The current conduction mechanisms (CCMs), temperature-sensitivities (S), energy-dependent interface traps (Nss), and origin of the intersection points in the forward bias (IF-VF) plots of the Al/Al2O3/Ge/p-Si heterostructure were investigated in wide temperature range of 90-420 K. Firstly, main electrical parameters, including reverse-saturation current (Io), ideality factor (n), zero-bias barrier-height (Phi Bo), and series-resistance (Rs) values, were extracted for each temperature. The lnIF-VF curves illustrate two distinct linear regimes at low and intermediate bias voltages. Despite the observed decline in n values as temperature rises, the corresponding Phi Bo values exhibit an upward trend. The conventional Richardson plots deviated from linearity at low temperatures, and the Richardson-constants (A*) value obtained from its linear part is quite lower than its theoretical value. Hence, Phi Bo- q/2 kT, Phi Bo- n, and n(kT)/q-(kT/q) correlations were plotted to seek indications of the Gaussian distribution (GD) of barrier heights (BHs) and tunneling mechanism. Temperate sensitivity (S = dV/dT) for 0.01, 0.10, 0.50, and 1 mu A was found as 2.30, 2.33, 2.34, and 2.35 mV/K, which indicated that the fabricated Al/Al2O3/ Ge/p-Si heterostructure is highly sensitive to temperature, rendering it suitable for use in temperature sensor applications. The observed crossing point at about 2.4V was explained by an increase in the apparent BH with temperature and the presence of Rs.

In this work, Al/Al2O3/Ge/p-Si heterostructures were fabricated by e-beam thermal evaporation. The EDX (energy dispersive X-ray spectroscopy) map visually obtained the basic distribution information in a two-dimensional graph. Three-dimensional atomic Force Microscope (AFM) analysis of the roughness of the Al/Al2O3/Ge/p-Si heterostructure shows that the Al2O3 particle has approximately 4.35 nm. Quantitative analysis via histogram plots for Al2O3 interlayer grown on p-Si shows a Gaussian-like distribution, and it has a sharp profile between 0 and 2 nm on silicon, located around 1.2 nm. The current-voltage (I-V) and capacitance-conductance-voltage (C-G/omega-V) measurements were used to investigate the electrical properties of the structure at room temperature. The I-V measurements revealed two distinct linear regions, attributed to barrier inhomogeneity and distribution of interfacial state/trap densities (D-it). For this reason, we obtained D-it distributions by considering the voltage dependence of the ideality factor n(V) in two regions. Diode parameters acquired through different methods are comparatively presented with a brief literature review. Then, the C-G/omega-V measurements were conducted across a broad frequency range (from 0.3 kHz to 3 MHz), and these measurements revealed notable alterations in the electrical parameters with regard to frequency. In order to probe interface states/traps, we employed the conductance/admittance method, which provided satisfactory information about trap lifetime, following the low-high frequency (LF-HF) and Hill-Coleman methods. The effects of these states/traps on the measurements according to voltage, frequency, and energy level (E-it-E-v) are discussed in detail.

Thermal imaging performance depends on many variables, ranging from the properties of the imaged object to atmospheric transmittance and system parameters. After clarification of the functional needs in system design or procurement, system parameters of the design that can meet these needs should be determined. Diagnosis/recognition from a distance is one of the foremost of these needs. The following briefly introduces the Forward Looking Infrared (FLIR) systems, followed by explanations for calculating the theoretical diagnostic range. After the theoretical information, sample systems are given, and high-performance FLIR systems are presented. To accurately analyze, measure and predict the performance of FLIR systems, a model should calculate summary performance measures of the system in the form of Minimum Resolvable Temperature (MRT) and Modulation Transfer Function (MTF) between a target and its background and estimate range for a given scenario electro-optical required for the performance evaluation of the system. The accuracy of these calculations will ultimately determine the accuracy of the model by which the performance of the FLIR system is evaluated.

All-dielectric metamaterials consisting of high-index, sub-wavelength, and periodically decorated arrays allow for efficient manipulation of electromagnetic permittivity and permeability with lower losses at the optical frequencies. In this study, we propose a planar multilayer structure composed of dielectric interlayers (Al2O3/Ge/ITO/Soda Lime Glass) to achieve perfect and broadband absorption of mid- and long-infrared (IR) wavelengths. Analyzing the spectral properties of the designed structure proved that it possesses exquisite importance in thermal application when considering the IR signature reduction in the long wavelength range, as well as the reduced radiated energy dissipation along with the undetected band and the requirements for IR camouflage. This intrinsic merit of dielectric metamaterials stems from their inherent selective absorption/emission. In that respect, Kirchhoff's law states that the emissive and absorptive powers of all bodies are similar for radiation of the same wavelength at the same temperature. The temperature difference may occur not only from the properties of the surfaces but also from the optical properties of materials and environmental conditions. Studying the thermal camouflage at different background temperatures found that the camouflage material substantially reduces the contrast between the target and the background. Beyond that, extensive assessments validated that the contrast in the resulting short tips is due to the differences in the reflective properties of the material and the background. Our simulations and experiments lay the groundwork for structuring cost-effective all-dielectric thermal camouflage metaplatforms with high performance and the strong potential to be employed in practical military and defense applications.

