Sharif Digital Repository

We report experimental evidence of Cu surface segregation in Ni/Cu system, during deposition of Ni film onto Cu substrate at room temperature and during heat treatment in vacuum. Auger electron spectroscopy (AES) and X-ray photoelectron spectroscopy (XPS) by Tougaard's analysis results show that surface segregation defeats in competition with increase in Ni thickness and terminates when thickness of Ni increase to more than 4 nm. Surface energy and concentration were calculated using contact angle measurements and the results confirm that segregation reduces the surface energy. Surface segregation during heat treatment at 150–220 °C range as a function of time initially shows linear mass... 

The renal capsule tissue of lamb was irradiated with ultraviolet-C light and the treated samples were analyzed by uniaxial tensile test, dynamic mechanical analysis, attenuated total reflectance Fourier transform infrared spectroscopy, X-ray photoelectron spectroscopy and contact angle measurements. It was shown that the skin cross-linking is dominant in low doses in accordance with the contact angle assessment. Conversely, the strong bulk degradation takes place at high doses. Similarly, the bulk cross-linking affects the mechanical tests as to enhance the stiffness at low doses, whereas strong degradation occurs at high doses that mainly arises from the strong bulk chain scission  

Graphene oxide (GO) sheets were synthesized through a modified Hummers' method. Using high resolution transmission electron microscopy the thickness of the GO sheets in a multilayer structure of stacked GO sheets was found ∼0.8 nm. A nanosecond pulsed laser (with wavelength of 532 nm and average power of 0.3 W) was applied for effective and environment friendly reduction of the GO sheets in an ammonia solution (pH ∼9) at room temperature conditions. The deoxygenation of the GO sheets by the pulsed laser reduction method was confirmed by using UV-visible, Fourier transform infrared, X-ray photoelectron spectroscopy (XPS) and thermo gravimetric analysis. Based on XPS analysis, the O/C ratio of... 

Vertically aligned ZnO@CdS nanorod heterostructure films with various loadings of CdS nanoparticle shell were synthesized and applied in photoinactivation of Escherichia coli bacteria under visible light irradiation. While neither the bare ZnO nanorods (with band-gap energy (Eg) of ∼3.28 eV) under visible light irradiation nor the nanorod heterostructures in dark exhibited any significant antibacterial activity, the ZnO@CdS nanorod heterostructures (with Eg ∼2.5-2.6 eV) could successfully inactivate the bacteria under visible light irradiation. Furthermore, it was found that an optimum loading of the CdS shell (corresponding to the effective thickness less than ∼15 nm) is required to achieve... 

Free-standing TiO2 nanotube array (TNA) films were fabricated via two-step anodization of a titanium sheet. The X-ray diffraction pattern indicated amorphous TNAs were transformed into anatase after annealing the films at 500 °C in air. The surface of TNA was modified by a sequential-chemical bath deposition (S-CBD) method to fabricate Ag2S nanoparticles and forming TNA/Ag2S-n nanostructure, by varying the number of cycles (n). Based on SEM observations, the produced films consisted of vertically ordered tubular structure arrays, each with 125 nm in diameter and 4.1 μm in length containing silver sulphide nanoparticles of ∼12 nm diameter. X-Ray photoelectron spectroscopy (XPS) confirmed the... 

Cuprous oxide powder was added to WO3 sol as a catalyst and the composite sol was deposited on alumina substrates by spin coating process and annealing at 500 °C for 1 hour. Sensing properties of the pure and doped tungsten oxide samples to H2S gas were analyzed. WO 3-Cu2O (1%) samples showed good sensitivity towards 250 ppb of the gas at 100 °C and 1 ppm at room temperature (25 °C). Crystal structure, morphology and chemical composition of the sample were studied by X-ray diffraction (XRD), Scanning Electron Microscopy (SEM), Energy Dispersive X-ray (EDAX) analyses and X-ray photoelectron spectroscopy (XPS). Based on these data, possible reaction mechanisms of hydrogen sulfide over WO... 

