Filament-to-dielectric band alignments in $$\hbox {TiO}_{2}$$ and $$\hbox {HfO}_{2}$$HfO2 resistive RAMs

The next-generation nonvolatile memory storage may well be based on resistive random access memories (RRAMs). \(\hbox {TiO}_{2}\) and \(\hbox {HfO}_{2}\) have been widely used as the resistive switching layer for RRAM devices. However, the electronic properties of the filament-to-dielectric interfaces are still not well understood yet, compared to those of the electrodes and the dielectric. In this work, we study the electronic structures of three typical filament and dielectric structures, \(\hbox {Ti}_{4}\hbox {O}_{7}/\hbox {TiO}_{2}\), \(\hbox {Hf}_{2}\hbox {O}_{3}/\hbox {HfO}_{2}\) and \(\hbox {Hf}/\hbox {HfO}_{2}\), using ab initio calculations. We implement the GGA-1/2 method, which rectifies the band gaps of GGA through self-energy correction. Our calculation predicts an ohmic contact for the \(\hbox {Ti}_{4}\hbox {O}_{7}/\hbox {TiO}_{2}\) interface, where the defective \(\hbox {Ti}_{4}\hbox {O}_{7}\) phase was experimentally identified as the filament composition in \(\hbox {TiO}_{2}\). However, there is a finite Schottky barrier existing in either \(\hbox {Hf}_{2}\hbox {O}_{3}/\hbox {HfO}_{2}\) interface (1.96 eV) or \(\hbox {Hf}/\hbox {HfO}_{2}\) interface (0.61 eV), the two probable filament–dielectric configurations in hafnia-based RRAM. Our results suggest that the distinct filament-to-dielectric band alignments in \(\hbox {TiO}_{x}\) and \(\hbox {HfO}_{x}\) systems account for the much larger resistance window for the latter.     

Structural,electrical and optical properties of $$\hbox {InGaZnO}_{4}$$ and $$\hbox {In}_{29}\hbox {Sn}_{3}\hbox {O}_{48}$$In29Sn3O48: a first-principles study

First-principles calculations were performed to investigate the electrical and optical properties of \(\hbox {In}_{29}\hbox {Sn}_{3}\hbox {O}_{48}\) with Sn-doped \(\hbox {In}_{2}\hbox {O}_{3}\) and \(\hbox {InGaZnO}_{4}\) (IGZO). The band structure, density of states, optical properties including dielectric function, loss function, reflectivity and absorption coefficient are calculated. The calculated total energy shows that the most stable crystal structures are type III for \(\hbox {In}_{29}\hbox {Sn}_{3}\hbox {O}_{48}\) and type II for \(\hbox {InGaZnO}_{4}\). The band structure indicates the both \(\hbox {In}_{29}\hbox {Sn}_{3}\hbox {O}_{48}\) and \(\hbox {InGaZnO}_{4}\) are direct gap semiconductors. The intrinsic band gap of \(\hbox {In}_{29}\hbox {Sn}_{3}\hbox {O}_{48}\) is much narrower than that of \(\hbox {InGaZnO}_{4}\), and results in a better electrical conductivity for \(\hbox {In}_{29}\hbox {Sn}_{3}\hbox {O}_{48}\). The density of states shows the main hybridization occurring between In-4d and O-2p states for \(\hbox {In}_{29}\hbox {Sn}_{3}\hbox {O}_{48}\) while between In-4d In-5p, Zn-4s and O-2p states for \(\hbox {InGaZnO}_{4}\) near the valence band maximum. The reflectivity index \(R({\omega })\) shows that the peak value of \(\hbox {In}_{29}\hbox {Sn}_{3}\hbox {O}_{48}\) and \(\hbox {InGaZnO}_{4}\) appears only in the ultraviolet range, indicating that these two materials have all excellent transparency. In addition, the absorption coefficient \({\alpha }({\omega })\) of both \(\hbox {In}_{29}\hbox {Sn}_{3}\hbox {O}_{48}\) and \(\hbox {InGaZnO}_{4}\) is high in the ultraviolet frequency range, and therefore they show, a high UV absorption rate.     

