Capacitance-voltage Characteristics Research Articles

Electrical properties of unintentionally doped β-Ga2O3 (010) thin films grown by a low-pressure hot-wall metalorganic chemical vapor deposition

We investigated the electrical properties of unintentionally doped (UID) Ga2O3 (010) layers grown by low-pressure hot-wall metalorganic chemical vapor depositions from device characteristics of Schottky barrier diodes (SBDs) fabricated on them. Highly resistive properties of the UID Ga2O3 layers were confirmed from current–voltage characteristics. The specific on-resistance of the SBD with the most resistive UID Ga2O3 layer was 2.2 × 107 Ωcm2. Capacitance–voltage characteristics revealed that most of the SBDs had complete depletion of the UID layers at thermal equilibrium, indicating that their residual effective donor densities were less than 3.0 × 1013 cm−3.

Peculiarities of Electric and Dielectric Behavior of Ni- or Fe-Doped ZnO Thin Films Deposited by Atomic Layer Deposition.

The physical properties of ZnO can be tuned efficiently and controllably by doping with the proper element. Doping of ZnO thin films with 3D transition metals that have unpaired electron spins (e.g., Fe, Co, Ni, etc.) is of particular interest as it may enable magnetic phenomena in the layers. Atomic layer deposition (ALD) is the most advanced technique, which ensures high accuracy throughout the deposition process, producing uniform films with controllable composition and thickness, forming smooth and sharp interfaces. In this work, ALD was used to prepare Ni- or Fe-doped ZnO thin films. The dielectric and electrical properties of the films were studied by measuring the standard current-voltage (I-V), capacitance-voltage (C-V), and capacitance-frequency (C-f) characteristics at different temperatures. Spectral ellipsometry was used to assess the optical bandgap of the layers. We established that the dopant strongly affects the electric and dielectric behavior of the layers. The results provide evidence that different polarization mechanisms dominate the dielectric response of Ni- and Fe-doped films.

DC current–voltage and impedance spectroscopy characterization of nCdS/pZnTe HJ

This paper describes the electrical and dielectric behavior of the nCdS/pZnTe HJ by current–voltage, capacitance–voltage characteristics, and impedance spectroscopy in a temperature interval 220–350 K. A microcrystalline p-ZnTe layer and n-CdS were grown on glass/ZnO substrate by closed space sublimation method. As frontal contact to CdS, the transparent ZnO and as a back contact to ZnTe, silver conductive paste (Ag) treated at 50 °C in vacuum were used. The current–voltage results of nCdS/pZnTe HJ show a rectifying behavior. The junction ideality factor, barrier height, and series resistance values were extracted from the rectifying curves at different temperatures. The built-in voltage, carrier concentration and depletion width were obtained from the capacitance–voltage measurements. Analysis of the J–V–T and C–V–T characteristics shows that the thermionic emission and recombination current flow mechanisms dominate in the nCdS/pZnTe HJ. The dielectric study reveals that the experimental values of the AC conductivity, dielectric constant, dielectric loss, the imaginary part of the electric modulus are found to be very sensitive to frequency and temperature. The dielectric constant and dielectric loss are observed to be high at the low frequency region. The increase in the values of electric modulus with the frequency implies an increase in the interfacial polarization at the interface of nCdS/pZnTe HJ. Jonscher’s universal power law shows that with increasing frequency, AC conductivity increased. The results conductivity show that the ionic conductivity and interfacial polarization are the main parameters affecting the dielectric properties of the device when the temperature changes.

Effect of temperature on polaronic transport in CeO2 thin-film.

