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Dielectric functions of CVD–grown boron nitride from 1.1 to 9.0 eV by spectroscopic ellipsometry
Ist Teil von
Applied physics letters, 2021-03, Vol.118 (11)
Ort / Verlag
Melville: American Institute of Physics
Erscheinungsjahr
2021
Link zum Volltext
Quelle
AIP Journals
Beschreibungen/Notizen
The optical properties of CVD-grown hexagonal boron nitride (h-BN) and turbostratic BN (t-BN) layers on Al2O3 substrates are investigated by spectroscopic ellipsometry in the range from 1.1 to 9.0 eV at room temperature. The absorption spectra and dielectric functions (DFs) are characterized for analyzing critical points from near and above the bandgap (Eg) by analyzing the multilayer optical model. The real part ε1 and imaginary part ε2 of DFs for the BN layers are derived from the B–spline function under the Kramers–Kronig relation. The DFs show a significant difference between the h-BN and t-BN layers. The h-BN layer presents stronger and sharper spectra of DFs compared to the t-BN layer. Judging from extended Tauc's plot, the indirect Eg value of the h-BN layer is determined to be 5.97 eV, which is 0.15 eV larger than that of the t-BN layer.