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Synthesis of Al-doped CdS/Si nanoheterojunction arrays and their electrical and electroluminescence properties
摘要： The Al-doped CdS/Si nanoheterostructures were prepared by growing Al-doped CdS films on silicon nanoporous pillar array (Si-NPA) through chemical bath deposition (CBD). Their structure, electrical, and electroluminescence properties were investigated as a function of [Al]/[Cd]. At low [Al]/[Cd], Al ions tend to enter the lattice substitutionally, decreasing the lattice constants, micro-strain along (0 0 2) plane, and resistivity, and enhancing average crystallite size and carrier mobility. However, this behavior is reversed at high [Al]/[Cd], because Al ions tend to enter the lattice interstitially. The electroluminescence (EL) properties were most affected by Al doping. As Al concentration increases, the EL intensity initially increased rapidly to a maximum with [Al]/[Cd] and then decreased with further increased [Al]/[Cd]. The maximum of EL intensity was observed in sample S-0.07. Its EL intensity is 320 times that of S-0 and its applied voltages are very low. It could be observed by the naked eyes even at 3 V. These results indicated that Al-doped CdS/Si-NPA might be a great potential in constructing optoelectronic nanodevices. The measured results show the incorporation of suitable amount of Al would improve significantly the performances of CdS/Si-NPA heterojunctions, increasing the uniformity of CdS thin film, decreasing the resistivity, enhancing carrier mobility, improving obviously the rectification behavior, and increasing greatly the EL emission intensity. These results indicated that Al-doped CdS/Si-NPA might be a great potential in constructing optoelectronic nanodevices.
关键词： optoelectronic nanodevices,electrical properties,chemical bath deposition,electroluminescence properties,Al-doped CdS/Si nanoheterostructures
更新于2025-09-09 09:28:46
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AIP Conference Proceedings [Author(s) 6TH INTERNATIONAL CONFERENCE ON PRODUCTION, ENERGY AND RELIABILITY 2018: World Engineering Science & Technology Congress (ESTCON) - Kuala Lumpur, Malaysia (13–14 August 2018)] - Investigation of optical and electrical properties of nitrogen- and boron-doped carbon dots films
摘要： The optical properties of two types of carbon dots (CDs) doped by nitrogen and boron atoms and the electrical properties of ?lms from the obtained CDs in a polyvinyl alcohol (PVA) matrix were investigated. Synthesis of CDs was carried out using the hydrothermal treatment method. The resulting CDs have a crystalline structure with functional groups on the edges and surface (lateral sizes of CDs is vary in the range of ～7 ?28 nm). The thin ?lms from aqueous suspensions of CDs were obtained by the spin-coating method inside an electrically inert polymer matrix of PVA. The current-voltage characteristics of this obtained ?lms were measured.
关键词： optical properties,polyvinyl alcohol matrix,current-voltage characteristics,carbon dots,electrical properties,spin-coating method,hydrothermal treatment,nitrogen-doped,boron-doped
更新于2025-09-09 09:28:46
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AIP Conference Proceedings [Author(s) SolarPACES 2017: International Conference on Concentrating Solar Power and Chemical Energy Systems - Santiago, Chile (26–29 September 2017)] - Carbon-titanium multilayer films: Synthesis and characterization
摘要： To synthesize Carbon-Titanium (C-Ti) multilayer thin films deposited on silicon substrates was used Thermionic Vacuum Arc (TVA) method. The coated layers consisted of a base layer of about 100 nm of Carbon deposited at low evaporation rates. Subsequently, seven Carbon and Titanium layers were deposited alternatively on top of Carbon base layer, each of them has a final thickness up to 40 nm. In this study we obtained different batches of samples by variation of the substrate temperature between 0oC and 300oC, and the ion acceleration voltage applying a negative substrate bias voltage between 0V and -700V. To characterize the microstructure properties of as prepared C-Ti multilayer structures were used Electron Microscopy techniques (TEM, SEM, STEM) and Raman Spectroscopy. Results of tribological measurements are associated with the occurrence of atomic diffusion processes at Ti/C interface. To characterize the electrical conductive properties, the electrical resistance versus temperature have been measured.
