Phonon-assisted Electron Tunneling Research Articles

Octafluorobiphenyl-4,4’-diyl 9-oxothioxanthene-1,4-diyl polyether – a promising material for organic film based memristors: synthesis, memristive effect and charge transport mechanism

Polycondensation of perfluorobiphenyl with 1,4-dihydroxy- thioxanthen-9-one resulted in the title highly thermally stable polyether containing the thioxanthenone-type electron acceptor in-chain blocks in its structure. Model resistive memory devices based on it as the active medium exhibited a bipolar switching memristive effect with a 4-order difference in resistance between the low and high resistance states. The charge transport in this polyether is quantitatively described by the Nasyrov–Gritsenko model of phonon-assisted electron tunneling between traps.

Comprehensive Review on the Impact of Chemical Composition, Plasma Treatment, and Vacuum Ultraviolet (VUV) Irradiation on the Electrical Properties of Organosilicate Films.

Organosilicate glass (OSG) films are a critical component in modern electronic devices, with their electrical properties playing a crucial role in device performance. This comprehensive review systematically examines the influence of chemical composition, vacuum ultraviolet (VUV) irradiation, and plasma treatment on the electrical properties of these films. Through an extensive survey of literature and experimental findings, we elucidate the intricate interplay between these factors and the resulting alterations in electrical conductivity, dielectric constant, and breakdown strength of OSG films. Key focus areas include the impact of diverse organic moieties incorporated into the silica matrix, the effects of VUV irradiation on film properties, and the modifications induced by various plasma treatment techniques. Furthermore, the underlying mechanisms governing these phenomena are discussed, shedding light on the complex molecular interactions and structural rearrangements occurring within OSG films under different environmental conditions. It is shown that phonon-assisted electron tunneling between adjacent neutral traps provides a more accurate description of charge transport in OSG low-k materials compared to the previously reported Fowler-Nordheim mechanism. Additionally, the quality of low-k materials significantly influences the behavior of leakage currents. Materials retaining residual porogens or adsorbed water on pore walls show electrical conductivity directly correlated with pore surface area and porosity. Conversely, porogen-free materials, developed by Urbanowicz, exhibit leakage currents that are independent of porosity. This underscores the critical importance of considering internal defects such as oxygen-deficient centers (ODC) or similar entities in understanding the electrical properties of these materials.

“Can quantum dot in form of molecular ground be implied in IETS to measure the voltage effectively by sudden potential rise due to phonon assisted electron tunneling as Klein paradox?”

Abstract Sudden break in the passage of electron beam things conducting barrier shall either enhance or decrease electron beam with provided effect on spectral band of unknown metal, j/?dv –V at d2/dv2 plot gives characteristic of tunnel junction. At liquid helium temperature qv = hὐ implication for JV curve is observed at bias V where v denotes the frequency of molecular compounds present in the barrier, In case barrier emitting phonon interacts with the lattice of implied nano particles like Ga, As Ge Se coupled barrier in molecular state can be observed a specific band of Raman spectra and infra red thermally nactivated long wave spectra as IETS under Josephson effect. Single quantum dot in ultraclean carbonnanotube can be annexed with novel double quantum dot as result of klein paradox. At relatvistic QFT. In this context single spin1/2 can be confined with the hole emplacement and confinement as second double dot.

Phonon-assisted electron tunneling between traps in silicon oxide films treated in hydrogen plasma

The charge transport in thin thermal silicon oxide films treated in electron cyclotron resonance hydrogen plasma at different exposure times was investigated. X-ray photoelectron studies show that such treatment leads to the oxygen deficiency of the films. It was established that the treatment of the films in plasma leads to an increase of their conductivity by a factor of about 102. The film charge transport properties were studied at different temperatures and analyzed within four theoretical dielectric conductivity models. It was found that the charge transport mechanism is described by Fowler-Nordheim model in the initial silicon oxide and by the model of phonon-assisted electron tunneling between neutral traps after the treatment in hydrogen plasma. The thermal trap ionization energy value (Wt = 1.6 eV) measured from transport experiments is in agreement with that obtained from ab initio calculations for the oxygen vacancy (Si-Si bond) in SiO2.

Critical properties and charge transport in ethylene bridged organosilica low-κ dielectrics

Organosilicate-glass-based low-κ films containing both terminal methyl groups and an ethylene bridge between the silicon atoms are spin-on deposited by using 1,2-bis(trimethoxysilyl)ethane and methyltrimethoxysilane, Brij30 template, and thermal curing. The chemical composition, porosity, and internal defects are studied using Fourier-transform infrared spectroscopy, x-ray photoelectron spectroscopy, electron energy loss spectroscopy, UV induced luminescence, and ellipsometric porosimetry. It was found that the studied films contain oxygen-deficient centers (Si—Si bonds). The high defect density of the states near the valence-band edge of the studied low-κ films leads to a relatively small bandgap value of about 6.3 eV. The current–voltage characteristics at different temperatures were analyzed using six theoretical charge transport models where the transport is limited by the traps ionization. It was found that the best qualitative and quantitative agreement between the calculations and experimental data is achieved by using the model of phonon-assisted electron tunneling between the neutral traps and is supplemented by considering the space charge and charge carrier kinetics. Since the thermal and optical energies of the traps in the studied films are 1.6 eV and 3.2 eV, respectively, it is concluded that the traps are responsible for the charge transport in the Si—Si bonds.

