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Cold welding of organic light emitting diode: Interfacial and contact models
摘要： This paper presents the results of an analytical and computational study of the contacts and interfacial fracture associated with the cold welding of Organic Light Emitting diodes (OLEDs). The effects of impurities (within the possible interfaces) are explored for contacts and interfacial fracture between layers that are relevant to model OLEDs. The models are used to study the effects of adhesion, pressure, thin film layer thickness and dust particle modulus (between the contacting surfaces) on contact profiles around impurities between cold-welded thin films. The lift-off stage of thin films (during cold welding) is then modeled as an interfacial fracture process. A combination of adhesion and interfacial fracture theories is used to provide new insights for the design of improved contact and interfacial separation during cold welding. The implications of the results are discussed for the design and fabrication of cold welded OLED structures.
关键词： adhesion,OLED,thin films,Cold welding,interfacial fracture
更新于2025-09-09 09:28:46
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Substrate temperature dependent variation in the properties of cadmium telluride thin films deposited on glass
摘要： The present study relates to the variation in properties of cadmium telluride (CdTe) thin films deposited via electron beam and thermal vacuum evaporation methods at two different substrate temperatures. The influence of substrate temperature on structural, morphological, optical and electrical properties of CdTe thin films is investigated. For structural characterization, grazing incidence X-ray diffraction technique is used which revealed that thin films deposited at 200 °C temperature are more crystalline in nature as compare to the room temperature. The parameters such as average crystallite size (D), lattice strain (ε), number of crystallites per unit area (N) and texture coefficient TC (hkl) were calculated for both types of synthesized CdTe thin films. Surface morphology of thin films was recorded using scanning electron microscopy and found to be homogeneous in nature. The optical studies carried out using UV–Visible Spectrophotometer and Photoluminescence shown a decrease in band gap values for both electron beam and thermally deposited thin films samples at 200 °C substrate temperature. Electrical measurements recorded using two probes method showed the maximum value of current for CdTe thin films deposited by electron beam evaporation method at 200 °C substrate temperature.
关键词： Thermal vacuum evaporation,Optical properties,Thin films,Electron beam evaporation,Electrical properties,Structural properties,Substrate temperature,Cadmium telluride
更新于2025-09-09 09:28:46
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Effect of precursor flow rate on physical and mechanical properties of a-C:H:SiO <sub/><i>x</i> </sub> films deposited by PACVD method
摘要： In this paper the deposition of a-C:H:SiOx films by plasma activated chemical vapour deposition in a mixture of argon and polyphenylmethylsiloxane (PPMS) vapor with the impulse bipolar bias voltage applied to the substrate is presented. The paper discusses the dependence of the physico-mechanical properties of the deposited films on the flow rate of the PPMS precursor. The structure of the deposited films was determined by Fourier transform infrared spectroscopy and Raman spectroscopy. Mechanical properties characterization of a-C:H:SiOx films (hardness and elastic modulus) was made using the nanoindentation method. Hardness and elastic modulus were used to evaluate the endurance capability (H/E) and resistance to plastic deformation (H3/E2). The elastic recovery was calculated based on loading and unloading curves. It is shown that with an increase in the PPMS flow rate in the range of 35-287 μl/min, the films deposition rate increases from 17 to 221 nm/min. At this films mechanical properties, such as hardness, elastic modulus and elastic recovery did not deteriorate. The maximum values of the endurance capability and resistance to plastic deformation are obtained at a flow rate of 175 μl/min and equal to 0.12 and 203 MPa, respectively.
关键词： PPMS,a-C:H:SiOx films,PACVD,mechanical properties,nanoindentation
更新于2025-09-09 09:28:46
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Influence of Iodine Doping on the Structure, Morphology and Physical Properties of Manganese Phthalocyanine Thin Films
摘要： Doping with halide ions is a popular method to alter the properties of metal phthalocyanines (MPcs), particularly magnetic and electrical nature of organic semiconductors for applications in spintronic or electronic devices. Doping can cause a structural rearrangement in MPc packing and the physical properties may be correlated with molecular packing. Films of a planar and magnetic MPc, manganese(II)phthalocyanine (MnPc) is chosen for iodine doping study. The optical, magnetic and the electrical properties of pristine and iodine doped MnPc thin films are investigated and can be directly associated with their molecular structure. 2D grazing incidence Synchrotron X-ray diffraction reveals structural disorder in MnPc films upon iodine infusion induced by the reorientation of ordered, edge-on molecular configuration to tilted and face-on configurations in a random fashion. The film morphology changes accordingly, where in the uniform crystallites reorganize in a disordered manner. The ferromagnetic nature of the pristine film gets weakened due to iodine species and favors antiferromagnetic coupling. The study of electrical properties at room temperature by conducting atomic force microscopy reveals that the conductance is enhanced independently of the film thickness due to disorder induced by iodine inclusion.
