Спектры пропускания монокристаллов гибридных перовскитов MAPbI-=SUB=-3-=/SUB=- вблизи края фундаментального поглощения

The paper presents the transmission spectra of hybrid perovskite MAPbI3 single crystals near the fundamental absorption edge in a wide temperature range. The absorption coefficient α of the single crystal samples is estimated at a temperature T = 150 K for the light with a photon energy E = 1.6 eV and at T = 40 K for E = 1.8 eV. The obtained values turned out to be several orders of magnitude smaller than the values of α for thin-film samples known from the literature. A sharp shift of the fundamental absorption edge by ~ 100 meV was observed at a temperature T1 = 160 K of the structural phase transition from the tetragonal to the orthorhombic phase. The temperature hysteresis of the shift of the fundamental absorption edge near T1 was recorded, which is characteristic of a first-order phase transition.

LaTiO2N nanopowders (NPs) with low surface defect density via nitridation of flame made NPs retaining simple perovskite structure

LaTiO2N NP synthesized from flame made LaTiO3 NP exhibits less absorption background above the optical absorption edge than that synthesized from flame made La2Ti2O7 NP, suggesting a low surface defect density.

Electron Probe Microanalysis of Transition Metals using L lines: The Effect of Self-absorption

Electron microprobe-based quantitative compositional measurement of first-row transition metals using their L $\alpha$ X-ray lines is hampered by, among other effects, self-absorption. This effect, which occurs when a broad X-ray line is located close to a broad absorption edge, is not accounted for by matrix corrections. To assess the error due to neglecting self-absorption, we calculate the L $\alpha$ X-ray intensity emitted from metallic Fe, Ni, Cu, and Zn targets, assuming a Lorentzian profile for the X-ray line and taking into account the energy dependence of the mass absorption coefficient near the absorption edge. We find that calculated X-ray intensities depart increasingly, for increasing electron beam energy, from those obtained assuming a narrow X-ray line and a single fixed absorption coefficient (conventional approach), with a maximum deviation of $\sim$ 15% for Ni and of $\sim$ 10% for Fe. In contrast, X-ray intensities calculated for metallic Zn and Cu do not differ significantly from those obtained using the conventional approach. The implications of these results for the analysis of transition-metal compounds by electron probe microanalysis as well as strategies to account for self-absorption effects are discussed.

Forming of CdZnTe thin films grown by hot wall epitaxy and their properties

In this work morphological, X-ray structural and optical studies of CdZnTe films grown by hot wall epitaxy method at relatively low substrate temperatures were performed. Possible mechanisms and processes of self-organization that occur during the growth of such structures are considered. It is shown that at thickness of film more than 130 nm on the surface, large (lateral size 150 - 200 nm, height - up to 10 nm) and small crystals are observed. The thicknesses and energy of the band gap width of the CdZnTe films grown at different growth times were determined. It is shown that the film absorption edge in the transmission spectra depends on the film thickness and the reasons for the shift of the film absorption edge are discussed.

Optical Parameters of As-Deposited and Annealed (Ga0.3In0.7)2Se3 Thin Films

The (Ga0.3In0.7)2Se3 films deposited by the thermal evaporation technique are annealed in the inert atmosphere (argon) for 1 h at temperatures of 50, 100, and 150 ∘C. The spectral ellipsometry is applied for measuring the spectral dependences of the refractive and extinction coefficients of as-deposited and annealed (Ga0.3In0.7)2Se3 films. The optical transmission spectra, as well as the optical absorption spectra of (Ga0.3In0.7)2Se3 films, are studied depending on the annealing temperature. The optical absorption edge for annealed (Ga0.3In0.7)2Se3 films is shifted to the short-wavelength region and broadens, as the annealing temperature increases. Parameters of the Urbach absorption edge are determined for as-deposited and annealed (Ga0.3In0.7)2Se3 films. The spectral dependences of the refractive index are analyzed in the framework of the Wemple–DiDomenico model. The nonlinear increase of the energy pseudogap, Urbach energy, and refractive index with the annealing temperature are revealed.