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In this study, semitransparent lead films serve as substrates for depositing niobium pentoxide thin films, forming versatile electro‐optical devices. Using vacuum evaporation and ion sputtering techniques at ≈10−5 mbar, stacked layers of crystalline Pb and amorphous Nb2O5 are created. This process reduces free carrier absorption in Nb2O5 and forms Urbach tail states with a width of 0.91 eV. Pb/Nb2O5 thin films exhibit remarkable broadband absorption, exceeding 440% in the visible and 98% in the infrared. Moreover, Pb substrates induce a redshift in Nb2O5's energy bandgap. Electrical analysis using impedance spectroscopy on Pb/Nb2O5/Ag structures reveals their series/parallel resonance and bandstop filter properties. Notably, the bandstop filters exhibit reflection coefficient minima at a notch frequency of 1.66 GHz, with a bandwidth of 280 MHz, return loss of 26 dB, and voltage standing wave ratio of 1.13. These findings underscore the device's potential for wide‐ranging electro‐optical applications across the electromagnetic spectrum. [ABSTRACT FROM AUTHOR]

In the current study polycrystalline nanosheets of CrSe2 of thicknesses of 100 nm are deposited onto p - type silicon substrate by a vacuum evaporation technique under a vacuum pressure of 10–5 mbar. Experimental and theoretical structural investigations have shown the preferred growth of trigonal CrSe2. The unit cell parameters being a = b = 3.520 Å,c = 5.889 Å and P 3 ¯ m 1 164 fits well with the standards of trigonal CrSe2 structure. Nanosheets of chromium selenide displayed low defect density of the order of 1010 lines/cm2 along the a - and b axes. Surface morphology studies have shown that CrSe2 nanosheets is composed of spherical grains of average sizes of 200 nm. Optically the interfacing of the n– type CrSe2 nanosheets with p - type Si results in formation of a conduction and valence band offsets of 0.95 eV and 0.47 eV, respectively. These band offsets were found sufficient to allow running the Si/CrSe2 interfaces as pn junction devices. The devices displayed a biasing dependent rectification ratios (asymmetry). The ratios which reached value of 70 can be varied with the applied voltage. Deep analyses of the current transport mechanism of these rectifiers have shown the domination by thermionic and tunneling mechanisms under forward and reverse biasing conditions, respectively. Moreover the pn junction device showed features of band filters with cutoff frequency values suiting gigahertz technology making the device attractive for multifunction operations. [ABSTRACT FROM AUTHOR]

Herein, thin films of FeSe are coated onto glass and semitransparent Pb substrate of thicknesses of 200 nm. The produced glass/FeSe (GFS) and Pb/FeSe (PFS) are structurally, compositionally, and optically characterized. It is observed that Pb substrates induced the crystallinity of cubic FeSe and cubic PbSe. On average, 21% of the phases in FeSe films are identified as PbSe. Due to the strong orbital overlapping between Pb and FeSe, Pb substrate increases the light absorption, the dielectric constant, the optical conductivity, and the terahertz cutoff frequency by ≈150 %, 180 %, 263 %, and 101 %, respectively. In addition the direct and indirect energy bandgaps shrink from 2.49 and 2.80 to 2.41 and 2.50 eV, respectively. Moreover, treating GFS and PFS as terahertz optical resonators have shown that Pb substrates enhanced the drift mobility and increased the plasmon frequency making it adequate for 6G technology applications. An important feature of the PFS optical resonator is the stability of the terahertz cutoff frequency at 16 THz in the visible range of light. This feature together with the enhanced optical absorption in the visible light region makes the PFS films attractive for visible light communication technology. [ABSTRACT FROM AUTHOR]

In this work, iron selenide layers are deposited onto glass and lead substrates to perform as terahertz filters. The layers are deposited by the thermal evaporation technique under a vacuum pressure of 10–5 mbar. Glass/FeSe2 (GFS) and Pb/FeSe2 (PFS) films are structurally, morphologically and electrically characterized. The atomic composition of the GFS films contained excess selenium that reacted with Pb forming a PbSe layer. This layer induced the crystallinity of iron selenide. The preferred crystal structure of FeSe2 was cubic with cell parameters of a = b = c = 3.04 Å and space group P m 3 m . Lead substrates increased the room temperature electrical conductivity of GFS films from of 1.52 × 10 - 5 (Ω cm) - 1 to 6.88 × 10 - 2 (Ω cm) - 1 . Analyses of the electrical conduction mechanism in the temperature range of 25–330 K have shown that coating the films onto Pb substrates shifted the accepter level from 182 to 58 meV, decreased the degree of structural disorder, shorten the average hopping range from 59 to 19 Å and increased the density of localized states near Fermi level by two orders of magnitude. The conductivity of PFS films exhibited degenerate semiconductor characteristics in the temperature range of 120–28 K. This feature is followed by an evidence of exhibiting superconductivity at critical temperatures lower than 24 K. On the other hand the impedance spectroscopy measurements in the driving signal frequency domain of 0.01–1.0 GHz have shown that Pb/FeSe2/Ag interfaces can perform as band filters showing microwave cutoff frequency values reaching 100 GHz at driving signal frequency of 1.0 GHz. These band filters are ideal for 6G technology nominating PFS films for high frequency applications. [ABSTRACT FROM AUTHOR]

