Amorphization of nanocrystalline monoclinic ZrO(2) by swift heavy ion irradiation

Bulk ZrO(2) polymorphs generally have an extremely high amorphization tolerance upon low energy ion and swift heavy ion irradiation in which ballistic interaction and ionization radiation dominate the ion-solid interaction, respectively. However, under very high-energy irradiation by 1.33 GeV U-238, nanocrystalline (40-50 nm) monoclinic ZrO(2) can be amorphized. A computational simulation based on a thermal spike model reveals that the strong ionizing radiation from swift heavy ions with a very high electronic energy loss of 52.2 keV nm(-1) can induce transient zones with temperatures well above the ZrO(2) melting point. The extreme electronic energy loss, coupled with the high energy state of the nanostructured materials and a high thermal confinement due to the less effective heat transport within the transient hot zone, may eventually be responsible for the ionizing radiation-induced amorphization without transforming to the tetragonal polymorph. The amorphization of nanocrystalline zirconia was also confirmed by 1.69 GeV Au ion irradiation with the electronic energy loss of 40 keV nm(-1). These results suggest that highly radiation tolerant materials in bulk forms, such as ZrO(2), may be radiation sensitive with the reduced length scale down to the nano-metered regime upon irradiation above a threshold value of electronic energy loss.     

Investigation of O7+ swift heavy ion irradiation on molybdenum doped indium oxide thin films

Molybdenum (0.5 at%) doped indium oxide thin films deposited by spray pyrolysis technique were irradiated by 100 MeV O⁷⁺ ions with different fluences of 5×10¹¹, 1×10¹² and 1×10¹³ ions/cm². Intensity of (222) peak of the pristine film was decreased with increase in the ion fluence. Films irradiated with the maximum ion fluence of 1×10¹³ ions/cm² showed a fraction of amorphous nature. The surface microstructures on the surface of the film showed that increase in ion fluence decreases the grain size. Mobility of the pristine molybdenum doped indium oxide films was decreased from ～122 to 48 cm²/V s with increasing ion fluence. Among the irradiated films the film irradiated with the ion fluence of 5×10¹¹ ions/cm² showed relatively low resistivity of 6.7×10^?4 Ω cm with the mobility of 75 cm²/V s. The average transmittance of the as-deposited IMO film is decreased from 89% to 81% due to irradiation with the fluence of 5×10¹¹ ions/cm².     

Characterisation of BaBi2Nb2O9 powders and thin films prepared by a solution synthesis technique

Ba₂Bi₂NbO₉ (BBN) powders with the order of magnitude of nanometer were prepared by a metal organic decomposition (MOD) method. The thermal decomposition of the air-stable BBN precursor solution was studied using a thermal analyser and X-ray diffraction (XRD). Thin films of Ba₂Bi₂NbO₉ (BBN) have been deposited on both alumina (α-Al₂O₃) and Pt/TiO₂/SiO₂/(100)Si substrates by spin-coating of the obtained BBN precursor solution. The phase formation, crystallite size and morphology of the thin films were investigated by X-ray diffraction (XRD) and electron microscopy (EM). It is shown that a monophasic BBN phase with good crystallinity can be obtained in the form of thin films on both substrates without excess of bismuth in the precursor solution.     

Shape-controlled synthesis of ternary chalcogenide ZnIn2S4 and CuIn(S,Se)2 nano-/microstructures via facile solution route

We demonstrated in this paper the shape-controlled synthesis of ZnIn2S4, CuInS2, and CuInSe2 nano- and microstructures through a facile solution-based route. One-dimensional ZnIn2S4 nanotubes and nanoribbons were synthesized by a solvothermal method with pyridine as the solvent, while ZnIn2S4 solid or hollow microspheres were hydrothermally prepared in the presence of a surfactant such as cetyltrimethylammonium bromide (CTAB) or poly(ethylene glycol) (PEG). The mechanisms related to the phase formation and morphology control of ZnIn2S4 are proposed and discussed. The UV-vis absorption spectra show that the as-prepared nano- and micromaterials have strong absorption in a wide range from UV to visible light and that their band gaps are somewhat relevant to the size and morphology. The photoluminescence measurements of the ZnIn2S4 microspheres at room temperature reveal intense excitation at approximately 575 nm and red emission at approximately 784 nm. Furthermore, CuInS2 and CuInSe2 with different morphologies such as spheres, platelets, rods, and fishbone-like shapes were also obtained by similar hydrothermal and solvothermal synthesis.     

