Iron (Fe)-doped (0 to 4%) TiO(2) nano-crystalline (nc) films with the grain size of about 25 nm have been deposited on n-type Si (100) substrates by a facile nonhydrolytic sol-gel processing. X-ray diffraction measurements prove that the films are polycrystalline and present the pure anatase phase. X-ray photoelectron spectroscopy spectra indicate that the chemical valent state of Fe element is +3 and the Fe(3+) ions replace the Ti(4+) sites. The Fe dopant effects on the surface morphology, microstructure, and dielectric functions of the nc-Fe/TiO(2) films have been studied by atomic force microscope, ultraviolet Raman scattering and spectroscopic ellipsometry. With increasing Fe composition, the intensity of Raman-active mode B(1g) increases, while that of the A(1g) phonon mode decreases. The dielectric functions have been uniquely extracted by fitting ellipsometric spectra with the Adachi's dielectric function model and a four-phase layered model. It is found that the real part of dielectric functions in the transparent region and the optical band gap slightly decrease with the Fe composition due to the introduction of acceptor level Fe t(2g). Finally, the composition and temperature dependence of the surface and lattice defects in the Fe/TiO(2) films have been investigated by photoluminescence spectra in detail. At room temperature, the emission intensities decrease with increasing Fe compositions since the Fe incorporation could prolong the radiative lifetime and/or shorten the non-radiative lifetime. By analyzing the low temperature photoluminescence spectra, the intensities and positions of five emission peaks and shoulder structure can be unambiguously assigned. The phenomena could be reasonably explained by the physical mechanisms such as oxygen vacancies, localized excitons, self-trapped excitons, and indirect transitions, which are strongly related to the electronic band structure perturbed by the Fe doping.

Bismuth trioxide (Bi 2 O 3 ) ultrathin films were successfully synthesized on silicon substrates by means of atomic layer deposition (ALD) using Bi(thd) 3 (thd: 2,2,6,6-tetramethyl-3,5heptanedionato) and H 2 O as precursors. The optimum ALD window was about 270−300 °C, and an ALD-type growth mechanism via surface saturation reaction was identified; the growth rate was about 0.1 Å/cycle. The X-ray diffraction and high-resolution transmission electron microscopy investigation revealed that Bi 2 O 3 films crystallized into a predominant alpha phase above 250 °C. The resistivity at room temperature was about 1.2 × 10 6 Ω•cm, which is also proof of the α-phase of as-deposited Bi 2 O 3 films. In addition, a new method to obtain γ-Bi 2 O 3 film was discovered. The α-Bi 2 O 3 films (synthesized by ALD) transformed into metastable γ-Bi 2 O 3 with preferred orientation (222) after annealing above 512 °C, and γ-phase could persist at room temperature.

Iron-doped titanium dioxide nanocrystalline (nc-TiO 2 :Fe) films with the a composition from 2 to 10% have been deposited on Si(100) substrates by a facile nonhydrolytic sol-gel route. X-ray diffraction analysis shows that the films are polycrystalline and exhibit the pure tetragonal rutile phase structure. The Fe dopant effects on the surface morphology, microstructure, phonon modes, and dielectric functions of the nc-TiO 2 :Fe films have been investigated by atomic force microscopy, ultraviolet Raman scattering, far-infrared reflectance, and spectroscopic ellipsometry at room temperature. With increasing Fe composition, the first-order Ramanactive phonon modes E g , A 1g , and B 2g are shifted toward a lower frequency side of 10, 6, and 7 cm -1 , respectively. The four additional vibrations, which are strongly related to the surface structure of the films, can be observed due to the two-phonon scattering process. Moreover, the three infrared-active transverseoptic (TO) phonon modes E u (TO) can be located at about 183, 382, and 500 cm -1 , respectively. The dielectric functions of the films have been uniquely extracted by fitting the measured ellipsometric spectra with a fourphase layered model (air/surface rough layer/film/Si) in the photon energy range 0.73-4 eV (310-1700 nm). Adachi's dielectric function model has been successfully applied and reasonably describes the optical response behavior of the nc-TiO 2 :Fe films from the near-infrared to ultraviolet photon energy region. It is found that the real part of dielectric functions in the transparent region slightly decreases with increasing Fe composition. Furthermore, the optical band gap linearly decreases from 3.43 to 3.39 eV with increasing Fe composition due to the energy level of Fe t 2g , which is closer to the valence band. It is believed that the decrease of the optical constants and optical band gap for the nc-TiO 2 :Fe films with the Fe composition is mainly ascribed to the differences of the crystallinity and the electronic band structure, which can be perturbed by the transition metal introduction.

Ferroelectric lanthanum (La)-substituted bismuth titanate (Bi(4-x)La(x)Ti(3)O(12), BLT) nanocrystalline films with the composition range of 0 ≤x≤ 1 have been directly deposited on n-type Si (100) substrates by chemical solution deposition. The La substitution effects on the preferred orientation, surface morphology, phonon modes, emission bands and electronic band structures of the BLT films have been investigated by microscopy, Raman scattering, photoluminescence and spectroscopic ellipsometry at room temperature. X-Ray diffraction analysis shows that the films are polycrystalline and exhibit the pure perovskite phase structure. With increasing La composition, the (100)-orientation degree can be enhanced and the root-mean-square roughnesses slightly increase from 6.5 to 8.3 nm. It was found that the Raman-active mode A(1g)[Bi] at about 59 cm(-1) is unchanged while the B(1g) and A(1g)[Ti] phonon modes at about 648 and 853 cm(-1) are shifted towards higher frequency by about 36.6 and 8.4 cm(-1), respectively. Photoluminescence spectra show that the intensity of the peak located at about 2.3 eV increases with the La composition, except for the Bi(3)LaTi(3)O(12) film, due to the smallest grain size and oxygen vacancy defects. The optical constants of the BLT films have been uniquely extracted by fitting the measured ellipsometric spectra with a four-phase layered model (air/surface rough layer/BLT/Si) in the photon energy range of 0.73-4.77 eV. The Adachi dielectric function model has been successfully applied and reasonably describes the optical response behavior of the ferroelectric BLT films. Moreover, the film packing density decreases while the optical band gap linearly increases from 3.610 ± 0.066 to 3.758 ± 0.068 eV with increasing La composition. It is surmised that the phenomena are mainly ascribed to the variations of the electronic structure, especially for the conduction band, which is perturbed by the La doping.

Magnetocaloric effect is investigated in multiferroic Ba0.5Sr1.5Zn2(Fe0.92Al0.08)12O22 ceramic with Y-type hexagonal system. Three magnetic transitions, from alternating longitudinal conical to mixed conical at ∼240 K, to ferrimagnetic at ∼297 K, further to paramagnetic at ∼702 K, are unambiguously determined. Furthermore, obvious MCE is shown, and the maximum values of the magnetic entropy change and relative cooling power are evaluated to be 1.53 JKg−1K−1 and 280 JKg−1 for a field change of 7 T, respectively. In addition, inverse MCE is also observed, which might be associated with the first-order magnetic phase transition between two incommensurate longitudinal conical phases.