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The electrical responses of 55 nm silicon-oxide-nitride-oxide-silicon (SONOS) memory cells have been investigated under cryogenic conditions, and the changes of the read curves of SONOS in AC mode (programmed/erased with pulse voltage) and DC mode (programmed/erased with direct voltage sweeping) at low temperatures are compared. The experimental results show that with the decrease of temperature, the subthreshold swing of SONOS decreases, whereas the on-state current of SONOS increases. The difference in AC and DC operations causes the threshold voltage of the read curve to drift accordingly, leading to the different change in the memory window. However, in both modes of operations, the efficiencies of programming and erasing decrease at cryogenic temperatures. It is analysed that the reduction of programming efficiency at cryogenic temperatures is caused by the decrease in the quantity of pre-tunnelling electrons. The reduction in erasing efficiency is attributable to the suppression of the Poole-Frenkel effect at low temperatures, which makes it more difficult for electrons to be de-trapped.

It is proposed that the Poole–Frenkel effect be applied to predict radiation-induced charge accumulation in thermal silicon dioxide. Various conduction mechanisms of thermal silicon dioxide are considered, the conditions of the appearance of the Poole–Frenkel effect in it are determined, and the characteristics of donor centers participating in Poole–Frenkel electrical conductivity are calculated. A donor center level at an energy of 2.34 eV below the conduction-band bottom is determined and the concentration of ionized donor centers of 1.0 × 109 cm–3 at 400 K and a field strength of 10 MV/cm is found. It is concluded that the Poole–Frenkel effect can be applied not for prediction of the absolute value of the radiation-induced charge but for comparison of the samples in terms of the ability to accumulate it.

The field and temperature dependences of the electrical conductivity of europium sulfide are studied in the temperature range 160–430 K. It is found that the electrical conductivity increases in strong electric fields of up to 2 × 104 V/cm by the Poole–Frenkel mechanism.

We have examined the Poole-Frenkel mobility field dependence in a molecularly doped polymer (MDP) both experimentally and theoretically trying to separate two physically different contributions to this phenomenon, one constituting a real physical effect and the other arising from the fact that the charge carrier transport in MDP is not fully equilibrated. The former is ascribed to the influence of an electric field on the transport process itself affecting at least one of the model parameters. The latter should be associated with the mobility field effect under conditions when neither model parameter is field sensitive. Numerical calculations have been used to achieve their deconvolution. On the experimental front, we relied on the time of flight technique specifically modified to suit this task. Both approaches show that the contribution of the second (operational) field effect in the investigated MDP is quite appreciable. This result is compared with the traditional interpretation of the Poole-Frenkel effect in molecularly doped polymers.

We report on the conduction mechanisms at room temperature of hydrogenated amorphous silicon carbide (a-Si1-xCx:H) films deposited by 13.56 MHz plasma-enhanced chemical vapor deposition (PECVD). By analysing the current-voltage (J-V) characteristic of films with different thicknesses, it was possible to prove that space charge limited current (SCLC) enhanced by the Poole-Frenkel effect is the dominant charge transport mechanism for high electric fields. In addition, films with a variation of the Si–C ratio x (between 0.5 and 0.8) showed that higher Si content decreases the volume trap density. This result was in accordance to an observed decrease of the Urbach energy, indicating less long-range disorder.

With the rapid increase of electrical energy consumption in metropolises, more and more power cables are utilized in power grid or urban power network to transmit and distribute electrical energy. Silicone rubber is widely used as polymeric insulating materials of power cable accessories due to their excellent electrical and thermal performances. However, under high dc electric field space charges can accumulate inside the silicone rubber, which will distort the electric field in the bulk of the material, influencing the reliability and safety of operation. A bipolar charge injection and transport model is adopted to investigate the accumulation of space charges and distortion of electric field in silicone rubber. It is found that when charge injection rate is higher than the charge migration rate, space charges will accumulate in the material and the accumulation increases with an increase in electric field. The influence of the Poole-Frenkel effect is then studied. It is found that stronger Poole-Frenkel effect can enhance the nonlinearity of effective carrier mobility of silicone rubber, reducing the accumulation of space charges. This indicates that tuning the nonlinearity of effective carrier mobility by nano-doping can suppress space charges, improving the reliability of power cable accessories.

Germanium (Ge) is a promising material for next generation nanoelectronics and multiple junction solar cells. This work investigated the electrical properties in Cu/p-type Ge Schottky diodes, using current-voltage (I-V ) measurements. The Schottky barrier heights were 0.66, 0.59, and 0.70 eV from the forward ln(I)-V, Cheung, and Norde methods, respectively. The ideality factors were 1.92 and 1.78 from the forward ln(I)-V method and Cheung method, respectively. Such high ideality factor could be associated with the presence of an interfacial layer and interface states at the Cu/p-Ge interface. The reverse-biased current transport was dominated by the Poole-Frenkel emission rather than the Schottky emission.

