Potential Barrier Height Research Articles

Investigation of temperature dependant current transport mechanism in Ag/In2O3/p-Si/Al heterojunction

Employing the pulsed laser ablation technique nano-crystalline thin films of Indium oxide (In2O3) are deposited successfully on boron doped silicon substrate. The structural and morphological parameters of the films are investigated by using X-ray diffraction and atomic force microscopic (AFM) spectroscopy, respectively. The deposited films are the crystalline nanostructures with (400) as preferred diffraction peak and grain size of 56.56 nm approximately. The computed roughness (Rq) of In2O3 film is 1.02 nm. The AFM analysis validated the deposition of homogeneous smooth In2O3 films with surface roughness of the order of nanometer. UV–vis spectroscopy was used to study the optical properties of the films. Greater than 80% transparency in visible region was exhibited by the films. The value of the optical band gap was found to be 3.89 eV. The electrical parameters dominating the mechanism of current transport in n-In2O3/p-Si heterojunction were explored by observing the temperature-dependent current–voltage (I–V) properties. In the temperature range of 80–300 K, the ideality factor and barrier height were found to be strongly temperature dependent. It was noticed that with the decrease in temperature there is increase in ideality factor whereas decrease in barrier height which confirm the interfacial imperfections and inhomogeniety in potential barrier height distributions. The temperature dependence of I–V data has revealed the existence of double Gaussian distribution of barrier heights with mean values of 0.85eV and 0.78eV with standard deviation of 0.014 V and 0.012 V respectively. The modified Richardson's plot gives the average barrier height and Richardson's coefficient as 0.86eV and 4.7 × 105 Am−2K−2 in the temperature range 300 K–180 K and 0.77eV and 5.2 × 105 Am−2K−2, respectively in the temperature range 160 K–80 K. The values of Richardson's constants are of the order of known theoretical value of 3.2 × 105 Am−2 K−2.

Enhanced dielectric permittivity of novel ternary La2Cu–AgO4 nanocomposites with different ratios of 2-D Borophene nanofiller

Borophene is a monolayer of boron atoms that exhibits notable physical and chemical characteristics, making it the lightest two-dimensional material known to date. Simultaneously, the compositions of silver-copper oxide and lanthanum-copper oxide exhibited unique applications. The present study was motivated by the need to investigate the potential benefits of combining La2Cu–AgO4 ternary nano composition with 2-D Borophene. The successful synthesis of La2Cu–AgO4 nanoparticles and 2-D Borophene has been achieved through simple and cost-effective methods. The La2Cu–AgO4/Borophene composite, with varying weight percentages, has been subjected to various characterization techniques for analysis. The electrical properties of the prepared samples were analyzed. The present study indicates that Borophene has enhanced the dielectric properties of La2Cu–AgO4 nanoparticles by a factor of approximately 2–5. An additional fascinating characteristic of the La2Cu–AgO4/Borophene nanocomposites that were prepared is the presence of a negative Schottky barrier, which exhibits a small value. The incorporation of 2-D Borophene resulted in a reduction of the resistivity of La2Cu–AgO4 by 14–17% compared to its initial value. Moreover, in comparison to the pure La2Cu–AgO4 ternary nanocomposite, the nanocomposite samples of 2-D La2Cu–AgO4 demonstrated reduced activation energy, potential barrier height, and density. The results obtained from the study demonstrate that the material possesses a high dielectric constant value, low resistance, and is lightweight and cost-effective. These properties make it a promising candidate for use in telecommunications and solid-state semiconductor applications, as it can be easily applied.

