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Crystal structure, optical and electrical properties of metal-halide compound [C7H16N2][ZnCl4]
摘要： A new organic–inorganic hybrid compound [C7H16N2][ZnCl4] was synthesized by hydrothermal method and characterized by single-crystal X-ray diffraction, IR and Raman spectroscopy, optical absorption, differential scanning calorimetry and dielectric measurements. Single crystal diffraction results showed that [C7H16N2][ZnCl4] crystallizes in the monoclinic system, space group P21/c at room temperature. In the molecular arrangement, the tetrachlorozincate anions are connected to organic cations through N-H...Cl hydrogen bonds. The Raman and IR analyses confirm the presence of the organic groups and the anionic entities. UV–Visible absorption spectrum revealed the energy of the optical band gap. DSC measurements indicated that [C7H16N2][ZnCl4] undergoes three sequential phase transitions at 287, 338 and 356 K. The dielectric study proved the ferroelectric properties below the 338K and indicates their classical character for this compound. The analysis of Nyquist plots revealed the contribution of the bulk mechanism and the grain boundaries.
关键词： Phase transitions,Hybrid material,Crystal structure,Optical absorption,Ferroelectric properties,Conduction mechanism
更新于2025-09-23 15:23:52
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Electrical Transport Properties of Thin Film Composed of a-ZnO Nanorods
摘要： Background: Due to its wide band gap, high exciton binding energy and high breakdown strength, the nanostructures of ZnO may find applications for electronic, photonic devices, and high-frequency applications. Objective: The aim of the present work is to study electrical transport of thin film composed of a-ZnO nanorods. Method: Physical vapour condensation method was employed to fabricate the nanorods of ZnO. The morphology of these nanorods was investigated with the help of scanning electron microscope. X-ray diffraction pattern of as-prepared thin film was recorded using X-ray diffractometer. For dc conductivity measurements, four-probe method was used. Result: The as-prepared ZnO nanorods have diameter ranging from 10-20 nm and the length is of order of few hundred nanometers. XRD pattern of film composed of ZnO nanorods suggests the amorphous nature. Temperature dependence of dc conductivity has been studied over the temperature range of (297- 4.2K). For the temperature range of 297-120K, Mott’s three dimensional variable range hopping (VRH) is applied to explain the electrical conduction. For lower temperature range (120 - 4.2K), 2D-variable-range hopping in localized states near the Fermi level may be responsible for the transport of carriers. Conclusion: Variable range hopping mechanism (VRH) has been suggested for the entire temperature range (298-4.2K) on the basis of temperature dependence of dc conductivity data, which changes from 3D to 2D on moving to lower temperatures side (below 125K).
关键词： physical vapour condensation technique,variable range hopping,XRD,ZnO nanorods,SEM,Mott’s parameters,electrical conduction mechanism
更新于2025-09-23 15:22:29
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Gate Conduction Mechanisms and Lifetime Modeling of p-Gate AlGaN/GaN High-Electron-Mobility Transistors
摘要： The gate conduction mechanisms in p-gallium nitride (GaN)/AlGaN/GaN enhancement mode transistors are investigated using temperature-dependent dc gate current measurements. In each of the different gate voltage regions, a physical model is proposed and compared to experiment. At negative gate bias, Poole–Frenkel emission (PFE) occurs within the passivation dielectric from gate to source. At positive gate bias, the p-GaN/AlGaN/GaN “p-i-n” diode is in forward operation mode, and the gate current is limited by hole supply at the Schottky contact. At low gate voltages, the current is governed by thermionic emission with Schottky barrier lowering in dislocation lines. Increasing the gate voltage and temperature results in thermally assisted tunneling (TAT) across the same barrier. An improved gate process reduces the gate current in the positive gate bias region and eliminates the onset of TAT. However, at high positive gate bias, a sharp increase in current is observed originating from PFE at the metal/p-GaN interface. Using the extracted conduction mechanisms for both devices, accurate lifetime models are constructed. The device fabricated with the novel gate process exhibits a maximum gate voltage of 7.2 V at t1% = 10 years.
关键词： time-dependent breakdown (TDB),p-GaN gate,high-electron-mobility transistor (HEMT),enhancement mode,gallium nitride (GaN),Conduction mechanism
更新于2025-09-23 15:21:21
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Exploring conduction mechanism and photoresponse in <i>P-</i> GaN <i>/n-</i> MoS <sub/>2</sub> heterojunction diode
摘要： Mixed-dimensional heterostructures have shown their potential in electronic devices. However, their functionality is limited by a complete understanding of the contacts and the current transport behavior. Here, we explore the electrical properties of the P-n heterojunction diode fabricated using p-type gallium nitride and layered molybdenum disulfide. The resulting P-n diode is rectifying in nature with current rectification of three orders of magnitude. The careful choice of Ohmic contacts on both the semiconductors reveals distinctly rectifying behavior of the heterojunction diode. The as-fabricated diode is tested at various temperatures, and the conduction mechanism in the device is analyzed based on the temperature dependent electrical characterizations. In addition, photoresponse characterization reveals that the P-n heterojunction is highly sensitive to a 405 nm laser with a high responsivity of 444 A/W at a reverse bias voltage of 5 V and shows photovoltaic behavior. The heterojunction diode acts as a self-powered photodetector. Our findings show the potential of the MoS2/GaN heterojunction in highly efficient photodetector applications.