First-principle calculations of electronic and ferromagnetic properties of $$\hbox {Al}_{1-x}\hbox {V}_{x}\hbox {Sb}$$

We have used the first-principle calculations of density functional theory within full-potential linearized augmented plane-wave method to investigate the electronic and ferromagnetic properties of \(\hbox {Al}_{1-x}\hbox {V}_{x}\hbox {Sb}\) alloys. The electronic structures of \(\hbox {Al}_{0.25}\hbox {V}_{0.75}\hbox {Sb}, \hbox {Al}_{0.5}\hbox {V}_{0.5}\hbox {Sb}\) and \(\hbox {Al}_{0.75}\hbox {V}_{0.25}\hbox {Sb}\) exhibit a half-metallic ferromagnetic character with spin polarization of 100 %. The total magnetic moment per V atom for each compound is integral Bohr magneton of 2 \(\mu _{\mathrm{B}}\), confirming the half-metallic feature of \(\hbox {Al}_{1-x}\hbox {V}_{x}\hbox {Sb}\). Therefore, these materials are half-metallic ferromagnets useful for possible spintronics applications.     

Systematic study of elastic,electronic, and magnetic properties of lanthanum cobaltite oxide

The electronic structure, elastic constants, and magnetic properties of lanthanum cobaltite oxide \(\hbox {La}_{4}\hbox {Co}_{3}\hbox {O}_{9}\) compound, which crystallizes in orthorhombic space group Pnma, are investigated theoretically for the first time using the full potential linearized augmented plane wave (FP-LAPW) method based on the density functional theory plus Hubbard correction term (DFT \(+\) U). The calculated equilibrium lattice constants and fractional atomic coordinates are in a good agreement with available experimental data. Our result for the formation energy and elastic constants confirms that the predicted \(\hbox {La}_{4}\hbox {Co}_{3}\hbox {O}_{9}\) is mechanically stable. This compound is found to be ductile in nature in accordance with Pugh’s criteria. The anisotropy factors (\({A}_{1})\), (\({A}_{2})\), and (\({A}_{3})\) of \(\hbox {La}_{4}\hbox {Co}_{3}\hbox {O}_{9}\) material are also predicted through the elastic constants. The electronic band structures show metallic behavior; the conductivity is mostly governed by Co-3d and O-2p states. The total magnetic moments of the tetrahedral (\(\hbox {CoO}_{4})\) and octahedral (\(\hbox {CoO}_{6})\) environments are, respectively, 2.502 \(\mu _{B}\) and 2.874 \(\mu _{B}\), which are consistent with the experimental measurements.     

20-nm T-gate composite channel enhancement-mode metamorphic HEMT on GaAs substrates for future THz applications

In this paper, the RF and DC behaviours of a SiN-passivated 20-nm gate length metamorphic high electron mobility transistor (MHEMT) on GaAs substrate with \({\updelta }\)-doped sheets on either side of the composite channel are studied using the Synopsys TCAD tool. The 20-nm enhancement-mode MHEMT with \({\updelta }\)-doped sheets on either side of the \(\hbox {In}_{0.75}\hbox {Ga}_{0.25}\hbox {As}\)/InAs/ \(\hbox {In}_{0.75}\hbox {Ga}_{0.25}\hbox {As}\) multilayer channel shows a transconductance of 3000 mS/mm, cut-off frequency (\({f}_{\mathrm{T}}\)) of 760 GHz and a maximum-oscillation frequency (\({f}_{\mathrm{max}}\)) of 1270 GHz. The threshold voltage of the device is found to be 0.07 V. The room-temperature Hall mobilities of the two-dimensional sheet charge density (2DEG) are measured to be over \(12800\,\hbox {cm}^{2}\)/Vs with a sheet charge density larger than 4 \(\times \) \(10^{12}\,\hbox {cm}^{-2}\). These high-performance enhancement-mode MHEMTs are attractive candidates for future terahertz applications such as high-resolution radars for space research and also for low-noise wide-bandwidth amplifier for future communication systems.     

