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Comparison of the Optical and Electrical Properties of Al-Doped ZnO Films Using a Lorentz Model
摘要： In this research, zinc oxide (ZnO) films are doped with various amounts of Al dopants, from 0 to 13 at.%, using ion-beam co-sputtering for Zn and Al metallic targets at room temperature. The Al-doped ZnO (AZO) films appear to have lower transmittances in the UV and near-IR ranges. The electrical and optical properties of each film are successfully analyzed by using the spectroscopic ellipsometry of two Lorentz oscillators for the two lower transmittances. The optimal AZO film is deposited with an Al-dopant of 1.5 at.% at an oxygen partial pressure of 0.12 mTorr; it has the smallest resistivity of 7.8 × 10?4 Ω cm and high transmittance of > 80% in the visible regions. The free carrier concentration and mobility evaluated using ellipsometry are different from those measured using the Hall effect. This phenomenon was the result of the grain boundary scattering due to the small ~20-nm grain size of the AZO film used in this study.
关键词： ellipsometry,grain boundary scattering,Hall effect,Lorentz oscillators,Al-doped ZnO,ZnO
更新于2025-09-23 15:22:29
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Cu-Doped ZnO Electronic Structure and Optical Properties Studied by First-Principles Calculations and Experiments
摘要： The band structure, the density of states and optical absorption properties of Cu-doped ZnO were studied by the ?rst-principles generalized gradient approximation plane-wave pseudopotential method based on density functional theory. For the Zn1-xCuxO (x = 0, x = 0.0278, x = 0.0417) original structure, geometric optimization and energy calculations were performed and compared with experimental results. With increasing Cu concentration, the band gap of the Zn1-xCuxO decreased due to the shift of the conduction band. Since the impurity level was introduced after Cu doping, the conduction band was moved downwards. Additionally, it was shown that the insertion of a Cu atom leads to a red shift of the optical absorption edge, which was consistent with the experimental results.
关键词： absorption spectrum,electronic structure,?rst-principles calculations,Cu doped ZnO
更新于2025-09-23 15:22:29
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Preparation of La doped ZnO ceramic nanostructures by electrospinning–calcination method: Effect of La3+ doping on optical and photocatalytic properties
摘要： Ceramic nanostructures of ZnO doped with La3+ ions (0.02%, 1%, 2% and 4%) were prepared by electrospinning-calcination method. Polyvinylpyrrolidone (PVP) was used as an additional polymer to promote the electrospinning. And, the intermediate electrospun products were processed thermically at 700 °C for 3 h. The produced materials were characterized morphologically and structurally by using scanning/transmission electron microscopy (SEM/TEM) and X-ray diffraction (XRD). The XRD patterns showed the successful incorporation of La ions in the hexagonal wurtzite structure of ZnO. Optical band gaps of these ceramic nanostructures were estimated from reflectance data using Kubelka-Munk theory and were found to vary from 2.589 to 2.889 eV, depending on La3+ doping concentration. Photoluminescence spectra of undoped/doped ZnO with different contents of La3+ ion were investigated. The decay curves for the La3+ ion doped ZnO nanostructures were measured and the average lifetime was found to increase from 2.69 to 2.80 ns when La3+ content increased from 0 to 4%. The photocatalytic activity of doped products (ZnO:La) was investigated by using Congo-Red dye as a probe molecule for degradation under UV-light. Maximal color removal efficiency (97.63%) was observed experimentally for ZnO doped with 2% La3+ in dosage of 0.283 g/L. Finally, the recovered catalyst was thermally activated at 700 °C (1 h) and then successfully reused for the dye photodegradation.
