Temperature dependent optical properties of Mn doped (Pb,Sr)TiO3 ferroelectric films in absorption region: Electron–phonon interaction

Abstract

Articles you may be interested inEffects of Mn doping on dielectric and ferroelectric properties of ( Pb , Sr ) TiO 3 films on (111) Pt / Ti / SiO 2 / Si substrates J.Hopping conduction and low-frequency dielectric relaxation in 5 mol % Mn doped ( Pb , Sr ) TiO 3 films J. Appl. Phys.The 2 mol % Mn doped Pb 0.5 Sr 0.5 TiO 3 films were fabricated on sapphire substrates by chemical solution deposition. The complex dielectric functions and optical parameters of the films determined by transmittance spectroscopy in a broad temperature range of 80-500 K were investigated. Apparent thermally-driven band-gap energy shrinkage, line-width of interband electron transition broadening and the Urbach band tail behaviors were observed. The results can be mainly correlated with the renormalization of electronic band structure and band-gap energy due to the electronphonon interaction, which is well established in terms of the Bose-Einstein model.

Annealing temperature and oxygen-vacancy-dependent variation of lattice strain, band gap and luminescence properties of CeO2nanoparticles

“…[37] The Urbach energy of each sample is calculated using the equation a ¼ a 0 exp[E/E u ], where a is the absorption coefficient, E is the photon energy and E u is the Urbach energy. [37][38][39][40] Since absorption coefficient is proportional to absorbance (A or F(R)), we can write F(R) in place of a. [40] For the calculation of Urbach energy, lnF(R) is plotted against photon energy, E and from the reciprocal of the slope we obtain the Urbach energy.…”

“…Second is the thermal disorder due to the coupling of lattice phonons with excitons/electron. [39,41] The high magnitude of E u in CV200 is owing to the presence of large numbers of structural defects on the lattice site, grain boundary, surface, etc. The magnitude of Urbach energy decreases in CA200 and CA600 due to the increase in grain size and removal of structural defects.…”

“…At high temperature, the excited phonons interact with electrons/excitons and enhance the thermal disorder resulting in the increase of E u (lattice site oxygen vacancies have negligible contribution to E u ). [39] 3.5. Photoluminescence study Figures 7(a)-(d) show the PL spectra of CeO 2 samples excited at 320 nm.…”

Detection of Luminescence Centers in Colloidal Cd\(_{0.3}\)Zn\(_{0.7}\)S Nanocrystals by Synchronous Luminescence Spectroscopy

“…Remarkably, the absorption spectrum of Cd 0.3 Zn 0.7 S NCs has a tail in the low energy region. This tail is originated by absorption transitions from valence band to the localized states, from the localized states to conduction band, and between the localized states [19][20][21], which have smaller energy in comparison to the optical band gap energy. In other words, the appearance of the absorption tail is related not only to the surface states, but also to the native defects as well as the additional defects in the interface region between the Zb and Wz phases of Cd 0.3 Zn 0.7 S NCs.…”

Interface controlled photovoltaic effect in epitaxial Pb(Zr,Ti)O3 films with tetragonal structure

“…27,28 This variation can be explained by the presence of Urbach tails in the bandgap. [29][30][31] The extension of these tails in the gap might be different from one metal to another. This can account not only for gap variations but also for the variations of the potential barrier at the electrode interface and, through this, of the signal magnitude.…”