This paper investigates beam evolution and beam sizes variation of hyperbolic sinusoidal Gaussian (HSG) beam propagating in jet engine exhaust-induced turbulence. We find the received field by solving Huygens-Fresnel integral with a relevant power spectrum. Our results reveal that HSG loses its initial profile until 100m. Besides, beam with low displacement parameter value is more resistive against turbulence. In terms of beam size, beams with low Gaussian source size expand less as compared to the beams with larger Gaussian source size. In the light of our findings, optical systems in aircrafts like directed infrared counter measure (DIRCM) and laser designators can be developed.

All‐dielectric metamaterials that exhibit broadband absorption of infrared (IR) radiation are promising platforms for the development of modern and applied nanophotonic technologies ranging from precise biosensing to high‐resolution imaging and high photon‐yield light detection. Herein, bulk meta‐absorbers comprising dielectric layers to provide broadband absorption of mid‐IR light are structured and studied. Through computational investigations and experimental assessments, the geometric parameters of the metastructure are judiciously selected and the peak of absorption is tuned to encompass the mid‐wave IR (MWIR) to long‐wave IR (LWIR) wavelengths, where absorbance of over ≈95% is achieved in the conducted analyses. These results are obtained using numerical optimization to achieve the highest absorption peak values. Thus, based on the mechanistic understanding of the conducted study, the reported percentage is the highest possible absorption efficiency obtained by the absorber metastructure. Importantly, the projected meta‐absorber is polarization insensitive and performs consistently over a wide range of incidence angles. The engineered multilayer architecture based on artificial media provides new possibilities for the broadband manipulation and control of the IR light.

To investigate the capacitance and conductance characteristics of the Au/ZnO/n-GaAs (MIS) structures, impedance measurements were conducted at 200 kHz and 2 MHz frequency zones at ambient temperature. The experimental findings demonstrate that both the C and G / ω values have frequency dispersion in the accumulation zone. In addition, negative capacitance (NC) behavior has been found in the C - V graphs for high frequencies at roughly 1.5 V, and this behavior becomes more apparent as frequency increases. The minimum values of C observed at the accumulation zone correspond to the maximum values of G / ω , and this change between C and G / ω can be defined as inductive behavior. The impedance method was used to determine essential parameters that can significantly affect the performance of the structure, such as series resistance ( R s ) and concentration distribution of surface states ( N ss ). Also, some other parameters such as the Fermi energy level ( E F ), doping donor atom concentration ( N D ), and barrier height ( Φ B ) were determined from reverse bias C −2 versus V graphs for all frequencies.

In this work, both the Al-(p-Si) (MS) and Al-(Al2O3:PVP)-(p-Si) (MPS) structures were grown onto the same p-type Si wafer in the same conditions to determine the (Al2O3:PVP) organic-interlayer whether the MPS build improves performance or not. For this aim, first, X-ray diffraction (XRD) and field-emission scanning electron microscopy (FE-SEM) was used to investigate the structure of the (Al2O3-PVP) inter-layer. Secondly, both the current–voltage (I–V) and capacitance/conductance-frequency (C/G)-f measurements of them were performed at ambient temperature to the comparison of their electric and dielectric properties. Energy-dependence profile of surface states (Nss) was extracted from the positive bias I–V data by considering the voltage-dependence of BH and n. We found that the (Al2O3: PVP) inter-layer leads to a decrease in surface-states (Nss), ideality-factor (n), leakage-current, series-resistance (Rs), and increase in barrier (BH), shunt resistance (Rsh), rectification-ratio (RR = Ifor./Irev. at ± 6 V). Dielectric permittivity and loss (ε′, ε″), loss-tangent (tan δ), real & imaginary components of electric modulus (M′, M″), and ac-conductivity (σac) were extracted from the C-f and G-f measurements in the wide frequency range of 200 Hz-1 MHz at 1.5 V. The observed higher values in the ε′ and ε″ at lower frequencies for MS and MPS structures were attributed to the Nss and easy polarization of interlayer under electric field.

