Spectra (UV-Visible, IR transmission) of Sc3+, Fe3+ and Cu2+ tri-doped LiNbO3 crystals with various [Li]/[Nb] ratios

The Sc:Fe:Cu:LiNbO3 crystals were grown with Fe[Formula: see text](0.3 wt.%), Cu[Formula: see text](0.1 wt.%) and Sc[Formula: see text](1 mol.%) by the Czochralski method with various [Li]/[Nb] ratios (0.946, 1.05, 1.20 and 1.38). The influence of the [Li]/[Nb] ratios on the defect structure of Sc:Fe:Cu:LiNbO3 crystals was analyzed by the UV-Visible spectra and IR transmission spectra. The spectra show that the absorption edge shift to the red with [Li]/[Nb] ratios enhancing. The Sc:Fe:Cu:LiNbO3 crystals with [Li]/[Nb] ratio of 1.05 is nearly stoichiometric. A new narrow OH[Formula: see text] associated vibrational peak at 3505 cm[Formula: see text] was revealed in Sc:Fe:Cu:LiNbO3 crystals with the ratio of [Li]/[Nb] = 1.38. It is attributed to the (Sc[Formula: see text])-(OH)[Formula: see text]. The results show that the defect structure changes with the [Li]/[Nb] ratios variation.

The Study on the Structural and Optical Properties of C-F Codoped Zinc Oxide from Ab Initio Calculations

The structural and optical properties of C-doped and C-F colonel Zoo compounds are investigated by using a first principle method with the plane wave pseudopotential calculations, based on the density functional theory(DFT), within generalized-gradient approximation (GGA). We discuss the structural properties by comparison with C-Al and C-Ga doped systems and the calculated results demonstrate that the c/a is smaller than C doped ZnO when incorporating F into the system and C-F codoping causes a smaller lattice mismatch compared with the C-Al codoped ZnO. Moreover, we focus on the complex dielectric function in order to investigate the optical properties. By analysing the results, we remark that the absorption edge shift the lower energy region(red shift) when incorporating C-F into ZnO compound.

Nanocrystalline SnO2 Particles and Twofold-coordinated Sn Defect Centers in Sol-gel-derived SnO2–SiO2 Glasses

Semiconductive nanocrystals of stannic oxide (SnO2) were precipitated in silica (SiO2) glasses synthesized via a sol-gel route. Kayanuma's equation, which describes the quantum confinement of an electron–hole pair in a semiconductive particle, well explained the absorption-edge shift due to the SnO2 nanocrystals in the optical absorption spectra. The adequate anneal of the SnO2–SiO2 glass ceramics in H2 gas led to the decomposition of the SnO2 nanocrystals and concurrently the production of twofold-coordinated tin atoms (Sn20 ) that provided a violet photoluminescence. The thermal behavior was studied with the x-ray diffraction measurement and photoluminescence and photoluminescence excitation spectroscopy.

Modification of the electronic properties of a-Si1-xCx:H by Fe+ ion implantation

The electrical and optical properties of hydrogenated amorphous silicon-carbide alloy films (a-Si1-xCx:H), modified by Fe+ ion implantation (D = 1×1016 - 1×1017 cm-2), have been investigated. Optical transmission spectra have been measured in the visible range (400-900 nm) and considerable absorption edge shift to the longer wavelength region has been registered, together with well-defined decrease of transmittance in the whole measured range. These effects are increased with the dose and are similar for samples with different carbon content (x1=0.08 and x2=0.15). Room temperature (RT) surface electrical conductivity is also increased by Fe+ implantation and the effect is most pronounced for the highest doses (D ~ 1017cm-2). The temperature dependence of the conductivity was measured in the temperature range from RT to 250 oC. The activation energy is considerably reduced and the effect is again strongest for the highest doses. From the above results we conclude that high doses Fe+ implantation in a-Si1-xCx:H affects both the localised states deep in the gap and the shallow states in the band tails.