Analysis of the Current Transport Characteristics (CTCs) in the Au/n-Si Schottky Diodes (SDs) with Al2O3 Interfacial Layer over Wide Temperature Range

Temperature dependent electrical-parameters and CTCs in Au/Al2O3/n-Si SDs have been analysed between 200 K and 400 K using current/voltage (IV) characteristics. While the value of quality/ideality factor (n) decreases, zero bias potential barrier height (BH, ΦB0) increases with increasing temperature. The value of Richardson constant (A*) and activation energy (Ea) were also derived from the conventional Richardson plot (RP) as 0.567 eV and 7.34 × 10−3 A.cm−2K−2, respectively. This low A* value shows that deviation from standard thermionic-emission (TE) model and to determine whether this situation may be described by Gaussian-distribution (GD) model or not, ΦBo vs n and ΦBo vs q/(2kT) curves were illustrated. The Φ ¯ B value was found as 1.19 eV from the linear ΦB0 vs n plot for ideal case (n = 1). The mean-value of BH ( Φ ¯ B 0 ) and standart deviation (σ s) values were found from the ΦBo vs q/(2kT) curve as 1.130 eV and 0.127 V, respectively. By using value of σ s, RP was modified and then Φ ¯ B 0 and A* values were found as 1.128 eV and 108.88 Acm−2K−2, respectively, and this value of A* very close to its theoretical value (=112 Acm−2K−2). The surface state density (Nss) were also obtained from the forward bias IV data for three-temperatures.

Energy Harvesting System Whose Potential Is Mapped with the Modified Fibonacci Function.

In this paper, we compare three energy harvesting systems in which we introduce additional bumpers whose mathematical model is mapped with a non-linear characteristic based on the hyperbolic sine Fibonacci function. For the analysis, we construct non-linear two-well, three-well and four-well systems with a cantilever beam and permanent magnets. In order to compare the effectiveness of the systems, we assume comparable distances between local minima of external wells and the maximum heights of potential barriers. Based on the derived dimensionless models of the systems, we perform simulations of non-linear dynamics in a wide spectrum of frequencies to search for chaotic and periodic motion zones of the systems. We present the issue of the occurrence of transient chaos in the analyzed systems. In the second part of this work, we determine and compare the effectiveness of the tested structures depending on the characteristics of the bumpers and an external excitation whose dynamics are described by the harmonic function, and find the best solutions from the point view of energy harvesting. The most effective impact of the use of bumpers can be observed when dealing with systems described by potential with deep external wells. In addition, the use of the Fibonacci hyperbolic sine is a simple and effective numerical tool for mapping non-linear properties of such motion limiters in energy harvesting systems.

Voltage-margin limiting mechanisms of AlScN-based HEMTs

In this work, the off-state characteristics of AlScN/GaN high electron mobility transistors (HEMTs) grown by metalorganic chemical vapor deposition (MOCVD) were studied and directly compared to an AlGaN- and an AlN-HEMT grown in the same MOCVD. Pinch-off instability and leaky capacitive measurements were observed for AlScN-based HEMTs, which was correlated with a higher ideality factor and lower effective potential barrier height than the AlGaN and AlN-HEMTs. However, the reverse bias characteristics exhibited a sudden drain-current increase without a significant increase in gate-leakage current. The drain-leakage current is assumed to be related to a parasitic channel across the AlScN-barrier as a result of trap-assisted carrier transport with a Poole–Frenkel characteristic. The demonstrated pinch-off instability led to significant gain expansion in load-pull measurements and early soft-breakdown, which, in turn, limits the achievable voltage-margin. The results demonstrate a key issue to reveal the full potential of AlScN-based HEMTs for mm-wave applications.

The predicted value of potential barrier to internal rotation of benzaldehyde: Is there a conflict between the theory and the experiment or not?

The ratio of potential barrier heights for the internal rotation of benzaldehyde molecule calculated by quantum mechanical methods and determined experimentally from UV spectra has been discussed. Based on the joint analysis of the results of ab initio MP2/6-311G** calculations of normal vibrations of benzaldehyde in the ground state and the results of interpretation of the observed UV spectra of the compound, possible approximations for a correct description of the hindered internal rotation of the aldehyde group have been considered. The two-dimensional model including the kinematic interaction between torsion and out-of-plane deformation of aldehyde group has been established as more efficient for the correct description of the hindered rotation in benzaldehyde.