Metal-oxide-semiconductor field effect transistors (MOSFETs) with various doses of La-incorporated in Hafnium-based dielectrics were characterized to evaluate the effect of La on dielectric and device properties. It is found that the Poole-Frenkel emission model could explain our experimental leakage current conduction mechanism reasonably and barrier heights of localized Poole-Frenkel trap sites increase gradually with increasing La incorporation. Cryogenic measurement (from 100 K to 300 K) of MOSFETs reveals that, as the content of La incorporation in the dielectric increases, the more increase of maximum effective mobility has been found at low temperature. It is mainly attributed to the more reduction of phonon scattering due to higher content of La atoms at the interface of dielectric and channel. Though it is relatively small, the existence of La in dielectric reduces coulomb scattering rate as well.

We report on the growth and characterization of Ti/$La_{1/3}$$Ca_{2/3}$Mn$O_3$/Si$O_x$/n-Si memristive devices. We demonstrate that using current as electrical stimulus unveils an intermediate resistance state, in addition to the usual high and low resistance states that are observed in standard voltage controlled experiments. Based on thorough electrical characterization (impedance spectroscopy, current-voltage curves analysis), we disclose the contribution of three different microscopic regions of the device to the transport properties: an ohmic incomplete metallic filament, a thin manganite layer below the filament tip exhibiting Poole-Frenkel like conduction, and the SiOx layer with an electrical response well characterized by a Child-Langmuir law. Our results suggest that the existence of the SiOx layer plays a key role in the stabilization of the intermediate resistance level, indicating that the combination of two or more active RS oxides adds functionalities in relation to single-oxide devices. We understand that these multilevel devices are interesting and promising as their fabrication procedure is rather simple and they are fully compatible with standard Si-based electronics., 15 pages, 4 figures. To appear in Applied Physics Letters

This paper describes the effect of post-deposition annealing on the physical and electrical characteristics of high-k Dy 2 O 3 dielectric films deposited at 250 °C on p-GaAs substrate by electron beam deposition under ultra vacuum. The morphological and structural features of Dy 2 O 3 layer before and after postdeposition annealing were studied by atomic force microscopy (AFM) and X-ray diffraction (XRD). The surface topography analysis reveals that the Dy 2 O 3 film is granular, and contains numerous contacts between columnar grains. While investigating the electrical properties Dy 2 O 3 oxide, the current–voltage characteristics I ( V ) suggest a Poole–Frenkel (PF) type mechanism of carrier transport for as-deposited and annealed layers. A deviation from the PF leakage current course was found and attributed to the current carrier trapping. The ac impedance properties of the structures have been studied in a wide frequency range at different bias voltage. The Dy 2 O 3 annealed exhibited excellent electrical properties such as small density of interface state and low leakage current. This phenomenon is attributed to a rather crystallized Dy 2 O 3 structure and the reduction of the defects at the oxide/GaAs interface.

A new concept of SiO 2 /TiO 2 /SiO 2 (STS) sandwiched dielectrics has been successfully prepared by atomic-layer-deposition technique for high density MIM capacitor applications. Compared with pure TiO 2 dielectric, the addition of ultra-thin (2 nm) SiO 2 layers reduces significantly the leakage current and enhances the breakdown electric field of MIM capacitor. Accordingly, the STS MIM capacitor exhibits a high capacitance density of around 12.4 fF/μm 2 at 100 kHz, and a leakage current density of 8.8 × 10 −7 A/cm 2 at −1 V, which is about three orders of magnitude smaller than that of the pure TiO 2 MIM capacitor. Furthermore, the conduction mechanisms of the STS capacitor have been investigated, revealing that the Poole–Frenkel emission is dominated in the high field range, and the extracted energy barrier separating the traps from the conduction band is in a 0.85–0.90 eV range.

To eliminate the forming process in resistive random access memory (RRAM), we introduced nitrogen into ${\rm AlO}_{x}$ layer to generate a moderate amount of traps inside the film. The composition of nitrogen-doped ${\rm AlO}_{x}$ (N- ${\rm AlO}_{x}$ ) RRAM is revealed by X-ray photoelectron spectroscopy and X-ray diffraction analyses. To understand the current conduction mechanism of N- ${\rm AlO}_{x}$ RRAM, we investigated field and temperature dependence of the charge transport. Based on the extracted trap levels of high-resistance state and various low-resistance states, the current conduction is found to be governed by Frenkel–Poole emission. An energy band model is also proposed to clarify the current conduction mechanism and switching behavior of N- ${\rm AlO}_{x}$ RRAM.