关键词： Thin Films,Electrical properties,Structural rearrangement,Manganese Phthalocyanine,Iodine doping,Magnetic properties
更新于2025-09-09 09:28:46
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Shortening nucleation time to enable ultrafast phase transition in Zn1Sb7Te12 pseudo-binary alloy
摘要： Zn1Sb7Te12 thin films have been deposited by magnetron co-sputtering of ZnTe and Sb2Te3 targets. The microstructure, phase-change speed, optical cycling stability and crystallization kinetics have been investigated during thermal annealing and laser irradiation. The thermal-annealed and laser-irradiated films give clear evidence on coexistence of trigonal Sb2Te3 and cubic ZnTe phases, which are homogeneously distributed in a single alloy as confirmed by advanced scanning transmission electron microscopy. The formation of both phases increases initial nucleation sites, leading to the rapid phase-change speed in the Zn1Sb7Te12 film. The film has a minimum crystallization time of ~3 ns at 70 mW with almost no incubation period for the formation of critical nuclei compared to Ge2Sb2Te5 and other Zn-based films. Moreover, the complete crystallization of Zn1Sb7Te12 thin films is achieved within 10 ns. The ultrafast two-dimensional nucleation and crystal growth speed in Zn1Sb7Te12 obtained from the laser-irradiated system is almost 7 times faster compared to Ge2Sb2Te5 film. Controlling crystallization process through the doping ZnTe into Sb2Te3 is thus promising for the development of high-speed optical switching technology.
关键词： Optical spectroscopy,Thin films,Phase transformation kinetics,Optical materials,STEM HAADF
更新于2025-09-09 09:28:46
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STRUCTURING OF DIAMOND FILMS USING MICROSPHERE LITHOGRAPHY
摘要： In this study, the structuring of micro- and nanocrystalline diamond thin films is demonstrated. The diamond films are structured using the technique of microsphere lithography followed by reactive ion etching. Specifically, this paper presents a four-step fabrication process: diamond deposition (microwave plasma assisted chemical vapor deposition), mask preparation (by the standard Langmuir-Blodgett method), mask modification and diamond etching. A self-assembled monolayer of monodisperse polystyrene (PS) microspheres with close-packed ordering is used as the primary template. Then the PS microspheres and the diamond films are processed in capacitively coupled radiofrequency plasma using various plasma chemistries. This fabrication method illustrates the preparation of large arrays of periodic and homogeneous hillock-like structures. The surface morphology of the processed diamond films is characterized by scanning electron microscopy and with the use of an atomic force microscope. The potential applications of these diamond structures in various fields of nanotechnology are also briefly discussed.
关键词： polystyrene microspheres,nanostructuring,scanning electron microscopy,reactive ion etching,diamond thin films
更新于2025-09-09 09:28:46
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Effect of Aluminium doping on photoluminescence and third-order nonlinear optical properties of nanostructured CdS thin films for photonic device applications
摘要： The work presented here reports the influence of Aluminium (Al) doping on CdS thin films for the structural, morphological, optical and third-order nonlinear optical (NLO) properties. Thin films of Pure CdS and Al-doped CdS (Cd1-xAlxS) with x= 0, 0.01, 0.05 and 0.1 are prepared on the glass substrate at 350oC using the spray pyrolysis technique. The observed X-Ray Diffraction (XRD) patterns of CdS films are found to a polycrystalline hexagonal structure and are not much affected by Al doping. Also the films have been examined by Field Emission Scanning Electron Microscopy (FESEM) images. The transmittance of the CdS films is observed to be 50 to 60% in the visible region and that decreased at higher doping concentrations and with higher Al doping the direct optical band gap is decreased from 2.52 to 2.38 eV. To understand the defect states characteristics, the corresponding room-temperaturephotoluminescence (RTPL) spectra have also been taken and found the nonlinear behavior in a band to band-edge emission in the prepared samples upon Al incorporation. The sign and the magnitude of the third-order NLO properties were determined using the Z-scan technique with a continuous wave laser as the excitation source. It is observed that the material exhibit strong two-photon absorption (2PA) with the nonlinear absorption (NLA) coefficient (β) in the range of 10-4 cmW-1 and nonlinear refractive index (NRI) n2 ~10-9 cm2W-1. The third-order NLO susceptibility has found to be enhanced from 3.12 x10-5 esu to 6.36 x10-5 esu upon Al incorporation. Optical limiting characteristics of the prepared films are studied at the experimental wavelength. The results suggest that the Cd1-xAlxS is a promising material for nonlinear optical devices at 532 nm and optical power limiting applications.
