Evolution of the structure and surface morphology of thin films composed of two selenium based chalcogenide phases, AgInSe2 and Ag2Se on 140 MeV ion irradiation is reported. At this high energy, the projectile Ni ions sputtered the surface of the films through energy deposition to the target electrons. The sputtering led to decrease of silver and selenium concentration, but did not affect indium concentration. Surface analysis by field emission scanning electron microscopy study revealed nanoparticles of widely varying shapes and sizes on the surface of the films. Irradiation did not affect the particle size distribution which peaked at similar to 100 nm. The two phases, AgInSe2 and Ag2Se exhibited different sensitivity to 140 MeV Ni ion irradiations. While Ag 2 Se phase was insensitive, the AgInSe2 phase showed complex structural modifications at intermediate fluences, finally getting amorphized at high ion fluences. Analysis of the fluence dependence of Grazing Incidence X-ray Diffraction (GIXRD) peak area of AgInSe2 phase indicated that each ion that penetrated the film, created an amorphous column of 1.6 nm radius. Surrounding the amorphous column, a cylindrical crystalline AgInSe2 region of radius 8.2 nm, but with reduced lattice parameters formed. High resolution transmission electron microscopy image also confirmed registration of amorphized tracks and the modified crystalline region of similar radii around the path of 140 MeV Ni ions in a grain of AgInSe2 as obtained from GIXRD study.

Sensitivity of the anatase and rutile phases of titanium dioxide to Swift Heavy Ion (SHI) irradiation was experimentally probed and compared with the predictions of the Coulomb explosion, analytical and inelastic thermal spike models of ion-matter interaction. Conforming to the predictions of all these models, our study indicated higher sensitivity of anatase to these ions than the rutile phase. A detailed examination however revealed that Coulomb explosion model cannot explain either the nature of variation of the interaction cross section of SHI with the energy deposited by these ions, Se to the target electrons, or the relative values of the threshold electronic energy loss, Seth of anatase and rutile. The analytical thermal spike (a-TS) model, using the available physicochemical data for this oxide, predicted that tracks cannot form either in anatase or in rutile by 297 MeV and 511 MeV Ni ions, while inelastic thermal spike (i-TS) model predicted formation of ion tracks by 297 MeV Ni ions and their absence with 511 MeV Ni ions in both anatase and rutile. Our observation agreed with the predictions of i-TS model albeit with a difference in the radius of the tracks. In addition, we observed halo of defect ridden crystalline region of much larger radius around the ion track. Interestingly, the radius of the halo scales with the velocity of the ions, which is opposite to the conventionally observed velocity effect.

Modification of the microstructure of 300 nm thick NiO thin film deposited by pulsed laser deposition method under 120 MeV Au ion irradiation was studied by in-situ X-ray diffraction(XRD) at 300 K. Irradiation led to different effects on the crystallinity of the films at different ion fluences. In the low fluence regime, crystalline quality of the films improved with consequent increase in the XRD peak intensity and decrease of the full width at half maximum (FWHM) of the XRD peaks with increasing ion fluence up to 3 x 10(11) ions cm(-2). At higher ion fluences, the crystalline quality decreased. Thermal spike model with a transient temperature profile exceeding the melting temperature inside the track explains the second effect and a temperature radially decreasing away from the track region, but still high enough to anneal out the pre-existing defects in the region surrounding the ion tracks explains the first effect. Radius of the ion tracks (similar to 1.9 nm) calculated by fitting the fluence dependence of XRD peak intensity agrees with the value (2 nm) predicted by the inelastic thermal spike model. Low density of the disordered material in the track region created due to the electronic energy loss of the energetic ions exceeding the threshold value for track formation was found to produce radial compressive strain on the crystalline matrix around the ion tracks leading to shifting of XRD peaks towards higher angles with increasing ion fluence. Fitting the variation of the strain with ion fluence to Poisson relation yielded radius of the strained region as 6.9 nm. Our study thus suggests three modes of materials modification under the attendant ion beam: (i) annealing of defects in regions surrounding the ion tracks, (ii) creation of columnar defects along the ion path and (iii) a strained matrix around each ion track.