An analytical threshold voltage shift (ΔVth) model of thin-film transistor (TFT) under gate electrical stress is presented in this paper. The model is based on the kinetics of electron transfer in the gate dielectric, namely the channel electrons first inject into the dielectric traps near the interface through trap-assisted tunneling, and then move to the traps at the further positions by Poole-Frenkel conduction. An amorphous indium-gallium-zinc oxide (a-IGZO) TFT is used as the example to verify the proposed model since its ΔVth is mainly caused by the charge trapping effect. The results show that this model can provide not only a precise prediction to the ΔVth of the a-IGZO TFT, but also a detailed distribution of trapped electrons in the dielectric, and thereby help with understanding the recovery of the ΔVth. In addition, the dependence of the ΔVth on trap density NT and trap depth Φt is investigated, and the impact of the shallow oxide traps to the ΔVth is therefore manifested.

This work covers the use of solution-processed metal oxides as interface layers for organic solar cells. To study the interface properties, intrinsic and Al-doped ZnO x were chosen as reference systems. From the class of n-type metal oxides, ZnO x was chosen because it can be doped when it is solution processed. Furthermore, the influence of thin modification layers applied on top of the metal oxides is investigated.

Al/p-Si junction based on Organic Mixed Layer (OML) Methylene Blue (MB) and 2′-7′-dichlorofluorescein (DCF) was fabricated and the current–voltage ( I – V ) and the capacitance–voltage measurements of the structure have been obtained at room temperature. This combination resulted in both a good rectifying behavior and low leakage current. The characteristic parameters of the structure such as barrier height, ideality factor, interface states density and series resistance were determined from the electrical measurements. Also, Cheung functions and Norde method were used to evaluate the I – V characteristics and to obtain the characteristic parameters of the Schottky contact. High-low frequency capacitance–voltage characteristics have been observed to have a maximum. The maximum value of the capacitance is decreased with increasing frequency. The higher values of capacitance at low frequencies were attributed to interface states and the excess capacitance resulting from the interface states in equilibrium with the Si that can follow the alternating current signal. The J – V curves in the reverse direction are taken and interpreted via both Schottky and Poole–Frenkel effects. Poole–Frenkel effect was found to be dominant in the reverse direction.

We have investigated behavior of traps formed in hafnium oxide (HfO2) by electrical stress and their influence on the charge carrier transport through Si/SiO2/HfO2/poly-Si nanostructures. The traps govern the transport process assuming a capture of charge carriers followed by their ionization via the multiphonon transition mechanism. The multiphonon transitions via the Poole–Frenkel effect or electron tunneling as well as the multiphonon tunneling ionization of neutral traps have been carefully considered for charged traps. We also provide a set of parameters including the trap concentration, ionization energy, the frequency factor, the effective mass of charge carriers, optical energy, and phonon energy in order to reproduce and reasonably fit available experimental data.

The resistive switching (RS) properties as a function of temperature were studied for Ag/La$_{1-x}$Sr$_x$CoO$_3$ (LSCO) interfaces. The LSCO is a fully-relaxed 100 nm film grown by metal organic deposition on a LaAlO$_3$ substrate. Both low and a high resistance states were set at room temperature and the temperature dependence of their current-voltage (IV) characteristics was mea- sured taking care to avoid a significant change of the resistance state. The obtained non-trivial IV curves of each state were well reproduced by a circuit model which includes a Poole-Frenkel element and two ohmic resistances. A microscopic description of the changes produced by the RS is given, which enables to envision a picture of the interface as an area where conductive and insulating phases are mixed, producing Maxwell-Wagner contributions to the dielectric properties., Comment: 13 pages, 5 figures, to be published in APL. Corresponding author: C. Acha (acha@df.uba.ar)

We have performed the comprehensive analysis of the time of flight curves using the multiple trapping model with the Gaussian trap distribution. Our analysis shows that flat plateaus on the computed curves are rare events. We have shown numerically that plateau formation for the non-equilibrium transport may be due to the presence of a thin defective (depletion) layer on the sample surface (two-layer model of a polymer film). Also, to describe the Poole–Frenkel effect, we have explicitly introduced an analogous field dependence for the frequency factor.

A series of lateral junctions consisting of NiFe/Al2O3/p-Si/Al2O3/NiFe have been investigated for the understanding of manipulating the electronic spin in semiconducting channel. Devices with various conducting channel lengths between two electrodes were fabricated using a top-down technique. An ion beam sputtering was used for the required film stack and an electron beam lithography in combination with ion beam etching technique were adopted for patterning. The current-voltage measurements reveal a remarkable phenomenon of current enhancement, indicating a formation of the interface state in such devices. This transport behavior associated with trapping assistance has also been demonstrated with a fitting based on Poole-Frenkel effect. The results also show that a transition from trapping assisted process to direct tunneling process occurs when the semiconducting channel length is below 1 μm. In addition, the current enhancement may be suppressed with increasing the thickness of the oxide layer.

