Flow Of Charge Carriers Research Articles

3D-Mapping and Manipulation of Photocurrent in an Optoelectronic Diamond Device.

Establishing connections between material impurities and charge transport properties in emerging electronic and quantum materials, such as wide-bandgap semiconductors, demands new diagnostic methods tailored to these unique systems. Many such materials host optically-active defect centers which offer a powerful in situ characterization system, but one that typically relies on the weak spin-electric field coupling to measure electronic phenomena. In this work, charge-state sensitive optical microscopy is combined with photoelectric detection of an array of nitrogen-vacancy (NV) centers to directly image the flow of charge carriers inside a diamond optoelectronic device, in 3D and with temporal resolution. Optical control is used to change the charge state of background impurities inside the diamond on-demand, resulting in drastically different current flow such as filamentary channels nucleating from specific, defective regions of the device. Conducting channels that control carrier flow, key steps toward optically reconfigurable, wide-bandgap optoelectronics are then engineered using light. This work might be extended to probe other wide-bandgap semiconductors (SiC, GaN) relevant to present and emerging electronic and quantumtechnologies.

Temperature dependent electrocatalytic activity of molybdenum-based ZIF-67 nanorods for water splitting

Several strategies have been adopted to enhance the electrochemical features of metal-organic framework structures for water splitting, however, a suitable conditions can effectively boost the electrocatalytic activity. Herein, molybdenum-based zeolite imidazolate frameworks (Mo2gZIF-67 and Mo4gZIF-67) have been synthesized by solvothermal process and electrocatalytic activity was examined at various elevating temperatures of 1 M KOH electrolyte. Mo4gZIF-67 nanorods showed the overpotential (η10) of 358 mV at 20 °C, which was improved to 221 mV at 80 °C for the oxygen evolution reaction. Mo4gZIF-67 nanorods exhibited the Tafel slope of 77 mV dec−1 at 80 °C and followed the Volmer-Heyrovsky mechanism. LSV curves reveal that Mo4gZIF-67 nanorods showed a greater current density and a good turnover frequency (TOF) of 221.0 ms−1 at the fixed VRHE of 0.7 V. Similarly, Mo4gZIF-67 nanorods revealed the η10 of 181 and 93 mV at 20 and 80 °C, respectively for the HER process. Mo4gZIF-67 nanorods displayed a Tafel slope of 95 mV dec−1 and TOF of 213.50 ms−1. The enhanced electrocatalytic activity may be due to rising temperatures, enhanced electrical conductivity at rising temperatures, well defined nanorods shape and greater ECSA, which provided the active sites and facile the flow of charge carriers for oxygen and hydrogen evolution reaction. The electrocatalyst, Mo4gZIF-67 nanorods exhibited a uniform current density during stability tests for 30 h at 20 °C, which was increased at 80 °C. Temperature elevation remarkably enhanced the HER and OER characteristics of the Mo4gZIF-67 nanorods and suggested an effective electrocatalyst for water splitting.

CuO@N/C-ZnO nanoflowers with quantum dots derived from ZIF-8 for efficient CO2 photoreduction

In this pioneering work, an innovative photocatalyst, denoted as the porous erythrocytic-like nanoflower derived from zeolitic imidazolate framework (ZIF-8) (CuO@N/C-ZnONF), has been meticulously crafted. This design integrates a porous nanosheet of nitrogen and carbon co-doped ZnO, strategically refined with CuO nanosheets (CuONS) architecture originating from ZIF-8. This innovative nanomaterial serves as a nanoreactor for converting CO2 into CO and CH4. The distinctive porous nanoflower structure facilitates enhanced mobility of charge carriers throughout the accessible framework, maximizes exposure of active sites, and improves the flow of charge carriers while preventing their recombination. Additionally, the porous characteristics facilitate the diffusion of reactants and products. The synthesized 10CuO/N-C-ZnONF demonstrates superior photocatalytic performance, yielding high CO and CH4 outputs of 286.16 and 39.74 µmol g−1h−1, respectively, and exhibits excellent long-term stability.