A simulation study of voltage-assisted low-energy switching of a perpendicular anisotropy ferromagnet on a topological insulator

We present a novel memory device that consists of a thin ferromagnetic layer of Fe deposited on topological insulator thin film, \(\hbox {Bi}_{2}\hbox {Se}_{3}\). The ferromagnetic layer has perpendicular anisotropy, due to MgO deposited on its top surface. When current is passed on the surface of \(\hbox {Bi}_{2}\hbox {Se}_{3}\), the surface of the \(\hbox {Bi}_{2} \hbox {Se}_{3}\) becomes spin polarized and strong exchange interaction occurs between the d electrons in the ferromagnet and the electrons conducting the current on the surface of the \(\hbox {Bi}_{2}\hbox {Se}_{3}\). Part of the current is also shunted through the ferromagnet, which generates spin transfer torque in the ferromagnet. The exchange interaction torque along with voltage-controlled magnetic anisotropy allows ultralow-energy switching of the ferromagnet. We perform micromagnetic simulations and predict switching time of the order of 2.5 ns and switching energy of the order of 0.88fJ for a ferromagnetic bit with thermal stability of \(43\,k_\mathrm{{B}}T\). Such ultralow-energy and high-speed switching of a perpendicular anisotropy ferromagnet on a topological insulator could be utilized for energy-efficient memory design.     

First-principles investigation on transport properties of $$\hbox {Zn}_{2}\hbox {SnO}_{4}$$ molecular device and response toward $$\hbox {NO}_{2}$$NO2 gas molecules

The transport properties of a \(\hbox {Zn}_{2}\hbox {SnO}_{4}\) device along with adsorption properties of \(\hbox {NO}_{2}\) gas molecules on \(\hbox {Zn}_{2}\hbox {SnO}_{4}\) (ZTO) molecular devices are investigated with density functional theory using the non-equilibrium Green’s function technique. The transmission spectrum and device density of states spectrum confirm the changes in HOMO–LUMO energy level due to transfer of electrons between the ZTO-based material and the \(\hbox {NO}_{2}\) molecules. I–V characteristics demonstrate the variation in the current upon adsorption of \(\hbox {NO}_{2}\) gas molecules on the ZTO device. The findings of the present study clearly suggest that ZTO molecular devices can be used to detect \(\hbox {NO}_{2}\) gas molecules in the trace level.     

Numerical analysis of transmission coefficient,LDOS, and DOS in superlattice nanostructures of cubic $$\hbox {Al}_{x}\hbox {Ga}_{1-x}\hbox {N/GaN}$$ resonant tunneling MODFETs

Numerical analysis of the transmission coefficient, local density of states, and density of states in superlattice nanostructures of cubic \(\hbox {Al}_{x}\hbox {Ga}_{1-x}\hbox {N/GaN}\) resonant tunneling modulation-doped field-effect transistors (MODFETs) using \(\hbox {next}{} \mathbf{nano}^{3}\) software and the contact block reduction method is presented. This method is a variant of non-equilibrium Green’s function formalism, which has been integrated into the \(\hbox {next}\mathbf{nano}^{3}\) software package. Using this formalism in order to model any quantum devices and estimate their charge profiles by computing transmission coefficient, local density of states (LDOS) and density of states (DOS). This formalism can also be used to describe the quantum transport limit in ballistic devices very efficiently. In particular, we investigated the influences of the aluminum mole fraction and the thickness and width of the cubic \(\hbox {Al}_{x}\hbox {Ga}_{1-x}\hbox {N}\) on the transmission coefficient. The results of this work show that, for narrow width of 5 nm and low Al mole fraction of \(x = 20\,\%\) of barrier layers, cubic \(\hbox {Al}_{x}\hbox {Ga}_{1-x}\hbox {N/GaN}\) superlattice nanostructures with very high density of states of 407 \(\hbox {eV}^{-1}\) at the resonance energy are preferred to achieve the maximum transmission coefficient. We also calculated the local density of states of superlattice nanostructures of cubic \(\hbox {Al}_{x}\hbox {Ga}_{1-x}\hbox {N/GaN}\) to resolve the apparent contradiction between the structure and manufacturability of new-generation resonant tunneling MODFET devices for terahertz and high-power applications.     