Back-end-of-line integrated 1 × μm2 TiN/HfO2/Ti/TiN MIM memory devices in a 0.25- μm complementary metal-oxide-semiconductor technology were built to investigate the conduction mechanism and the resistive switching behavior as a function of temperature. The temperature-dependent I- V characteristics in fresh devices are attributed to the Poole-Frenkel mechanism with an extracted trap energy level at φ ≈ 0.2 eV below the HfO2 conduction band. The trap level is associated with positively charged oxygen vacancies. The electroformed memory cells show a stable bipolar switching behavior in the temperature range from 213-413 K. The off -state current increases with temperature, whereas the on-state current can be described by a weak metallic behavior. Furthermore, the results suggest that the I-V cycling not only induces significant changes in the electrical properties of the MIM memory devices, i.e., the increase in the off-state current, but also stronger temperature dependence. The temperature effect on the on-state and off-state characteristics is modeled within the framework of the quantum point-contact model for dielectric breakdown using an effective temperature-dependent confinement potential.

Aluminum has been perceived as a stable electrode for the reliability test of dielectric films. In this letter, using energy dispersive X-ray spectroscopy method, Al ions were detected in the dielectric after Al/SiCOH/SiO 2 /Si capacitor was subjected to bias-temperature stress (BTS). We investigated the impact of the drifted Al to the stability of the dielectrics by studying the leakage current of the capacitor. We showed that the increase of leakage current after BTS falls into the Poole–Frenkel conduction regime, indicating the Al ions act as electronic traps inside SiCOH. Our results question the compatibility between Al and low- k dielectrics.

Effect of external field on the exciton photoluminescence of GaSe crystals has been investigated and it has been observed that the PL is quenched with the applied field. The changes observed in the PL spectra have been analyzed with impact exciton, Franz–Keldysh and Pool–Frenkel effects. From the analyses of the experimental data, it has been found that the intensity of direct free, indirect free and bound exciton peaks decreased exponentially with the square root of applied field as I ∼exp– β √ E . The energy positions of emission peaks were found to shift to longer wavelength with the applied field as Δ E ∼ β √ E . From these findings, the Pool–Frenkel thermoelectric field effect is seen to be the dominant mechanism in the variation of exciton PL with the applied field even though the impact exciton and Franz–Keldysh effects contribute.

Antifuses are electronic devices that can be irreversibly converted from a high-resistance state to a low-resistance state. Thus, they are ideal candidates for one-time-programmable many-times-readable nonvolatile memories. In this paper, the reliability and the programming characteristics of Si-rich SiNx, antifuses have been studied using time-dependent dielectric breakdown and pulse-breakdown measurements on both single-device test structures and full read-only memories. Contrary to measurements on thick films in which the Poole-Frenkel barrier lowering dominates breakdown, these measurements on fully processed and integrated antifuses indicate that a Fowler-Nordheim-like mechanism governs both programming and long-term reliability.

The present paper reports the effect of electric field on the electrical parameters (activation energy and pre-exponential factor) in amorphous thin films of Se 70 Te 30− x Zn x ( x = 0, 6, 8). It is observed that, in a particular composition, at low electric field up to 10 3 V/cm neither activation energy nor pre-exponential factor depend on electric field as expected in case of ohmic region. However, at higher electric fields where non ohmic region is observed, activation energy and pre-exponential factor both vary with electric field. Similar behavior is observed in all the compositions used in this study. A correlation between activation energy and pre-exponential factor is also observed in these alloys, which is known as Meyer–Neldel rule (MN rule). Further MN rule is also observed in the present case which is explained by the model suggested by Yelon and Movaghar responsible for MN rule in chalcogenide glasses.

We investigated the photovoltaic properties of multi-layered devices consisting of ITO/oxide/Tetraphenyl porphyrin (H2TPP)/Fullerene (C60)/Bathocuproine (BCP)/Al structures. The VOC markedly increases with the insertion of NiO and MoO3 hole collection layers. However, the “kink” behaviors and temperature dependent properties are observed for the devices with and without MoO3 especially for the thick H2TPP film. We demonstrated the analysis of the photovoltaic properties using the Poole-Frenkel and Schottky models based on the dielectric behaviors of porphyrin and MoO3 layers.

In this work we study the electric field dependence of mobility extracted from Electroluminescence Transient (ELT) measurements in both single carrier and double carrier Polymer Light emitting Diode (PLED) configurations by varying the cathode. We have chosen two different families of conjugated light emitting polymers (structurally different hole transporting materials). The Poole–Frenkel (P–F) plot of mobility μ as a function electric field F ( log μ ∝ F ) shows negative slope (β

We report on the electrical properties of polycrystalline NbO2 thin film vertical devices grown on TiN coated SiO2/Si substrates using pulsed laser deposition. First, we analyzed the thickness and contact size dependences of threshold switching of NbO2 films grown in 10 mTorr Ar/O2 mixed growth pressure, where 25.1%/74.9% of NbO2/Nb2O5 surface composition content was estimated by ex-situ x-ray photoelectron spectroscopy. Then the threshold switching and self-sustained current oscillatory behavior of films with different NbO2/Nb2O5 composition ratios was measured and analyzed. The current-voltage measurement revealed that the leakage current property in the insulating state was dominated by the trap-charge assisted Poole-Frankel conduction mechanism. All films showed threshold switching behavior in agreement with the previously proposed Joule heating mechanism. The second film was grown in lower (1 mTorr) growth pressure, which resulted in a higher (34.2%/65.8%) NbO2/Nb2O5 film surface composition. The film grown in higher growth pressure demonstrated lower off-state leakage current, faster switching, and self-sustained oscillations with higher frequency than the film grown in lower growth pressure.

