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Effect of Terraces at the Interface on the Structural and Physical Properties of La <sub/>0.8</sub> Sr <sub/>0.2</sub> MnO <sub/>3</sub> Thin Films
摘要： Employing atomic force microscopy, transmission electron microscopy and the second harmonic generation technique, we carefully explore the structural properties of 6-unit-cell-thick La0.8Sr0.2MnO3 films grown on SrTiO3 with atomically flat TiO2-terminated terraces on the surface. The results clearly demonstrate that the terraces on the surface of TiO2-terminated SrTiO3 can improve the layer-by-layer epitaxial growth of the manganite films, which results in uniform film coverage at the beginning of growth and thus reduces the substrate-induced disorder at or near the interface. Comparing the magnetic and transport properties of La0.8Sr0.2MnO3 films with the thicknesses varying from 6 unit cells to 80 unit cells grown respectively on as-received SrTiO3 and TiO2-terminated SrTiO3, it is found that these atomically flat terraces on the surface of TiO2-terminated SrTiO3 can greatly enhance the Curie temperature and conductivities of the ultrathin La0.8Sr0.2MnO3 films with thickness less than 50 unit cells, while no obvious difference is detected in the magnetic and transport properties of the 80 unit-cell thick films.
关键词： La0.8Sr0.2MnO3,transport properties,SrTiO3,terraces,magnetic properties,structural properties
更新于2025-09-23 15:21:21
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Structural Properties of (Sn1?xMgxO) Thin Films and Optical Parameter Dependence with Gamma Ray Irradiation
摘要： Tin-Magnesium oxide (Sn1?xMgxO) thin films were prepared on glass substrates using the chemical spray pyrolysis technique, whereupon the samples were irradiated by gamma rays using a Co-60 radioactive source. X-ray diffraction showed that all prepared films were polycrystalline in nature with a tetragonal structure and a preferential growth of crystallites in the (110) plane. In general, the average crystallite size, lattice constants, dislocation density and crystallite density decreased with increasing Mg doping from 0% to 8%. Further, atomic force microscopy showed that the thin films were smooth and homogenous. The optical properties were obtained by ultraviolet–visible spectrophotometry, and the transmittance and absorbance spectra before and after gamma ray irradiation were compared for all samples, whereby the absorption and extinction coefficients and real and imaginary parts of the dielectric were studied before and after irradiation. It was found that the energy band gap values decreased from 3.94 eV to 3.72 eV with increasing Mg doping from 0% to 8% before irradiation, and from 3.92 eV to 3.59 eV after irradiation. All optical constants increased with doping percentage before and after irradiation. Energy-dispersive x-ray spectroscopy showed that all structures contained Sn and O elements in the undoped state, and contained SnO2 and Mg in the doped state.
关键词： doping,SnO2 thin films,gamma ray,energy-dispersive x-ray technology,chemical spray pyrolysis,structural properties
更新于2025-09-23 15:21:21
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Vital role of Ar ambient pressure in controlled properties of nanocrystalline CdS thin films
摘要： A report on the manipulation of structural, optical, and electrical properties of nanocrystalline CdS (ncCdS) thin films in the framework of varying Ar ambient pressure in pulsed laser deposition (PLD) is presented here. Increase in Ar ambient pressure results in reduction of crystallite size which in turns increases the structural imperfections and structural phase transformation of ncCdS thin films. The most significant observation here is the bleaching of multiphonon Raman modes (MRMs) particularly LO + 2E2, 2LO + 2E2, etc. in ncCdS thin films. An acute investigation on the reason of bleaching of LO + 2E2, 2LO + 2E2, etc. modes is carried out here and concluded that it is due to the fading of E2 mode with increasing Ar pressure as confirmed by low-frequency micro-Raman measurements. UV–visible absorption and photoluminescence spectroscopies are used to examine the optical properties like bandgap and possible electronic transitions in ncCdS thin films. Further, transport properties of ncCdS thin films are investigated using Hall measurement and I–V characteristics.