BiFeO3 thin films deposited by sol-gel spin coating method were irradiated by 200 MeV Ag ions. Irradiation induced modification of the microstructure of the films was studied by X-ray diffraction (XRD), micro Raman, UV-Visible spectroscopy, atomic force microscopy and current-voltage (I-V) measurements. XRD analysis revealed that the pristine films are crystalline BiFeO3 phase. Ion irradiation led to fragmentation of the crystallites in the films up to the fluence of 3 x 10(12) ions cm(-2) and amorphization beyond this fluence. The crystallite size showed a monotonic decrease with increasing ion fluence. XRD peaks shifted to lower angles with increasing ion fluence, thus indicating irradiation induced increase of lattice parameter. Irradiation induced lattice expansion is understood on the basic of reduction of crystallite size. In agreement with this observation, the optical band gap showed blue shift with increasing ion fluence. I-V measurement showed a three orders of magnitude decrease of the leakage current density with increasing ion fluence up to 3 x 1012 ions cm(-2). This dramatic decrease of leakage current density is explained on the basis of widening of the band gap, which is a direct consequence of SHI induced crystallite size reduction.

Thermally evaporated gold thin films of 10 to 50 nm thickness deposited on Si (100) substrate were annealed at 250 degrees C under vacuum for different period. The as-deposited and annealed films were characterized by glancing angle X-ray diffraction (GAXRD), atomic force microscopy (AFM), scanning electron microscopy (SEM), Rutherford backscattering spectrometry (RBS) and d. c. resistivity. GAXRD indicated improvement of crystallite size up to 2 hours of annealing and degradation of the same thereafter. In agreement with XRD result, AFM and SEM indicated grain growth with annealing time up to 2 hours and stagnation or even decrease of grain size thereafter. The dependence of the grain size evolution with annealing time on the thickness of the film was seen from RBS, which corroborated the XRD, AFM and SEM results. The electrical resistivity of the films of different thickness also showed the same trend of evolution with annealing time, clearly indicating the importance of microstructure in controlling the electrical conduction in the films. Power spectral density (PSD) analysis of AFM images indicated that surface morphology evolution in gold thin films under annealing is dominated by surface diffusion mass transport. This unusual result of the suppression of crystallinity on annealing beyond a particular period is understood by two competing processes: grain growth due to accelerated particle diffusion across rough surfaces under annealing and smoothening of grain surface with formation of grooves at the boundary between adjacent grains inhibiting further grain growth.

BiFeO 3 (BFO) thin films of thickness about 800 nm deposited on Si (100) substrates by sol–gel spin coating method were irradiated by 200 MeV Ag ions. Modification of structure and surface morphology of the films under irradiation was studied using glancing incidence X-ray diffraction (GIXRD) and atomic force microscope (AFM). Fluence dependence of GIXRD peak intensity indicated formation of 10 nm diameter cylindrical amorphous columns in crystalline BFO due to 200 MeV Ag ion irradiation. AFM analysis indicated that the pristine film consists of agglomerated grains with diffuse grain boundary. Irradiation led to reduced agglomeration of the grains with the formation of sharper grain boundaries. The rms roughness ( σ rms ) estimated from AFM analysis increased from 6·2 in pristine film to 12·7 nm when the film irradiated at a fluence of 1 × 10 11 ions cm − 2 . Further irradiation led to decrease of σ rms which finally saturated at a value of 7–8 nm at high ion fluences. The power spectral density analysis indicated that the evolution of surface morphology of the pristine film is governed by the combined effect of evaporation condensation and volume diffusion processes. Swift heavy ion irradiation seems to increase the dominance of volume diffusion in controlling surface morphology of the film at high ion fluences.

In this study, rutile titanium dioxide thin films deposited on Si (100) substrates by DC magnetron sputtering are irradiated by 79 MeV Br ions. Though each Br ion is expected to amorphize the medium along its path, the film remains crystalline even at the highest fluence of irradiation. The evolution of surface of the films with Br ion fluence is studied using atomic-force microscopy. The films were found to smoothen under dense electronic excitation of Br ions. The irregular shape grain of the pristine films convert to circular shape at a fluence of 1 x 10(13) Br ions cm(-2). Power spectral density (PSD) analysis of the AFM images indicates that irradiation induced smoothing of the surfaces is governed by the surface diffusion process.

In the present study, we probe into evolution of microstructure and surface morphology of gold thin films of 10 to 50 nm thickness deposited on Si (100) substrate by thermal evaporation method. These films were annealed at 250 degrees C under vacuum. The as-deposited and annealed films were characterized by glancing angle X-Ray diffraction (GAXRD) and atomic force microscopy (AFM), techniques. XRD indicated improvement of crystallinity up to 2 hours of annealing and degradation of the same thereafter. In agreement with XRD result, the grain size distribution histogram obtained from AFM indicated grain growth with annealing time up to 2 hours and saturation or decrease of grain size thereafter. The observed result is explained by the occurrence of two competing phenomena like roughening induced grain growth and smoothening induced inhibition of grain growth with increasing annealing time.