In this paper, we present the effects of ultrathin Si interfacial layer on the physical and electrical properties of GaAs MOS capacitors fabricated using RF-sputtered HfAlOx gate dielectric. It is found that HfAlOx/Si/n-GaAs stack exhibits excellent electrical properties with low frequency dispersion (∼4.8%), hysteresis voltage (0.27 V) and interface trap density (1.3 × 1012 eV−1 cm−2). The current density of 3.7 × 10−5 A/cm2 is achieved with an equivalent-oxide-thickness of 1.8 nm at VFB + 1 V for Si-passivated HfAlOx films on n-GaAs. X-ray photoelectron spectroscopy (XPS) analysis shows that the suppression of low-k interfacial layer formation is accomplished with the introduction of ultrathin Si interface control layer (ICL). Thus the introduction of thin layer of Si between HfAlOx dielectrics and GaAs substrate is an effective way to improve the interface quality such as low frequency dispersion, hysteresis voltage and leakage current. Additionally, current conduction mechanism has been studied and the dominant conduction mechanisms are found to be Schottky emission at low to medium electric fields and Poole–Frenkel at high fields and high temperatures under substrate injection. In case of gate injection, the main current conduction at low field is found to be the Schottky emission at high temperatures.

The effects of vanadium doping on resistive switching (RS) characteristics and mechanisms of RF-sputtered SrZrO3 (SZO)-based thin films are investigated in this paper. The physical and electrical properties of SZO-based thin films are modulated by vanadium doping due to the Zr4+ ion replaced by V5+, further affecting the RS parameters of SZO-based thin films. The conduction mechanisms of SZO-based thin films are dominated by ohmic conduction (hoping conduction) and Frenkel-Poole emission for the low resistance state (LRS) and the high resistance state (HRS), respectively. The turn-on process might be attributed to the formation of conducting filaments consisting of oxygen vacancies with the effective barrier height (φB,eff) in the range of 0.10-0.13 eV, whereas the turn-off process might result from thermally assisted oxidation of oxygen vacancies by the Joule heating effect. Furthermore, the introduction of the high valence cation (V5+) in a Zr4+ site of SZO crystalline structure can suppress the formation of oxygen vacancies due to the charge neutrality restriction. Such suppression leads to the changes in the forming voltage, turn-on voltage, HRS resistance, dielectric constant, and φB,eff with vanadium doping concentration up to 0.2 mol%, which is within the solid solubility limit based on our measured lattice constants and Vegard's law.

We have investigated the temperature dependent current–voltage (I–V) characteristics of Ti Schottky contacts to p-type InP. The Ti/p-type InP Schottky diode yielded an ideality factor of 1.08 showing good rectifying behavior with a barrier height of 0.73 eV at 300 K. The capacitance–voltage (C–V) characteristics of the Ti Schottky contact to p-type InP have been measured at room temperature and at different frequencies. The barrier heights from C–V measurements are calculated to be 0.71, 0.72 and 0.77 eV at 10 kHz, 100 kHz and 1 MHz, respectively. The discrepancy of barrier heights obtained from I–V at 300 K and C–V characteristics measured at f = 1 MHz at 300 K is negligible due to homogenous nature of Schottky diode structures. The characteristic energy of the diode at 300 K showed thermionic emission to be the dominating current mechanism. The analysis of the reverse current–voltage characteristics of the Ti Schottky contact to p-type InP reveals that the main process involved in leakage current could be associated with the Frenkel–Poole emission at 300 K, while at 350 K and 400 K, the Schottky emission.

Charge transport in 5,5′-(2,6-di-tert-butylanthracene-9,10-diyl)bis(2-p-tolyl-1,3,4-oxadiazole) is investigated as a function of temperature and organic layer thickness. The thickness dependence of the current indicates towards the trap charge limited conduction (TCLC) with a field and temperature dependent mobility. The density of trap states has been found to be dependent on sample thickness. As the thickness has increased from 80 nm to 120 nm, trap energy has correspondingly increased from 78 meV to 130 meV. TCLC model with Poole Frenkel type field dependent mobility has been fitted into the data and has been found in excellent agreement. Temperature dependency of zero field mobility (μ0) and β has been estimated from the model.

n-Type 4H-SiC bulk samples with a net doping concentration of 2.5 × 1017 cm−3 were irradiated at room temperature with 1-MeV electrons. The high doping concentration plus a reverse bias of up to −13 V ensures high electric field in the depletion region. The dependence of the emission rate on the electric field in the depletion region was measured using deep-level transient spectroscopy (DLTS) and double-correlation deep-level transient spectroscopy (DDLTS). The experimental data are adequately described by the phonon-assisted tunneling model proposed by Karpus and Pere.