Improved optical, dielectric, and nonlinear properties of CaCu3Ti4O12 thin films by chromium doping

In the present work, the optical and dielectric properties, microstructures, and nonlinear electrical performances were systematically investigated for Ca1-xCrxCu3Ti4O12 (x = 0.00 - 0.40) thin films prepared on Pt/Ti/SiO2/Si substrates using the sol-gel method. X-ray photoelectron spectroscopy (XPS) verified that Cr3+ and Cr6+ were present in the thin films. Additionally, the content of secondary phase of titanium oxide (TiO2) increased, the grain size decreased, and the surface roughness improved with the increase in the doped content of Cr. Due to the reduced grain size and oxygen vacancy concentration, the optical energy band gap increased from 2.92 to 3.54 eV. The change in the dielectric constants (Ɛr) of the thin films followed the internal barrier layer capacitor model. Doping was found to decrease the dielectric loss (tan δ) and enhance the nonlinear properties, which was due to the presence of TiO2 secondary phase, high density, reduced grain size, incremental potential barrier height and grain boundary resistance. The Ca0.8Cr0.2Cu3Ti4O12 thin film had a high Ɛr of around 9340, low tan δ of around 0.012 at 1 kHz, nonlinear coefficient of about 4.64, and breakdown field of ca. 89 kV/mm. These results indicated that the doping of an appropriate amount of Cr could effectively modify the microstructure of CaCu3Ti4O12 thin films and improve their optical and electrical properties.

Dipol'naya plazmonnaya moda v nanorazmernykh poluprovodnikovykh kvantovykh tochkakh tipa "yadro-obolochka" s geteroperekhodom vtorogo roda

Excited states of nanosize two-component semiconductor core–shell crystals with a type II heterojunction are analyzed. It is demonstrated that the dipole plasmon resonance dominates in their photoabsorption spectra. It is found that the variation of the potential barrier height between the core and the shell in a comparatively narrow range leads to a fundamental change in the form of the collective mode from the surface plasmon resonance typical of the photoabsorption spectra of conducting nanosize particles to the rotational plasmon mode, for which only angular degrees of freedom are excited.

Performance Improvement of AlGaN‐Based Deep‐Ultraviolet Light‐Emitting Diodes with Multigradient Electron Blocking Layer and Triangular Last Quantum Barrier

The performance improvements of AlGaN‐based deep ultraviolet light‐emitting diodes (DUV‐LEDs) with multigradient electron blocking layer (EBL) and triangular last quantum barrier (LQB) are investigated. The results show that the maximum internal quantum efficiency (IQE) is improved by 44.9% and light output power (LOP) is improved by 58.1% at 200 A cm−2, exhibiting a tremendous improvement compared to the conventional structure. These improvements are mainly attributed to the fact that both multigradient EBL and triangular LQB can generate negative polarization charges in the graded composition layer, which leads to a significant increase in hole concentration compared to the conventional EBL and LQB structures. Meanwhile, the multigradient EBL can transform the conventional triangular barrier into an arc‐shaped barrier, increasing the electron potential barrier height and decreasing the hole potential barrier height. This unique design suppresses electron leakage and enhances hole injection, leading to a significant enhancement of the IQE and alleviation of the efficiency droop.

Constructing highly flexible dielectric sponge for enhancing triboelectric performance

Functional materials that are with high dielectric constant are finding extensive applications in the conversion and storage of energy, which may also be the key for enhancing the output performance of triboelectric nanogenerator (TENG) by dielectrically modulating the charge trapping capability of the triboelectric interface. Here, CaCu3Ti4O12@BaTiO3 (CCTO@BT) is facilely synthesized for forming in polydimethylsiloxane (PDMS) layer. Due to the strengthened charge induction, the composite sponge with high flexibility and charge trapping capability is developed, and the polymeric sponge TENG (with 2 wt% CCTO@BaTiO3) demonstrates a high open-circuit voltage of 291.14 V, a short-circuit current of 35.49 µA, and a transfer charge quantity of 80 nC, which are far superior 206% higher than that are modulated by pure CCTO and 480% higher than pure PDMS (the short-circuit current). Dielectric enhancement mechanism was comparatively proved and demonstrated in the CCTO@BT/PDMS composites. To unravel the origin of the significantly enhanced triboelectric performance, permittivity and work function in the sponge were studied in-depth, and the strong internal polarization and potential barrier height were demonstrated. Moreover, the as-fabricated TENG can act as self-powered sensor for monitoring human motions, such as walking, jogging, and jumping ropes. This work provides a new insight into the unique potential of dielectric-modulated output enhancement strategy for unblocking the potential of TENG in energy harvesting and biophysical monitoring.