关键词： photoluminescence,spray pyrolysis,Al-doped CdS thin films,Z-scan,structural,nonlinear optical properties
更新于2025-09-09 09:28:46
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Structural, morphological and optical properties of Cu2ZnxFe1-xSnS4 thin films grown by thermal evaporation
摘要： In this study, Cu2ZnxFe1-xSnS4 (CZFTS) (0≤x≤1) thin films were grown under vacuum evaporation on unheated glass substrates followed by sulfurization at 400 °C. The effects of sulfurization on the structural, morphological and optical properties were investigated for CZFTS material by varying Fe content. Crystal structure and phase of CZFTS thin films were analyzed by X-ray diffraction technique and Raman spectroscopy. In addition, the elemental composition and the stoichiometry of films were studied using energy dispersive spectroscopy. Surface morphology of samples was examined by scanning electron microscopy. Optical properties such as absorption coefficient, and gap energies were determined by the measurement of transmittance and reflectance in the spectral range 300-1800 nm. X-ray analysis indicates that all sulfurized CZFTS films present a polycrystalline nature and exhibit a preferential orientation along (112) plane. Cu2FeSnS4 (x=0) and Cu2ZnSnS4 (x=1) crystallize in stannite structure with I-42m and kesterite structure with I-4 space group, respectively. Raman analysis and elemental composition confirm that only the Cu2ZnSnS4 (x=1) and CZ0.75F0.25TS (x=0.75) phases are present with good crystallinity. Transmittance and reflectance spectra revealed that the films are homogenous mostly for x=0.75 and 1. Structural and optical parameters like crystallite size, absorption coefficient and band gaps were estimated for all the x values.
关键词： Sulfurization,Scanning electron microscopy,X-ray diffraction,Copper zinc iron tin sulfide,Evaporation,Thin films
更新于2025-09-09 09:28:46
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Simple TiO <sub/>2</sub> Coatings by Sol–Gel Techniques Combined with Commercial TiO <sub/>2</sub> Particles for Use in Heterogeneous Photocatalysis
摘要： TiO2 coatings were obtained by a combination of a sol–gel process with the addition of commercial TiO2 particles (Degussa-Evonik P25). Simple and composite (with P25) sols were deposited by dip-coating on glass plates giving simple and composite coatings. The order of addition of reagents in the preparation of sols, the incorporation of P25 to the sols, and the thermal treatments were analyzed as variables to improve the photocatalytic activity. The samples were completely characterized with respect to the amount of deposited TiO2, the crystal structure (XRD) and the morphology (SEM). The activity of the supported photocatalysts (simple, composite and P25 coatings) was evaluated using 4-chlorophenol degradation and Cr(VI) reduction in the presence of EDTA as model photocatalytic systems. The stability of sols and the photocatalytic activity of the resulted coatings depended strongly on the order of addition of the reagents to obtain the simple sol. Sols prepared by adding the alcohol-water-HCl mixture to the precursor were the simple sols presenting a very good stability that permitted the incorporation of powdered P25 without the addition of additives. The composite coatings prepared from these simple sols were the most active in both photocatalytic systems and also presented the highest resistance to scratch.
关键词： TiO2 Films,Sol–Gel,Heterogeneous Photocatalysis
更新于2025-09-09 09:28:46
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Effect of the Substrate Temperature on the Structural and Morphological Properties of MoO2 Thin Films Obtained by Pulsed Injection MOCVD
摘要： Molybdenum oxides is of great technological interest due to their outstanding optical, electronic and catalytic properties. In this work, molybdenum dioxide (MoO2) thin films were deposited onto Si wafers and stainless steel substrates at different substrate temperatures. The growth of the films was achieved by using a vertical metal organic chemical vapor deposition reactor working in pulsed injection mode. A powder of molybdenum hexacarbonyl mixed in a toluene solution was used as precursor. An effective pulsed injection system to supply the precursor, usually used for fuel injection in internal combustion devices, delivers a precise amount of liquid precursor to the reactor through injectors, whose pulse intervals (injection frequency) are controlled by a computer-driven system. The use of a liquid solution as precursor along with the experimental parameters provide thermodynamically favorable conditions to fabricate a thin solid film, homogenously deposited onto the whole substrate. The MoO2 film structure and morphology were studied by X-ray diffraction, Raman scattering spectroscopy and scanning electron microscopy. Moreover, a comparative study was undertaken whereby the catalytic activity of stainless steel substrate for hydrogen evolution reaction was related to that of MoO2 thin film.
关键词： catalytic activity,MOCVD,MoO2 thin films,molybdenum oxides
更新于2025-09-09 09:28:46