A solution growth technique for the preparation of copper (II) selenide thin films

A solution growth technique has been developed for the deposition of thin films of copper(II) selenide on glass substrate using a copper(II) salt solution, triethanolamine, ammonia, and sodium selenosulfate as the reacting agents. The material has been characterized through X-ray powder photography, optical absorption, and Hall measurements at room temperature. The films are found to be degenerate and p type with a Moss-Burstein shifted direct band gap of 2.14 eV.     

Effect of crystallization route on the properties of LiMn2O4 thin films prepared by spin coating

LiMn₂O₄ thin films were prepared by spin coating through intermediate amorphous layer route (IALR) and intermediate crystallized layer route (ICLR). The phase identification, surface morphology, and electrochemical properties of the films prepared by different crystallization routes were studied by X-ray diffraction, scanning electron microscopy, and galvanostatic charge–discharge experiments. The results show that both films prepared by different crystallization routes are homogeneous and crack free. Compared with the film prepared by IALR, the film prepared by ICLR shows smaller grain size and is smoother and denser. The LiMn₂O₄ film prepared by ICLR delivers the specific capacity of 39.8 μAh?cm^?2?μm^?1, which is higher than 35.6 μAh?cm^?2?μm^?1 for the one prepared by IALR. The capacity loss of the film prepared by ICLR after being cycled 100 times is 3.4 %, which is smaller than that of 5.5 % for the film prepared by IALR. The film prepared by ICLR shows higher specific capacity and better cycling behavior than the one prepared by IALR.     

Structural and optical properties of TiO2 thin films prepared by spin coating

Transparent semiconducting thin films of titanium oxide (TiO₂) were deposited on glass substrates by the sol–gel method and spin-coating technique. The physical properties of the prepared films were studied as a function of the number of spun-cast layers. The microstructure and surface morphology of the TiO₂ films were characterized by X-ray diffraction (XRD) and atomic force microscopy (AFM), with respect to the film thickness. The XRD analysis reveals that the films are polycrystalline with an anatase crystal structure and a preferred grain orientation in the (101) direction. The morphological properties were investigated by AFM, which shows a porous morphology structure for the films. The optical properties of the films were characterized by UV–Visible spectrophotometry, which shows that the films are highly transparent in the visible region and their transparency is slightly influenced by the film thickness, with an average value above 80 %. The dependence of the refractive index (n), extinction coefficient (k), and absorption coefficient (α) of the films on the wavelength was investigated. A shift in the optical band gap energy of the films from 3.75 to 3.54 eV, as a function of the film thickness, has been observed.     

Effect of the sputtering parameters on the physical properties and photocatalytic reactivity of TiO2 thin films prepared by an RF magnetron sputtering deposition method

Visible light-responsive TiO₂ (Vis-TiO₂) thin films were successfully developed by applying a radio-frequency magnetron sputtering deposition method by controlling various sputtering parameters such as the substrate temperature, Ar gas pressure, and the target-to-substrate distance. UV–Vis, XRD and SEM investigations revealed that optical property, the crystal structure, and photocatalytic activity of Vis-TiO₂ are strongly affected by the sputtering parameters during the deposition step. Vis-TiO₂ was found to act as an efficient photocatalyst for the H₂ and O₂ evolution from water under visible light irradiation (λ ≥ 420 nm). SIMS investigations have revealed that a slight decrease in the O/Ti ratio of the TiO₂ thin films plays an important role in the modification of the electronic properties of Vis-TiO₂ thin films, enabling them to absorb visible light.     

Preparation and characterization of CuAlO2 transparent thin films prepared by chemical solution deposition method

CuAlO₂ thin films were prepared on quartz glass and sapphire substrates by chemical solution deposition method using copper acetate monohydrate, aluminum nitrate nonahydrate and 2-methoxyethanol as starting precursor and solvent. The effects of annealing temperature on the structural, morphological, electrical and optical properties have been studied. Via the optimized annealing treatment condition, CuAlO₂ film annealed at 850 °C in nitrogen flow of 400sccm under atmosphere pressure exhibits the best performance with the lowest room temperature resistivity of 3.6 × 10² Ω cm and the highest optical transmission in the visible region (>70% at around 600 nm wavelength). CuAl₂O₄ and CuO phases, not CuAlO₂ phase are obtained when annealing temperature is lower than 850 °C. However, a further increase of annealing temperature weakens the crystallization quality and deteriorates the surface morphology of CuAlO₂ films as the annealing temperature exceeds 850 °C, leading to an increase in the resistivity and a decrease of the optical transmission in the visible region of CuAlO₂ films.     