Photodetectors suitable for visible light communication (VLC) technology were fabricated and characterized in this study. The photodetectors were designed using two p-type stacked layers of SeO2 and SiO2, which were coated onto n - type Si thin wafers. These stacked layers were deposited in a vacuum medium under a pressure of 10–5 mbar using the thermal evaporation technique. p-SiO2 thin layer enriched the hole concentration of p-SeO2 layer forming p + n type heterojunction and prevented SeO2 from environmental contaminations. The microstructure, surface morphology, and photoelectrical properties of the n-Si/p-SeO2/p-SiO2 (SSS) detectors were explored. It was observed that the SSS detectors exhibited biasing and light power dependent asymmetry. The asymmetry varied in the range of 77–178 as the light power increased from zero to 77 mW. In addition, the SSS photodetectors demonstrated a current responsivity, external quantum efficiency, and specific detectivity reaching values of 123 mA/W, 15.6%, and 1.3 × 1010 Jones, respectively. These values are considered adequate for VLC technology. Practical tests have shown that the device can transmit wireless square-wave pulses with frequencies up to approximately 10–100 kHz. The growth and decay response times were found to be 1.15 ms and 0.89 ms, respectively. The features of the SSS detectors make them suitable for use as light-controlled current rectifiers and VLC detectors. [ABSTRACT FROM AUTHOR]

Magnesium selenide thin films are coated onto glass and semitransparent Pt substrates (nanosheets) by the vacuum evaporation technique under a vacuum pressure of 10−5 mbar. The effect of Pt nanosheets of thicknesses of 100 nm on the structural, compositional, optical, and electrical properties of MgSe is explored. It is found that platinum nanosheets enhance the light absorbability in the visible and infrared ranges of light. They slightly redshift the energy bandgap and decrease the dielectric constant. The strong interaction between Pt and MgSe increases the electrical conductivity by five orders of magnitude. Pt forms shallow impurity levels in the energy bandgap of MgSe allowing the tunneling process at the Pt/MgSe interfaces. Practically, a Pt/MgSe/Pt tunneling type device is fabricated and tested by the microwave impedance spectroscopy technique. It is found that Pt/MgSe/Pt devices can exhibit resonance–antiresonance and negative capacitance effects which are important in electronic circuits as parasitic capacitance cancelers, signal amplifiers, and noise reducers. In addition, evaluation of the cutoff frequency spectra has shown the ability of using the Pt/MgSe/Pt devices as microwave resonators appropriate for 5G/6G technologies. A cutoff frequency larger than 70 GHz can be achieved by imposing ac signal of amplitude of 0.10 V. [ABSTRACT FROM AUTHOR]

Herein, powders of SeO2 are subjected to hydraulic pressure in the range of 1.0–12 MPa and heating cycles in the range of 290–383 K. The pressure and temperature effects on the crystalline nature, plane orientations, structural parameters, surface morphology, composition, electrical resistivity, capacitance spectra and conductance spectra are explored. It is observed that hydraulic pressure value of 6.0 MPa is a critical value at which the tetragonal SeO2 grains prefer (020) plane orientation over (011) planes. The (020) plane orientations resulted in remarkable changes in the lattice parameters, structural parameters, electrical resistivity, capacitance and conductance spectra. In addition, the heating and cooling cycles of the samples pressed at 10 MPa have shown that the transition of the planes is permanent. The heated and cooled pellets displayed resonance–antiresonance in the capacitance spectra near 0.43 GHz. The resonance–antiresonance phenomena are accompanied with negative conductance effect near 0.43 GHz. The enhancements in the properties of SeO2 powders that are achieved via pressure and temperature effects make them appropriate for electronic circuit technological applications. [ABSTRACT FROM AUTHOR]

Herein, the effects of insertion of Ag2O nanosheets of thicknesses 25–75 nm between stacked layers of GeO2 on the structural, morphological, and optical properties of germanium dioxide are explored. While the stacking of GeO2/Ag2O/GeO2 layers does not alter the amorphous nature of the structure, significant effects on the transmittance, reflectance, absorption coefficient, Urbach's tails, and dielectric constant are observed. Silver oxide nanosheets successfully enhance the light absorbability of germanium dioxide in the visible and the infrared (IR) range of light. The light absorbability is increased by more than 12 times after the insertion of 75 nm‐thick Ag2O nanosheets. In addition, a widening in Urbach's tails and narrowing in the indirect bandgap of GeO2 are detected as a result of increasing Ag2O layer thickness. The dielectric constant and optical conductivity are also increased by ≈59.6% and 191.4% in the IR range of light. The enhancement in the optical properties of GeO2 that results from the insertion of Ag2O nanosheets makes germanium dioxide more appropriate for optoelectronic applications. [ABSTRACT FROM AUTHOR]

Herein, polycrystalline films of ZnSe which are coated onto Au substrates and recoated with amorphous layers of GeO2 are used as active material to perform as bandstop filters. The stacked layers of Au/ZnSe/GeO2 are coated under pressure of 10−5 mbar. The device is characterized by X‐ray diffraction, X‐ray photoelectron, X‐ray fluorescence, and impedance spectroscopy techniques. It is observed that when the device is contacted with carbon point contacts, it exhibits resonance–antiresonance phenomena near 1.0 GHz. The Au/ZnSe/GeO2/C devices display negative capacitance effect in the frequency domain of 0.96–1.80 GHz. Analyses of the conductivity and capacitance spectra in the frequency domain of 0.01–1.80 GHz reveal the domination of conduction by quantum mechanical tunneling below 0.58 GHz and by the correlated barriers hopping above 0.58 GHz. In addition, characterizations of the impedance, reflection coefficient, return loss (Lr) and voltage standing wave ratios (VSWRs) spectra of the device indicated ideal bandstop filter features. The notch frequency of the filter is 1.56 GHz. At this critical frequency, the Au/ZnSe/GeO2/C devices display ideal characteristics presented by VSWR of 1.0, Lr value of 28.9 dB. These features make the Au/ZnSe/GeO2/C heterojunction devices promising for use in telecommunication technology. [ABSTRACT FROM AUTHOR]