Analysis of Photo-Generated Carrier Escape in Multiple Quantum Wells

Recent experiments have shown that more than 85% of photo-generated carriers can escape from multiple quantum wells (MQWs) sandwiched between p-type and n-type layers (PIN). In this work, we quantitatively analyze the relationship between the energy of carriers and the height of potential barriers to be crossed, based on the GaAs/InGaAs quantum well structure system, combined with the Heisenberg uncertainty principle. It was found that that the energy obtained by electrons from photons is just enough for them to escape, and it was found that the energy obtained by the hole is just enough for it to escape due to the extra energy calculated, based on the uncertainty principle. This extra energy is considered to come from photo-generated thermal energy. The differential reflection spectrum of the structure is then measured by pump–probe technology to verify the assumption. The experiment shows that the photo-generated carrier has a longer lifetime in its short circuit (SC) state, and thus it possesses a lower structure temperature than that in open circuit (OC). This can only explain a thermal energy reduction caused by the continuous carrier escape in SC state, indicating an extra thermal energy transferred to the escaping carriers. This study is of great significance to the design of new optoelectronic devices and can improve the theory of photo-generated carrier transports.

Energies of the ground and excited states of confined two-electron atom in finite potential well

For the ground and excited configurations, we have carried out the energy eigenvalues and corresponding wavefunctions of two-electron atom enclosed by finite confining potential by using Quantum Genetic Algorithm (QGA) procedure and Hartree-Fock Roothaan (HFR) method. Besides, we have analysed in detail orbital energies and probabilities of finding electron for the configurations 1S (1s2), 3S (1s2s), 3P (1s2p), 3D (1s3d) and 3F (1s4f). The results reveal that the potential barrier height plays a significant role on average energies, state energies, orbital energies and probabilities of finding electrons in orbitals. As dot size is extremely small and extremely large, the energies for 1snl configurations are getting close to each other, but between these two extreme situations they are separating from each other. While going to higher excited states, singlet and triplet states are almost the same due to the weakening of the exchange energy.

Novel DAZO Film with a Negative Temperature Coefficient Effect and Its Application Prospects for the Thermal Runaway Warning System in Batteries

A novel dopamine- and aluminum-doped zinc oxide (DAZO) sensing film was prepared by blending DAZO nanoparticles with silicone latex; this film has promising applications for the thermal runaway warning system of new energy batteries. The DAZO nanoparticles were generated by the coprecipitation–calcination method through the structure-orienting modification of eco-friendly polydopamine biomaterials, followed by the doping of aluminum and nitrogen into the zinc oxide lattice. Dopamine was used as a nitrogen source; it easily self-polymerizes to form polydopamine, which is then pyrolyzed and doped into the zinc oxide lattice. The negative temperature coefficient (NTC) effects of the DAZO film and the aluminum-doped zinc oxide (AZO) film below 150 °C were tested and compared. The results showed that the DAZO film had a more pronounced NTC effect than the AZO film because of the doped nitrogen element. DAZO films exhibited good recyclability and thermal stability during the high-low temperature NTC cycle test. X-ray diffraction, transmission electron microscopy, scanning electron microscopy, Fourier transform infrared spectroscopy, thermogravimetry/mass spectrometry (TG–MS), and energy dispersive X-ray spectroscopy were performed to characterize the fabrication of the synthesis mechanism of the DAZO nanoparticles. The NTC effects of DAZO films with varying aluminum doping amounts, varying dopamine doping amounts, and different pH values were investigated. Nitrogen doping in the conventional AZO nanoparticles enhanced the sensitivity and low-temperature NTC effect; this is because of the increase in the DAZO grain size due to doping and the structure–orientation of polydopamine, which further leads to the increase in the height of the grain boundary potential barrier. On the basis of the test results, an alarm response device at different temperatures was initially established, and its alarm response at different temperatures was simulated and tested, which showed the possibility of the application of the DAZO film to the runaway warning system for the new energy batteries.

