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Strain induced enhancement of erasable domain wall current in epitaxial BiFeO <sub/>3</sub> thin films
摘要： The characteristic of electronic transport at the ferroelectric domain boundary is intensively studied for the potential application in random access memory due to its unique resistance switching mechanism along with polarization reversal. Such high conductivity in artificially created domain walls is not only affected by the material defect chemistry, such as oxygen vacancies, but also pertinent to the multiple polarization states of the sample. Here, we show the enhanced domain wall current in BiFeO3 thin films that could be obtained by the optimization of epitaxial strains from substrates. The leakage current analysis reveals the electronic transport of domain wall current in line with the space-charge-limited conduction mechanism. It is believed that the uncompensated polarization charge arouses the band bending at the domain boundary, which profoundly affects the wall current. Free carriers are easily concentrated in the domain boundary region for the compensation of the enhanced polarization by the strain, resulting in an abrupt increase of the conductivity.
关键词： ferroelectric domain boundary,BiFeO3 thin films,space-charge-limited conduction,epitaxial strains,electronic transport
更新于2025-09-09 09:28:46
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Impact of molarity on structural, optical, morphological and electrical properties of copper oxide thin films prepared by cost effective jet nebulizer spray pyrolysis technique
摘要： Copper oxide (CuO) thin films were prepared by simple and cost effective jet nebulizer spray pyrolysis method with different molar concentration 0.1, 0.2 and 0.3 M named as J1, J2 and J3 respectively. The impact of molarity on structural, optical, morphological and electrical of properties of CuO thin film was studied. The structural studies confirmed that the prepared CuO thin films are monoclinic crystal structure matching with standard JCPDS card No. 89-5899. The thickness of CuO thin films determined by surface profilometer found to be increasing while increasing molar concentration. The optical energy band gaps were determined using Kulbelka–Munk (K–M) method are found to be 2.1 eV, 1.9 eV and 1.8 eV for J1, J2 and J3 respectively. The morphological properties and chemical composition of CuO thin film were investigated via field-emission scanning electron microscope (FESEM) and energy dispersive analysis from X-ray spectroscopy (EDAX). According to FESEM all the prepared CuO thin films are well covered and adhered to the substrate with good homogeneity and EDAX spectra confirms the presence of copper (Cu) and oxygen (O). The adhesion strength has been determined in accordance with test method D3330 using scotch tape test. The electrical conductivity of CuO thin films were investigated. The maximum conductivity value of the CuO thin film is observed 2.75 × 10?8 S/cm.
关键词： Thin films,Molar concentration,Copper oxide,Morphological properties,Jet nebulizer spray pyrolysis,Structural properties,Optical properties,Electrical properties
更新于2025-09-09 09:28:46
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High Ferroelectricities and High Curie Temperature of BiInO <sub/>3</sub> PbTiO <sub/>3</sub> Thin Films Deposited by RF Magnetron Sputtering Method
摘要： Properties of ferroelectric ??BiInO3-(1 ? ??)PbTiO3 (??BI-(1 ? ??)PT) thin films deposited on (101) SrRuO3/(200) Pt/(200) MgO substrates by rf magnetron sputtering method and effects of deposition conditions are investigated. The structures of the ??BI-(1???)PT films are characterized by x-ray diffraction and scanning electron microscopy. The results indicate that the thin films are grown with mainly (001) orientation. The chemical compositions of the films are analyzed by scanning electron probe and the results indicate that the loss phenomena of Pb and Bi elements depend on the pressure and temperature during the sputtering process. The sputtering parameters including target composition, substrate temperature, and gas pressure are adjusted to obtain optimum sputtering conditions. To decrease leakage currents, 2 mol% La2O3 is doped in the targets. The ?? –?? hysteresis loops show that the optimized ??BI-(1 ? ??)PT (?? = 0.24) film has high ferroelectricities with remnant polarization 2??r = 80 ??C/cm2 and coercive electric field 2??c = 300 kV/cm. The Curie temperature is about 640°C. The results show that the films have optimum performance and will have wide applications.
关键词： ferroelectric,rf magnetron sputtering,BiInO3-PbTiO3,thin films,Curie temperature
更新于2025-09-09 09:28:46
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Al-doped ZnS thin films: Physical and electrochemical characterizations
摘要： This study evaluated the effect of Al incorporation on the structural, optical, electrical and electrochemical properties of ZnS thin films. An electrochemical route was used to synthesize the studied un- and Al-doped ZnS thin films on indium tin oxide (ITO) glass substrates using an aqueous solution of ZnCl2 and Na2S2O3. The Al-doped ZnS samples were prepared by adding different amounts of AlCl3 to the main electrolyte. Cyclic voltammetry determined (cid:1)0.9 to (cid:1)1.1 V as the appropriate potential range for deposition of the ZnS thin films. In addition, appearance of a new reduction peak in the cyclic voltammograms of the Al-doped ZnS samples approved the presence of the Al dopant in the structure of the electrodeposited films. The recorded X-ray diffraction (XRD) patterns exhibited that all deposited samples contain cubic ZnS crystals and indicated that Al-doping decreases the crystallite size of the ZnS samples. Field emission scanning electron microscopy (FESEM) demonstrated that all samples are composed of big grains with 150e600 nm dimension distributed in a background phase including 15e60 nm grains. The photoluminescence (PL) spectra showed that all samples emit five PL peaks due to their different crystal defects. UVeVis spectroscopy clarified that Al-doping decreases the band gap energy of the ZnS samples from 3.93 to 3.50 eV. Furthermore, it showed that the Al-doped ZnS samples present a lower capacitance and a shorter response time, which are suitable properties for application of these materials in fast photodetectors. The Mott-Schottky plots demonstrated n-type conductivity for all samples and revealed that the existence of the Al dopant increases the carrier concentration of the ZnS thin films. The electrochemical impedance spectroscopy (EIS) results confirmed that Al incorporation reduces the time constant and capacitance of the ZnS samples. Consequently, all results declared that Al incorporation has significant effects on the physical, optical and electrical properties of ZnS thin films.
