Effect of SHI irradiation on the morphology of SnO2 thin film prepared by reactive thermal evaporation

SnO₂ thin films prepared by reactive thermal evaporation on glass substrates were subjected to 120 MeV Ag⁹⁺ ion irradiation. The surface topography progression using the swift heavy ion irradiation was studied. It shows creation of unique surface morphologies and regular structures on the surface of the SnO₂ thin film at particular fluences. Field Emission Scanning electron microscopy (FE-SEM) and Atomic force microscopy (AFM) are used for investigating the effect of Ag ions at different fluences on the surface of SnO₂. The morphological changes suggest that ion assisted/induced diffusion process play a significant role in the evolution of nanostructures on SnO₂ surface. The roughness increases from 9.4 to 14.9 with fluence upto 1 × 10¹² ions/cm² and beyond this fluence, the roughness decreases. Ion-beam induced recrystallization at lower fluences and amorphization or disordering of crystals at higher fluences are understood based on the thermal spike model.     

Swift heavy ion induced structural,optical and luminescence modification in NaSrBO3:Dy3+ phosphor

The effect of 120 MeVAg⁹⁺ ion irradiation on the structural, optical and luminescence properties of NaSr_1-xBO₃:xDy³⁺ (x = 0.5–2.5 mol%) phosphor synthesized by the conventional solid state reaction route is reported. The samples were irradiated with Ag⁹⁺ swift heavy ions (SHIs) using fluences of 1 × 10¹², 5 × 10¹² and 1 × 10¹³ ions cm^?2. The unirradiated as well as irradiated samples were characterized by powder X-ray diffraction (PXRD), diffuse reflectance (DR) and photoluminescence techniques. PXRD confirms no change in the phase after irradiation except that loss of crystallinity had been observed which may be due to the fragmentation caused by the SHI. A blue shift in the absorption band of the DR was observed, resulting in an increase in the band gap from 5.61 eV to 5.77 eV, after ion irradiation. An increase in photoluminescence intensity (excited at 385 nm) was observed with increased ion fluences. The ratio of the blue to yellow emission peaks (I₄₈₃/I₅₇₇) was calculated and found to be varying with ion fluences suggesting that the white light can be achieved by tailoring this yellow to blue ratio. The Commission Internationale de l’Eclairage coordinates were calculated and found to move toward the white region after irradiation.     

Liquid phase deposition of BiFeO3 thin film on self-assembly monolayers

BiFeO₃ (BFO) thin films were successfully deposited on self-assembled monolayers (SAMs) by the liquid phase deposition method. The measurement of contact angle and atomic force microscopy (AFM) showed that after immersion in an octadecyl trichlorosilane (OTS) solution for 30 min, the surface of the substrate was covered with a smooth, hydrophobic layer. After UV irradiation for 30 min, the smooth hydrophobic layer changed into a serrated hydrophilic layer. This indicated that the OTS-SAMs played an active role as chemical templates in controlling nucleation and growth of the BFO thin film. The phase and the surface topography of the BFO film were investigated respectively by X-ray diffraction, Field emission scanning electron microscopy (FE-SEM) and AFM. The results showed that the optimum annealing temperature and deposition temperature for preparing the BFO thin film were 600 and 70 °C respectively. The films were annealed at 600 °C for 2 h. As-prepared thin films were smooth, uniform, and dense with the height varying between 20 and 100 nm. Moreover, patterned BFO nanoarrays were prepared.     

Energetic ion irradiation induced crystallization of Ni–Mn–Sn ferromagnetic shape memory alloy thin film

The ion irradiation induced crystallization of Ni–Mn–Sn ferromagnetic shape memory alloy (FSMA) thin film is investigated. Thin films of Ni–Mn–Sn FSMA synthesized by DC magnetron sputtering on Si substrate at 200 °C are irradiated by a beam of 120 MeV Ag ions at different fluence varying from 1 × 10¹² to 6 × 10¹² ions/cm². X-ray diffraction pattern reveals that the pristine film grows in L2₁ cubic austenite phase with poor crystallinity and crystallinity of the film improves with increasing ion fluence, which is attributed to the strain relaxation by the energy deposited by incoming ions and promotes the grain growth. Grain growth is further confirmed by Atomic force microscopy. The temperature dependent magnetization measurements show improvement in the magnetic and shape memory properties of the films with increasing fluence, which is ascribed to the ordering of austenite phase. Nanoindentation measurements show that with increasing fluence of 120 MeV Ag ions, films exhibit a greater stiffness and smaller tendency towards plastic deformation.     