We report the preparation of multiferroic BiFeO3 thin films on ITO coated glass substrates through sol-gel spin coating method followed by thermal annealing and their modification by swift heavy ion (SHI) irradiation. X-ray diffraction and Raman spectroscopy studies revealed amorphous nature of the as deposited films. Rhombohedral crystalline phase of BiFeO3 evolved on annealing the films at 550°C. Both XRD and Raman studies indicated that SHI irradiation by 200 MeV Au ions result in fragmentation of particles and progressive amorphization with increasing irradiation fluence. The average crystallite size estimated from the XRD line width decreased from 38 nm in pristine sample annealed at 550°C to 29 nm on irradiating these films by 200 MeV Au ions at 1 × 1011 ions cm−2. Complete amorphization of the rhombohedral BiFeO3 phase occurs at a fluence of 1 × 1012 ions.cm−2. Irradiation by another ion (200 MeV Ag) had the similar effect. For both the ions, the electronic energy loss exceeds the threshold electronic energy loss for creation of amorphized latent tracks in BiFeO3.

Gold films of thickness 10 and 20 nm grown on float glass substrate by thermal evaporation technique were irradiated with 107 MeV Ag8+ and 58 MeV Ni5+ ions at different fluences and characterized by Grazing Incidence X-ray Diffraction (GIXRD) and Atomic Force Microscopy (AFM). The pristine films were continuous and no island structures were found even at these small thicknesses. The surface roughness estimated from AFM data did not show either monotonic increase or decrease with ion fluences. Instead, it increased at low fluences and decreased at high fluences for 20 nm thick film. In the 10 nm film roughness first increased with ion fluence, then decreased and again increased at higher fluences. The pattern of variation, however, was identical for Ni and Ag beams. Both the beams led to the formation of cracks on the film surface at intermediate fluences. The observed ion-irradiation induced thickness dependent topographic modification is explained by the spatial confinement of the energy deposited by ions in the reduced dimension of the films.

We report preparation of phase pure BiFeO3 thin films on glass, ITO and Si(100) substrates through chemical route using spin coating technique. Sol-gel process was adopted to prepare the films using bismuth nitrate and iron nitrate as precursors. X-Ray diffraction and Raman spectroscopy studies revealed amorphous nature of the as deposited films. Rhombohedral crystalline phase of BiFeO3 evolved on annealing the films at 500°C, but with Bi2Fe4O9 and Bi24Fe2O39 as impurity phases. Increasing the annealing temperature to 550°C caused a drastic reduction of the impurity phases and at 600°C, the films were phase-pure BiFeO3. Micro Raman spectra showed features consistent with the reported characteristic peaks of BiFeO3 crystalline phase for films annealed at 500 and 550°C. Crystallite size obtained from X-ray diffraction line width analysis are within 30 to 40 nm. Atomic force microscopy (AFM) however showed grain size of ∼192 nm, indicating polycrystalline nature of the grains.

We report in situ x-ray diffraction (XRD) study of 200 MeV Ag ion irradiation induced structural modification in c-axis oriented YBa2Cu3O7−y (YBCO) thin films at 89 K. The films remained c-axis oriented up to a fluence of 2×1013 ionscm−2, where complete amorphization sets in. The amorphous ion tracks, the strained region around these tracks, and irradiation induced point defects are shown to control the evolution of the structure with ion fluence. Secondary electrons emanating from the ion paths are shown to create point defects in a cylindrical region of 97 nm radius, which corresponds to their maximum range in the YBCO medium. The point defects are created exclusively in the CuO basal planes of fully oxygenated YBCO, which has not been possible, by other techniques including low energy ion irradiation and thermal quenching. The point defects led to a faster decrease in the integral intensity of XRD peaks at very low fluences of irradiation (Φ≤3×1010 ionscm−2) than what can be expected from amorphous tracks. The radius of amorphous ion tracks, estimated from the fluence dependence of integral XRD peak intensity beyond this fluence, was found to be 1.9 nm. Both point defect and the strained region around amorphous ion tracks are shown to contribute to the increase in the c-parameter at 89 K. The full width at half maximum (FWHM) of XRD peaks arising mostly due to the strained region around the ion tracks showed an incubation effect up to 1012 ionscm−2, before increasing at higher fluences. Fluence dependence of FWHM gives the cross section of the strained region as 37.9 nm2, which is more than three times the cross section of the amorphous ion tracks.