The outstanding catalytic property of cerium oxide (CeO2) strongly depends on the polaron formation due to the oxygen vacancy (V̈O) defect and Ce4+ to Ce3+ transformation. Temperature plays an important role in the case of polaron generation in CeO2 and highly influences its electrical transport properties. Therefore, a much needed attention is required for detailed understanding of the effect of temperature on polaron formation and oxygen vacancy migration to get an idea about the improvement in the redox property of ceria. In this work, we have probed the generation of polarons in CeO2 thin-film deposited on a silicon (Si) substrate using the resonance photoemission spectroscopy (RPES) study. The RPES data show an increase in polaron density at the substrate-film interface of the thermally annealed film, indicating the formation of an interfacial Ce2O3 layer, which is, indeed, a phase change from the cubic to hexagonal structure. This leads to a modified electronic band structure, which has an impact on the capacitance-voltage (C-V) characteristics. This result nicely correlates the microscopic property of polarons and the macroscopic transport property of ceria.

Vertical Schottky diode on (113) oriented homoepitaxial diamond

Vertical Schottky diodes were fabricated on (113) oriented diamond substrates produced from thick heavily boron doped (NA ∼ 3.5 × 1020 cm−3) diamond layers grown on HPHT-grown synthetic Ib diamond crystals. The p+-substrates were overgrown by a low doped p-epilayer whose surface layer was compensated up to the depth of 0.1 to 0.3 μm. The surface was then oxygen terminated and covered by evaporated Mo/Au Schottky contacts. The bottom ohmic contact to p+-substrate was formed by Ti/Au bi-layer. Current- and capacitance-voltage characteristics of the realized diodes were measured at temperatures ranging from 25 to 180 °C. At room temperature, the realized diodes show high forward current densities JF = 100 A/cm2 and low differential ON-state specific resistance Ron_sp = 3.7 mΩ.cm2 at forward voltage VF = 4 V and a very low leakage (JR < 10−9 A/cm2) in the blocking regime. At 180 °C, forward characteristics significantly improve (JF = 5 kA/cm2, Ron_sp = 0.2 mΩ.cm2 at VF = 4 V) while the blocking characteristics remain almost unchanged (JR = 6 × 10−8 A/cm2 at VR = 4 V). The breakdown electric field is about 3 MV/cm and the rectification ratio keeps at the level of 1011. Characteristics of realized diodes, which are fully comparable to those of Schottky-pn diodes prepared on (111) oriented boron doped diamond, confirm the suitability of (113) orientation for realization of vertical diamond power devices.

Role of defects in tailoring the structural, electrical and optical properties of Schottky diodes based on GaAsBi alloy through gamma radiation

This work provides an extensive study of the influence of γ-rays on structural, electrical, and optical characteristics of GaAsBi Schottky diodes fabricated through Molecular Beam Epitaxy (MBE) on GaAs substrates. An important finding is the direct correlation observed between the radiation dose and the consequent increase in the turn-on voltage of the devices. X-ray diffraction (XRD) showed that only phases related to the GaAs and GaAs1-xBix layers were observed. Raman spectroscopy proved to be a powerful tool to elucidate the effects of ionizing radiation on GaAsBi samples. From the results of electrical measurements, such as current density-voltage, the characteristic parameters of the devices improved as a function of the radiation dose. Conversely, the Capacitance-Voltage (C–V) characteristics indicated a rise in the concentration of free carriers in all irradiated samples, suggesting an enhancement in the performance of the diodes. Assessment through Deep Level Transient Spectroscopy (DLTS) further revealed a reduction in the number of electrically active traps following irradiation. Consequently, the findings presented here highlight the potential improvements in diode performance resulting from sample irradiation. Upon subjecting the samples to irradiation doses of 50 kGys and 100 kGys, we identified the presence of three and two electron traps, respectively. This differs from the unirradiated diodes, which displayed four electron traps. Interestingly, the photoluminescence intensity of the main peak exhibited an increment with increasing irradiation dose. This observation implies an enhancement in the optical characteristic, as well as annihilation/contribution of Bi-related traps. These findings corroborate the electrical results obtained in our study. Finally, the Raman results showed that the decrease in the lifetime of the photoexcited carriers leads to a higher recombination rate which in turn leads to a higher photoluminescence (PL) intensity after radiation.