Influence of applied bias on direct conversion X-ray sensing capability of nanocrystalline Ca9Ag(PO4)6(OH)2

Silver (Ag) doping in hydroxyapatite (HAP) can enhance the attenuation coefficient (μ) 0.65 cm2/g at photon energy 70 keV as compared with pure hydroxyapatite (μ = 0.31 cm2/g). In this study, direct conversion X-ray sensors were fabricated using pure HAP (Ca10(PO4)6(OH)2) and Ag-doped HAP (Ca9Ag(PO4)6(OH)2) to realize superior X-ray sensing capability. Thick films of wet-chemical route derived nanocrystalline samples were deposited on interdigitated electrodes by glass rod sliding technique and its X-ray instigated photocurrent characteristics at 2 V biased condition were recorded for different low doses (mGy). The observed sensitivity at 7.97 mGy dose reveals ten folds enhancement from 0.19 nC/mGy cm3 to 1.00 nC/mGy cm3. According to the “Grain boundary double Schottky potential barrier height model”, the formation of potential barrier height (φb) at the interface of grain and grain boundaries of nanocrystalline samples is identical to the Schottky barrier. By increasing the applied bias, the conduction band starts to bend and suppresses the potential barrier height (φb). In higher biased conditions, φb does not exist. Hence, the influence of applied bias on direct conversion X-ray sensing capability of Ca9Ag(PO4)6(OH)2 was investigated and discussed in detail.

Electrical properties of tin oxide based varistors with PbO addition in humid air

In order to decrease the humidity sensitivity of SnO2–Co3O4–Nb2O5–Cr2O3 varistor ceramics, lead oxide was added and the electric characteristics of synthesized materials with the PbO concentration of 0, 0.1, 0.5, 0.7, 1 and 2 mol.% in the air with relative humidity of 10–86% were investigated. All tested samples have non-linear current–voltage characteristics with large values of the nonlinearity coefficient of 38–51. The optimal concentration of PbO addition in ceramics is 0.5–0.7 mol.%. The addition of such quantity of lead oxide to the ceramics leads to the decrease of the breakdown electric field up to 4390 V/cm and the humidity sensitivity coefficient up to 172. The increase of the PbO concentration provides the increase of the electrical conductivity of samples at low fields. The barrier mechanism of electrical conductivity of the studied ceramics is proved by the obtained values of potential barrier heights of 0.85–0.90 еV on the SnO2 crystallite boundaries.

Modeling of Stacking Faults in 4H-SiC n-Type Epilayer for TCAD Simulation

Current–voltage characteristics of an n-type 4H-silicon carbide (SiC) epilayer containing a stacking fault (SF) were analyzed using a technology computer-aided design (TCAD) simulation. In the simulation, the SF was modeled by a quantum well (QW) formed in the conduction band, which traps electrons and induces a potential barrier. The simulation analysis clarified that the electron conductance in the n-type epilayer containing a SF was dominantly determined by the potential barrier height. Based on this insight and the experimental results obtained from our previous study, the energetic depth and width of the QW in the conduction band were deduced for four types of SFs. The temperature dependence of the experimental current–voltage characteristics of Schottky barrier diodes (SBDs), containing the SF, was effectively reproduced by adopting the deduced QW depth and width, proving the feasibility of the proposed simulation model quantitatively predicting the impacts of SFs on SiC unipolar device performances.

Driven particle in a two-dimensional periodic substrate: Nonmonotonic dependence of drift velocity on temperature.

