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Hybrid‐Functional Study of Native Point Defects and Ti/Fe Impurities in α ‐Al 2 O 3
Author(s) -
Palakawong Nirawith,
Sukharom Siwakorn,
Limpijumg Sukit,
Jungthawan Sirichok,
Limkumnerd Surachate,
Boonchun Adisak,
Reunchan Pakpoom,
TThienprasert Jiraroj
Publication year - 2021
Publication title -
physica status solidi (b)
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.51
H-Index - 109
eISSN - 1521-3951
pISSN - 0370-1972
DOI - 10.1002/pssb.202000498
Subject(s) - sapphire , vacancy defect , impurity , crystallographic defect , materials science , doping , band gap , absorption (acoustics) , molecular physics , crystallography , analytical chemistry (journal) , atomic physics , optoelectronics , chemistry , optics , physics , laser , organic chemistry , chromatography , composite material
First‐principles calculations with the most accurate hybrid functional are used to investigate the effect of native point defects and Ti/Fe impurities on electrical and optical properties of α ‐Al 2 O 3 . For dominant native point defects, the Al vacancy ( V Al ), O vacancy ( V O ), and Al interstitial (Al i ) defects are considered, and it is found that only V Al defect provides the absorption line in the visible light region. Regarding Ti‐doped or Fe‐doped sapphire, it is found that their colors should be related to intra‐atomic d – d transitions. For the Ti–Fe pair, it is found that the ground‐state configuration is Ti III –Fe III , and its binding energy is very high, indicating that this pair can exist in high concentration. The calculated optical absorption energy associated with Ti–Fe pair is ≈1.92 and 1.84, which is appropriate for sapphire to be blue. It is, therefore, suggested that the intervalence charge transfer (IVCT) mechanism is the cause of blue color in blue sapphire.