Spectroscopic and structural study of adsorption of benzene on silver using DFT

Lowest energy structures of benzene after adsorption on silver, investigated based on density functional theory, indicate binding interactions through the \(\pi \)-electrons. Binding energy calculations of B-\(\hbox {Ag}_{{n}}\) clusters show that B-\(\hbox {Ag}_{3}\) and B-\(\hbox {Ag}_{9}\) are more stable with the shortest C-Ag distance for B-\(\hbox {Ag}_{3}\). Natural bond orbital analysis indicates intra- and intermolecular interactions from orbital overlaps between \(\pi \)(C–C) to \(\pi \)*(C–C) and \(\pi \)(C–C) to \(\sigma \)*(Ag–Ag) orbitals. Vibrational spectra confirm the charge transfer and adsorption mechanism. Chemically reactive sites are identified through Fukui functions. Localization in the electron density and charge transfer account for enhancement in the polarization. The lower band gap of benzene after adsorption on silver suggests its potential roles in the design of organic semiconductor devices.     

A GMR device based on a magnetic nanostructure with a $$\updelta $$-doping

We study how to manipulate by the \(\updelta \)-doping a giant magnetoresistance (GMR) device, which can be realized experimentally by depositing two parallel ferromagnetic stripes on top and bottom of the semiconductor \(\hbox {GaAs/Al}_{x}\hbox {Ga}_{1-x}\mathrm{As}\) heterostructure. We demonstrate an obvious GMR effect in the device with a \(\updelta \)-doping. We also reveal that the magnetoresistance ratio depends not only on the weight but also on the position of the \(\updelta \)-doping. These interesting results will be helpful for designing controllable GMR devices.     

Theoretical study of structural,electronic and optical properties of novel ternary alloys $$\hbox {MgO}_{1-{x}}{\hbox {Se}}_{{x}}$$ ($$x =$$x= 0.25, 0.50 and 0.75)

We report on the investigation of the structural, electronic, and optical properties of binary compounds (MgO and MgSe) and their ternary \(\hbox {MgO}_{1-{x}}\hbox {Se}_{{x}}\) (\(x=0.25, 0.5, 0.75\)) alloys within the density functional theory based on the full-potential linearized augmented plane wave method as implemented in the WIEN2k code. We have used the revised Perdew–Burke–Ernzerhof generalized gradient approximation (GGA-PBEsol) to calculate the structural properties and analyze the effect of the Se composition on the lattice constant and the bulk modulus of \(\hbox {MgO}_{1-{x}}\hbox {Se}_{{x}}\). The calculated electronic properties by employing the GGA-PBEsol and TB-mBJ approaches show that \(\hbox {MgO}_{1-{x}}\hbox {Se}_{{x}}\) alloys have a direct band gap \(\Gamma \)–\(\Gamma \) for \(x = 0, 0.25, 0.5\) and 0.75, suggesting the possibility of their use in the long wavelength optoelectronic applications. The optical properties such as the real and imaginary parts of the dielectric function, the refractive index, and the reflectivity of \(\hbox {MgO}_{1-{x}}\hbox {Se}_{{x}}\) are computed by using the accurate TB-mBJ potential. The wide band gaps larger than 3.1 eV mean that \(\hbox {MgO}_{1-{x}}\hbox {Se}_{{x}}\) alloys can be used in the applications of the ultraviolet region of the spectrum. Our data for all studied bowing parameters of \(\hbox {MgO}_{1-{x}}\hbox {Se}_{x}\) may serve as references for future experimental studies.     