Dielectric metamaterials rationally engineered in both bulk and quasi-infinite planar fashions with optical properties beyond natural materials have emerged as promising platforms for the development of resonant architectures with sub-wavelength dimensions. The main criterion that distinguishes all-dielectric metamaterials from their plasmonic counterparts is that they exhibit negligible losses in the infrared and visible spectral regions, possessing an immense potential to be employed in the development of ultradense and efficient devices [1] , [2] . Advances in the nanofabrication and design of dielectric metamaterials enabled the miniaturization of photonic metadevices for coming generation technologies. In particular, dielectric-metamaterial coatings possess strategic applications in diverse technologies through controlling the characteristic reflection/transmission responses. In this study, multi-layer metamaterials were produced by coating with e-beam thermal evaporation system, which is one of the highly developed micro fabrication techniques, sequentially without vacuum breaking. Beyond that, the design, fabrication and characterization of Al 2 O 3 /Ge/ITO on Soda Lime Glass planar dielectric metamaterial and absorber platform as a novel and exquisite composite for multi-spectral absorption at infrared frequencies are presented. This includes the semi-infinite media, finite thickness dielectric layers and lossy dielectric layers. In the nanocavity architecture with three planar layers, the ITO layer acts as a reflective metal by providing a high absorption in the MWIR band. Moreover, in this configuration, the Al 2 O 3 layer performs as an antireflective coating (ARC) that matches air impedance with the impedance of Ge layer to reduce the reflection losses from the top surface, thus further enhancing the absorption [3] . To that end, extensive numerical and experimental assessments were conducted to illustrate multiple spectral absorption across the infrared spectrum across the mid-wave infrared (MWIR) to long-wave infrared (LWIR). Besides, the mechanism behind the absorption properties is demonstrated and argued. To further investigate the spectral behavior of the proposed structure, we performed numerical studies using finite-difference time-domain (FDTD) modelling. The influence of the thickness of the Al 2 O 3 layer on the spectral properties of the entire structure was analyzed and evaluated. Ultimately, the experimentally achieved electromagnetic wave propagation results using Fourier Transform Infrared System (FTIR) is verified by numerical calculations.

The surface states (N-ss), relaxation time (tau), and series resistance (R-s) values as a function of frequency for various bias voltage of the metal-insulator-semiconductor (MIS) structure were obtained by using the impedance measurements which is including capacitance (C) and conductance (G/omega) in the frequency range of 0.5-500 kHz at room temperature. C/G-V plots for each frequency have inversion-depletion-accumulation regions and show a strong frequency and voltage-dependent at low-moderate frequencies due to the existence of N-ss, R-s and Zinc Oxide (ZnO) interlayer. The parallel conductance (G(p)/omega) between -2 and 1.5 V shows a distinctive peak for almost every voltage and its position shifts to higher frequencies with increasing voltage. The values barrier height (Phi(B)), concentration of donor atoms (N-D), and depletion layer thickness (W D ) were calculated from the slope and intercept C-2-V plots as function of frequency. On the other hand, ideality factor (n), barrier-height (Phi(Bo)) and R-s of the structure were calculated from both the thermionic-emission (TE) and Cheung functions which are usually good consisted with each other, some little discrepancies in them were attributed to the voltage-dependent of them and the nature of the used technique.

In this study, an application-oriented approach was made by utilizing the absorptive properties of thin, periodic metal-dielectric multilayer materials based on their effective metamorphic properties and resonant response mechanism. Based on this mechanism, versatile, thin, polarization-independent, highly efficient ITO/Al 2 O 3 /ZnS/Al structure in a frequency range from UV to IR was designed, manufactured and tested. Thermally evaporated ITO thin films have been used as the substrate for the detector. For the preparation of sapphire nanostructures, first sapphire Nanopowders have been synthesized by sol-gel method and then the prepared powder annealed at 1200°C. The optical properties of the prepared materials used in the structure and the prepared thin films were defined by UV-Vis spectroscopy and a comparative investigation have been done. Also, the surface morphology, elemental analysis and structural properties of the materials used for fabrication of ITO/Sapphire/ZnS/Al superlattice have been investigated by scanning electron microscopy (SEM), X-ray diffraction (XRD), and energy dispersed X-ray (EDX). In the next step, sapphire nanostructures in the thin film form have been coated on ITO substrate using a simple casting method. A drop of an aqueous solution of Al 2 O 3 nanostructures was dispersed on the substrate, and the product was kept to form a thin film of the nanostructure after evaporation of water from the surface of the substrate a drop of sonochemically prepared ZnS nanostructure was dispersed using the same method. For the preparation of aqueous Al 2 O 3 and ZnS dispersion, 0.01 of each material in powder form dispersed in distilled water in order to provide well-dispersed material, the solution was kept under the ultrasonic bath.

The objective of this study is to investigate the effect of (Al2O3-PVP) on the electrical characteristics in Al/p-Si (MS) and Al/(Al2O3-PVP)/p-Si (MPS) structures. At the first stage of this study, the preparation mechanism of A2O3nanostructures and its structural and morphological properties have been reported. Finally, the fabricated Schottky structures on the base of (Al2O3-PVP) nanocomposites have been reported. The forward and reverse bias I-V measurements at room temperature were also have been investigated and compared with each other to see the effect of organic interfacial layer on the main electrical characteristics.