Performance analysis of un-doped and doped titania (TiO ) as an electron transport layer (ETL) for perovskite solar cells.

Density functional theory (DFT) calculations are carried out on pure and doped rutile TiO . The bandgap (E ) for pristine, S-doped, Fe-doped, and Fe/S co-doped materials is direct, with values of 2.98 eV, 2.18 eV, 1.58 eV, and 1.40 eV. The effective mass of charge carriers (m*) and ratio of effective masses of holes to effective masses of electrons (R) are also investigated, and it is discovered that Fe/S co-doped materials have the lowest charge carrier recombination rate. The Fe/S co-doped material has the highest . of doped materials shifted into the visible range. Due to the high dopant concentration in Fe and Fe/S-doped cases, the E is lowered to a relatively small value; hence, only pristine and S-doped materials are verified as electron transport layer (ETL). A solar cell device analysis employing pure and S-doped rutile TiO as ETL is completed using DFT-derived parameters in SCAPS-1D modeling software for the first time. For the optimized solar cells, current-voltage (IV) characteristics, quantum efficiency (QE), capacitance-voltage (CV) characteristics, and capacitance-frequency (Cf) characteristics are provided. The aim of the present study is to improve efficiency of perovskite solar cell by doping as well as to improve accuracy of simulation by applying DFT extracted parameters as input. From the analysis, improvement is found in efficiency of doped TiO compared to un-doped TiO . The efficiency of the PSC with S-doped ETL is 1.418% higher than the PSC with un-doped ETL. Quantumwise Automistic Tool Kit (ATK) is used to extract DFT parameters. Using these DFT parameters as input in SCAPS-1D (Solar Cell Capacitance Simulator), solar cells for doped and un-doped material are simulated. The density functional theory (DFT)-based orthogonalized linear combination of atomic orbital (OLCAO) technique is used. Structural optimization is done using the LBFGS (Limited-memory Broyden-Fletcher-Goldfarb-Shanno). PBESol-GGA (Perdew-Burke-Ernzerhof solid-generalized gradient approximation) is applied as exchange correlation for calculating structural parameters, while MGGA-TB09 (meta-generalized gradient approximation-Tran and Blaha) is applied as exchange correlation for calculating optical and electronic properties.

Sol-Gel Multilayered Niobium (Vanadium)-Doped TiO2 for CO Sensing and Photocatalytic Degradation of Methylene Blue.

Multilayered TiO2 films doped either with Niobium or Vanadium (1.2 at. %) were deposited by the sol-gel dip coating method on c-Si and glass substrates. The films on glass substrates were tested for CO sensing and photocatalytic degradation of methylene blue. X-ray diffraction data analysis showed that all the TiO2:Nb(V) films were nanocrystalline in the anatase phase, with a uniform and compact microstructure and a homogeneous superficial structure of small grains with diameters in the range of 13-19 nm. For the electrical characterization, the TiO2:Nb(V) films were incorporated in Metal-Insulator-Semiconductor (MIS) structures. The specific resistivity is of the order of 104 Ωcm and its value decreases with increasing the electrical field, which testifies to the injection of electrons into these layers. From the analysis of the current-voltage curves taken at different temperature- and frequency-dependent capacitance-voltage and conductance-voltage characteristics, the density and parameters of deep levels in these TiO2 films are evaluated and the electron charge transport mechanism is established. It was shown that the current in these TiO2:Nb(V)-Si MIS structures is mainly carried out by inter-trap tunneling via deep levels energetically distributed in the TiO2 bandgap. Testing these sol-gel TiO2:Nb(V) layers for gas sensing and photocatalytic capabilities proved that they could serve such purposes. In particular, the results of the V-doped sol-gel TiO2 film confirm its CO detection capability, which is rarely reported in the literature. For the photodegradation of methylene blue, the Nb-doped TiO2 samples were superior, with nearly double the photocatalytic efficiency of undoped TiO2.