Photoluminescence and Raman studies in swift heavy ion irradiated polycrystalline aluminum oxide

Polycrystalline aluminum oxide is synthesized by combustion technique and XRD studies of the sample revealed the α-phase. The synthesized sample is irradiated with 120 MeV swift Au⁹⁺ ions for the fluence in the range from 1 × 10¹¹ to 1 × 10¹³ ions cm⁻². A broad photoluminescence (PL) emission with peak at ∼ 447 nm and two sharp emissions with peak at ∼ 679 and ∼ 695 nm are observed in pristine when sample was excited with 326 nm. However, in the irradiated samples the PL intensity at ∼ 447, 679 and 695 nm decreases with increase in ion fluence. The α-Al₂O₃ gives rise to seven Raman modes with Raman intensity with peaks at ∼ 253, 396, 417, 546, 630, 842, 867 cm⁻¹ observed in pristine. The intensity of these modes decreases with increase in ion fluence. However, the Raman modes observed at lower fluences are found to disappear at higher fluence.     

Synthesis of zirconium silicide in Zr thin film on Si and study of its surface morphology

Zirconium silicide was synthesized on Si (100)/zirconium interface by means of swiftly moving 150 MeV Au ion beam. Thin films of zirconium (~60 nm) were deposited on Si (100) substrates in ultra high vacuum conditions using the electron-beam evaporation technique. The system was exposed to different ion fluencies ranging from 3 × 10¹³ to 1 × 10¹⁴ ions/cm² at room temperature. Synthesized zirconium silicide thin film reasonably affects the resistivity of the irradiated system and for highest fluence of 1 × 10¹⁴ ions/cm² resistivity value reduces from 84.3 to 36 μΩ cm. A low resistivity silicide phase, C-49 ZrSi₂ was confirmed by X-ray analysis. Schottky barrier height was calculated from I–V measurements and the values drops down to 0.58 eV after irradiation at 1 × 10¹⁴ ions/cm². The surface and interface morphologies of zirconium silicide were examined by atomic force microscopy (AFM) and scanning electron microscopy (SEM). AFM shows a considerable change in the surface structure and SEM shows the ZrSi₂ agglomeration and formation of Si-rich silicide islands.     

Enhancement of dielectric and magnetic properties in phase pure,dense BiFeO<Subscript>3</Subscript> nanoceramics synthesized by spark plasma sintering techniques

Phase pure, dense BiFeO₃ (BFO) ceramics with average grain sizes of ~?110 nm, ~?450 nm, and ~?1.15 µm were fabricated by spark plasma sintering method. BFO ceramics exhibited grain-size-dependent magnetic properties, which ascribed to the antiferromagnetism–ferromagnetism (AFM–FM) transition. For BFO nanoceramics (~?110 nm), such transition was much significant, and contributed to a large exchange bias field of H_EB?=?500 Oe at 5 K. In addition, BFO nanoceramics (~?110 nm) exhibited lower leakage current and higher resistivity compared to the larger-grained BFO ceramics (~?450 nm and ~?1.15 µm). The calculated activation energies (E_a) and X-ray photoelectron spectroscopy analyses revealed the existence of different types of defects in BFO ceramics with different grain sizes.     

Structural and optical properties of Ag doped tungsten oxide (WO<Subscript>3</Subscript>) by microwave-assisted chemical route

The present study explores, the pure and silver (Ag) doped WO₃ nanoparticles synthesized by microwave irradiation method. Powder X-ray diffraction results reveal that the WO₃ doped with Ag concentration from 0 to 10 wt% crystallizes in monoclinic structure. TEM analysis shows both pristine and silver doped WO₃ nanoparticles. They are having spherical morphology with a average size from 30 to 40 nm. Scanning electron microscopy studies depicts that both the pristine and Ag doped WO₃ form in spherical shaped morphology with an average diameter of 40–30 nm, which is in proper agreement with the average crystallite sizes calculated by Scherrer’s formula. A considerable red shift in the absorbing band edge and a decrease in the band gap energy from 3.00 to 2.85 eV for Ag doped samples were observed by using UV–DRS spectra analysis. The defects in crystal and oxygen deficiencies were analyzed by photoluminescence spectra analysis.     