关键词： La-doped ZnO nanostructures,Photodegradation kinetics,Photocatalyst,Optical properties,Electrospinning
更新于2025-09-23 15:22:29
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Synthesis of Mn doped ZnO nanopowders by MW-HTS and its structural, morphological and optical characteristics
摘要： In this study, undoped and Mn doped ZnO nanopowders were synthesized by using the microwave assisted hydrothermal (MW-HTS) method. Doping ratio of Mn in the ZnO was set to 1, 5 and 10%. The effect of Mn concentration on the structural and morphological properties of ZnO nanopowders was investigated using XRD, SEM, XPS and FTIR. XRD results showed that the nanopowders have hexagonal wurtzite structure. The lattice parameters increased with increasing Mn incorporation. SEM images showed that all the samples were formed in nanorod structure and the average diameter of the rods decreased with the Mn concentration. XPS results veri?ed the presence of Mn as a doping element into ZnO crystal lattice and the oxidation states of Mn and Zn. The chemical interactions of ZnO and ZnO:Mn nanopowders were determined for using FTIR spectrum.
关键词： FTIR,Mn doped ZnO,XPS,Microwave assisted hydrothermal,Nanorods
更新于2025-09-23 15:22:29
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Investigation of optical and electrical properties of lithium doped ZnO nano films
摘要： Investigation of undoped and lithium doped ZnO nano films deposited on glass substrates by sol-gel spin coating method have been carried out. The structural and morphological properties of the films with optimum post annealing temperature of 350°C have been investigated using X-ray Diffractometer (XRD) and Field emission scanning electron microscopy (FESEM) respectively. The XRD spectrum reveals that all the synthesised samples have single crystal structure having strong intense peak oriented along (002) c-axis. Crystalline size of undoped and Li doped ZnO nano films were deduced to be 34.66 nm and 32.59 nm respectively. FESEM exhibits uniform chromosome type structure. Nano films show transmittance above 90 % in the range of wavelength 350 nm to 800 nm. I-V characteristic shows linear and ohmic behaviour.
关键词： sol-gel,Li doped ZnO,Nano films
更新于2025-09-23 15:22:29
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Influence of thickness on the optical properties of Sb doped ZnO thin films
摘要： Sb doped ZnO thin films having various thicknesses have been prepared onto glass substrate by using thermal evaporation method. The atomic compositions of the grown films have been determined by Energy Dispersive Analysis of X-ray (EDAX) method. The optical properties were measured by using a UV-VIS-NIR spectrophotometer (300 to 2500 nm). The EDAX analysis revealed that Sb is doped into the ZnO films. Optical properties showed high absorption coefficient (~105/cm) that direct allowed transition band gap. The optical band gap of the ZnO thin films became reduced due to the doping of Sb.
关键词： Composition,Sb doped ZnO thin films,Optical properties,Thickness
更新于2025-09-23 15:22:29
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Ultraviolet electroluminescence from nanostructural SnO2-based heterojunction with high-pressure synthesized Li-doped ZnO as a hole source
摘要： We report an ultraviolet (UV) electroluminescence (EL) in n-SnO2/p-ZnO heterojunction light-emitting diodes with the nanostructural SnO2 as an n-type layer and the Li-doped ZnO (ZnO:Li) synthesized by high-temperature high-pressure (HTHP) method as a high hole concentration p-type layer. Two kinds of SnO2 nanostructures including nanobelts (NBs) and nanowires (NWs) were used to fabricate n-type layers in the heterojunctions. The two heterojunctions with different SnO2 nanostructures demonstrate different light-emission feature in EL measurements. The SnO2 NBs/p-ZnO heterojunction shows a blue emission band centered at 416 nm under forward-bias voltage. A strong UV emission peak located at 391 nm was observed for the SnO2 NWs/p-ZnO heterojunction. Photoluminescence (PL) spectra indicate that the difference in EL is attributed to morphology-dependent light-emission feature in nanostructural SnO2 layer. Our results suggest that the nanostructural SnO2/ZnO:Li heterojunction is a potential and promising system in the UV optoelectronic field.
