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Herein, the formation, structural, morphological, compositional, optical, dielectric, photoelectrical and electrical properties of the CdSe/GeO2 heterojunctions are explored. While the surface displayed formation of deficient GeO, the bulk of the films exhibited correct stoichiometry of GeO2 and CdSe. It is found that stacking of GeO2 onto CdSe enhances the crystallinity of CdSe by reducing the defects concentrations. It blue shifts the energy band gap of CdSe from 1.74 eV to 2.60 eV. The stacked layers of CdSe/GeO2 displayed conduction and valence band offsets of 2.34 eV and 1.23 eV, respectively. In addition, the Drude-Lorentz model analyses have shown that the coating of GeO2 onto CdSe, highly increases the drift mobility of charge carriers and tunes the plasmon frequency making it more appropriate for optoelectronic device applications. When exposed to light irradiation, an illumination intensity dependent photosensitivity is observed. The photoconduction mechanism is governed by the sublinear recombination with exponential trap distribution. Moreover, the capacitance –voltage characteristics of the device revealed metal-oxide-semiconductor field effect transistors (MOSFET) characteristics. The built in potential for this device under reverse biasing conditions reached 4.74 eV. WOS:000628707900003 Q2

In this work, the effect of glass/Ge and Au/Ge substrate on the structural, optical and electrical properties of the GaSe thin films is investigated by means of X-ray diffraction, ultraviolet-visible light spectrophotometry and impedance spectroscopy techniques, respectively. While the glass/Ge, glass/GaSe and glass/Ge/GaSe are observed to exhibit amorphous nature of structure, the Au/Ge, and Au/Ge/GaSe are of polycrystalline nature. The formation of the Ge/GaSe interface exhibited high conduction band offset of value of ∼0.90 eV and enhanced the light absorbability of GaSe at 1.47 eV by 80 times. In addition, the modeling of the dielectric spectra for the Ge/GaSe interface revealed optical conductivity parameters presented by scattering time at femtosecond level and improvement of the drift mobility. Moreover, the impedance spectroscopy measurements have shown that with the increasing frequency, the Au/Ge/GaSe/Yb interface exhibit increasing trend of variation in the resistance causing high impedance mode associated with negative capacitance values below 1300 MHz. The effect is completely reversed in the higher range of frequency. These features of the Ge/GaSe interface nominate it as plasmonic interface, microwave cavities and as voltage amplifiers in low power nanoscale devices.

In this work, we have explored the effects of the ytterbium nanosandwiching on the structural and optoelectronic properties of CdSe thin films. A ytterbium layer of thickness of 200 nm was sandwiched between two layers of CdSe (1.0 μ m ). The structural investigations have shown that the hexagonal structure of CdSe is deformed by 1.9% and 0.8% along the a and c - a x e s , respectively, by the inclusion of the Yb in the structure of CdSe. In addition, a systematic redshifts in the interference patterns of the optical transmittance and reflectance were observed. Accordingly, the optical absorption coefficient spectra of CdSe which displayed two energy gap values of 1.62 and 1.36 eV, are also redshifted. On the other hand, when exposed to blue light irradiation, the steady state and time dependent photocurrent analysis revealed a remarkable enhancement presented by a three orders of magnitude increase in the responsivity of CdSe upon Yb sandwiching. The photocurrent was observed to be limited by the saturation of the surface states and traps that causes longer relaxation constant compared to that of pure CdSe.

In this work, an indium layer of 50 nm thicknesses is sandwiched between two 500 nm thick Ga 2 S 3 layers. The effect of indium nansandwiching on the composition, structure, morphology, light absorbability, capacitance and reactance spectra, and temperature dependent electrical conductivity of the Ga 2 S 3 films are investigated by means of X-ray diffraction, scanning electron microscopy, energy dispersion X-ray spectroscopy, Raman spectroscopy, visible light spectrophotometry, impedance spectroscopy and current voltage characteristics. While the nansandwiched films are observed to exhibit an amorphous nature of structure with indium content of Owing to the nucleation mechanisms that take place during the film growth, the accumulation of some unit cells in groups to form grains should be a significant reason for the existence of many different sizes of grains in the nanosandwiched films (Alharbi and Qasrawi, 2016). O, the Raman spectra displayed three vibrational modes at 127.7, 145.0 and 274.3 cm −1 . It was also observed that the indium insertion in the structure of the Ga 2 S 3 shrinks the energy band gap by 0.18 eV. The nanosandwiched films are observed to exhibit a semiconductor −metal (SM) transition at 310 K. The SM transition is associated with thermal hysteresis that exhibited a maximum value of 16% at 352 K. This behavior of the nanosandwiched films nominate it for use as thermally controlled electric switches. In addition, the impedance spectral analysis in the range of 10–1800 MHz has shown a capacitance tunability of more than 70%. The measurements of the wave trapping property displayed a bandpass/reject filter characteristics above 1.0 GHz which allow using the Ga 2 S 3 /In/Ga 2 S 3 thin films as microwave resonator.