关键词： Ti/C multilayer,TVA,STEM,tribological properties,SEM,EDX,Raman,electrical properties,TEM
更新于2025-09-09 09:28:46
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Structural transformations and physical properties of (1-x) Na<sub>0.5</sub>Bi<sub>0.5</sub>TiO<sub>3-x</sub> BaTiO<sub>3</sub> solid solutions near morphotropic phase boundary
摘要： Piezoelectric and other physical properties are significantly enhanced at (or near) a morphotropic phase boundary (MPB) in ferroelectrics. MPB materials have attracted significant attention owing to both fundamental physics as well as the possibility of well-regulated energy and information storage devices which are dominated by lead (Pb)-based materials. Here, we report the crystal structure, Raman spectra, dielectric constant and polarization near the MPB of lead free (1-x) Na0.5Bi0.5TiO3 - x BaTiO3 (NBT - BT) (0.00 ≤ x ≤ 0.10) solid-solution, prepared by sol-gel auto combustion technique and sintered by microwave sintering technique. With the addition of BaTiO3 into Na0.5Bi0.5TiO3, it induces a structural phase transition from R3c (a single phase) to R3c+P4mm (a dual phase) close to x = 0.06 and 0.07 and transform to a high symmetry tetragonal phase P4mm at higher compositions (x = 0.08 to 0.10) as evident from our X-ray Rietveld refinement and Raman spectroscopic results. In the prepared solid solution, an anomalous enhancement of remnant polarization (2Pr0) was observed for x = 0.06 and 0.07, which has been explained based on the existence of the MPB. On the other hand, the value of coercive field EC0 was found to be decreased linearly from x = 0.00 to 0.06; it is constant for higher compositions. Further details of the ferroelectric properties on the electric field poled samples have been studied and compared with the as-grown (unpoled) samples. We perform first-principles calculations based on density functional theory that confirm a structural transition from a rhombohedral to a tetragonal phase under increasing x.
关键词： First-principles calculations,Crystal structure,Morphotropic Phase Boundary,Microwave sintering,Lead-free ferroelectric materials,Electrical properties,NBT-BT solid solution
更新于2025-09-09 09:28:46
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Modifying the electrical properties of graphene by reversible point-ripple formation
摘要： Strain, ripples and wrinkles in graphene reduce the charge-carrier mobility and alter the electronic behaviour. In few-layer graphene the anisotropy between the in-plane and cross-plane resistivity is altered and a band gap can be opened up. Here we demonstrate a method to reversibly induce point ripples in electrically isolated few-layer graphene with the ability to select the number of layers used for transport measurement down to single layer. During ripple formation the in-plane and cross-plane sheet resistances increase by up to 78% and 699% respectively, confirming that microscopic corrugation changes can solely account for graphene's non-ideal charge-carrier mobility. The method can also count the number of layers in few-layer graphene and is complimentary to Raman spectroscopy and atomic force microscopy when n ≤ 4. Understanding these changes is crucial to realising practical oscillators, nano-electromechanical systems and flexible electronics with graphene.
关键词： charge-carrier mobility,graphene,electrical properties,flexible electronics,nano-electromechanical systems,point-ripple formation
更新于2025-09-09 09:28:46
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Performance analysis of fiber reinforced piezoelectric lead zirconate titanate/poly(vinylidene fluoride) composites
摘要： In this paper, the PZT/PVDF composites were prepared by hot-pressing method. The effects of different PZT volume fractions on dielectric, piezoelectric, mechanical and microstructure properties of the composites were investigated. The ratio range of the composites constituent components was determined to enhance mechanical properties. Carbon fiber was used as reinforcing material to enhance the mechanical properties of PZT/PVDF composites. The results showed that PZT/PVDF composites doping with properly carbon fiber had a good compactness, and the relative dielectric constant (εr), the piezoelectric strain constant (d33) and the polarisability were all increased. Finally, the optimal proportion of PZT/PVDF was 50%/50% and carbon fiber content was 0.25%, the d33 of composite increased 14.2%, bending strength increased 7.2% and tensile strength increased 11.5%.
关键词： Tensile Strength,PZT/PVDF,Carbon Fiber,Electrical Properties,Bending Strength
更新于2025-09-09 09:28:46
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Enhanced structural and electrical properties of nonpolar a-plane p-type AlGaN/GaN superlattices
摘要： The nonpolar a-plane p-AlxGa1-xN/GaN superlattices (SLs) were successfully grown with metal organic chemical vapor deposition technology. The surface morphology, carrier concentration, layer thickness, and Al composition for the nonpolar a-plane p-AlxGa1-xN/GaN SLs were characterized by various kinds of technical tools. It was demonstrated that the thickness of the AlxGa1-xN and GaN layers in SLs was calculated to be 12 and 14.5 nm, respectively and the Al composition of the AlxGa1-xN layers in SLs was around 30%. Meanwhile, the results reveal that the surface morphology and carrier concentration of the nonpolar p-SLs could be improved remarkably with the Al composition-graded AlGaN buffer layer and the Mg-δ-doping process. Consequently, a root mean square value of 0.6 nm and a hole concentration of 4.2 × 1017 cm?3 were achieved.