Swift heavy ion irradiation effect on Cu-doped CdS nanocrystals embedded in PMMA

Semiconductor nanocrystals (NCs) have received much interest for their optical and electronic properties. When these NCs dispersed in polymer matrix, brightness of the light emission is enhanced due to their quantum dot size. The CdCuS NCs have been synthesized by chemical route method and then dispersed in PMMA matrix. These nanocomposite polymer films were irradiated by swift heavy ion (SHI) (100 MeV, Si⁺⁷ ions beam) at different fluences of 1 × 10¹⁰ and 1 × 10¹² ions/cm² and then compared their structural and optical properties by XRD, atomic force microscopy, photoluminescence, and UV-Vis spectroscopy before and after irradiation. The XRD spectra showed a broad hump around 2θ ≈ 11·83° due to amorphous PMMA and other peaks corresponding to hexagonal structure of CdS nanocrystals in PMMA matrix. The photoluminescence spectra shows a broad peak at 530 nm corresponding to green emission due to Cu impurities in CdS. The UV-Vis measurement showed red shift in optical absorption and bandgap changed from 4·38–3·60 eV as the irradiation fluency increased with respect to pristine CdCuS nanocomposite polymer film.     

Nano/micro-structuring of oxide thin film under SHI irradiation

In the present work, we have studied the nano/micro-patterning of the surface of NiO thin films on different substrates (SiO₂, Si and Al) using 100 MeV Ag ions at LN₂ temperature and at an incidence angle of 75^° with the beam axis. The surface morphology of the irradiated surface is observed by Atomic force microscopy (AFM). AFM images of ion beam irradiated samples show the restructuring of initially flat and coherent NiO film into an almost periodic NiO lamellae structure. The quite regular lamellae with width, height and average distance of hundreds of nm are oriented perpendicular to the beam direction. Section analysis of the AFM images reveal that the width of the lamellae is less in case of NiO films deposited on SiO₂ substrate in comparison to Al substrate. The cracking and the development of lamellae structure is observed at higher fluence in the case of Al substrate in comparison to other substrates.     

Ion beam induced interface mixing of Ni on PTFE bilayer system studied by quadrupole mass analysis and electron spectroscopy for chemical analysis

We have investigated interfacial chemistry in a 100 nm Ni on PTFE (polytetrafluoroethylene) bilayer system induced by 120 MeV Au ions with fluences varying from 1 × 10¹² to 5 × 10¹³ ions/cm². In-situ quadrupole mass analysis (QMA) shows emission of Fluorine (F) and different fluorocarbons (C_xF_y) such as CF, CF₃, C₂F₃ etc. during irradiation. Electron spectroscopy for chemical analysis (ESCA) studies show that Ni reacts with chemically reactive species such as F⁻/F and C_xF_y ions or radicals emitted during irradiation forming NiF₂ and metal-polymer complexes (-CFNi-). Rutherford backscattering spectrometry (RBS) was used to analyze the atomic transport at the interface and strong interface mixing is observed at the ion fluence 5 × 10¹³ ions/cm². Atomic force microscopy (AFM) studies before and after irradiation show that surface roughness is increased from 6.9 to 12.4 nm with increasing fluence. Observed results have been explained on the basis of the chemical reactions taking place within molten ion tracks in the polymer and hot zones around the ion paths created in the Ni film. The studies show that swift heavy ion irradiation introduces strong chemical alteration in the system and induces chemical reactions within the ion track, which enhance ion beam mixing in Ni-PTFE bilayer systems.     

Annealing influence on electrical transport mechanism of electroless deposited very thin Ag(W) films

Morphology and conductivity (σ) of the non-tarnishing electroless Ag(W) films for interconnect were studied as a function of thickness (d) by Atomic Force Microscopy (AFM) and Tunneling Atomic Force Microscopy methods. For d ≤ 100 nm the conductivity dependence on thickness can be modeled as percolation of the electrical transport while for thicker d > 100 nm layers it was independent on d (σ = σ₀). A simple electrical circuit model that described the experimental dependence σ(d) for both thin and thick layers was proposed. The AFM study has shown that the small network changes in the film morphology, due to vacuum annealing cause the significant (few orders of magnitude) improvements in electrical conductivity. Although, near bulk conductivity was achieved for the thicker sample, vacuum annealing was not sufficient to achieve such conductivity for very thin Ag(W) films.     