关键词： conduction mechanism,heterojunction diode,photoresponse,P-GaN,n-MoS2
更新于2025-09-19 17:13:59
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Sensors, Circuits and Instrumentation Systems (2018) || Investigation of Optoelectronic Properties of Amorphous Silicon Germanium Photodetectors
摘要： Cost consideration of the development of electronic devices is one of prime importance. One simple approach to lower the cost of production of photovoltaic and detectors is by using low cost materials such as amorphous silicon and germanium. These two semiconductors have different optoelectronic properties, such as energy gap, photoconductivity and absorption coefficient. The use of an alloy from the mixing of silicon with certain percentages of germanium would produce photodetectors with improved electronic characteristics and photoconductivity. A number of a-SiGe alloy thin films with different quantities of germanium have been fabricated using thermal vacuum evaporation technique. Conduction mechanism and activation energy of the prepared samples had been calculated and analyzed. The I–V characteristics, the photogenerated current and detectivity of these samples are subjected to measurement and discussion. Hall measurements are also conducted so to calculate the Hall I–V characteristics, Hall mobility, carrier concentration and type identification of the samples.
关键词： Amorphous silicon germanium photodetector,photoconductivity,detectivity,Hall measurements,activation energy,conduction mechanism
更新于2025-09-16 10:30:52
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Dielectric and electrical properties of annealed ZnS thin films. The appearance of the OLPT conduction mechanism in chalcogenides
摘要： The annealing temperature (Ta) dependence of the structural, morphological, electrical and dielectric properties of ZnS thin films was investigated. In this work, we consider the as-deposited and annealed ZnS thin films at different temperatures. The as-deposited films were amorphous in nature. However, the films annealed at Ta ≥ 673 K, exhibited a hexagonal structure with (002) preferential orientation. The post annealing caused an improvement in crystallinity. The best one was observed at Ta = 723 K. Grain size increased from 7 nm to 25 nm as annealing temperature was increased from 673 K to 723 K. The surface of annealed samples is homogenous and uniform and the rms roughness is dependent on the annealing temperature: it increases with temperature within the range 5–50 nm. The film electrical conductance is found to be dependent on frequency measurement and annealing temperature: the dc conductance exhibits semi-conductor behavior for all ZnS films over the explored range of temperature and the conductance was found to enhance with increasing annealing temperature up to 623 K. In addition, it was observed that the highest conductance and lowest activation energy of ZnS films were obtained at an annealing temperature of 623 K. The mechanism of alternating current ac conductance can be reasonably explained in terms of the overlapping-large polaron tunnelling (OLPT) model for samples annealed at 623 K and 673 K. To our knowledge, this conduction mechanism was rarely found in chalcogenide materials. A significant change of Nyquist plot with annealing temperature was noted permitting the correlation between the microstructure and its electrical properties. The impedance analysis investigated that the relaxation process is well pronounced for the both annealed films at 623 K and 673 K. The dielectric behavior was associated to the polarization effect, an improvement on the dielectric constant 30 and dielectric loss 300 with annealing was noticed.
关键词： electrical properties,dielectric properties,annealing temperature,OLPT conduction mechanism,ZnS thin films
更新于2025-09-16 10:30:52
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Electrical and photoresponse characteristics of 8-(1H-indol-3-ylazo)-naphthalene-2-sulfonic acid/n-Si photodiode
摘要： In this paper, of primary interest is to synthesis 8-(1H-indol-3-ylazo)-naphthalene-2-sulfonic acid (INSA) and to evaluate the main parameters of Au/INSA/n-Si/Al diode in dark and under illumination. Different techniques are used for interpreting the proposed INSA chemical structure. The dark current-voltage measurements were achieved in the temperature range of 293?413 K. It is noticed that INSA films modify the interfacial barrier height of classical Au/n-Si junction. At low applied voltages, the I–V relation shows exponential behavior. The values ideality factor, n, and the barrier height, ?, are improved by heating. The abnormal trend of n and ? is discussed, and a homogenous barrier height of 1.45 eV is evaluated. The series resistance is also calculated using Norde’s function and it changes inversely with temperature. The space charge limited current ruled with exponential trap distribution dominates at relatively high potentials, trap concentration and carriers mobility are extracted. The reverse current of the diode has illumination intensity dependence with a good photosensitivity indicating that the device is promising for photodiode applications.