The effect of complexing agent on crystal growth,structure and properties of nanostructured Cu_（2-x）S thin films

Thin films of Cu2 x S（x = 0, 1） were deposited on self-assembled, monolayer modified substrates in the copper–thiosulfate system with various concentrations of ethylene diamine tetraacetic acid（EDTA） at a low temperature of 70 8C. The thin films were characterized by means of X-ray diffraction（XRD）, X-ray photoelectron spectroscope（XPS）, field emission scanning electron microscopy（FESEM）, transmission electron microscopy（TEM）. The optical and photoelectrochemical（PEC） properties of the Cu2 x S semiconductor films were investigated by ultraviolet–visible（UV–vis） absorption spectroscopy and a three-electrode system. It is found that EDTA plays a key role in the process of Cu2 x S nanocrystals formation and growth. The compositions of the Cu2 x S nanocrystals varied from Cu2S（chalcocide） to Cu S（covellite） through adjusting the concentration of EDTA, which is used as a complexing agent to yield high-quality Cu2 x S films. The growth mechanisms of Cu2 x S nanocrystals with different EDTA concentrations are proposed and discussed in detail.     

Dielectric relaxation behavior of C5+ (70 MeV) swift heavy ion irradiated polyetheretherketone (PEEK) using TSDC technique

The dielectric relaxation characteristics of polyetheretherketone (PEEK) irradiated with C⁵⁺ (70 MeV) ion, have been investigated in the temperature range 60–230° as a function of poling temperature T _P (50, 100, 150, and 200°C), poling field E _P (200, 300, 400, and 500 kV/cm), and storage time t _s (2, 24, 48, and 120 h), using thermally stimulated discharge current (TSDC) technique. The TSDC spectra show a prominent maximum around glass transition temperature (T _g ～ 143°C) named as α-peak. This peak is attributed to the movement of ketone dipoles linked with the main chain. It is observed that the magnitude of α-peak increases with the increase in poling temperature and poling field. The peak current and area under the α-peak are found to be diminished with the increase of storage time t _s for electrets. The β-peak (space charge peak) is absent in irradiated PEEK samples as compared to pristine PEEK samples. The results obtained, in the present studies, are compared with the results on pristine samples. The activation energies and pre-exponential factor for PEEK samples determined using Bucci plot method.     

Effect of Pt loading on the photocatalytic reactivity of titanium oxide thin films prepared by ion engineering techniques

Platinum-loaded titanium oxide thin-film photocatalysts were prepared by using an ionized cluster beam (ICB) deposition method and a RF magnetron sputtering (RF-MS) deposition method as dry processes. From the results of the photocatalytic oxidation of acetaldehyde with O₂ under UV light irradiation, small amounts of Pt loading (less than 10 nm film thickness) were found to dramatically enhance the photocatalytic reactivity. However, when TiO₂ thin films were loaded with relatively larger amounts of Pt (more than 30 nm as the film thickness), the photocatalytic reactivity became lower than for the pure TiO₂ thin films. Moreover, investigations of the ratio of Pt loaded onto the surface of the thin film catalysts by XPS measurements revealed that the small amounts of Pt loaded exist as very small clusters working to efficiently enhance the charge separation, whereas, large amounts of Pt covers the entire surface of the TiO₂ thin films, resulting in a decrease of the photocatalytic reactivity.     

Effect of deposition temperature on the growth mechanism of chemically prepared CZTGeS thin films

The Cu₂ZnSnGeS₄ (CZTGeS) thin films were deposited by the spray pyrolysis method at different substrate temperatures without further sulfurization. The influence of various deposition temperatures on the surface morphology, microstructure, optical properties, chemical, and phase composition were investigated. The substitution mechanism of Sn/Ge in the crystal lattice of CZTGeS depending on deposition temperatures was studied. It was shown that a variation in substrate temperature has a strong effect on the surface morphology of the films. The X-ray diffractometer (XRD), transmission electron microscope (TEM), and Raman spectroscopy (RS) analysis showed that CZTGeS films were polycrystalline with a kesterite-type single-phase structure and a preferential orientation of (112). The RS-mapping analysis showed the distribution of intensities on the surfaces of the films. Optical measurements showed that CZTGeS films are highly absorbing in the visible region, and the optical band gap is shifted from 1.89 to 1.84 eV.     