The error in making a mean field approximation when analysing space charge limited currents in organic light emitting diodes has been assessed. Using a Poole Frenkel-like, exp ( γ E ) , field dependent mobility, space charge limited currents have been simulated using zero field mobilities from 10 −10 m 2 /V s to 10 −4 m 2 /V s and field dependent parameter γ from 10 −7 (m/V) 0.5 to 10 −2 (m/V) 0.5 . The simulated current–voltage data has been fitted using a mean field approximation to a modified Mott–Gurney equation and the deviation of zero field mobility and γ from the real values has been calculated. It was found that for a significant range of the simulations the error in both the zero field mobility and the γ factor was invariant, but systematically underestimated by 2% and 15% respectively. We conclude that the mean field approximation is a useful method with which to assess mobility using space charge limited currents in organic semiconductor devices, but the accuracy of such an analysis can be improved by accounting for the systematic error.

We have investigated electrical properties of laminated atomic layer deposited films: ZrO"2-Ta"2O"5, ZrO"2-Nb"2O"5-Ta"2O"5, ZrO"2-Ta"xNb"1"-"xO"5 and Ta"2O"5-Zr"xNb"yO"z. Even though the capacitances of laminates were often higher compared to films of constituent materials with similar thickness, considerably higher charge storage factors, Q, were achieved only when tetragonal ZrO"2 was stabilized in ZrO"2-Ta"2O"5 laminate and when the laminate thickness exceeded 50nm. The decreased Q values in the case of most laminates were the result of increased leakage currents. In the case of thinner films only Ta"2O"5-Zr"xNb"yO"z stack possessed capacitance density and Q value higher than reference HfO"2. Concerning the conduction mechanisms, in the case of thinner films, the Ta"2O"5 or Ta"xNb"1"-"xO"5 apparently controlled the leakage either by Richardson-Schottky emission or Poole-Frenkel effect.

Regardless of used metal contact combinations, bulk-limited electrical behaviors were observed in metal/hydrogenated diamond-like carbon (DLC)/metal (MSM) devices through the study of I-V curves and temperature dependence of conductivity. For MSM devices with DLC deposited at a substrate bias of −50 V, the I-V curves exhibited ohmic electrical behaviors in the range of 0–1 V and followed the Poole-Frenkel mechanism in the range of 1–5 V. Moreover, the carrier transport was dominated by the thermally activated process with an activation energy of 0.1576 eV in the temperature range of 160–400 K. The bulk-limited behaviors of MSM devices could be attributed to the relatively high bulk resistance of the DLC layer. This result offers the fundamental insight into DLC based electrical devices and brings forward the concept to fabricate functional carbon based materials.Regardless of used metal contact combinations, bulk-limited electrical behaviors were observed in metal/hydrogenated diamond-like carbon (DLC)/metal (MSM) devices through the study of I-V curves and temperature dependence of conductivity. For MSM devices with DLC deposited at a substrate bias of −50 V, the I-V curves exhibited ohmic electrical behaviors in the range of 0–1 V and followed the Poole-Frenkel mechanism in the range of 1–5 V. Moreover, the carrier transport was dominated by the thermally activated process with an activation energy of 0.1576 eV in the temperature range of 160–400 K. The bulk-limited behaviors of MSM devices could be attributed to the relatively high bulk resistance of the DLC layer. This result offers the fundamental insight into DLC based electrical devices and brings forward the concept to fabricate functional carbon based materials.

We report the switching characteristics of Mg-doped HfO2-based ReRAM devices consisting of Ru/ Mg:HfO2/TiN/W stacks. The concentration of the Mg dopant was varied from 0% to 20% for four samples to show the impact on the forming voltage. In addition to reducing the forming voltage from 2.8 to 1.7 V, Mg doping in HfO2 also improved the repeatability in the initial device characteristics, switching characteristics, and retention. The mechanism of conduction was identified as Frenkel-Poole emission in doped and undoped samples in virgin resistance state (VRS). Further analysis showed that the increased conductance in the doped samples in VRS was due to higher carrier concentration.

Thick cubic and sp2-bonded boron nitride (cBN and sp2BN) films are deposited on Ti substrates by plasma jet enhanced chemical vapor deposition using the chemistry of fluorine, and their direct current-voltage characteristics are studied for Ni-BN-Ti capacitor structures. The resistivity of the cBN film measured at room temperature is of the order of 108 Ωcm, which is three to four orders of magnitude lower than that of the sp2BN film. At high electric fields, Frenkel-Poole emission dominates the conduction of the sp2BN film, while thermionic emission is better able to describe the conduction of the cBN film at temperatures up to 473 K. A lower leakage current indicates lower densities of carriers and trap sites associated with defects, suggesting that a higher-quality cBN film with higher crystallinity and stoichiometry is potentially promising as an ultrahard dielectric material in high temperature condition.