关键词： electrical properties,optical properties,Ar ambient pressure,structural properties,pulsed laser deposition,nanocrystalline CdS thin films
更新于2025-09-23 15:21:01
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A study on structural, spectral, and magnetic properties of Pr–Bi co-doped M-type barium–strontium hexaferrites via the solid-state reaction method
摘要： Pr–Bi co-doped M-type Ba–Sr hexaferrites with nominal compositions Ba0.35Sr0.65?xPrxFe12.0?xBixO19 (0.00 ≤ x ≤ 0.40) were synthesized for the first time by the solid-state reaction method. These hexaferrites were characterized by X-ray diffractometer (XRD), Fourier transformer infrared (FT-IR) spectroscopy, field emission scanning electron microscopy (FE-SEM), vibrating sample magnetometer (VSM) and thermogravimetric analyzer (TGA). XRD patterns showed that the single M-type hexaferrite phase was obtained only if Pr–Bi content (x) ≤ 0.24. FT-IR frequency bands in the range (608–610) cm?1 and (445–447) cm?1 correspond to the formation of tetrahedral and octahedral clusters of metal oxides in the hexaferrites, respectively. FE-SEM micrographs indicated that the grains were of platelet-like shapes. The saturation magnetization (Ms), remanent magnetization (Mr), magnetic anisotropy field (Ha), first anisotropy constant (K1) and coercivity (Hc) first increased with Pr–Bi content (x) from 0.00 to 0.08, and then decreased when Pr–Bi content (x) ≥ 0.08. The Curie temperature (Tc) decreased with increasing Pr–Bi content (x) from 0.00 to 0.40.
关键词： Pr–Bi co-doped,structural properties,solid-state reaction method,spectral properties,magnetic properties,M-type barium–strontium hexaferrites
更新于2025-09-23 15:21:01
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Excellent structural, optical, and electrical properties of Nd-doped BaSnO <sub/>3</sub> transparent thin films
摘要： We epitaxially grew 7 mol. % Nd-doped BaSnO3 (NBSO) thin films on double-side polished SrTiO3 (001) single-crystal substrates and optimized the oxygen pressure (PO2), substrate temperature (TS), and film thickness (t) to achieve excellent structural, optical, and electrical performance. By keeping TS (?800 (cid:2)C) constant, NBSO films prepared at PO2 ? 10 Pa show the best crystallization, yielding a full-width at half-maximum (FWHM) of the x-ray diffraction rocking curve of 0.079(cid:2) and exhibiting a room-temperature resistivity (q) of (cid:3)1.85 mX cm and a volume carrier density (n) of (cid:3)8.5 (cid:4) 1020/cm3. By keeping PO2 (?10 Pa) constant, the room-temperature q of NBSO films could be reduced to as low as 0.5 mX cm by increasing TS from 700 to 825(cid:2); meanwhile, the volume carrier density and mobility show the maximum of 5.04 (cid:4) 1020/cm3 and 24.9 cm2/Vs, respectively, for TS ? 825 (cid:2)C. For all as-grown NBSO thin films, the optical transmittance in the visible wavelength region is larger than 80%. The optimized comprehensive properties of the NBSO films with FWHM ? 0.11(cid:2), q ? 0.5 mX cm, l ? 24.9 cm2/Vs, and T > 80% are superior to those of other rare-earth and 4d- and 5d-transition metal-doped BaSnO3 thin films.