Transport studies of $$\hbox {CeO}_{2}$$ molecular device and adsorption behavior of CO on $$\hbox {CeO}_{2}$$ device: a first-principles investigation

Using density functional theory and the non-equilibrium Green’s function formalism, the transport and CO adsorption properties of \(\hbox {CeO}_{2}\) molecular device are studied. The band structure shows that \(\hbox {CeO}_{2}\) nanostructure exhibits semiconducting nature. The electron density is found to be more in oxygen sites rather than in cerium sites along \(\hbox {CeO}_{2}\) nanostructure. The density of states spectrum shows the variation in density of charge upon adsorption of CO on CeO\(_2\) device. The transmission spectrum provides the insights on the transition of charge in \(\hbox {CeO}_{2}\) molecular device upon adsorption of CO along the scattering region. I–V characteristics confirm the adsorption of CO with the variation of current along \(\hbox {CeO}_{2}\) molecular device. The findings show that \(\hbox {CeO}_{2}\) two probe molecular device can be efficiently used for CO detection in the atmosphere.     

Theoretical investigation of electronic performance,half-metallicity,and magnetic properties of Cr-substituted BaTe

We have investigated the structural, electronic, and ferromagnetic properties of chromium (Cr)-doped rocksalt BaTe (\(\hbox {Ba}_{1-x}\hbox {Cr}_{x}\hbox {Te}\)) compounds with compositions \(x = 0.25\), 0.5, and 0.75, based on density functional theory with generalized gradient approximation of Wu–Cohen (GGA-WC) and Tran–Blaha-modified Becke–Johnson (TB-mBJ) potential using the WIEN2k package. We found that the electronic structure showed half-metallic ferromagnetic character with spin polarization of 100 % around the Fermi level. In addition, the minority-spin bands depicted a half-metallic ferromagnetic (HMF) gap and half-metallic (HM) gap. The improved HMF and HM gaps found with the TB-mBJ potential are higher than with the GGA-WC approximation. These large HM gaps make \(\hbox {Ba}_{1-x} \hbox {Cr}_{x}\hbox {Te}\) compounds promising candidates for use in spintronics applications.     

First-principles simulation of oxygen vacancy migration in $$\hbox {HfO}_{ x}$$, $$\hbox {CeO}_{ x}$$CeOx,and at their interfaces for applications in resistive random-access memories

Transition metal-oxide resistive random-access memories seem to be a viable candidate as the next-generation storage technology because transition metals have multiple oxidation states and are good ionic conductors. A wide range of transition metal oxides have recently been studied; however, fundamental understanding of the switching mechanism is still lacking. Migration energies and diffusivity of oxygen vacancies in amorphous and crystalline \(\hbox {HfO}_{2}\) and \(\hbox {CeO}_{2}\) and at their interface are investigated by employing density functional theory. We found that oxygen dynamics is better in \(\hbox {CeO}_{2}\) compared to \(\hbox {HfO}_{2}\), including smaller activation energy barriers and larger diffusion pre-factors, which can have implications in the material-selection process to determine which combination of materials offer the most efficient switching. Furthermore, we found that motion of vacancies is different at the interface of these two oxides as compared to that within each constituents, which provided insight into the role of the interface in vacancy motion and ultimately using interface engineering as a way to tune material properties.     