A Z-scheme LaFeO3-CuFe2O4 composite for sulfate radical-based photocatalytic process: Synergistic effect and mechanism

The sulfate radical-based photocatalytic process is supposed to be the most promising way to degrade organic pollutants. However, the development of a suitable and efficient photocatalyst is very challenging. The 40LaFeO3-CuFe2O4 (40LFO-CFO) nanocomposite was constructed and its catalytic performance was studied using Rhodamine B (RhB) as the target pollutant. 40LFO-CFO exhibited excellent RhB degradation by the persulfate (PS) - assisted photocatalytic process compared to the pristine LFO and CFO. The degradation rate constant for RhB by 40LFO-CFO in the Vis/PS system was 2.22 h -1 which is 3.04 times and 5.05 times higher than the pristine LFO (0.73 h -1) and CFO (0.44 h -1) respectively. Furthermore, the trapping experiment and EPR proved that h+ plays a leading role in the bleaching of RhB for the 40LFO-CFO/PS/Vis system. The enhanced photocatalytic oxidation activity of 40LFO-CFO could be attributed to the unique charge carriers flow in 40LFO-CFO due to the Z-scheme and the cooperation effect between photocatalysis and PS activation. The recycle tests confessed the stability of 40LFO-CFO. Additionally, the intermediates and products of RhB are detected by liquid chromatography-mass spectrometry (LC-MS), and the photocatalytic degradation routes of RhB for the 40LFO-CFO/Vis/PS system were proposed. Moreover, the 40LFO-CFO nanocomposite has a superior catalytic performance for other organics, suggesting that it is a promising heterocatalyst because of its high catalytic activity and stability for the PS-assisted photocatalytic process.

Dual-drive strategy-based modulation of the interfacial charge of S-scheme heterojunction and photoelectrochemical ultrasensitive detection of CD44

The efficacy of charge carrier separation plays a crucial role in influencing the practical application of photoelectrochemical (PEC) detection platforms, which can be meticulously engineered to realize highly sensitive detection at the sensing interface. Hence, a novel dual-drive strategy was proposed to integrate thermally-assisted external drive behavior with the internal drive behavior of sulfur vacancies (SVs), realizing the rapid separation of charge at the S-scheme heterojunction sensing interface. On the one hand, unabsorbed solar energy was utilized an external driving force to facilitate efficient photothermoelectric conversion within the In2S3/CdS heterojunction, achieving the photocurrent response intensity 1.5 times higher than conventional PEC detection methods. On the other hand, introducing sulfur vacancies (SVs) as internal driving forces induced ordered migration and directional flow of charge carriers. Moreover, density functional theory (DFT) calculations and experimental results demonstrated that photo-generated carriers achieved rapid separation along the S-scheme heterojunction. Under the optimal conditions, a biosensor constructed based on the dual-drive strategy exhibited high sensitivity for the CD44 (cluster of differentiation-44) cluster, with a low detection limit of 0.132 pg mL−1and a wide linear range of 0.001 ∼ 1000 ng mL−1. The proposed strategy offers new insights into how to effectively harness excess energy in the traditional ultraviolet spectral range for ultrasensitive biosensors.

Manipulating the morphology and charge accumulation driven- Schottky functionalized type II-scheme heterojunction for photocatalytic hydrogen evolution and SERS detection

Inspired by energy conversion and sensing strategies, the construction of a type-II heterojunction proves advantageous in enhancing interfacial charge transfer, redox capabilities, and sensitive detection. Herein, we have developed as-prepared a hierarchical heteronanostructure composed of 2D ultrathin g-C3N4 (g-CN) nanosheets, 3D SrTiO3 (STO) nanocubes, and Ag plasmonic nanoparticles (NPs) with a well-controlled configuration and intimate contact for improved practical applications. This multifunctional heterojunction not only exhibits outstanding hydrogen evolution reaction (HER) performance but also shows excellent SERS detection. The creation of hybrid morphologies and type II schemes contributes to expanding visible light absorption and shortening the path of charge carrier transition. The ternary sample also exhibits an efficient photocatalytic HER rate of 9378 μmol g−1 h−1, which is 13.3 and 26.3 times higher than that of STO (703 μmol g−1 h−1) and g-CN (356 μmol g−1 h−1), respectively. Photoluminescence spectroscopy and linear sweep voltammetry (LSV) measurements suggest that the synergistic effect among g-CN nanosheets, STO nanocubes and Ag contributes to enhanced charge separation, as indicated by the applied potential of −0.9 V vs. saturated Ag/AgCl to obtain a photocurrent density of −15 mA cm−2 for the HER. The obtained STO/g-CN/Ag sample exhibits significant capability in enriching small molecules, facilitating the determination of organic pollutants even at ultralow concentrations. Additionally, it exhibits impressive SERS sensitivity and photocatalytic performance. Crystal Violet (CV) at low concentrations can be distinguished and undergoes almost complete degradation under visible-light illumination. The detection platform exhibits ultralow detection capability down to 10−10 M for CV. The outstanding SERS detection may be assigned to the combined enrichment abilities of g-CN, STO and the localized surface plasmon resonance (LSPR) of Ag NPs. Furthermore, the type-II heterojunction of the ternary photocatalyst and the mechanisms governing charge carrier flow and transfer on the conductive Ag co-catalyst were also investigated. This work provides novel insights and techniques for effectively engineering 3D STO-like semiconductors, facilitating both green energy production and the detection of trace molecules.

