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Exploring point defects in hexagonal boron‐nitrogen monolayers
Author(s) -
Korona Tatiana,
Chojecki Michał
Publication year - 2019
Publication title -
international journal of quantum chemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.484
H-Index - 105
eISSN - 1097-461X
pISSN - 0020-7608
DOI - 10.1002/qua.25925
Subject(s) - delocalized electron , vacancy defect , monolayer , crystallographic defect , boron , spectral line , density functional theory , impurity , atom (system on chip) , molecular physics , atomic physics , materials science , electronic structure , carbon fibers , chemistry , crystallography , computational chemistry , nanotechnology , physics , organic chemistry , astronomy , composite number , computer science , embedded system , composite material
A comprehensive theoretical study of selected point defects for a monolayer of hexagonal boron nitride ( h ‐BN) is presented. Two‐dimensional structures were simulated through large h ‐BN molecular clusters and used to examine various defects, like: atom vacancies, atom substitutions, or distortions of the hexagonal lattice. Since carbon contaminations are very common in the h ‐BN technology, a particular attention has been paid to carbon impurities. The calculations of IR spectra for the doped molecular clusters reveal the presence of additional frequencies, which in many cases correspond to defect‐bound modes. In particular, when two carbon atoms are close to each other, a localized stretching CC mode of a high intensity has been found, with a frequency value of about 100‐200 cm –1 higher than for collective BN stretch frequencies. Absorption UV‐Vis spectra obtained from time‐dependent density functional theory show that the inclusion of impurities results in an emergence of several low‐energy electronic excitations, from which some are localized on a defect, while other are delocalized. Energies of these excitations are strongly dependent on the defect type, and they range from about 0.7 to 6.1 eV for the lowest excitations. Based on UV‐Vis spectra we propose several candidates which could be responsible for the experimental 4 eV color band. These defects are built from two or four adjacent carbon atoms and have the lowest excitation ranging from 3.9 to 4.8 eV, which is strongly localized on the defect.