Jute-polyesteramide(BAK) composite specimens having 45, 50, 55, 60 and 65% of jute by mass were prepared following film stacking method by compression molding technique. It was found that with increase in jute content, the flexural strength and modulus increased from 25.89 and 4709 MPa (45% jute) to 41.75 and 8613 MPa (60% jute) respectively and thereafter decreased with higher loading of fiber. For tensile strength and modulus, the same trend was observed. At 45% jute content, the values were 33.61 and 2599 MPa respectively, whereas at 60% jute content the values were 41.23 and 3346 MPa respectively. The thermogravimetric analysis of jute felt, BAK film and jute-BAK composites (60% jute) were made. The biodegradability of the composite specimens were studied by soil burial test, IR and SEM analyses.

Jute fibers in the form of slivers have been reinforced with epoxy resins to prepare composites. The solution impregnation method have been adopted in an attempt to increase the percentage of fiber loading. Both untreated (control) and chemically modified (bleached) slivers have been used to prepare composites. The optimization study of fiber loading in Composites is done with control slivers through tensile: property assessment. Composites having 50% sliver (control) by weight are observed to give the best tensile characteristics. The tensile, flexural, impact, and hardness properties of the composites of both bleached and control slivers have been investigated and it is observed that although the latter have better tensile properties, the former possesses unusually high flexural properties. Both Izod and Charpy impact tests reflect that the composites with bleached slivers have higher impact strengths. In comparison to the composites with control slivers, they also exhibit greater (Rockwell) hardness.

The scanning electron micrographs (SEM) were taken at different magnifications with respect of the fractured surfaces of the polymer composites prepared from unsaturated polyester resin and jute sliver with 60% fiber loading by weight. The composite specimens were prepared using both untreated (control) and chemically modified (bleached) jute fibers by solution impregnation and hot curing methods and are designated as JPH-60(C) and JPH-60(B), respectively. The method of preparation of the composite specimens have been discussed. The specimens were subjected to tensile and flexural tests and the Fractured surfaces were observed under SEM as stated. The fiber surface morphology was also studied from the SEM photographs in the case of the control and bleached jute filaments. The SEM photographs of the Fractured surfaces of the composites showed varied extents of fiber pull-outs under both tensile and flexural failure modes. The nature of interfacial adhesion has been discussed on the basis of the SEM study. A good correlation between the SEM study and the mechanical strength properties of the composites could be established. Exceptionally high flexural strength of the composites JPH-60(B) compared to JPH-60(C) could be explained from the SEM study.

Jute–polyester composites were fabricated with untreated (control) and bleached slivers with 60% loading of fiber by weight and were designated as JPH(C) and JPH(B), respectively. Both types of composite specimens were subjected to water absorption and outdoor weathering tests to assess their relative performance under environmental conditions. While both composites showed low water absorption, JPH(B) showed lesser water absorption (8.48%) than did JPH(C) (12.25%). The mechanical properties like tensile and flexural strengths were measured for both the weathered and unweathered specimens and compared. The tensile strength of JPH(C) and JPH(B) decreased while the tensile modulus increased after weathering. The flexural strength, moduli, and ILSS of the weathered specimens were less than those of the unweathered ones. The nature of the fiber–matrix adhesion could be established from these results. The cause of every observation is explained. Thermal analyses (TG/DTG and DSC) of the composite specimens were also done. The overall thermal stability of JPH(C) was found to be better than that of JPH(B). © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 78: 1671–1679, 2000

The development of high performance composites from a cheap natural fiber, jute, as reinforcement is particularly significant from an economic point of view. In this work, jute fiber-unsaturated polyester(GP) composites having appreciable mechanical properties were prepared by using solution impregnation and hot curing methods. Both unbleached (control) and bleached jute slivers with various percentages of fiber loadings were used to prepare the composites and were named JPH (C) i.e., Jute Polyester Hot Curing (control), and JPH (B) i.e., Jute Polyester Hot Curing (bleached), respectively. Mechanical properties such as tensile and flexural strain, toughness, and moduli of both the grades have been compared. Composites having 60 wt% of jute fiber yielded the best results. JPH (B) showed much better flexural properties than JPH (C), although the tensile properties of the latter were better. The inter-laminar shear strength (ILSS) of the JPH (B) was found to be higher than JPH (C). The nature of fiber-resin bonding was studied from scanning electron micrographs of the specimens subjected to tensile and flexural fracture. Dynamic mechanical properties were found to be very high, superior even to those of glass fibre reinforced composites. The flexural storage modulus was found to be 12.3 GPa at 30 degrees C and to decrease slowly with temperature. The major finding in this work is the attainment of high mechanical properties of composite specimens with 60 wt% fiber loading. On a weight and cost basis, bleached jute fibres were found to be better reinforcements than other fibers with usual surface modification by coating or grafting processes.