Motion of a driven particle in a two-dimensional (2D) periodic potential of square symmetry is studied by means of Brownian dynamics simulations. The average drift velocity and long time diffusion coefficients are obtained as a function of driving force and temperature. For driving forces above the critical depinning force, a reduction of drift velocity is observed as temperature is increased. The drift velocity reaches a minimum for temperatures at which k_{B}T is of the order of the barrier height of the substrate potential and then increases and saturates to the value of drift velocity for the substrate free case. Depending on the driving force, the drop in drift velocity can be as large as 36% of its value at low temperatures. While this phenomenon is observed in 2D for different types of substrate potentials studied and for various drive directions, studies using the exact result show no such dip in drift velocity in one dimension (1D). As in the case of 1D, a peak is observed in the longitudinal diffusion coefficient as the driving force is varied at a fixed temperature. But unlike in 1D, the location of the peak is temperature dependent. Approximate analytical expressions for the average drift velocity and the longitudinal diffusion coefficient are formulated using the exact results in 1D by finding a temperature dependent effective 1D potential to model the motion in the presence of a 2D substrate. This approximate analysis is successful in qualitatively predicting the observations.

Gate‐Tunable Potential Barrier on Dual‐Gate Graphene Transistor with Fluorocarbon Thin Film

AbstractThis article reports on the charge transport characteristics across the potential barrier generated by a local dual‐gate modulation at the surface of p‐doped graphene via surface contact on a fluorocarbon (CF) thin film. Owing to simple physical contact, the strong electron affinity of the fluorine atoms in CF stably increases the hole density of graphene, which leads to a massive p‐doping effect in graphene. Then, potential barrier height can be generated and modulated across the channel by forming a local dual‐gate device structure. Different gate biases in dual‐gate operation can split electrical characteristics of a single graphene into highly conductive region and region of sparse charge density, creating large chemical potential difference at the boundary between the two which determines the value of barrier height. Moreover, the device characteristics follow a simple model of the metal–semiconductor junction well in addition to the effect of charge concentration discrepancy in graphene. These results reveal that it is possible to create an ideal and controllable potential barrier composed of a single material using the highly doped graphene with the local dual‐gate structure.

Tunable nonlinear conductive behavior without percolation threshold and high thermal conductivity of epoxy resin/SiC ceramic foam co-continuous phase composites

Smart dielectrics with self-adaptive capabilities can exhibit desirable electric field-grading performance as the applied electric field exceeds a critical value. However, the conventional approaches to such dielectrics need heavy doping rate, which will not only increase the interface thermal resistance and limit the improvement of thermal conductivity, but also severely sacrifice the mechanical property. In this contribution, a new type of electric field-grading co-continuous phase composite (EP/SiCcf) composed of epoxy resin and SiC ceramic foam was prepared to realize tunable nonlinear conductive performance, while simultaneously improving thermal and mechanical properties. Results show that there is no percolation threshold for all EP/SiCcf composites. The volume loadings of EP/SiCcf composites range from 8.7 vol% to 15.6 vol%, while the nonlinear coefficient subjected to potential barrier height increases from 2.1 to 4.5 and the switching field tuned by barrier width decreases from 1008 V/mm to 686 V/mm. The EP/SiCcf40 still exhibits sharp thermal conductivity enhancement of about 1000% and glass transition temperature enhancement of 10.8 °C. The surface temperature fluctuation over time during heating and cooling has illustrated the prospective application of thermal management capability. In addition, the dynamic mechanical analysis reveals that all EP/SiCcf composites have the significantly improved storage modulus and crosslinking density ascribed to the intact SiC skeleton. The novel co-continuous phase composite provides a new approach for global enhancement of smart dielectric composites in potential applications.

Investigation of electronic structure of a lithium atom confined by a finite spherical cavity

In this study, we have calculated the average energies of the ground and excited configurations of a lithium atom enclosed by a spherical potential well with finite barrier height, and we have also carried out calculations of orbital energies, confining potential energies and probabilities of finding the electrons in 1s and nl orbitals as a function of confinement radius for the 1s2nl configurations [nl = 2s, 2p, 3d and 4f]. Quantum Genetic Algorithm (QGA) and Hartree-Fock Roothaan (HFR) methods are used to calculate the energy eigenvalues and corresponding wave functions of the confined system. The results show that potential barrier height and confinement radius have a strong influence on the energies and the probabilities of finding the electrons inside and outside the well. It is found that 1s orbital energy increases suddenly at a critical confinement radius, at which the electron in nl orbital is trapped by the confining potential.