Graphene is usually synthesized through deoxygenation of graphene oxide (GO) by hydrazine as the most common and one of the strongest reducing agents. But, due to the high toxicity of hydrazine, it is not a promising reductant in large-scale production of graphene. Here, for the first time, we used melatonin (MLT), as a powerful antioxidant and a biocompatible competitor of hydrazine in reduction of GO suspension. X-ray photoelectron spectroscopy (XPS), current-voltage and optical characteristics of the sheets indicated that the deoxygenation efficiency of the GO suspensions by MLT and under heating in an alkaline condition for 3 h was comparable with the efficiency obtained by hydrazine in... 

Solar cells with high efficiency, low cost, and high stability are the target for the new generation of solar cells. A fully printable perovskite (CH3NH3PbI3) solar cell (PSC) with device architecture FTO/TiO2/Al2O3/NiOx/C is fabricated in the current research as a low-cost and relatively stable structure and is investigated to determine how different fabrication factors such as the thickness of the insulating spacer layer (Al2O3) or treatments such as heat and UV-O3 treatments can affect the interfacial properties of this multilayer mesoporous structure. X-ray photoelectron spectra (XPS) show that UV-O3 treatment increases the Ni3+(Ni2O3) phase on the surface of the black nickel oxide layer... 

The control of thin film nanocomposite (TFN) membranes cross-linking degree is an important factor to design new membranes and optimizing permeation characteristics. The Fe3O4 nanoparticle's based TFN membranes due to potentially added magnetic responsive properties to the membrane has a great importance in developing membrane architectures. Fe3O4/polyamide (PA) TFN membranes filled with nanoparticles in different sizes and concentrations have been synthesized. Cross-linking degree of PA layer characterized with Fourier transform spectroscopy (FTIR) and x-ray photoelectron spectroscopy (XPS) methods to evaluate size dependency of the cross-linking degree of PA layer network. Obvious... 

WO3 thin film photoanodes containing different concentrations of Ag nanoparticles were synthesized by solegel method. Based on UV-visible spectra, presence of a surface plasmon resonance peak at 470 nm of wavelength indicated formation of silver nanoparticles in the WO3 films. According to atomic force microscopy (AFM) analysis, the highest value for surface roughness and the effective surface ratio was observed for the sample containing 2 mol% of Ag. X-ray diffraction (XRD) patterns revealed that WO 3 nanocrystalline structure was formed in the monoclinic phase with the average size of about 18.2 nm while Ag nanocrystals were determined in cubic phase. X-ray photoelectron spectroscopy (XPS)... 

Ce-doped ZnO nanocomposite thin films with Ce/Zn ratio fixed at optimum value (10 at.%) have been prepared via sol-gel method at different annealing temperatures varied from 180 to 500 °C. The synthesized samples were characterized employing atomic force microscopy (AFM), X-ray photoelectron spectroscopy (XPS), and X-ray diffraction (XRD) techniques. According to AFM analysis, the average grain size increased from about 70 nm to 150 nm by increasing the annealing temperature from 300 to 500 °C. Moreover, based on the XPS data analysis, it was found that three major metal ions namely Ce 3+, Ce4+, and Zn2+ coexist on the surface of the nanocomposite films. XPS data analysis also revealed that... 

Transition metal oxides are being more frequently used as hole injection layer (HIL) in organic light emitting diodes (OLEDs), in place of polymer HILs such as PEDOT:PSS. The very thin films of the metal oxide HILs are usually deposited using vapor deposition, in order to create uniform films. Here, we report OLEDs fabricated using solution processed MoOx films as the HIL and super yellow as the emissive layer. The performance of the devices is comparable to PEDOT:PSS based devices, while the stability tests show the lifetime of MoOx-based devices is 4 × 106 h, about 40 times longer than PEDOT:PSS devices, at typical working condition. X-ray photoelectron spectroscopy (XPS) indicates both... 

Modified tungsten oxide films by vanadium oxide provide neutrally coloring electrochromic electrodes for smart windows technology. In this study W-V-O mixed oxide films were fabricated by Nd:YAG pulsed laser deposition (PLD), λ=1064 nm, from mixed pressed powders of (WO3)1-x(V2O5)x, x=0, 0.09, 0.17, 0.23, 0.29 and 0.33, at 13.3 Pa oxygen partial pressure and 200 °C temperature on glass substrates. X-ray photoelectron spectroscopy (XPS) revealed V5+, V4+, W6+ and W5+ surface oxide states, where the ratio of W5+/W6+ enhances by the amount of vanadium in the films. Surface morphology was studied by scanning electron microscope (SEM) and optical properties by transmission-reflection spectra.... 