关键词： EIS,Photoluminescence,Electrodeposition,Al incorporation,ZnS thin films
更新于2025-09-09 09:28:46
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Plasma Etching of SiO <sub/>2</sub> Using Heptafluoropropyl Methyl Ether and Perfluoropropyl Vinyl Ether
摘要： As alternative to perfluorocompounds, hydrofluoroether and perfluoroalkyl vinyl ether were used for SiO2 etching. SiO2 was etched in heptafluoropropyl methyl ether (HFE-347mcc3)/Ar and perfluoropropyl vinyl ether (PPVE)/Ar plasmas, separately, and their etch characteristics were compared at bias voltages ranging from ?400 to ?1200 V. The etch rate of SiO2 in a HFE-347mcc3/Ar plasma was approximately 2.5 times higher than that in a PPVE/Ar plasma at a bias voltage of ?400 V. However, the difference in the etch rates decreased with increasing bias voltage, reaching nearly zero at a high bias voltage of ?1200 V. The change in the etch rate of SiO2 was attributed to not only the amount of F radicals but also the characteristics in the steady-state fluorocarbon films formed on the SiO2 substrate. In the low-bias voltage regime (?400 to ?800 V), higher etch rates in a HFE-347mcc3/Ar plasma than those in a PPVE/Ar plasma were obtained because both the thickness and fluorine-to-carbon (F/C) ratio of the steady-state fluorocarbon film controlled the etch rate of SiO2. On the other hand, the F/C ratio of the steady-state fluorocarbon film, rather than its thickness, limited the etch rate of SiO2 in the high-bias voltage regime (?800 to ?1200 V).
关键词： fluorocarbon films,perfluoroalkyl vinyl ether,hydrofluoroether,SiO2 etching,plasma etching
更新于2025-09-09 09:28:46
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Thermophysical properties of methacrylic polymer films with guest-host and side-chain azobenzene
摘要： The methacrylic polymer films containing azobenzenes with different peripheral substituents in the form of side-chain (P) and guest-host (A) systems were thermally investigated. The azo polymers with thicknesses below 1 μm were deposited on glass substrates using spin coating method. Photothermal radiometry (PTR) and scanning thermal microscopy (SThM) were used for determination of thermophysical properties of polymer samples. The topography of studied compounds was examined by atomic force microscopy (AFM). The results showed the influence of peripheral substituents as well as that of the polymer system on the thermophysical properties of studied azo polymers. Thermal diffusivity (α) extracted from PTR measurements is between 5.56 10-8 m2s-1 and 11.3?10-8 m2s-1 for A samples, 2.76 10-8 m2s-1 and 7.62?10-8 m2s-1 for P samples depending on the substituent. Likewise, thermal effusivity (ε) changes from 474 Ws1/2m-2K-1 to 532 Ws1/2m-2K-1 for A, and from 473 Ws1/2m-2K-1 to 564 Ws1/2m-2K-1 for P samples. The volumetric heat capacity (Cv) and in-depth thermal conductivity (κ) were calculated on the base of PTR results. Local κ obtained from SThM measurements is between 0.15 Wm-1K-1 and 0.22 Wm-1K-1 due to different substituents and polymer system. Thermal studies performed in this work provide valuable information for engineers designing azobenzene polymer thin films based devices and supplement the knowledge of their thermal behavior in the system.
关键词： polymer,nanomaterials,thermophysical properties,thin films,azobenzenes
更新于2025-09-09 09:28:46
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Surface engineering of polystyrene–cerium oxide nanocomposite thin films for refractive index enhancement
摘要： Polymer nanocomposites have gained much importance in the field of optoelectronics due to their unique optical properties. Refractive index engineering using nanoparticles is an effective strategy that could be applied for the fabrication of optical devices. Herein, we report three different strategies which are employed to enhance the refractive index of polymer thin films. These include incorporating cerium oxide nanoparticles onto the polystyrene matrix, secondly adding cerium oxide nanoparticles onto the cross-linkable polystyrene and thirdly by embedding functionalized cerium oxide nanoparticles onto the cross-linkable polystyrene. Refractive index of the polystyrene thin films was enhanced by dispersing neat CeO2 nanoparticles and functionalized CeO2 nanoparticles into the polystyrene matrix. 1.38% enhancement in the refractive index of the polymer nanocomposite thin films could be achieved using our technique. The blending of polystyrene with cerium oxide nanoparticle presents a prospective way to engineer the refractive index of polymer thin films. We firmly believe that the study will be an effective guide towards future research in the area of surface engineering of polymer thin films for refractive index enhancement.