Frequency response of nanoscale core-shell of silicon wires doped with boron and nickel

In this work, silicon microcrystals doped with a boron impurity to concentrations corresponding to the metal-dielectric transition in silicon of 5.5·1018 cm−3 and a nickel impurity in the temperature range of 4.2 ÷ 70 K under alternating current in the frequency range of 0.010 ÷ 250 kHz were studied. The features of the frequency response of silicon microcrystals are determined. On the basis of Nyquist diagrams, an equivalent conductivity scheme at low temperatures is proposed. The frequency response of the samples was evaluated and the mechanisms of charge carrier flow were proposed depending on the observation conditions. Conduction mechanisms from quantum mechanical tunneling (QMT) to superlinear power law (SLPL), which can be implemented in crystals, are considered.

Promoting nitrogen photofixation for the synthesis of ammonia using oxygen-vacant Fe2O3/ZrO2 visible light photocatalyst with straddling heterojunction and enhanced charge transfer

Photocatalytic nitrogen (N2) fixation is a promising and environmentally friendly alternative approach to the energy-intensive Haber-Bosch process to produce green ammonia (NH3) with zero carbon emissions. However, the unique setbacks rest on developing an active photocatalyst with an accelerated charge transfer that could efficiently adsorb and activate the chemically inert N2 into useful NH3. Herein, an oxygen-vacant Fe2O3/ZrO2 photocatalyst with straddling heterojunction was successfully synthesised by the hydrothermal method followed by calcination at 450 °C. The addition of oxygen vacancy-inducing ferromagnetic material on ZrO2 increased the adsorption and activation of N2, broadened the solar absorption window (680 nm extending to 910 nm). It also accelerated light-induced charge separation of the photocatalyst thereby greatly enhancing the production of NH3 (1.301 mmol h−1 g−1) with about a 7-fold increase in comparison to ZrO2 at ambient conditions under sunlight irradiation. This work therefore sheds light on the effect of oxygen vacancies and the flow of charge carriers in the effective photofixation of N2 to NH3 synthesis through a sustainable route.

Thermoelectric Performance Improvement in the ZrNiSn-Based Composite via Modulating Si Addition.

To ensure optimal performance, ZrNiSn is required to possess a low thermal conductivity and exhibit minimal bipolar effects under high-temperature conditions. This study demonstrates the integration of silicon (Si) at different doping levels into ZrNiSn. The composites consist of secondary phases of in situ ZrNiSi and Si. At a temperature of 873 K, the Seebeck coefficient experiences a 16% increase, despite the charge carrier concentration increasing three times as a result of the electron injection from ZrNiSi. The phenomenon can be elucidated by the introduction of Si, which causes energy filtering and inhibits the flow of minority charge carriers. When the doping levels in n- or p-type Si reach high levels (1019 to 1020 cm-3), the mixed interfaces ZrNiSn/ZrNiSi and ZrNiSn/Si reduce the thermal conductivity by 15%, resulting in a 50% increase in zT. These findings indicate that electron transfer in ZrNiSn can be regulated by precise doping in Si. They also demonstrate that incorporating an optimal p-type semiconductor can enhance the thermoelectric performance of n-type ZrNiSn. Additionally, a novel approach is proposed to separate electrical conductivity and the Seebeck coefficient by designing unique secondary phase interfaces.