Optical and structural properties of aluminium oxide thin films prepared by a non-aqueous sol–gel technique

Clear aluminium oxide sols without precipitation were synthesized via a non-aqueous sol–gel technique using three different alcohols (ethanol, isopropanol and n-butyl alcohol) as solvent, aluminium sec-butoxide as a precursor and acetyl acetone as a chelating agent. Although all sols could be successfully used to prepare thin films, the most stable one was prepared with n-butyl alcohol. Highly transparent, homogenous and amorphous aluminium oxide thin films were obtained on Si substrates after a heat treatment at 500 °C. X-Ray photoelectron spectroscopy (XPS) and Fourier transform infrared absorption (FT-IR) spectroscopy revealed all films were hydroxide free. The optical and structural properties of the films were particularly investigated. Any significant difference except from thickness on the film properties was not observed by changing the alcohol. Refractive index was used as an indication of the porosity of the films and ranged from 1.54 to 1.60.     

Effect of annealing temperature on titania thin films prepared by spin coating

Essentially fully dense titania thin films were spin coated on fused quartz substrates under identical conditions and subjected to annealing over the range 750°–900°C. The films were of a consistent ~400 nm thickness. The anatase → rutile phase transformation temperature was between 750°C and 800°C, with first-order kinetics; annealing at 900°C yielded single-phase rutile. Silicon contamination from the fused quartz substrate was considered to be critical since it suppressed both titania grain growth (maintaining constant grain size) and the phase transformation (occurring at an unusually high temperature); its presence also was considered to be responsible for the formation of lattice defects, which decreased the transmittances and the band gaps.     

Preparation and characterization of nanostructured Ni(OH)2 and NiO thin films by a simple solution growth process

Nanostructured Ni(OH)2 thin films were prepared by a simple solution growth process with F(-) and NH3 used as Ni2+ coordination agents, and ammonia hydroxide solution used as OH(-) supplier to accelerate the hydrolyzation of nickel complex species. The results showed Ni(OH)2 thin films were constructed mainly with hexagonal beta-Ni(OH)2 nanorods; the F(-) and NH3 in reactive solutions played important roles in the film growth process; and solution pH had great influence on the morphologies of thin films, which was explained by the competition of Ni(OH)2 nucleation and growth in solutions. NiO crystallinity thin films were obtained by annealing Ni(OH)2 thin films at 400 degrees C for 2 h and the morphologies of the Ni(OH)2 thin films were sustained well during the annealed process.     

Electron Spectroscopy (ESCA) on technical oxidic thin films prepared by different methods

Summary Technical oxidic thin films (SiO₂, TiO₂, Ta₂O₅ and WO₃) prepared by different deposition methods (dip coating, evaporation and ion plating) have been analysed by electron spectroscopy (ESCA). Different peak structures were obtained in the spectra depending on the deposition technique and the conditions during the coating process. The differences in the spectra due to the binding states were analysed by means of deconvolution and fitting of the spectra. The obtained results are discussed in connection with further investigations.     

Microstructure and optical properties of Ag-doped ZrO2 thin films prepared by sol gel method

Ag doped ZrO₂ thin films were deposited on quartz substrates by sol–gel dip coating technique. The effect of Ag doping on tetragonal to monoclinic phase transformation of ZrO₂ at a lower temperature (500 °C) was investigated by X-ray diffraction. It is found that the Ag doping promotes the phase transformation. The phase transformation can be attributed to the increase in the tetragonal grain size and concentration of oxygen vacancies in the presence of the Ag dopant. Accumulation of the Ag atoms at the film surface and surface morphology changes in the films were observed by AFM as a function of varying Ag concentration. X-ray photoelectron spectroscopy gave Ag 3d and O 1s spectra on Ag doped thin film. The chemical states of Ag have been identified as the monovalent state of Ag⁺ ions in ZrO₂. The Ag doped ZrO₂ thin films demonstrated the tailoring of band gap values. It is also found that the intensity of room temperature photoluminescence spectra is suppressed with Ag doping.