Abstract Herein, the structural, morphological, compositional, optical, electrical and dielectric properties of Bi1.5Zn0.92Nb1.5-6x/5WxO6.92 (BZN) solid solutions are reported. Tungsten substituted BZN ceramics which are fabricated by the solid state reaction technique exhibited solubility limits at substitution level below x=0.18. Remarkable engineering in the structural, optical, electrical and dielectric properties of the pyrochlore ceramics is achieved via W substitution. Namely, shrinkage in both of the lattice parameters and in the energy band gap accompanied with decrease in the microstrain, in the dielectric constant and in the electrical resistivity is observed upon increasing the W content below the solubility limit. The increase in the W content in the BZN ceramics enhances the densification of the pyrochlore and leads to higher light absorbability and larger crystallites growth. The temperature dependent electrical resistivity measurements has also shown that the pyrochlore exhibit thermal stability below 380 K.

InSe based heterojunction devices gain importance in optoelectronic applications in NIR range as multipurpose sensors. For this reason, InSe/Sb2Te3 heterojunctions are constructed as NIR sensors by the thermal evaporation technique. The structural, optical, dielectric and photoelectric properties of InSe/Sb2Te3 heterojunctions are explored by X-ray diffraction and ultraviolet-visible light spectrophotometry techniques. The structural analyses revealed the preferred growth of polycrystalline hexagonal Sb2Te3 onto amorphous InSe as a major phase. Optically, the coating of Sb2Te3 onto InSe enhanced the light absorbability of InSe by more than 18 times, redshifts the energy band gap, increased the dielectric constant by ~5 times and increased the optical conductivity by 35 times in the NIR range of light. A conduction and valance band offsets of 0.40 and 0.68 eV are determined for the InSe/Sb2Te3 heterojunction devices. In addition, the Drude-Lorentz fittings of the optical conductivity indicated a remarkable increase in the plasmon frequency values upon depositing of Sb2Te3 onto InSe. The illumination intensity and time dependent photocurrent measurements resulted in an enhancement in the photocurrent values by one order of magnitude. The response time of the devices is sufficiently short to nominate the InSe/Sb2Te3 heterojunction devices as fast responding NIR sensors suitable for optoelectronic applications.

Herein, cadmium bromide thin film devices are designed for possible use in communication technology. The 1.0 μ m thin layer of CdBr2 is sandwiched between two Au (1.0 μ m thick) layers using the thermal evaporation technique under a vacuum pressure of 10-5 mbar. The Au/CdBr2/Au devices are structurally morphologically and electrically characterized. It is observed that the hexagonal cadmium bromide exhibits large lattice mismatches with cubic Au substrates. The randomly distributed nano- rod like grains is accompanied with average surface roughness of ~26 nm. When an ac signal of low amplitude is imposed between the terminals of the Au/CdBr2/Au devices, a negative capacitance effect in the frequency domain of 10-1800 MHz is observed. In addition, analysis of the impedance spectra in the same domain has shown that the device behaves as band pass/stop filters suitable for 4G technology. The microwave based standard analysis of the Au/CdBr2/Au band filters have shown that it displays a notch ( f c o) frequency of 2.0 GHz. The cutoff frequency at f c o reaches 7.86 GHz. The features of the Au/CdBr2/Au devices nominate it for use as microwave resonators and as negative capacitance devices suitable for; 4G technology, noise reduction and for parasitic capacitance cancellation.

Abstract In this study, the design and characterization of CdO/InSe thin film transistors (TFT) that are grown onto Au substrates are investigated. The devices are also subjected to a vacuum annealing process at 300 oC to enhance the structure and electrical performance. It was observed that the growth of polycrystalline monoclinic In6Se7 phase of InSe is preferred at this annealing temperature when coated onto Au/CdO substrates. Electrically, noisy negative capacitance effect accompanied with resonance-antiresonance phenomena is observed in the capacitance spectra of the as prepared TFT devices. The annealing of the TFT devices reduced the noise in the capacitance, conductance, impedance, and reflection coefficient and return loss spectral responses. The heat treated TFT devices displayed low bandpass, high bandpass and bandstop filter characteristics in the studied frequency domain (0.01-1.80 GHz) indicating the applicability of these devices as radio wave-microwave resonators.

In this work, the optical dynamics and the structural properties of the zinc phthalocyanine which are coated onto 150 nm thick Au substrates are studied by the X-ray diffraction and optical spectrophotometry techniques. The Au/ZnPc interfaces appears to be strongly affected by the large lattice mismatches at the interface. It is observed that the coating ZnPc onto Au substrates increases the light absorbability by 4.7 and 128.2 times in the visible and infrared regions of light, respectively. Au substrates activated the free carrier absorption mechanism in the ZnPc thin films in the infrared range of light. In addition, the transparent Au substrates forced narrowing the energy band gap in both of the Q and B bands. It also increased the dielectric constant value by ~3.5 times in the IR range. The enhancements in the optical properties of ZnPc that resulted from the thin Au substrates make the ZnPc more suitable for optoelectronic, nonlinear optical applications and for electromagnetic energy storage in the infrared range of light.