Small Molecule Additives to Suppress Bundling in Dimensional‐Limited Self‐Alignment Method for High‐Density Aligned Carbon Nanotube Array

AbstractSemiconducting single‐walled carbon nanotube (CNT) is a promising candidate as a channel material for advanced logic transistors, attributed to the ultra‐thin 1‐nm cylindrical geometry, high mobility, and high carrier injection velocity. However, the presence of undesired CNT bundles in the CNT arrays for wafer‐scale device fabrication, even when utilizing the state‐of‐the‐art dimension‐limited self‐alignment (DLSA) method, poses challenges. These CNT bundles degrade the transistor gate's efficiency in controlling the flow of charge carriers in the CNT channel, leading to pronounced device‐to‐device variability. Here, a novel method is introduced to alleviate bundling in CNT arrays assembled via DLSA, by involving small molecule additive to screen the attractive van der Waals force between neighboring CNTs during the DLSA process, resulting in over 50% reduction in CNT bundling. Furthermore, a pioneering methodology for quantifying CNT bundles is presented and employed experimentally to assess bundles in dense CNT arrays assembled by DLSA using transmission electron microscopy. Both experimental data and molecular dynamics simulation reveal that CNT bundling originates from van der Waals attraction between CNTs, and the disturbed liquid‐liquid interface by accumulating excess polar molecules. These findings illuminate new pathways for realizing dense, bundle‐free CNT arrays.

Coating of Felt Fibers with Carbon Nanotubes and PEDOT with Different Counterions: Temperature and Electrical Field Effects.

The use of wearable devices has promoted new ways of integrating these devices, one of which is through the development of smart textiles. Smart textiles must possess the mechanical and electrical properties necessary for their functionality. This study explores the impact of polymer-felt microstructure variations on their morphology, electrical, and mechanical properties. The application of thermal treatment, along with an electric field, leads to a substantial structural reorganization of the molecular chains within pristine felt. This results in a system of nanofibrils coated with MWCNT-PEDOT, characterized by highly ordered counterions that facilitate the flow of charge carriers. Both temperature and an electric field induce reversible microstructural changes in pristine felt and irreversible changes in coated felt samples. Furthermore, electropolymerization of PEDOT significantly enhances electrical conductivity, with PEDOT:BTFMSI-coated fabric exhibiting the highest conductivity.

Exploring the Enhanced Catalytic Activity of Pt Nanoparticles Generated on the Red Phosphorus/Graphitic Carbon Nitride Binary Heterojunctions in the Photo-assisted Hydrolysis of Ammonia Borane.

Ammonia borane (AB) holds great promise for chemical hydrogen storage, but its slow dehydrogenation kinetics under ambient conditions requires a suitable catalyst to facilitate hydrogen production from AB. Here, we fabricated binary red phosphorus/graphitic carbon nitride (RP/g-CN) heterojunctions decorated with Pt nanoparticles (NPs, denoted Pt/RP/g-CN) with a facile ultrasound-assisted two-step protocol as a photo-assisted catalyst for the hydrolysis of AB (HAB). The heterojunction established through intimate P-O-N bonds was proven to have improved photophysical properties such as a lower electron-hole recombination and enhanced visible light utilization compared to the pristine components. With the incorporation of Pt NPs, the optical properties of RP/g-CN heterojunctions were further improved through Schottky junction formation between semiconductors and Pt NPs, enabling a superb hydrogen gas (H2) generation rate of 142 mol H2·mol Pt-1·min-1 under visible light irradiation. Even though g-CN is a well-known host material for many metal NPs, here we discovered that the interaction of Pt NPs with RP in the ternary heterojunction structure is more favorable than that of g-CN, stressing the key role of RP as a support material in the designed ternary heterostructure. The band alignment of the ternary heterojunction catalyst along with the flow of charge carriers was also studied and shown to be a type-II heterojunction structure without hole migration, namely, a complex type-II heterojunction. Several scavenger experiments were also conducted to explain the mechanism of the photo-assisted HAB. To the best of our knowledge, this is the first example of a dual mechanism proposed for the visible light-assisted HAB. While the majority of the H2 was believed to be produced on the Pt NPs surface with the traditional B-N bond dissociation mechanism, the strong oxidizing action of OH• radicals formed by the heterojunction photocatalyst was also speculated to account for the 33% increase in the activity upon visible light irradiation through another mechanism.

