A.A. Albassam

Huge operation by energy gap of novel narrow band gap Tl1−x In1−x B x Se2 (B = Si, Ge): DFT, x-ray emission and photoconductivity studies

It is shown that narrow band gap semiconductors Tl1−x In1−x GexSe2 are able effectively to vary the values of the energy gap. DFT simulations of the principal bands during the cationic substitutions is done. Changes of carrier transport features is explored. Relation with the changes of the near the surface states is explored . Comparison on a common energy scale of the x-ray emission Se Kβ 2 bands, representing energy distribution of the Se 4p states, indicates that these states contribute preliminary to the top of the valence band. The temperature dependence of electrical conductivity and spectral dependence photoconductivity for the Tl1−x In1−x Ge x Se2 and Tl1−x In1−x Si x Se2 single crystals were explored and compared with previously reported Tl1−x In1−x Sn x Se2. Based on our investigations, a model of centre re-charging is proposed. Contrary to other investigated crystals in Tl1−x In1−x Ge x Se2 single crystals for x = 0.1 we observe extraordinarily enormous photoresponse, which exceed more than nine times the dark current. X-ray photoelectron core-level and valence-band spectra for pristine and Ar+-ion irradiated surfaces of Tl1−x In1−x GexSe2 (x = 0.1 and 0.2) single crystals have been studied. These results indicate that the relatively low hygroscopicity of the studied single crystals is typical for the Tl1−x In1−x Ge x Se2 crystals, a property that is very important for handling these quaternary selenides as infrared materials operating at ambient conditions.

Novel poly(aryl ether ketone) with electro-optic chromophore side chains for light modulators

Organic nonlinear optical materials have been widely explored because of their advantages in the design of materials with large electro-optic coefficients used in the fabrication of novel optoelectronic and telecommunication devices. However, the huge dipole–dipole interactions between organic nonlinear optical chromophores have limited further improvements in the electro-optic coefficients and long-term material stability. Here, a novel polymer based on poly(aryl ether ketone) was designed and prepared to enhance the electro-optic coefficients and achieve higher long-term stability. This novel poly(aryl ether ketone) has a relatively high glass transition temperature and offers active functional groups for the attachment of organic nonlinear optical chromophores. After attachment of nonlinear optical chromophores the materials showed higher chromophore loading density, less inter-molecular interaction, and suitable solubility. This resulted in better film-forming ability, higher electro-optics coefficients and better long-term stability. Quantum chemical simulations of the second order hyperpolarizabilities and ground sate dipole moments were done to understand the origin of the effects.