In the current study, we report the effect of insertion of a 200 nm thick Ge film between two layers of InSe. The Ge sandwiched InSe films are studied by means of X-ray diffraction technique, energy dispersion X-ray spectroscopy attached to a scanning electron microscope, optical spectrophotometry and light power dependent photoconductivity. It was observed that, The InSe prefers the growth of InSe monophase when deposited onto glass and the growth of γ−In2Se3 when deposited onto InSe/Ge substrate. The three layers interface (InSe/Ge/γ−In2Se3) exhibits a Ge induced crystallization process at annealing temperature of 200 °C. The optical analysis has shown that the InSe films exhibit a redshift upon Ge sandwiching. In addition, the conduction and valence bands offsets at the first interface (InSe/Ge) and at the second (Ge/γ−In2Se3) interface are found to be 0.55 eV and 1.0 eV, and 0.40eVand 1.38 eV, respectively. Moreover, the photocurrent of the Ge sandwiched InSe exhibited higher photocurrent values as compared to those of InSe. On the other hand, the dielectric spectral analysis and modeling which lead to the identifying of the optical conduction parameters presented by the plasmon frequency, electron scattering time, free electron density and drift mobility have shown that the Ge sandwiching increased the drift mobility values from 10 cm2/Vs to ∼42 cm2/Vs. The main plasmon frequency also increased from 1.08 to 1.68 GHz.

In this work, the X-ray diffraction, the Scanning electron microscopy, the energy dispersive X-ray, the Raman, The UV–vis light and the impedance spectral techniques are employed to explore the structural, vibrational, optical and electrical properties of the Au/InSe and Y/InSe thin film interfaces. It was shown that with its amorphous nature of crystallization, the InSe thin films exhibited n-type conductivity due to the 3% excess selenium. For this form of InSe, the only active Raman spectral line is 121 (cm −1 ). In addition to the design of the energy band diagram, the analysis the dielectric spectra and the optical conductivities were possible in the frequency range of 270–1000 THz. The modeling of the optical conductivities of the Au, Y, Au/InSe and Y/InSe with the help of Lorentz approach for optical conduction, assured that the conduction is dominated by the resonant plasmon-electron interactions at the metals and metals/semiconductors interfaces. It also allowed tabulating the necessary parameters for possible applications in terahertz technology. These parameters are the electron effective masses, the free electron densities, the electron bounded plasmon frequencies, the electron scattering times, the reduced resonant frequencies and the drift mobilities. On the other hand, the impedance spectral analysis of the Y/InSe/Au interfaces in the frequency range of 0.01–1.80 GHz, revealed negative capacitance effect associated with band filter features that exhibit maximum transition line at 1.17 GHz. This value nominates the interface as a member of filter classes in the gigahertz technology.

In this work, the effects of insertion of Ag slabs of thicknesses of 50, 100 and 200 nm between layers of arsenic selenide are reported. The glassy structured As2Se3 is characterized by X-ray diffraction, energy dispersive X-ray spectroscopy, scanning electron microscopy, ultraviolet-visible light spectrophotometry and impedance spectroscopy techniques. While the two stacked layers of As2Se3 exhibited high absorption and energy band gap values that nominate them for optoelectronic applications, the Ag slabs enhanced the light absorbability by 3.98, 5.77, 6.13 times and shrunk the energy band gap by 1.16 %, 7.40 % and 13.8 % for Ag slabs of thicknesses of 50, 100 and 200 nm, respectively. In addition, even though the As2Se3/As2Se3 layers exhibited negative capacitance effect in the frequency domain of 0.01–1.80 GHz, the insertion of Ag slabs removed the negative capacitance effect and forced the capacitance spectra to exhibit resonance at critical frequency of value of 0.23 GHz. The modeling of the capacitance spectra have shown that the geometrical capacitance is increased by one order of magnitude upon Ag slabs insertion. The dynamic capacitance is limited by electrons (holes) plasmonic interaction at the interface between the As2Se3/Ag/As2Se3 layers. Furthermore, the capacitance- voltage characteristics of the As2Se3/Ag/As2Se3 films confirmed the suitability of the devices to exhibit MOS device features. The characteristics of the stacked layers of As2Se3 indicate their multi-functionality as an optical absorbers/receivers and as microwave cavities.

In this work, the optical conduction mechanism in GaSe thin films was explored by means of dielectric spectral analysis in the 270–1000 THz range of frequency. The GaSe films which are found to be amorphous in nature are observed to follow the Lorentz approach for optical conduction. The modeling of the optical conductivity which takes into account the damped electronic motion resulting from the collision of photogenerated carriers with impurities, phonons and other damping sources allowed determining the optical conduction parameters. Particularly, an average carrier scattering time, a free carrier density, a reduced resonant frequency, a field effect mobility and an electron bounded plasma frequency of 0.142 (fs), 1.7 × 10 19 (cm −3 ), 875.8 (THz), 1.25 (cm 2 /V s) and 82.8 (THz), respectively, were determined. These parameters are promising as they indicate the applicability of GaSe in the technology of mid-infrared plasmonic nanoantennas. In addition, the dielectric optical signal which displayed a resonance peak at 500 THz seems to be attractive for use in passive modes operating optoelectronic devices like field effect transistors as they exhibit an increasing signal quality factor with decreasing incident light frequency

In this work, two stacked layers of ZnSe thin films are nanosandwiched with aluminum slabs of variable thickness in the range of 10–100 nm. The films which are studied by the X-ray diffraction and ultra-violet visible light spectroscopy techniques exhibit interesting features presented by extension of the cubic lattice parameter, increase in the grain size and reduction in both of the microstrains and defect density. The Al nanosandwiching successfully engineered the energy band gap through narrowing it from 2.84 to 1.85 eV. In addition, the Al nanosandwiching is observed to form interbands that widens upon increasing the Al layer thickness. It also changed the electronic transition nature from direct allowed to direct forbidden type. Moreover, remarkable enhancement in the light absorbability by 796 times is observed near 1.72 eV for two stacked ZnSe layers nanosandwiched with Al slab of thickness of 100 nm. The dielectric constant is also increased three times and the dielectric tunability vary in the range of 3.0-1.2 eV. The nonlinearity in the dielectric spectra and the engineering of the band gap that become more pronounced in the presence of Al slabs make the ZnSe more attractive for nonlinear optical applications.