G-C3N4 sheet nanoarchitectonics with island-like crystalline/amorphous homojunctions towards efficient H2 and H2O2 evolution

Photocatalystic evolution of H2O2 from water and oxygen has attracted significant attention because of environmentally friendly. The absorption in visible and hydrophilic feature of graphitic carbon nitride (g-C3N4) make it a good candidate. In this paper, a rapid post-treatment at high temperature was developed to obtain g-C3N4 nanosheets with abundant crystalline/amorphous interfaces to form homojunctions, which optimized uniplanar carrier mobility dynamics. The conversion from bulk to two-dimensional g-C3N4 resulted from the breakage of interplanar hydrogen bonds and interlayer Van der Waals force. The unique morphology not only rendered photocatalyst with larger specific surface area but also inhibited the robust volume recombination of charge carriers. The accelerated charge carriers flow at the interface, interplane and interlayer together ameliorated the separation and transfer of electrons and holes. A new-emerged n→π* transition ameliorated the poor light utilization efficiency. Beyond the increased photocatalytic H2 evolution property (779.2 μmol g−1 h−1), optimized sample displayed a H2O2 evolution activity as high as 4877.1 μM g−1 h−1 under visible light illumination, which was ∼5.8 times of that of bulk g-C3N4. Detailed photocatalytic mechanism investigation manifested that the two-step single-electron oxygen reduction process occupied the dominant status in H2O2 evolution. This work proposed a novel strategy for obtaining g-C3N4 homojunctions as a promising bi-functional metal-free catalyst to be applied in clean energy production field.

Improvement in conductivity of lead-free CH3NH3SnI3 perovskite thin film using multi-walled carbon nanotubes as a transporter

CH3NH3SnI3 is a lead-free perovskite material that gains significant attention due to its favourable properties for optoelectronic device applications. It is a potential replacement for lead-based perovskite materials. However, the presence of traps, defects, and oxidation vacancies within these perovskite-based devices hinders the flow of charge carriers, causing them to become trapped or recombined within the device before reaching the electrodes. This limits the electrical performance of the device. To address this issue, this study focuses on improving the electrical performance of CH3NH3SnI3 perovskite by incorporating MWCNTs. Thin films of CH3NH3SnI3 perovskite were prepared both with and without MWCNTs. By employing the Van der Pauw method, resistivity measurements revealed that the electrical conductivity of the film increased to 7.80 × 10−2 S/m with the presence of MWCNTs, compared to 8.4 × 10−4 S/m without them. I-V measurements of the thin films-based Schottky devices showed that the conductivity increased from 1.21 × 10−5 S/m to 1.02 × 10−4 S/m with MWCNTs, while the barrier height decreased from 0.51 eV to 0.43 eV, and the ideality factor decreased from 4.01 to 2.56. The improved electrical performance observed when MWCNTs were incorporated, suggested that they formed a charge transfer pathway for carriers within the perovskite material. This pathway reduced trap energy, enabling charge carriers to percolate between grains and reach the electrodes. These findings highlight the significance of MWCNTs as a means to enhance the charge transfer dynamics in environmentally friendly CH3NH3SnI3 perovskite-based devices. Such improvements have promising implications for the development of future perovskite-based devices.

Toward High‐Efficiency CIGS‐based Thin‐film Solar Cells Incorporating Surface Defects Layer, through a Comparative Study of Electrical Characteristics—SCAPS 1D Modeling

This research contribution investigates a way of improving performance of CIGSe‐based second‐generation thin‐film solar cells by analyzing output parameters of two reference cells using cadmium sulfide and zinc sulfide as buffer layers. The performances are improved by acknowledging both the exceptional properties of ZnS as a buffer layer, and the beneficial contributions of an indium‐enrich layer, which form a surface defect layer at the ZnS/CIGSe heterojunction. SCAPS‐1D numerical modeling software is used to conduct calculations, and the structure using ZnS enables achieving an efficiency of 24.31%. Deeper investigation on the effects of variation of functional layers properties such as bandgap, electron affinity, doping level, and thickness enables retaining an optimized structure, and results show an improved efficiency of 25.22% and a fill factor of 80.26%, indicating of a fluid flow of charge carriers, thus a more stable device. All simulations are performed considering experimental environment parameters, an external temperature of 300 K, light illumination of AM1.5G, and defects states are assumed in both the bulk and at interfaces.