In this paper the results of DC-conductivity investigation of 1,4-cis-polybutadiene thin films doped with 5% weight of silicon carbonate (SiC) of nanocrystalline form with the size of grains being about 20 nm are presented. The aim of the study was to receive a knowledge about the electrical properties and DC-conductivity mechanisms depending on film thickness, temperature and electric field magnitude. The investigated films thickness ranged from 1 to 12 μm. The investigations were carried out for both undoped and doped with nanocrystalline SiC polymers. The current flow through the material bulk changed from 10−12 to 10−4 A with applied electric fields of 0 to 3 × 107 V/m and temperature of the film varying from 15 to 325 K. It was observed that the magnitude of the current flow through the investigated material bulk is governed by a phase state of the polymer and the presence of SiC in the bulk. The charge transport through the material bulk is controlled by the Poole-Frenkel phenomenon as well as by hopping. The determined activation energies were between kT and 0.36 eV.

The results of experimental investigations of the dislocation-related DLTS-peaks originated from the dislocation networks (DN) are presented. Samples with DNs were produced by direct bonding of p-type silicon wafers and no enhancement of oxygen concentration was detected near the DN plane. Origins of the DLTS peaks were proposed and a correlation with the dislocation-related photoluminescence data was established based on known dislocation structure of the samples. Two types of shallow DLTS peaks exhibited Pool-Frenkel effect, which could be linked to the dislocation deformation potential. One of the shallow DLTS peaks was related to straight parts of screw dislocations and another - to the intersections of the dislocations.

Field-quenching via Frenkel-Poole excitation of Coulomb attractive hole traps limits the field in the CdS part of the junctions to 50 kV/cm. This is far below the field in typical other pn-junctions of thin-film semiconductors, which exceeds 100 kV/cm and approaches tunneling fields that make junctions leaky, hence reduces both V oc and FF. Field-quenched CdS may become electronically inverted, thereby providing a possibility that the junction of the CdS/CdTe cell may extend into the CdS, with the cell becoming a hetero structure. With field quenching a region of negative differential conductivity is created causing a high-field domain that prevents the maximum electric field in the junction to exceed 50kV/cm, avoiding tunneling, hence electron leakage through it. A preliminary band model of this cell is proposed.

The paper presents a systematic investigation of the dielectric charging and discharging process in silicon nitride thin films for RF-MEMS capacitive switches. The SiN films were deposited with high frequency (HF) and low frequency (LF) PECVD method and with different thicknesses. Metal–Insulator–Metal capacitors have been chosen as test structures while the Charge/Discharge Current Transient method has been used to monitor the current transients. The investigation reveals that in LF material the stored charge increases with the film thickness while in HF one it is not affected by the film thickness. The dependence of stored charge on electric field intensity was found to follow a Poole–Frenkel like law. Finally, both the relaxation time and the stored charge were found to increase with the electric field intensity.

The electron beam induced self-consistent charge injection and transport in a layered insulator SiO 2 –Al 2 O 3 is described by means of an electron–hole flight–drift model FDM and an iterative computer simulation. Thermal and field-enhanced detrapping are included by the Poole–Frenkel effect. The surface layer with a modified electric surface conductivity is included which describes the surface leakage currents. Furthermore, it will lead to particular charge incorporation at the interface between the surface layer and the bulk substrate. As a main result the time-dependent spatial distributions of currents j ( x , t ), charges ρ ( x , t ), field F ( x , t ), and potential V ( x , t ) are obtained. The spatial charge distribution with depth shows a quadro-polar plus–minus–plus–minus structure in nanometer dimension.

Two GaPN epilayers, with different N contents of 0.3% and 0.9%, i.e., at the low-doping level and in the dilute-content range, respectively, have been examined by deep level transient spectroscopy (DLTS) and thermal admittance spectroscopy (TAS). DLTS revealed a main peak below 200K and a low-intensity broad signal above 250K. For the dominant peak, Arrhenius plots revealed an activation energy of 0.4eV below the conduction band and a corresponding trap density above 1017cm−3, in both the samples. The higher N-content sample features for this level a broader line shape and about one-order-of-magnitude larger cross section, as compared with the low N-content epilayer. TAS Arrhenius plots yielded a compressed discrepancy between the signatures of this trap in the two samples, pointing to a common physical origin, likely corresponding to N-split interstitials, and to a possible incidence of Poole–Frenkel effect on this trap behavior. However, the main discrepancy between the results from the two techniques lay in the concentrations as calculated for the signal above 250K. It was found that DLTS underestimates its intensity by at least one order of magnitude. Based on the extension of TAS data at high temperatures, this controversial signal resulted to correspond to Ga interstitials, which can also form complexes and can thus account for the strong compensation effects observed in these epilayers.Two GaPN epilayers, with different N contents of 0.3% and 0.9%, i.e., at the low-doping level and in the dilute-content range, respectively, have been examined by deep level transient spectroscopy (DLTS) and thermal admittance spectroscopy (TAS). DLTS revealed a main peak below 200K and a low-intensity broad signal above 250K. For the dominant peak, Arrhenius plots revealed an activation energy of 0.4eV below the conduction band and a corresponding trap density above 1017cm−3, in both the samples. The higher N-content sample features for this level a broader line shape and about one-order-of-magnitude larger cross section, as compared with the low N-content epilayer. TAS Arrhenius plots yielded a compressed discrepancy between the signatures of this trap in the two samples, pointing to a common physical origin, likely corresponding to N-split interstitials, and to a possible incidence of Poole–Frenkel effect on this trap behavior. However, the main discrepancy between the results from the two techniques l...