Enhancement in CO gas sensing properties of hydroxyapatite thick films: Effect of swift heavy ion irradiation

This paper investigates the effect of swift heavy ion (SHI) irradiation on surface morphology of Hydroxyapatite (HAp) thick films and modification in gas sensing characteristics. The HAp nanopowder is synthesized by wet chemical process and the thick films are prepared by screen printing technique. These films are irradiated with Ag⁷⁺ ions with energy of 100 MeV at different fluences ranging from 3 × 10¹⁰ to 3 × 10¹³ ions/cm². X-ray diffraction and atomic force microscopy tools are employed to examine the phase and surface modification in HAp thick films due to swift heavy ion irradiation. The ion irradiation study shows that crystallinity decreases and grain size changes with increase in ion fluence. A precise study on gas sensing is carried out to confirm operating temperature of HAp thick film sensor to detect CO gas. Saturation region of the film with increasing gas concentration and other parameters such as response and recovery time are also investigated from the point of view of using HAp films as a sensor device. SHI irradiated HAp thick film shows enhancement in the gas response and saturation limit for CO gas. Furthermore, the irradiated HAp film shows fast response and recovery time for CO gas. The study concludes that nanoceramic HAp thick film is an excellent CO gas sensor at an operating temperature of 195 °C.     

Structure transition and multiferroic properties of Mn-doped BiFeO3 thin films

Pure BiFeO₃ (BFO) and Mn-doped BiFe_1?yMn_yO₃ thin films were prepared on FTO/glass (SnO₂: F) substrates by using a sol–gel method. The effects of Mn-doping on the structure and electric properties of the BFO thin films were studied. The X-ray diffraction (XRD) analysis reveals a structure transition in the Mn-doped BiFe_0.96Mn_0.04O₃ (BFMO) thin film. The Rietveld refined XRD patterns conform the trigonal (R3c: H) and tetragonal (P422) symmetry for the BFO and BFMO thin films, respectively. The structure transition and the mixed valences of Mn ions substantially improve the electric properties of the BFMO thin film. The remnant polarization (P _r) of the BFMO thin film was 105.86 μC/cm² at 1 kHz in the applied electric field of 865 kV/cm. At an applied electric field of 150 kV/cm, the leakage current density of BFMO thin film is 1.42 × 10^?5 A/cm². It is about two orders of magnitude lower than that of the pure BFO thin film (1.25 × 10^?3 A/cm²). And the enhanced saturated magnetization of the BFMO thin film is 4.45 emu/cm³.     

Lattice distortion and room-temperature ferroelectric properties of (Sm, Cr) co-doped BiFeO3 thin films

Pure BiFeO₃ (BFO) and Bi_0.85Sm_0.15Fe_0.97Cr_0.03O₃ (BSFCO) thin films were prepared on FTO/glass (SnO₂: F) substrates by using a chemical solution deposition method. The effects of (Sm, Cr) co-doping on the microstructure and ferroelectric properties of the BSFCO thin films were studied. The X-ray diffraction and Raman scattering spectra proved that the co-doped BSFCO thin film has a lattice distortion compared with the pure BFO thin film. The remnant polarization (2P _r) of the BSFCO thin film was 153.67 μC/cm² at 1 kHz in the applied electric field of 1,270 kV/cm. At an applied electric field of 100 kV/cm, the leakage current density of the co-doped BSFCO thin film (2.12 × 10^?6 A/cm²) was 3 orders lower than that of the pure BFO thin film (3.8 × 10^?3 A/cm²). The improved properties of the co-doped thin film could be attributed to lattices distortion, more grain boundaries, higher binding energy of Sm–O and the mixed-valence states of Cr³⁺ and Cr ⁶⁺.     

Modifications induced by silicon and nickel ion beams in the electrical conductivity of zinc nanowires

This paper presents the modification in electrical conductivity of Zn nanowires under swift heavy ions irradiation at different fluences. The polycrystalline Zn nanowires were synthesized within polymeric templates, using electrochemical deposition technique and were irradiated with 80 MeV Si⁷⁺ and 110 MeV Ni⁸⁺ ion beams with fluence varying from 1 × 10¹² to 3 × 10¹³ ions/cm². I–V characteristics of exposed nanowires revealed a decrease in electrical conductivity with increase in ion fluence which was found to be independent of applied potential difference. But in the case of high fluence of Ni ion beam (3 × 10¹³ ions/cm²), electrical conductivity was found to increase with potential difference. The analysis found a significant contribution from grain boundaries scattering of conduction electrons and defects produced by ion beam during irradiation on flow of charge carriers in nanowires.     