Graphene Transistors for In Vitro Detection of Health Biomarkers

AbstractBiomarkers are primary indicators for precise diagnosis and treatment. The early identification of health biomarkers has been sustained by the evolutionary success in sensor technologies. Among them, graphene field‐effect transistor (GFET) biosensors have exhibited major advantages such as an ultrashort response time, high sensitivity, easy operation, capability of integration, and label‐free detection. Owing to the atomic thickness, graphene restricts charge carrier flow merely at the material surface and responds to foreign stimuli directly, leading to effective signal acquisition and transmission. Here, this review summarizes the latest advances in GFET biosensors in a comprehensive manner that contains the device design, working principle, surface functionalization, and proof‐of‐concept applications. It provides a comprehensive survey of GFET biosensors with regard to biomarker analysis at the single‐device level and integrated prototypes that include wearable sensors, biomimetic systems, healthcare electronics, and diagnostic platforms. Moreover, there is discussion on the long‐standing research efforts and outlook for the future development of GFET sensor systems from lab to fab.

Mechanisms responsible for the onset of selective laser flash sintering of 8‐YSZ

AbstractSelective laser flash sintering (SLFS) is a variation of flash sintering where the only external heat source is a scanning laser. The scanning laser locally heats a region of the sample between two electrodes, initiating measured current flow at a threshold electric field and laser energy density. This study focuses on understanding how charge transport occurs during stage I SLFS in 8 mol% yttria stabilized zirconia. Two potential charge transport mechanisms are considered: (1) a continuous current moving along a hot line between electrodes and (2) charge transported in a discrete bundle within a hot spot, localized to the area under the laser beam. Two laser scan patterns are employed to experimentally determine how charge is transported during stage I SLFS. Numerical modeling is used to estimate the temperatures at which SLFS initiates, which allows the calculation of charge carrier densities and mobilities relevant for the onset of SLFS. Results demonstrate that both a discrete bundle of charges and continuous flow of charge carriers contribute to the current at the onset of SLFS.

Phase Control of Organometal Halide Perovskites for Development of Highly Efficient Solar Cells

To develop a highly efficient solar cell using organometal halide perovskites, its microscale structure control is one of the most important factors because the microstructural defects inside the organometal halide perovskite are harmful to charge carrier flow and, thus, degrade device performance. In this study, we confirmed the existence of large physical gaps at the grain boundary in a methylammonium iodide (MAPbI3, MA = CH3NH3) perovskite with transmission electron microscopy (TEM) analysis and revealed that the physical gap prevents charge carrier flow in the MAPbI3 perovskite. To minimize the physical gap and its negative influences, the grain size of the MAPbI3 perovskite was optimized by increasing the portion of the cubic phase via microstructural phase control using liquid nitrogen (LN2). Through microstructural phase control of the MAPbI3 perovskite, its grain boundaries and physical gap were significantly decreased, and 20.23% power conversion efficiency (PCE) was achieved with a single cation MAPbI3 perovskite solar cell.

Realization of smooth side profile using diffusion-controlled wet chemical etching for HgTe/(Hg,Cd)Te heterostructures

We utilize a diffusion-controlled wet chemical etching technique to fabricate microstructures from two-dimensional HgTe/(Hg,Cd)Te-based topological insulators. For this purpose, we employ a KI: I2: HBr: H2O-based etchant. Investigation of the side profile of the etched heterostructure reveals that HgTe quantum wells protrude from the layer stack as a result of the different etch rates of the layers. This constraint poses challenges for the study of the transport properties of edge channels in HgTe quantum wells. In order to achieve a smoother side profile, we develop a novel approach to the etching process involving the incorporation of a sacrificial design element in the etch mask. This limits the flow of charge carriers to the ions in the electrolyte during the etching process. The simplicity of the method coupled with the promising results achieved thereby should make it possible for the new approach introduced here to be applied to other semiconductor heterostructures.

Nonlinear Properties of an Inhomogeneous Diode Structure in a Strong Microwave Field

Results of experimental investigation of detection (rectification) of high power X-band microwave signal in diodes of various design (semiconductor p-n-junction, point-contact, Schottky, Metal-Isolator-Metal—MIM) are reported. The maximum of the detected direct voltage V vs. power P of microwave signal and subsequent polarity reversal, previously found in MIM diodes in the optical and microwave bands, have found to be characteristic of all investigated diodes as well. After the reversal of polarity, this dependence comes linear, and the sign of the voltage corresponds to thermoEMF. In some diodes, the hysteresis on V(P) was observed. All 5 types of V(P) of MIM diodes (have made from different pairs of metals), reported earlier, were reproduced on same p-n-junction diode by variable external DC bias. These results joined with abnormal frequency cutoff forced to suggest that there is an unknown mechanism for direct flow of charge carriers (and for generate direct current) in the high-frequency electrical field, which differs from the conventional rectification.