Machine learning-based method for predicting C–V-T characteristics and electrical parameters of GaAs/AlGaAs multi-quantum wells Schottky diodes

In this work, two models of artificial neural networks are developed to predict the electrical parameters and capacitance-voltage characteristics of GaAs/AlGaAs multi-quantum wells Schottky diodes at different temperatures. Capacitance-Voltage-Temperature (C–V-T) characteristics for voltages and temperatures in the ranges (-4 V–0 V) and (20 K–400 K), respectively, were used to assess the effectiveness of the proposed approach. The first model (Model 1) is used to evaluate how well the neural network predicts the C–V-T characteristics. The second simulation, known as Model 2, was constructed to simultaneously overcome the problems of determining the electrical parameters and predicting C–V-T characteristics. Model 2 allows the calculation of the built-in voltage, effective density, and capacitance. Three-fold cross-validation and mean square error are used to assess the effectiveness of the developed models. The results clearly demonstrate the high prediction accuracy of the electrical parameters and C–V characteristics at all temperatures. After training, Model 1 Mean Square Error performance is 1.5033×10−6 at 1450 epochs, whereas Model 2 MSE is 4.9951×10−6 at 642 epochs. According to the error distribution frequency histogram, about 95 % of errors for Model 1 and Model 2 lie between [0.00535 and 0.005608] and [0.00328 and 0.00333], respectively. The R-values that correspond to the training and validation datasets for both models are close to one (0.9999). Parameters determination results have been compared against those obtained using ant lion optimizer based method. It was found that the results obtained from the neural networks models strongly agree with the experimental data.

Analysis on the capacitance-voltage characteristics of metal-insulator-semiconductor capacitors based on thermally evaporated WOx on n- and p- type crystalline silicon

Tungsten oxide (WOx) thin films were deposited on n- and p-type crystalline silicon (c-Si) wafers by thermal evaporation technique at room temperature. The electrical characterization of Ag/WOx/n-Si and Ag/WOx/p-Si metal–insulator-semiconductor (MIS) capacitors were examined by the capacitance- and conductance-voltage measurements as a function of applied frequency in the 10 kHz 10 MHz range. The admittance properties of both MIS devices have been evaluated by analyzing the interfacial nature and bulk c-Si in accumulation, depletion, and inversion regimes. The capacitance responses of interface traps, bulk c-Si, depletion, and shallow states at the WOx/c-Si interface indicated the appearance of the capacitance peaks in depletion and inversion regimes for Ag/WOx/n-Si and Ag/WOx/p-Si devices. From C-V characterization, various parameters such as the depletion layer width, depletion capacitance, flat-band voltage, total charge density, and net ionized state density were calculated as a function of applied frequency. For Ag/WOx/n-Si device, the total charge density and barrier height values of 7.642 × 10−9 C and 1.119 eV at 1 MHz, respectively, were obtained. The same parameters were calculated to be 5.887 × 10−8 C and 1.107 eV for Ag/WOx/p-Si. The results demonstrated that interfacial nature of WOx film significantly governs the electronic characteristics of the c-Si based MIS devices.

Correction to: Quantization Effect in N-Channel Inversion Mode Si, In0.53Ga0.47As and Ge Based Double Gate MOSFET Using Quasi-Static Capacitance–Voltage Characteristics for Upcoming Sub 10 nm Technology Node

Correction to: Quantization Effect in N-Channel Inversion Mode Si, In0.53Ga0.47As and Ge Based Double Gate MOSFET Using Quasi-Static Capacitance–Voltage Characteristics for Upcoming Sub 10 nm Technology Node

Investigation of dual work function metal (DWFM) gate stacks with ALD TaAlN and TaAlC for multi threshold voltages (VTHs) engineering in MOS device integration

