonal boron nitride (h-BN) through density functional theory (DFT) calculations. The objective is to analyze the geometric structure, electronic structure, and optical properties of monolayer h-BN with stone–wales crystal defects. The calculations employ the generalized gradient approximation (GGA) exchange-correlation functional based on the Perdew–Burke–Ernzerhof (PBE) formulation, with ultrasoft pseudopotentials. Convergence tolerance parameters are set to 10-5 eV/atom for energy, 0.03 eV/Å for maximum force, 0.05 GPa for maximum stress, and 0.001 Å for maximum atomic displacement. The Stone–Wales defect model is constructed by rotating one boron–nitrogen bond by 90°. Geometrically, this defect generates two pentagonal and two heptagonal rings, reduces the system's point group symmetry to C₁h, and causes variations in bond lengths and nearest-neighbour atomic distances. Stone-wales defects can form new energy levels in the electronic structure of monolayer h-BN, thereby reducing the electronic bandgap to 3.303 eV. In the optical properties, stone-wales defects cause redshift in the absorption to 382 nm, along with a reduction in the optical band gap to 3.238 eV and reduction absorption peak. These results suggest that stone–wales defects significantly alter the intrinsic properties of pristine monolayer h-BN, potentially enhancing its application in photonic devices, particularly for quantum emitter applications.

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