关键词： optical properties,Nd-doped BaSnO3,electrical properties,transparent thin films,structural properties
更新于2025-09-23 15:21:01
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A facile spray pyrolysis fabrication of Sm:CdS thin films for high-performance photodetector applications
摘要： Achievement of high-performance photodetectors based on CdS is a key field of research and challenge in the current scenario. Here, facile fabrication and characterization of novel samarium (1, 3 and 5 wt.% Sm)-doped CdS thin films for the photodetector applications have been demonstrated. The fabricated films show good crystallinity with crystallites size ranging 18–30 nm. The morphology and homogeneity of Sm-doping ingrown films were confirmed through scanning electron microscopy/energy-dispersive X-ray spectroscopy (SEM/EDX). Field emission SEM study reveals the low dimension nanograins formation and the films are free from voids and cracks. The effects of Sm-doping on linear and nonlinear optical properties of the fabricated thin films have been elucidated. The optical parameters such as refractive index, energy gap, susceptibilities were noticed to be reduced by Sm-doping in CdS thin films. An emission peak around 536 nm was observed in PL spectra of pure CdS which was found to be shifted and quenched by Sm-doping. Finally, the photodetector performance of the fabricated thin films has been investigated for 532 nm laser light. The photodetector based on the 1 wt.% Sm:CdS shows an improved performance (higher responsivity of 1.01 AW?1, higher detectivity of 2.21 × 1012 Jones, excellent photosensitivity of ～4.9 × 103, and very high external quantum efficiency (EQE) of 257 %) compared to pure CdS (responsivity of 0.213 AW?1, detectivity of 7.43 × 1011 Jones, photosensitivity of ～2.0 × 103, and EQE of 49.70 %). These results propose a much simpler route to achieve high-quality CdS films for photodetector applications.
关键词： Photoluminescence,Structural properties,CdS,Optical properties,Photodetector,Sm-doping,Thin films
更新于2025-09-23 15:21:01
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Effect of surface modification and laser repetition rate on growth, structural, electronic and optical properties of GaN nanorods on flexible Ti metal foil
摘要： The effect of flexible Ti metal foil surface modification and laser repetition rate in laser molecular beam epitaxy growth process on the evolution of GaN nanorods and their structural, electronic and optical properties has been investigated. The GaN nanostructures were grown on bare- and pre-nitridated Ti foil substrates at 700 °C for different laser repetition rates (10–30 Hz). It is found that the low repetition rate (10 Hz) promotes sparse growth of three-dimensional inverted-cone like GaN nanostructures on pre-nitridated Ti surface whereas the entire Ti foil substrate is nearly covered with film-like GaN consisting of large-sized grains for 30 Hz growth. In case of the GaN growth at 20 Hz, uniformly-aligned, dense (～8 × 109 cm?2) GaN nanorods are successfully grown on pre-nitridated Ti foil whereas sparse vertical GaN nanorods have been obtained on bare Ti foil under similar growth conditions for both 20 and 30 Hz. X-ray photoemission spectroscopy (XPS) has been utilized to elucidate the electronic structure of GaN nanorods grown under various experimental conditions on Ti foil. It confirms Ga–N bonding in the grown structures, and the calculated chemical composition turns out to be Ga rich for the GaN nanorods grown on pre-nitridated Ti foil. For bare Ti substrates, a preferred reaction between Ti and N is noticed as compared to Ga and N leading to sparse growth of GaN nanorods. Hence, the nitridation of Ti foil is a prerequisite to achieve the growth of dense and aligned GaN nanorod arrays. The X-ray diffraction, high resolution transmission electron microscopy and Raman studies revealed the c-axis growth of wurtzite GaN nanorods on Ti metal foil with good crystallinity and structural quality. The photoluminescence spectroscopy showed that the dense GaN nanorod possesses a near band edge emission at 3.42 eV with a full width at half maximum of 98 meV at room temperature. The density-controlled growth of GaN nanorods on a flexible substrate with high structural and optical quality holds promise for potential applications in futuristic flexible GaN based optoelectronics and sensor devices.