关键词： Refractive index,Polystyrene,Polymer nanocomposites,Thin films,Cerium oxide,Surface engineering
更新于2025-09-09 09:28:46
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Ion irradiation effects on Sb-rich GaSb films
摘要： Here we show the formation of amorphous, non-stoichiometric GaSb films by magnetron sputtering and the ion irradiation effects on the films. GaSb films in the 20–300 nm thickness range were deposited by magnetron sputtering on SiO2/Si substrates at room temperature and subsequently irradiated with 17 MeV Au+7 ions at different fluences. Structural, compositional, and morphological characterizations were performed by means of x-ray diffraction, Rutherford backscattering spectrometry, x-ray photoelectron spectroscopy, scanning electron microscopy and x-ray absorption fine structure analyses. We could verify that, throughout the above-mentioned thickness range, films were amorphous, with excess Sb to the ratio 1:2 (Ga:Sb). The initially compact films attained a foam-like structure after irradiation, with significant swelling that is dependent on the initial film thickness: the thicker the film, the more it swelled. The excess Sb attained different oxidation states depending on film thickness and this influenced the final density of the films, thus influencing the swelling. The local atomic structure around Ga atoms was also investigated, revealing a decrease in Ga–Sb scattering contribution with increasing irradiation fluence, at the same time as the increase in Ga–O scattering for irradiation fluence above 1×1014 at/cm2 (inclusive).
关键词： XPS,XAFS,RBS,GaSb films,ion irradiation,XRD,magnetron sputtering
更新于2025-09-09 09:28:46
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Comparative study of the accuracy of characterization of thin films a-Si on glass substrates from their interference normal incidence transmittance spectrum by the Tauc-Lorentz-Urbach, the Cody-Lorentz-Urbach, the optimized envelopes and the optimized graphical methods
摘要： Two RF magnetron sputtered a-Si thin films one of them several times thicker than the other are characterized by four methods. Since most literature data indicate presence of Urbach tails in the bandgap of a-Si, the two inverse synthesis methods based on the Tauc-Lorentz-Urbach model (TLUM) and the Cody-Lorentz-Urbach model (CLUM) are employed. It is clarified that the conventional envelope methods tend to overestimate the average thickness df, and to underestimate the refractive index nf(λ) of the film. Therefore, the recently proposed optimized envelope method (OEM) and the optimized graphical method (OGM) are also employed. The accuracies of characterizations by these four methods are compared using a figure of merit (FOM), representing RMS deviation of the computed transmittance spectrum Tc(λ) obtained using the computed film characteristics, from the measured transmittance spectrum T(λ) of the specimen. The most accurate characterization of the thinner film is achieved by OEM, providing average film thicknesses df = 785 nm, its thickness non-uniformity Δdf = 23.5 nm, and FOM = 2.63×10-3. Although absorbance data for this film show that its band tails can be approximated as exponential (Urbach tails), the FOMs for the respective TLUM and CLUM characterizations are more than 38% larger than for OEM. The most accurate characterization of the thicker film is achieved again by OEM, providing df = 3939.1 nm, Δdf = 53.1 nm, and FOM = 6.99×10-3. TLUM and CLUM fail to characterize the thicker film with acceptable accuracy, which is attributed to presence of non-exponential band tail, revealed by absorbance data for this film. The superior performance of OEM is explained considering that it does not assume particular band tails shapes, unlike TLUM and CLUM, neither it uses existence of a wide spectral region of film transparency as an initial approximation, unlike OGM.
关键词： optimized graphical method,optical characterization,thin films,Tauc-Lorentz-Urbach model,Cody-Lorentz-Urbach model,a-Si,optimized envelope method
更新于2025-09-09 09:28:46
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Concentration of defects responsible for persistent photoconductivity in Cu(In,Ga)Se2: Dependence on material composition
摘要： Persistent photoconductivity PPC in thin Cu(In,Ga)Se2 films is discussed within a model of relaxing defects acting as donors or acceptors depending on their configurational and charge state. The aim of this work is to identify the factors related to technological processes which affect the magnitude of PPC. We established a method of evaluation of the concentration of metastable defects in thin Cu(In,Ga)Se2 films relating it to the position of the Fermi level in thermodynamic equilibrium and used it to compare and discuss the impact of preparation details on the PPC value. The main result is that deviation from Cu/(Ga+In)Se2 stoichiometry does not change the concentration of metastable defects. Post deposition annealing in selenium affects the PPC depending on the presence of sodium during the treatment, while the impact of sodium itself on the metastable defect concentration apparently depends on whether it is present during the Cu(In,Ga)Se2 deposition process or whether it is supplied during post-deposition treatment.
关键词： Thin films,Photoconductivity,Copper indium gallium selenide,Metastability,Defects
更新于2025-09-09 09:28:46