关键词： Electrical properties,p-AlGaN/GaN superlattice,Nonpolar,Epitaxial growth
更新于2025-09-09 09:28:46
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Structural, optical and electrical properties of reactively sputtered CrxNy films: Nitrogen influence on the phase formation
摘要： The properties of various CrxNy films grown by direct current (DC) reactive sputtering process with different values of nitrogen partial pressures (0, 2×10-4, 3.5×10-4 and 5×10-4 mbar) were studied. The structural analysis of the samples was performed by using X-ray diffraction and transmission electron microscopy (TEM), while an elemental analysis was realized by means of Rutherford backscattering spectrometry. By varying nitrogen partial pressure the pure Cr layer, mixture of Cr, Cr2N and CrN phases, or single-phase CrN was produced. TEM analysis showed that at pN2 = 2×10-4 mbar the layer has dense microstructure. On the other hand, the layer deposited at the highest nitrogen partial pressure exhibits pronounced columnar structure. The optical properties of CrxNy films were evaluated from spectroscopic ellipsometry data by the Drude or combined Drude and Tauc-Lorentz model. It was found that both refractive index and extinction coefficient are strongly dependent on the dominant phase formation (Cr, Cr2N, CrN) during the deposition process. Finally, the electrical studies indicated the metallic character of Cr2N phase and semiconducting behaviour of CrN.
关键词： spectroscopic ellipsometry,thin films,chromium nitrides,electrical properties,microstructure
更新于2025-09-09 09:28:46
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Interfacial influence on electrical injection and transport characterization of CoFeB|MgO|GaAs-InGaAs quantum wells hetero-structure
摘要： The quality of interfaces is a key factor for efficient electrical spin injection into quantum well light emitting diodes. Here, we investigate the interfacial influence on the electrical transport properties in CoFeB|MgO|GaAs-InGaAs quantum wells hetero-structure, by considering textured MgO tunnel barrier fabricated by two different techniques: sputtering and molecular beam epitaxy (MBE). From forward and reverse current–voltage characteristics, it is found that the threshold voltage decreases as the annealing temperature changes from room temperature to 300°C for sputtered samples, however there is not much difference in threshold voltage with the annealing temperature for MBE-grown samples. In combination with transmission electron microscope (TEM) studies, it is found the MgO|GaAs interface by MBE is sharp for both grown and annealed states. However, there is a thin (~0.4 nm) amorphous MgO layer at the MgO|GaAs interface for sputtered samples with grown state, and the amorphous MgO can be improved and crystallized after annealing. The MgO|GaAs interface plays a role in modulating the band structure and has an influence on electrical injection. Our work demonstrated that CoFeB|MgO|GaAs interfaces are important and can be engineered thanks to the use of two types of growth for the textured MgO tunnel barriers, which ensures efficient electrical injection.
关键词： Spin light emitting diode,Structural and electrical properties,MIS structure,Interfacial states
更新于2025-09-09 09:28:46
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Effect of Environmental Humidity in the Electrical Properties of Lead Halide Perovskites
摘要： In large quantities, water is detrimental to lead halide perovskite solar cells, mainly because of the decomposition of the perovskite layer. On the contrary, the presence of small quantities of water has been observed to play a key role in the crystallization of the perovskite and in the performance of the corresponding devices. However, it is still under debate the exact role of water during the operation of perovskite solar cells. In this paper, impedance spectroscopy is used to analyze the changes produced by environmental humidity in the electronic properties of methylammonium lead triiodide perovskite. Our results show that water absorbed from environmental humidity induces a huge increase in the capacitance of this material. This capacitance can reach values as large as the accumulation capacitance found in devices based in perovskite, which is the responsible of the characteristic large hysteresis observed between forward and reverse J-V curves. In parallel to this outstanding rise of the capacitance, water absorption produces a significant rise of the conductivity, in agreement with previous reports in the literature. Activation energy of 0.52 eV is found for electronic transport, a value in line with activation energy of ionic transport found in literature, what suggests ambipolar diffusion as the transport mechanism that links these two phenomena.
关键词： impedance spectroscopy,environmental humidity,electrical properties,lead halide perovskites,capacitance,conductivity
更新于2025-09-09 09:28:46