Analytical evaluation of the charge carrier density of organic materials with a Gaussian density of states revisited

An analytical solution for the calculation of the charge carrier density of organic materials with a Gaussian distribution for the density of states is presented and builds upon the ideas presented by Mehmeto?lu (J Comput Electron 13:960–964, 2014) and Paasch et al. (J Appl Phys 107:104501-1–104501-4, 2010). The integral of interest is called the Gauss–Fermi integral and can be viewed as a particular type of integral in a family of the more general Fermi–Dirac-type integrals. The form of the Gauss–Fermi integral will be defined as

$$\begin{aligned} G\left( \alpha ,\beta ,\xi \right) =\mathop {\displaystyle \int }\limits _{-\infty }^{\infty }\frac{ e^{-\alpha \left( x-\beta \right) ^{2}}}{1+e^{x-\xi }}\hbox {d}x\text {,} \end{aligned}$$

where \(G\left( \alpha ,\beta ,\xi \right) \) is a dimensionless function. This article illustrates a technique developed by Selvaggi et al. [3] to derive a mathematical formula for a complete range of parameters \(\alpha \), \(\beta \), and \(\xi \) valid \(\forall \) \(\alpha \) \( \varepsilon \) \( {\mathbb {R}} \ge 0\), \(\forall \) \(\beta \) \(\varepsilon \) \( {\mathbb {R}} \), and \(\forall \) \(\xi \) \(\varepsilon \) \( {\mathbb {R}} \).

     

Analog and RF performance of doping-less tunnel FETs with $$\hbox {Si}_{0.55} \hbox {Ge}_{0.45}$$ source

This paper reports studies of a doping-less tunnel field-effect transistor (TFET) with a \(\hbox {Si}_{0.55} \hbox {Ge}_{0.45}\) source structure aimed at improving the performance of charge-plasma-based doping-less TFETs. The proposed device achieves an improved ON-state current (\(I_{{\mathrm{ON}}} \sim {4.88} \times {10}^{-5}\,{\mathrm{A}}/\upmu {\mathrm{m}}\)), an \(I_\mathrm{ON}/I_\mathrm{OFF}\) ratio of \({6.91} \times {10}^{12}\), an average subthreshold slope (\(\hbox {AV-SS}\)) of \(\sim \) \({64.79}\,{\mathrm{mV/dec}}\), and a point subthreshold slope (SS) of 14.95 mV/dec. This paper compares the analog and radio of frequency (RF) parameters of this device with those of a conventional doping-less TFET (DLTFET), including the transconductance (\(g_{{\mathrm{m}}}\)), transconductance-to-drain-current ratio \((g_\mathrm{m}/I_\mathrm{D})\), output conductance \((g_\mathrm{d})\), intrinsic gain (\(A_{{\mathrm{V}}}\)), early voltage (\(V_{{\mathrm{EA}}}\)), total gate capacitance (\( C_{{\mathrm{gg}}}\)), and unity-gain frequency (\(f_{{\mathrm{T}}}\)). Based on the simulated results, the \(\hbox {Si}_{0.55}\hbox {Ge}_{0.45}\)-source DLTFET is found to offer superior analog as well as RF performance.     

Optimal design of the multiple-apertures-GaN-based vertical HEMTs with $$\hbox {SiO}_{2}$$ current blocking layer

Gallium nitride (GaN) based vertical high electron mobility transistor (HEMT) is very crucial for high power applications. Combination of advantageous material properties of GaN for high speed applications and novel vertical structure makes this device very beneficial for high power application. To improve the device performance especially in high drain bias condition, a novel GaN based vertical HEMT with silicon dioxide \((\hbox {SiO}_{2})\) current blocking layer (CBL) was reported recently. In this paper, effects of the thickness of CBL layer and the aperture length on the electrical and breakdown characteristics of GaN vertical HEMTs with \(\hbox {SiO}_{2}\) CBL are simulated by using two-dimensional quantum-mechanically corrected device simulation. Intensive numerical study on the device enables us to optimize and conclude that devices with \(0.5\hbox {-}\upmu \hbox {m}\)-thick \(\hbox {SiO}_{2}\) layer and \(1\hbox {-}\upmu \hbox {m}\)-long aperture will be beneficial considerations to improve the device performance. Notably, using the multiple apertures can effectively reduce the on-state conducting resistance of the device. On increasing the number of apertures, the drain current is increased but the breakdown voltage is decreased. Therefore, device with four apertures is taken as an optimized result. The maximum drain current of 84 mA at \(\hbox {V}_\mathrm{G}= 1\,\hbox {V}\) and \(\hbox {V}_\mathrm{D}= 30\,\hbox {V}\), and the breakdown voltage of 480 V have been achieved for the optimized device.     