关键词： High-temperature high-pressure method,Light-emitting diode,Nanobelt,Nanowire,SnO2,Li-doped ZnO
更新于2025-09-23 15:22:29
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Polarity Control in Growing Highly Ga-doped ZnO Nanowires with Vapor-liquid-solid Process
摘要： Surface behavior modification by forming surface transparent conductive nanowires (NWs) is an important technique for many applications, particularly when the polarities of the NWs can be controlled. The polarities of Ga-doped ZnO (GaZnO) NWs grown on templates of different polarities under different growth conditions are studied for exploring a polarity control growth technique. The NWs are formed on Ga- and N-face GaN through the vapor-liquid-solid (VLS) process using Ag nanoparticles as growth catalyst. The NWs grown on templates of different polarities under the Zn- (O-) rich condition are always Zn (O) polar. During the early stage of NW growth, because the lattice sizes among different nucleation islands formed at the triple-phase line are quite different, high-density planar defects are produced when lateral growths from multiple nucleation islands form a GaZnO double-bilayer. In this situation, frequent domain inversions occur and GaZnO polarity is unstable. Under the Zn- (O-) rich condition, because the lateral growth rate of GaZnO in the Zn- (O-) polar structure is higher due to more available dangling bonds, the growth of Zn- (O-) polar structure dominates NW formation such that the NW eventually becomes Zn (O) polar irrespective of the polarity of growth template. Therefore, the polarity of a doped-ZnO NW can be controlled simply by the relative supply rates of Zn and O during VLS growth.
关键词： catalyst,Ga-doped ZnO nanowire,vapor-liquid-solid growth,triple-phase line,polarity
更新于2025-09-23 15:21:21
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Investigations on structural, optical and dielectric properties of Mn doped ZnO nanoparticles synthesized by co-precipitation method
摘要： Mn doped ZnO (ZnO:Mn) nanopowders with Mn:ZnO ratio from 0 to 3% were successfully synthesized by co-precipitation method. Their structural, optical, dielectric and conducting properties were investigated. All samples crystallize in the hexagonal wurtzite structure. The change in lattice parameters, bond length and preferential crystalline orientation for Mn doped ZnO samples indicates Mn2+ ions incorporation in ZnO lattice. Both micro-strain and dislocation density decrease due to doping whereas the average crystallite size increases suggesting the improvement of crystalline quality. The optical transmission in the visible region was improved as a result of doping. The observed decrease in ac conductivity (??????) with increasing Mn content is associated with the increase of defects amount. Cole-Cole plots of all samples were fitted to a circuit consisting in a parallel combination of a resistance and a constant phase element (CPE).
关键词： conductivity,optical properties,Mn doped ZnO,dielectric properties,XRD
更新于2025-09-23 15:21:21
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Fe doped ZnO/BiVO4 heterostructure based large area, flexible, high performance broadband photodetector with ultrahigh quantum yield
摘要： Pristine ZnO has been widely explored for UV photodetectors; however it’s utility in broadband photodetectors is still an impediment due to absorbance in UV region only with low quantum efficiency and responsivity that can be accredited to high recombination rate of photo generated charge carriers. To address this issue, we report Fe metal doped 2D ZnO thin films through band gap engineering and 1D electrospun mixed inorganic monoclinic BiVO4 nanofibers heterostructure on ITO coated PET substrate based broadband photodetector (PD) with ultra-high responsivity and EQE values in comparison to PDs fabricated using expensive cleanroom techniques. BiVO4 plays the dual role of captivating photons in the visible and NIR regions and creating local electric fields at the interface of Fe doped ZnO (FZO)-BiVO4 heterostructure which helps in separation of electron-hole pairs. The robustness of the flexible PD was further examined under repeated conditions of bending cycles (upto 500) yielding stable response. The responsivity values obtained for UV, Visible and NIR lights are 7.35 A/W, 3.8 A/W and 0.18 A/W with very high EQE values of 2501.7 %, 851.2 % and 28.3 % respectively. The facile and cost-effective fabrication of the device with high performance gives a new approach for developing flexible electronics and high-performance optoelectronics devices.
关键词： Heterostructure,Broadband photodetector,Fe doped ZnO,BiVO4,ultrahigh quantum yield
更新于2025-09-23 15:21:01