Nano/micro-structuring of oxide thin film under SHI irradiation

In the present work, we have studied the nano/micro-patterning of the surface of NiO thin films on different substrates (SiO₂, Si and Al) using 100 MeV Ag ions at LN₂ temperature and at an incidence angle of 75^° with the beam axis. The surface morphology of the irradiated surface is observed by Atomic force microscopy (AFM). AFM images of ion beam irradiated samples show the restructuring of initially flat and coherent NiO film into an almost periodic NiO lamellae structure. The quite regular lamellae with width, height and average distance of hundreds of nm are oriented perpendicular to the beam direction. Section analysis of the AFM images reveal that the width of the lamellae is less in case of NiO films deposited on SiO₂ substrate in comparison to Al substrate. The cracking and the development of lamellae structure is observed at higher fluence in the case of Al substrate in comparison to other substrates.     

Analysis of organometallics dispersed polymer composite irradiated with oxygen ions

Thin films of polymethyl methacrylate (PMMA) were synthesized. Ferric oxalate was dispersed in PMMA films. These films were irradiated with 80 MeV O⁶⁺ ions at a fluence of 1×10¹¹ ions/cm². The radiation induced changes in electrical conductivity, Mössbauer parameter, microhardness and surface roughness were investigated. It is observed that hardness and electrical conductivity of the film increases with the concentration of dispersed ferric oxalate and also with the fluence. It indicates that ion beam irradiation promotes (i) the metal to polymer bonding and (ii) convert the polymeric structure into hydrogen depleted carbon network. Thus irradiation makes the polymer harder and more conductive. Before irradiation, no Mössbauer absorption was observed. The irradiated sample showed Mössbauer absorption, which seems to indicate that there is significant interaction between the metalion and polymer matrix. Atomic force microscopy shows that the average roughness (R _a) of the irradiated film is lower than the unirradiated one.     

Adhesion and proliferation of keratinocytes on ion beam modified polyethylene

Polyethylene (PE) foils were modified by irradiation with ArE ⁺ and XeE ⁺ ions to different fluences and different physico-chemical properties of the irradiated PE were studied in relation to adhesion and proliferation of keratinocytes on the modified surface. Changes in the PE surface roughness were examined using the AFM technique, the production of conjugated double bonds and oxidized structures by UV-VIS and FTIR techniques respectively. The surface polarity was determined by measuring surface contact angle and two-point technique was used for the determination of PE sheet resistance. Adhesion and proliferation of keratinocytes was characterized using the MTT-test. The ion irradiation leads to creation of conjugated double bonds which, together with progressive carbonization, contribute to the observed decrease of sheet resistance. Oxidation of the irradiated PE surface layer during the ion implantation is observed. Besides oxidation, the PE surface polarity is affected by other factors. The observed increase of the PE surface roughness due to the ion irradiation is inversely proportional to the ion size. The adhesion and proliferation of keratinocytes on the ion irradiated PE is significantly higher than on the pristine PE. Distribution of results in keratinocyte cultivation and the number of cells is related to the ion fluence applied and to ion species as well.     

Structure transition and enhanced ferroelectric properties of (Mn, Cr) co-doped BiFeO3 thin films

Pure BiFeO₃ (BFO) and (Mn, Cr) co-doped BiFe_0.96?yMn_0.04Cr_yO₃ thin films were prepared on FTO/glass (SnO₂:F) substrates by using a sol–gel method. The effects of (Mn, Cr) co-doped on the microstructure and electric properties of the BiFeO₃ thin films were studied. The result indicates that the co-doped BiFe_0.94Mn_0.04Cr_0.02O₃ (BFMCO) thin film has a structure transition and better ferroelectric properties compared with the pure BFO thin film. The Rietveld refined XRD patterns of BFO and BFMCO thin films conform the trigonal (R3c:H) and the biphasic (R3c:H + R3m:R) structure, respectively. The co-existence of two phases and the mixed valences of Cr^3+/6+ and Mn^2+/3+, which apparently improves the electric properties of the (Mn, Cr) co-doped BFMCO thin films. The remnant polarization (P _r) of the BFMCO thin film was 93.58 μC/cm² at 1 kHz in the applied electric field of 636 kV/cm. At an applied electric field of 100 kV/cm, the leakage current density of (Mn, Cr) co-doped BFMCO thin film is 6.2 × 10^?6 A/cm². It is about three orders much lower than that of the BFO thin film (1.43 × 10^?3 A/cm²).