We report the effect of annealing on electrical and physical characteristics of HfO"2, HfSi"xO"y and HfO"yN"z gate oxide films on Si. Having the largest thickness change of 0.3nm after post deposition annealing (PDA), HfO"yN"z shows the lowest leakage current. It was found for both as-grown and annealed structures that Poole-Frenkel conduction is dominant at low field while Fowler-Nordheim tunneling in high field. Spectroscopic ellipsometry measurement revealed that the PDA process decreases the bandgap of the dielectric layers. We found that a decreasing of peak intensity in the middle HfO"yN"z layer as measured by Tof-SIMS may suggest the movement of N toward the interface region between the HfO"yN"z layer and the Si substrate during the annealing process.

Current–voltage ( I – V ) characteristics have been studied in as-deposited amorphous Ge 2 Sb 2 Te 5 films. At low electric fields, ohmic behavior is observed. On the other hand, at high electric fields ( E > 10 6 V/m) the current becomes non-ohmic. Analysis of the data shows the existence of Poole–Frenkel conduction in which ln I vs V 1/2 curves are found to be straight lines. Pre-switching behaviors are also discussed from electrode configuration.

Ga2Se3 films were deposited by the thermal evaporation of the bulk material onto pyrographite substrates under vacuum. The I–V characteristic curves were found to be typical for a memory switch. They exhibited a transition from an ohmic region in the lower-field region to a non-ohmic region in the high-field region in the preswitching region, which has been explained by the Poole–Frenkel effect. The temperature dependence of the resistance in the ohmic region was found to be that of a thermally activated process. It was also found that the mean value of the switching voltage increased linearly with increasing film thickness in the range from 291 nm to 516 nm, while it decreased exponentially with increasing temperature in the range from 298 K to 393 K. The results were explained in accordance with the electrothermal model for the switching process.

Understanding carrier transport in carbon nanotubes (CNTs) and their networks is important for harnessing CNTs for device applications. Here, we report multishell carrier transport in individual multiwalled CNTs, and films of randomly dispersed multiwalled CNTs, as a function of electric field and temperature. Electrical measurements and first-principles density functional theory calculations indicate transport across CNT shells. Intershell conduction occurs across an energy barrier range of 60-250 meV in individual CNTs, and ~ 60 meV in CNT networks. In both cases, the conductance behavior can be explained based upon field-enhanced carrier injection and defect-enhanced transport, as described by the Poole-Frenkel model.

In this paper, we evaluate the potentialities of hafnium-aluminates (HfAlO) materials as possible candidates for the interpoly dielectrics of future Flash memory devices. HfAlO layers of different thicknesses and compositions are integrated in single-layers and in Oxide/HfAlO/Oxide (OHO) triple-layer stacks, and analyzed in terms of coupling and insulating capabilities. We demonstrate that increasing the Hf content allows reducing the leakage current at high voltages but it results in a stronger leakage current at low voltages. We also show that once normalized in electric fields, the leakage current characteristics are independent of the high-k thickness. The electron conduction modes in these materials, at different temperatures, are also investigated. The activation energy increases with the Hf concentration in the HfAlO alloy, resulting in a higher leakage current at elevated temperatures. Finally, it is demonstrated that the conduction in triple-layer stacks is limited by a Poole–Frenkel conduction in the high-k layers, while the trap contribution in the case of single-layers becomes dominant when the HfAlO layer is thicker than 8 nm.

Amorphous Se 70 Te 30– x Cd x ( x = 0, 10) are obtained by thermal evaporation under vacuum of bulk materials on pyrographite and glass substrates. The I – V characteristic curves for the two film compositions are typical for a memory switch. They exhibited a transition from an ohmic region in the lower field followed by non-ohmic region in the high field region in the preswitching region, which has been explained by the Poole-Frenkel effect. The temperature dependence of current in the ohmic region is found to be of thermally activated process. The mean value of the threshold voltage $\bar{V}_{th}$ increases linearly with increasing film thickness in the thickness range (100–491 nm), while it decreases exponentially with increasing temperature in the temperature range (293–343 K) for both compositions. The results are explained in accordance with the electrothermal model for the switching process. The effect of Cd on these parameters is also investigated.