关键词： Ti metal foil,laser molecular beam epitaxy,optical properties,GaN nanorods,structural properties,surface modification,electronic properties,laser repetition rate
更新于2025-09-23 15:19:57
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Controlled optoelectronic properties and abrupt change in photosensitivity by suppressing density of oxygen vacancies in SnO <sub/>2</sub> nanocrystalline thin films prepared at various spray-deposition temperatures
摘要： Nanostructured SnO2 thin films were synthesized at various substrate temperatures using a modified chemical spray pyrolysis (MCSP) technique. The x-ray diffraction (XRD) patterns confirmed the presence of a rutile SnO2 with tetragonal structure for all the resultant film samples. The XRD results ascertained increase in the grain growth rate and consequent enhancement in crystallinity with increasing the spray-deposition temperature. The optical spectroscopic analysis revealed a significant increase in the optical transmission within the visible region as well as a considerable increase in the optical bandgap by increasing the deposition temperature. However, the spectral distribution of the absorption coefficient ascertained the dominance of direct allowed transition for the SnO2 film samples. The analysis of the current-voltage characteristic curves revealed that the variation of the spray-deposition temperature strongly influences the photosensitivity of the film samples. Based on the electrical results, these film samples reveal a semiconductor behaviour of the transport property over the entire investigated range of the working temperature, with two different conduction mechanisms. The optical and electrical results were combined to evaluate the influence of varying the deposition temperature on the figure of merit (FOM) factor for the SnO2 film samples.
关键词： MCSP technique,optical spectroscopic analysis,electrical transport properties,figure of merit,structural properties,spray deposition temperature
更新于2025-09-23 15:19:57
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Construction of Cr2O3:ZnO Nanostructured Thin Film Prepared by Pulsed Laser Deposition Technique for NO2 Gas Sensor
摘要： Rhombohedral structure of chromium oxide (Cr2O3) thin-film doped hexagonal zinc oxide (ZnO) nanoparticles have been prepared using pulsed laser deposition technique at a different weight percent of ZnO from 0 to 9 wt%. The results of X-ray diffraction analysis shown that the doped films are polycrystalline, and the average crystallite size of the synthesized thin films is found to be dependent on the ZnO concentration. The surface morphology of the prepared thin films was characterized by atomic force microscopy. The optical properties are investigated using ultraviolet–visible light (UV–Vis) absorption spectroscopy. The optical bandgap ranged from 2.45 to 2.68 eV, showing the shift towards longer-wavelength compared to bulk Cr2O3 (~ 3 eV). The sensitivity, response, and recovery times of the sensor towards nitrogen dioxide (NO2) gas were studied and discussed. The sensitivity increase with increasing the doping concentration, and started to decrease when ZnO concentrations reach 7 wt%. The optimal ZnO concentrations for NO2 gas sensitivity is 5 wt%, which attain maximum sensitivity of 87.5% at temperature of 523 K.
关键词： Cr2O3:ZnO nanostructure,Structural properties,Optical properties,Gas sensitivity,PLD technique
更新于2025-09-23 15:19:57
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Optimization of structural and optical properties of nanoporous silicon substrate for thin layer transfer application
摘要： A study on optical and structural properties of nanoporous silicon is presented in this paper. The samples were prepared by electrochemical etching a heavily boron doped silicon wafer in a hydrofluoric acid electrolyte and flowed by in-situ sintering in ultra-high vacuum chemical vapor deposition reactor (UHVCVD) under hydrogen atmosphere at high temperature varied between 900 and 1100 °C. The structural and morphological properties were carried out using atomic force microscopy (AFM), scanning electronic microscopy (SEM) and high resolution transmission electronic microscopy (HRTEM). The optical properties were performed using the photoluminescence Spectroscopy (PL), Time Resolved Photoluminescence (TRPL), RAMAN spectroscopy and Fourier-transform infrared spectroscopy (FT-IR). It is shown that the in-situ heating at 900 °C desorbs the native oxide from the porous layer and closes the pores forming a continuous defects-free surface at the top of porous layer. The process allows obtaining stable porous layer with enhanced structural and optical properties and also tailoring the morphological properties and the visible optical emission. This paper aims at a comprehensive determination of the physical properties of sintered porous silicon, in particular, its structural and optical properties.
关键词： structural properties,optical properties,nanoporous silicon,thin layer transfer,sintering
更新于2025-09-23 15:19:57