This study investigates methods to modulate the effective work function (EWF) and control the multiple threshold voltages (VTHs) of metal-oxide-semiconductor (MOS) devices by applying metal electrodes with different work function materials (WFMs), including a single layer of n-type (TaAlC) and p-type (TaAlN) as well as their stacked structures, through atomic layer deposition (ALD). Dual-Work-Function-Metal (DWFM) gate is a crucial aspect of confirming the feasibility of metal gate stacks in MOS devices for a complementary metal-oxide-semiconductor (CMOS) integration scheme. The gate stack structure of p-Si/IL (Inter layer)/HfO2/DWFM (p/n-type compatible metal stack)/W exhibits good adhesion and even chemical composition distribution, as evidenced by transmission electron microscope (TEM) and energy dispersive spectrometer (EDS) analysis. By fabricating MOS capacitors using this WFM structure and extracting EWF from the measured capacitance-voltage (C–V) characteristics, EWF values of 4.62 eV and 4.99 eV were identified both before and after annealing using forming gas, indicating pWFM-like properties. These properties are attributed to the strengthened Al–O bonds and reduced CO peaks seen in x-ray photoelectron spectroscopy (XPS) analysis. The use of different Ta precursor from Tris(diethylamido)(tert-butylimido)tantalum(V) (TBTDET) as well as TaCl5 resulted in the increase of the EWF following the unique p-WFM like feature. As candidates for WFM electrode in metal-oxide-semiconductor field effect transistor (MOSFET) with the DWFMs (n/p stacks) were evaluated, resulting in a VTH of 0.84 V that places in the middle of the VTH shift range from 0.6 V (nWFM) to 1.16 V (pWFM), approximately. The DWFMs allow for modulation of the EWF, which in turn reduces ambiguity in addressing replacement metal gate (RMG) challenges and opens up new avenues for achieving multi-VTH solutions in CMOS integration schemes.

ИМПЕДАНСНЫЙ АНАЛИЗ ПРОЦЕССОВ ПЕРЕНОСА ЗАРЯДА В СТРУКТУРЕ МЕТАЛЛ/ПОЛИМЕР/МЕТАЛЛ

The reaserch is devoted to the experimental study of charge transfer processes in thin films of an electroactive polymer from the class of polyarylene phthalides – poly (diphenylene phthalide). The method of impedance analysis of thin polymer films was used in this work. The material is quite well studied using other methods, such as thermally stimulated methods, optical spectroscopy, etc. However, frequency measurements were carried out mainly only in the field of determining capacitance-voltage characteristics. And since the polymer is electroactive, we should expect to identify features associated with charge transfer in the alternating field mode. In this regard, the work carried out an impedance analysis of thin films of poly (diphenylene phthalide) in the frequency range from 0.1 to 106 Hz. Typically, in impedance analysis, in addition to an ac field, a small DC bias voltage is applied to the metal/polymer/metal structure. This makes it possible to obtain data on surface polarization, charge carrier mobility, and the Maxwell-Wagner effect in the case of studying multilayer films. However, taking into account the electrical activity of the studied material, even impedance analysis in an alternating field, but with an effective voltage range from 0.1 to 10 V, made it possible to evaluate some of the electrophysical characteristics of the behavior of thin films. It was found that the slope of the impedance curve depends on the mechanism of transport of charge carriers in the polymer film. As the voltage increases from 0.1 to 10 V, an increase in the slope of the graph is observed. With an increase in the magnitude of the effective voltage, a transition occurs from the ohmic to the injection mechanism of transport of charge carriers limited by traps. When reaching 2 V, a mode of complete filling of the traps is observed, as a result of which an increase in voltage ceases to affect the slope of the frequency response. The dependence of the transition frequency fc on voltage has been plotted. This frequency corresponds to the transition from the predominance of the active to the reactive component of the impedance. Here, an exponential dependence on the magnitude of the applied voltage is observed, which also indicates the dependence of the mechanisms of transport of charge carriers in the polymer film on voltage (electric field).