A comparison of X-ray photoemission spectroscopy of Mg doped Cu0.5Tl0.5Ba2Ca1.5Mg 0.5Cu3O10-δ and Mg free Cu0.5Tl0.5Ba2Ca2Cu 3O10-δ superconductor samples have been made. The main objective of these studies is to see the effect of Mg doping in developing better inter-plane coupling among the CuO2 planes and its effects on the chemical shift of the bonding species. Through these studies it is observed that thallium is in Tl+1 oxidation state in the Cu0.5Tl0.5Ba2O4- δ charge reservoir layer in both Mg doped and Mg free samples, however, the XPS line related to Ba atoms are shifted to higher binding energy side by 0.32 eV in Mg doped sample. This chemical shift is most likely due to presence of... 

Porous silicon samples were obtained by the electrochemical method and were impregnated with Pd by the electroless process. X-ray photoelectron spectroscopy illustrated that the surface of the samples is oxidized during the palladium deposition. Scanning electron microscopy showed how factors such as morphology and pre-oxidations of porous samples and the plating parameters including Pd-salt concentration, HCl concentration, temperature of the electroless solution and the time of process affect the growth and nucleation of Pd particles. Observations demonstrated that the illumination-assisted process on p-type samples has a drastic effect on the growth of palladium. Hydrogen sensing of these... 

In this work, formation of gold nanoparticles in radio frequency (RF) reactive magnetron co-sputtered Au-SiO 2 thin films post annealed at different temperatures in Ar + H 2 atmosphere has been investigated. Optical, surface topography, chemical state and crystalline properties of the prepared films were analyzed by using UV-visible spectrophotometry, atomic force microscopy (AFM), X-ray photoelectron spectroscopy (XPS) and X-ray diffractometry (XRD) techniques, respectively. Optical absorption spectrum of the Au-SiO 2 thin films annealed at 800 °C showed one surface plasmon resonance (SPR) absorption peak located at 520 nm relating to gold nanoparticles. According to XPS analysis, it was... 

Titania was deposited on glass fibers with a partial epoxy layer coating from a solution containing TiO2 nanoparticles at T = 90°C, and the adsorption process was examined by X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM), energy-dispersive spectroscopy (EDS), Fourier transform infrared (FT-IR) spectroscopy, and photocatalytic activity measurements. XPS data demonstrated that about 25% of the surface was covered with TiO2 nanoparticles, with 10% on the epoxy layer and 15% on the glass body. It was found that TiO2 nanoparticles can be readily adsorbed on epoxy groups, whereas they have a low tendency to adsorb on carbon polymer chains. This difference can be... 

The Co nanowires were electrodeposited in polycarbonate membrane (PCT). SEM, TEM and XPS techniques were used to characterize the morphology, structure and size of nanowires as well as chemical composition. The influence of different mediums was studied on the optical absorption of dispersed cobalt nanowires. The absorption spectrum of cobalt nanowires in water showed a broad shoulder at 290 nm, but in ethanol solution it was not observed in the visible region of the spectra up to 200 nm. Cobalt nanowires dispersed in methanol presented a peak at 236 nm. We attribute the data to oxidation of cobalt in water and low dielectric constant of methanol relative to ethanol and water. We found... 

X-ray photo-emission spectroscopy (XPS) studies of Cu1-xTlxBa2Ca3Cu4 O12-y superconductor thin films have been carried out for understanding the mechanism of superconductivity and to find out the reasons for the increase of zero resistivity critical temperature Tc(R = 0) with post-annealing in a nitrogen atmosphere. It is observed from these studies that reduction of charge state of thallium is a source of doping of carriers to the CuO2 planes. The reduced charge state of thallium (i.e. Tl1+) promotes lower oxygen concentration in the charge reservoir layer, which possibly results in movement of electrons to the conducting CuO2 planes. The higher density of electrons in the CuO2 planes...