$${ SIM}^2{ RRAM}$$: a physical model for RRAM devices simulation

In the last few years, resistive random access memory (RRAM) has been proposed as one of the most promising candidates to overcome the current Flash technology in the market of non-volatile memories. These devices have the ability to change their resistance state in a reversible and controlled way applying an external voltage. In this way, the resulting high- and low-resistance states allow the electrical representation of the binary states “0” and “1” without storing charge. Many physical models have been developed with the aim of understanding the mechanisms that control the resistive switching. In this work, we have compiled the main theories accepted as well as their corresponding models for the conduction characteristics. In addition, simulation tools play a very important role in the task of checking these theories and understanding these mechanisms. For this reason, the simulation tool called \(\hbox {SIM}^{2}\hbox {RRAM}\) has been presented. This simulator is capable of replicating the global behavior of RRAM cell based on \(\hbox {HfO}_{x}\).     

Comparative study on interfacial properties of Mo,Nb, and W contacts with monolayer $$\hbox {MoS}_{2}$$

In this work, we make a comparative study on the interfacial properties of top contact for Mo, Nb, and W metals with monolayer \(\hbox {MoS}_{2 }\,(\hbox {mMoS}_{2})\) by employing first-principles based on density functional theory (DFT) calculations. We evaluate the heights of Schottky barrier (SBH) and orbital overlap of the three models by carefully observing band structure and the density of the states relative to the Fermi level. Also, the tunnel barriers and electron densities of the three systems are analyzed. In accordance with the DFT simulations, \(\hbox {mMoS}_{2}\) forms an n-type Schottky contact with Mo, Nb, and W electrodes with electron SBH of 0.28, 0, and 0.6 eV, respectively. Besides, \(\hbox {Nb-mMoS}_{2}\) contact exhibits higher average electron density and lower tunneling barriers, demonstrating that Nb can form a better top contact with \(\hbox {mMoS}_{2}\) and should have prior electron injection efficiency and backgated regulation of current compared to the \(\hbox {mMoS}_{2}\) contacts with Mo and W.     

Simulation of dielectric behavior in RFeO$$_{}$$ orthoferrite ceramics (R = rare earth metals)

Due to their colossal dielectric constant (CDC), \(\hbox {RFeO}_{3}\), orthoferrite ceramics (R = rare earth metal) have recently attracted much attention. In the present research, the dielectric constants of \(\hbox {RFeO}_{3}\) orthoferrite ceramics, whether with or without CDC, have been simulated. The type of synthesis method, the type of R material, temperature, and frequency as the effective parameters on the dielectric behavior are introduced to the model. Another input parameter is the ratio of \(\hbox {Fe}^{+2}/\hbox {Fe}^{+3}\) peak area (in the XPS diagram), which is the most important parameter that affects the CDC behavior. Initially, a colossal database is formed by means of WebPlotDigitizer software and 2930 experimental data, and then the simulation is carried out through gene expression programming. Two case studies are also performed on \(\hbox {PrFeO}_{3}\) and \(\hbox {NdFeO}_{3}\) orthoferrite ceramics to validate the accuracy of the presented model. \(\hbox {PrFeO}_{3}\) exhibits significant CDC behavior whereas the \(\hbox {NdFeO}_{3}\) ceramic samples possess little CDC property, both of which were precisely simulated by the model. Two-dimensional tenth-degree equations resulting from the model predict the dielectric constant variations accurately.