Channel engineering for optimizing the electro‐thermal characteristics in p‐type GAA nanosheet transistors

AbstractIn this paper, we report simulation results for capacitance–voltage characteristics and temperature distribution in the cross‐section of p‐type gate‐all‐around nanosheet channel using an in‐house developed numerical simulator. The effects of material, channel width, and crystallographic orientation on electrical and thermal properties of p‐type nanosheet transistor are comprehensively investigated. The effect of channel engineering is analyzed, by evaluating density‐of‐states, hole density, current densities as well as distributions of temperature in the channel cross‐section. Finally, the thermal reliability of the device is addressed in terms of thermal resistance. The density‐of‐states and the hole density distribution at the oxide/channel interface can well explain the effective intrinsic capacitance obtained from the simulation. The better uniformity of the hole density distribution across the cross‐section of (110)/[001] channel, shows good promise for less performance fluctuation in terms of the thermal reliability issue.

AlGaN/GaN devices with metal–semiconductor or insulator–semiconductor interfacial layers: Vacuum level step due to dipole and interface fixed charge

We have systematically investigated effects of metal–semiconductor or insulator–semiconductor interfacial layers (ILs) in AlGaN/GaN devices, where AlOx, TiOx, or NiOx is employed as an IL. From capacitance–voltage characteristics of metal/IL/AlGaN/GaN devices with a metal–semiconductor IL between the gate metal and AlGaN, it is shown that the IL modulates the threshold voltage Vth, attributed to the vacuum level step induced by the dipole of the IL. We find negative vacuum level steps for AlOx and TiOx ILs, and positive for NiOx, from which the IL dipole density is estimated for each IL material. The two-dimensional electron gas carrier concentration in the metal/IL/AlGaN/GaN devices is also modulated by the vacuum level step. On the other hand, from capacitance–voltage characteristics of metal/Al2O3/IL/AlGaN/GaN devices with an insulator–semiconductor IL between Al2O3 and AlGaN, the fixed charge density of the Al2O3/IL/AlGaN interface is evaluated by the Al2O3 thickness dependence of Vth. For AlOx and TiOx ILs, the fixed charge density is higher than that of the Al2O3/AlGaN interface with no IL, while lower for NiOx. The fixed charge density for an IL shows a positive correlation with the IL dipole density, suggesting that the fixed charge is related to the unbalanced IL dipole. Furthermore, using the conductance method, we find a low trap density of the Al2O3/IL/AlGaN interface for AlOx and NiOx ILs, in comparison with that of the Al2O3/AlGaN interface with no IL.

Impact of Graded AlGaN Buffer Layer Thickness on the DC, RF, Linearity, Intermodulation and Off-State Breakdown Characteristics of AlGaN Channel HEMT

This study examines the extraction of small-signal equivalent circuit parameters, linearity and intermodulation metrics, and capacitance–voltage characteristics for both AlGaN and GaN channel HEMTs. Compared to GaN channel HEMTs, AlGaN channel HEMTs have better linearity and intermodulation distortion. In the instance of AlGaN channel HEMTs, the device parasitics are decreased. Additionally, the effect of graded AlGaN buffer layer thickness on breakdown characteristics and linearity is examined. For breakdown characteristics, the 200 nm-graded AlGaN buffer layer thickness yields superior results with VBOff 157 V for a thickness of 200 nm (147 V in the case of 500 nm). At 200 nm thickness, the linearity and intermodulation distortion FOMs are also reasonably good, and the remaining device properties are essentially unchanged. Hence, the graded AlGaN buffer thickness can be reduced for high-voltage applications. For higher-voltage applications, the graded AlGaN buffer thickness can, therefore, be decreased.