关键词： Diode parameters,Photodiodes,Conduction mechanism,Azo compounds
更新于2025-09-12 10:27:22
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Atomic-layer-deposited (ALD) Al2O3 passivation dependent interface chemistry, band alignment and electrical properties of HfYO/Si gate stacks
摘要： In this work, the effects of atomic-layer-deposited (ALD) Al2O3 passivation layers with different thicknesses on the interface chemistry and electrical properties of sputtering-derived HfYO gate dielectrics on Si substrates have been investigated. The results of electrical measurements and X-ray photoelectron sepectroscopy (XPS) showed that 1-nm-thick Al2O3 passivation layer is optimized to obtain excellent interfacial properties for HfYO/Si gate stack. Then, the metal-oxide-semiconductor capacitors with HfYO/1-nm Al2O3/Si/Al gate stack were fabricated and annealed at different temperatures in forming gas (95% N2+5% H2). Capacitance-voltage (C-V) and current density-voltage (J-V) characteristics showed that the 250oC-annealed HYO high-k gate dielectric thin film demonstrated the lowest border trapped oxide charge density (-3.3 × 1010 cm-2), smallest gate-leakage current (2.45 × 10-6 A/cm2 at 2 V) compared with other samples. Moreover, the annealing temperature dependent leakage current conduction mechanism for Al/HfYO/Al2O3/Si/Al MOS capacitor has been investigated systematically. Detailed electrical measurements reveal that Poole-Frenkle emission is the main dominant emission in the region of low and medium electric fields while direct tunneling is dominant conduction mechanism at high electric fields.
关键词： Al2O3 passivation layer,Electrical properties,Annealing,Co-sputtering HYO films,Conduction mechanism
更新于2025-09-10 09:29:36
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High temperature impedance properties and conduction mechanism of W <sup>6+</sup> -doped CaBi <sub/>4</sub> Ti <sub/>4</sub> O <sub/>15</sub> Aurivillius piezoceramics
摘要： Effects of W6+ doping on the phase structural and electrical properties, especially the conduction mechanism at a higher temperature of CaBi4Ti4O15 Aurivillius piezoceramics, have been investigated systematically. The conductivity properties at a temperature range from 500 °C to 650 °C have been characterized by complex impedance spectroscopy. The conductivity shows a nature of ionic conduction mechanism and non-Debye relaxation process at a higher temperature. The non-Debye relaxation behavior and conduction process are dominated by the jump of charge carriers, which can be demonstrated by the similar values of the relaxation activation energy (1.45 eV), hopping conduction energy (1.50 eV), and dc conduction energy (1.39 eV). Meanwhile, the piezoelectric coef?cient d33 of CaBi4Ti4O15 has been improved from 7.5 pC/N to 17.8 pC/N and keeps good temperature stability up to 650 °C with appropriate W6+ doping. These results provide a profound insight into the conduction process and mechanism from the viewpoint of microstructure, which is greatly bene?cial for the high-temperature application of Aurivillius piezoceramics.
关键词： Aurivillius piezoceramics,impedance properties,conduction mechanism,CaBi4Ti4O15,high temperature,W6+-doped
更新于2025-09-09 09:28:46
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Dynamic mechanical and electric behaviors of La-doped BiVO4
摘要： Bismuth vanadate (BiVO4) is an important semiconductor with wide applications, but it is still lack of in-depth understanding for its fundamental dynamic behaviors. To address this issue, the comprehensive analysis of structure, internal friction (IF), modulus, dielectric and impedance spectra was employed to unambiguously disclose the dynamic mechanical and electric behaviors for a series of Bi1-xLaxVO4 ceramics (0 ≤ x ≤ 0.15). In the sensitive mechanical measurement, five IF peaks, corresponding modulus anomalies and high-temperature creep behavior have been observed in our Bi1-xLaxVO4 ceramics. Through analyzing their related kinetic parameters, defect formations and evolution processes, the complex evolution model of ferroelastic domains including four different stages and the origin of grain boundary relaxation are well established. As for the electric experiment, there are two apparently different activation processes in low and high temperature regions, respectively. In conjunction with structural and mechanical characterizations, we confirm that the mixed electric/oxide ionic conduction dominates from 433 to 633 K, undergoing a structural change (633-673 K) to the complicated defect conduction at higher temperatures (673-833 K). Our findings smooth the track for better realization of the fundamental dynamic behaviors as well as extending practical application of BiVO4-based material.
关键词： Bismuth vanadate,dynamic mechanical behaviors,electric behaviors,ferroelastic domains,grain boundary relaxation,electric conduction mechanism,BiVO4,La-doped
更新于2025-09-09 09:28:46