Multiphonon trap ionization transport in nonstoichiometric SiNx

It is generally accepted that the charge transport in dielectrics is governed by coulombic trap ionization due to a barrier lowering in high electric fields (Frenkel effect). In this paper, the charge transport mechanism in Si3N4 and nonstoichiometric silicon rich SiNx is experimentally studied and quantitatively analyzed with five theoretical models: Frenkel model of Coulomb traps ionization, Hill-Adachi model of overlapping Coulomb traps, Shklovskii-Efros percolation model, Makram-Ebeid and Lannoo model of multiphonon isolated traps ionization and Nasyrov-Gritsenko model of phonon-assisted electron tunneling between nearby traps. It is shown that the charge transport in Si3N4 and SiNx is qualitatively described by Frenkel effect, but Frenkel effect predicts an enormously low attempt to escape factor value. The charge transport at traps energies Wt = 1.6 eV and Wopt = 3.2 eV in Si3N4 and SiNx can be described by an increase in traps concentration in the framework of Makram-Ebeid and Lannoo model and Nasyrov-Gritsenko model. The Makram-Ebeid and Lannoo model quantitatively describes the charge transport in Si3N4 and SiNx with low silicon enrichment. The charge transport in nonstoichiometric SiNx with high silicon enrichment is well explained by Nasyrov-Gritsenko model.

Effect of oxalic acid concentration on the magnetically enhanced capacitance and resistance of AAO humidity sensor

The enhanced capacitance and resistance behavior of anodic aluminum oxide (AAO) humidity sensor by both the high concentration of oxalic acid and applied magnetism has been investigated. At low relative humidity (RH, ≤45%), the enhanced capacitance response from high concentration of oxalic acid was attributed to phonon-assisted electron tunneling mechanism that was promoted by more acid anions within the AAO pore wall and barrier layer. The other enhancement from magnetic addition was due to the magnetic field induced more orderly arrangement of water molecules for higher capacitance. At high RH (>45%), the capacitance of AAO sensors at different acid concentrations (0.3–0.7M) with magnetic field was larger than that without magnetic field under the same mechanisms at low RH. Moreover, the medium-concentration AAO sensor exhibited the highest capacitance at RH over 60% due to the enhanced sensing surface area and pore conductance. The short and reliable capacitance response/recovery time was also obtained from the high-concentration AAO sensor under presence or absence of a magnetic field. In addition, the applied magnetism can significantly enhance the ordinary magnetoresistance response of humidity sensors at different acid concentrations at low-to-high RH for more linear-like relationship between the resistance and RH.

Theory of phonon-mediated relaxation in doped quantum dot molecules

A quantum dot molecule doped with a single electron in the presence of diagonal and off-diagonal carrier-phonon couplings is studied by means of a nonperturbative quantum kinetic theory. The interaction with acoustic phonons by deformation potential and piezoelectric coupling is taken into account. We show that the phonon-mediated relaxation is fast on a picosecond time scale and is dominated by the usually neglected off-diagonal coupling to the lattice degrees of freedom leading to phonon-assisted electron tunneling. We show that in the parameter regime of current electrical and optical experiments, the microscopic non-Markovian theory has to be employed.

Memory characteristics of InAs quantum dots embedded in GaAs quantum well

The memory characteristics of InAs based quantum dot (QD) memory devices has been investigated by carrying out capacitance-voltage and current-voltage measurements. The dots which were embedded in the GaAs quantum well were charged by the electrons from the two dimensional electron gas and a clockwise hysteresis loop is observed on cyclically sweeping the gate bias. The number of trapped electrons is found to be two orders of magnitude lesser than the QD density. Interdot Coulombic interactions and phonon assisted electron tunneling was found to significantly affect the charge trapping ability of the QDs.

Phonon-assisted tunneling between singlet states in two-electron quantum dot molecules

We study phonon-assisted electron tunneling in semiconductor quantum dot molecules. In particular, singletsinglet relaxation in a two-electron-doped structure is considered. The influence of Coulomb interaction is discussed via comparison with a single-electron system. We find that the relaxation rate reaches similar values in the two cases but the Coulomb interaction shifts the maximum rates toward larger separations between the dots. The difference in electron-phonon interaction between deformation potential and piezoelectric coupling is investigated. We show that the phonon-induced tunneling between two-electron singlet states is a fast process, taking place on the time scales of the order of a few tens of picoseconds.

Localized phonon-assisted electron tunneling in DBRT structure in quantizing magnetic field

A theory of confined and interface optical phonon-assisted electron tunneling in GaAs/AlAs double barrier resonant tunneling structure in the presence of quantizing magnetic field is developed. The excess current is calculated employing transfer matrix method. Electron interaction with confined LO phonons described by Huang and Zhu, slab mode and guided mode models is considered. The effect of interface modes is also incorporated. Numerical results obtained, based on Huang and Zhu model, are in conformity with experimental observations.

Electron and hole tunneling times in GaAs/AlGaAs asymmetric double quantum well heterostructures

We present CW and time-resolved photoluminescence measurements on GaAs/AlGaAs asymmetric double quantum well heterostructures. Several samples (eight) have been considered in order to study the influence, on the carrier tunneling process, of both barrier thickness and energy separation between the levels in the different wells. A comparison between photoluminescence decay time of excitonic recombinations in the narrow well and wide well, under resonant and non resonant excitation, allows us to determine both the electron and hole tunneling times. Evidence of non resonant and LO phonon-assisted electron tunneling, resonant and near-resonant hole tunneling is found and discussed.