Study of bulk damage of high dose gamma irradiated p-type silicon diodes with various resistivities

The bulk damage of p-type silicon detectors caused by high doses of gamma irradiation has been studied. The study was carried out on three types of n+-in-p silicon diodes with comparable geometries but different initial resistivities. This allowed to determine how different initial parameters of studied samples influence radiation-induced changes in the measured characteristics. The diodes were irradiated by a Cobalt-60 gamma source to total ionizing doses ranging from 0.50 up to 8.28 MGy, and annealed for 80 minutes at 60 °C. The Geant4 toolkit for simulation of the passage of particles through matter was used to simulate the deposited energy homogeneity, to verify the equal distribution of total deposited energies through all the layers of irradiated samples, and to calculate the secondary electron spectra in the irradiation box. The main goal of the study was to characterize the gamma-radiation induced displacement damage by measuring current-voltage characteristics (IV), and the evolution of the full depletion voltage (V FD) with the total ionizing dose, by measuring capacitance-voltage characteristics (CV). It has been observed that the bulk leakage current increases linearly with total ionizing dose, and the damage coefficient depends on the initial resistivity of the silicon diode. The effective doping concentration and therefore V FD significantly decreases with increasing total ionizing dose, before starting to increase again at a specific dose. We assume that this decrease is caused by the effect of acceptor removal. Another noteworthy observation of this study is that the IV and CV measurements of the gamma irradiated diodes do not reveal any annealing effect.

Carrier density distribution in AlGaAs/GaAs superlattices with different numbers of quantum wells determined by capacitance-voltage profiling

The charge carrier density distribution in uniformly doped AlGaAs/GaAs superlattices with layer thicknesses of 1.5/10 nm and different numbers of quantum wells was studied. Both energy band theory and capacitance–voltage profiling were used to determine the carrier concentration profiles of the structures. During the analysis of the experimental and simulated capacitance–voltage characteristics, it was found that the maximum electron concentrations increase with an increase in the number of quantum wells from ∼ 7.1⋅1016cm−3 for three wells to ∼ 9.3⋅1016cm−3 for 25 wells with an overall superlattice doping level of ∼ 1017cm−3.

Size-induced high electrocaloric response of dense ferroelectric nanocomposites

Analytical results obtained within Landau-Ginzburg-Devonshire approach and effective media models, predict that the synergy of Vegard stresses and size effects can significantly enhance the electrocaloric cooling (up to 7 times) of the BaTiO3 nanoparticles in comparison with a bulk BaTiO3. To compare with the considered effective media models, we measured the capacitance-voltage and current-voltage characteristics of the dense nanocomposites consisting of (28–35) vol% BaTiO3 nanoparticles incorporated in organic polymers and determined experimentally the effective dielectric permittivity and losses of the composites. Generalizing obtained analytical results, various ferroelectric nanoparticles spontaneously stressed by elastic defects, such as oxygen vacancies or any other elastic dipoles, which create a strong chemical pressure, can cause the giant electrocaloric response of dense ferroelectric nanocomposites. We have shown that the advantages of the studied lead-free dense nanocomposites are the good tunability of electrocaloric cooling temperature due to the strain and size effects in ferroelectric nanoparticles and the easy control of the high electrocaloric cooling by electric fields. This makes the dense ferroelectric nanocomposites promising for cooling of conventional and innovative electronic elements, such as FETs with high-temperature superconductor channels.

Negative Capacitance and Dielectric Constant of Nanocomposite SiAlzOxNy(Si) Films with Semiconductor Nanoparticles.

The electrical properties of nanocomposite SiAlzOxNy(Si) films containing Si nanoclusters embedded into amorphous SiAlzOxNy matrix have been studied by measurements of DC current-voltage and AC capacitance-voltage characteristics. Analysis of the results allowed us to conclude the existence of a negative dielectric constant. The temperature dependence of the negative dielectric constant has been obtained and analyzed. The negative capacitance has been revealed during measurements of capacitance-voltage characteristics at testing signal frequency of 2 kHz. The negative capacitance also points out the appearance of a negative dielectric constant effect. The qualitative model for explanation of negative dielectric constant based on peculiarities of SiAlzOxNy(Si) films polarization due to electron capture at Si nanoparticles-amorphous SiAlzOxNy matrix interface traps near cathode region has been proposed. In the case of AC C-U measurements, a negative capacitance is observed if conductivity current through the nanocomposite film is relatively high.