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Towards developing next generation scalable TiO2-based resistive switching (RS) memory devices, the efficacy of 50 keV Ar+-ion irradiation to achieve self-organized nano-channel based structures at a threshold fluence of 5×1016 ions/cm2 at ambient temperature is presented. Although x-ray diffraction results suggest the amorphization of as-grown TiO2 layers, detailed transmission electron microscopy study reveals fluence-dependent evolution of voids and eventual formation of selforganized nano-channels between them. Moreover, gradual increase of TiO/Ti2O3 in the near surface region, as monitored by x-ray photoelectron spectroscopy, establishes the upsurge in oxygen deficient centers. The impact of structural and chemical modification on local RS behavior has also been investigated by current-voltage measurements in conductive atomic force microscopy, while memory application is manifested by fabricating Pt/TiO2/Pt/Ti/SiO2/Si devices. Finally, the underlying mechanism of our experimental results has been analyzed and discussed in the light of oxygen vacancy migration through nano-channels. [ABSTRACT FROM AUTHOR]

We show that ZnMoO4 remains in stable phase under thermal annealing up to 1000 °C, whereas it decomposes to ZnO and MoO3 under transient thermal spike induced by 100MeV Ag irradiation. The transformation is evidenced by X-ray diffraction (XRD), Raman spectroscopy, and X-ray photoelectron spectroscopy (XPS). Thin films of ZnMoO4 were synthesized by thermal evaporation and subsequent annealing in oxygen ambient at 600 °C for 4 h. XRD results show that as the irradiation fluence increases, the peak related to ZnMoO4 decreases gradually and eventually disappear, whereas peaks related to ZnO grow steadily up to fluence of 3×1012 ions/cm² and thereafter remain stable till highest fluence. This indicates that polycrystalline ZnMoO4 film has transformed to polycrystalline ZnO thin film. The Raman lines related to ZnMoO4 are observed to have disappeared with increasing irradiation fluence. XPS results show modification in bonding and depletion of Mo from near surface region after the ion irradiation. Cross-sectional transmission electron microscopy result shows the formation of ion track of diameter 12-16 nm. These results demonstrate that ion beam methods provide the means to control phase splitting of ZnMoO4 to ZnO and MoO3 within nanometric dimension along the ion track. The observation of phase splitting and Mo loss are explained in the framework of ion beam induced thermal spike formalism. [ABSTRACT FROM AUTHOR]

We report on the application of high energy light ions (Li and O) irradiation for modification of defects, in particular, for annihilation of point defects using electronic energy loss in GaAs to minimize the defects produced by nuclear collisions. The high resolution x-ray diffraction and micro-Raman spectroscopy have been used to monitor that no lattice damage or amorphization take place due to irradiating ions. The effects of irradiation on defects and their energy levels have been studied using thermally stimulated current spectroscopy. It has been observed that till an optimum irradiation fluence of 1013 ions/cm2 there is annihilation of native defects but further increase in irradiation fluence results in accumulation of defects, which scales with the nuclear energy loss process, indicating that the rate of defects produced by the binary collision process exceeds rate of defect annihilation. Defect annihilation due to electronic energy loss has been discussed on the basis of breaking of bonds and enhanced diffusivity of ionized native defects. [ABSTRACT FROM AUTHOR]

We have prepared germanium nanoparticles embedded in SiO2 matrix by atom beam co-sputtering (ABS) of Ge+SiO2 on Si substrate. The as-deposited films were annealed at various temperatures in Ar+H2 atmosphere and irradiated with various energies with fixed fluence. The pristine and irradiated samples were characterized by Raman, X-ray diffraction and atomic force microscopy (AFM). Rutherford back scattering (RBS) was used to quantify the concentration of Ge in the SiO2 matrix and the film thickness. Raman studies of the films indicate the formation of Ge crystallites as a result of swift heavy ion (SHI) irradiation. Moreover, the crystalline nature of Ge improves with an increase in energy. Glancing angle X-ray diffraction and Raman results also confirm the presence of Ge crystallites in the irradiated samples. Similarly, 400 keV Ge+ ions implanted into silicon substrate at higher fluence at 573 K have been irradiated with 100 MeV Au8+ions at RT. These irradiated implanted samples were subsequently characterized by XRD and Raman to understand the crystallization behavior. We also studied the surface morphology of a high-energy irradiated sample by AFM. The irradiation results were compared with those obtained by thermal annealing in ABS. The basic mechanism for crystallization induced by SHI in these films has been investigated. [ABSTRACT FROM AUTHOR]

Abstract: In the present work, we report the formation of SiGe nanoparticles embedded in SiO2 film by atom beam sputtering method in conjunction with Rapid Thermal Annealing (RTA). Crystalline SiGe nanoparticles in the co-sputtered films are formed after rapid thermal annealing at 900 °C and 1000 °C for 1 min in N2 gas ambient. These nanoparticles were characterized using UV–vis absorption, GXRD, FTIR and Raman measurements. UV–vis spectra show blue shift of absorption edge with the increase in annealing temperature. GXRD pattern shows that particles formed are crystalline. The average size of the nanoparticle estimated from GXRD is 15 nm to 30 nm for the films annealed at temperatures 800 °C and 1000 °C respectively. FTIR spectra show the phase separation between SiGe nanoparticles and SiO2 matrix after RTA. Raman spectra show that SiGe phase is formed with c-Ge as core and c-SiGe as shell in the SiO2 matrix. [Copyright &y& Elsevier]

Zinc oxide (ZnO) and Ni-doped zinc oxide (ZnO:Ni) films are prepared by atom beam sputtering with an intent of growing transparent conducting oxide (TCO) material and understanding its physical properties. The crystalline phases of the films are identified by the grazing angle X-ray diffraction (GAXRD) technique. Thicknesses of the films are measured by ellipsometry. Chemical states of the elements present in the films are investigated by X-ray photoelectron spectroscopy (XPS), which indicates the presence of Ni in the ZnO environment in a divalent state. Average transmission across the ZnO:Ni film was determined to be ∼83% in the visible region, which is less than that (∼90%) of undoped ZnO films. The resistivity measured by van der Pauw technique of the ZnO:Ni film (∼9×10-3 Ω cm) is two orders of magnitude smaller as compared to its undoped counterpart (1 Ω cm). For ZnO:Ni film an average carrier concentration of ∼1.4×1019 cm-3 was observed by Hall measurements. Two important mechanisms reported in the literature viz. influence of d–d transition bands and electron scattering from crystallites/grains are discussed as the possible causes for the increase in conductivity on Ni doping in ZnO. [ABSTRACT FROM AUTHOR]

Impact of ion irradiation on thin films is an emerging area for materials modification. CdTe thin films grown by thermal evaporation on flexible molybdenum (Mo) substrate were irradiated with Swift (100 MeV) Ag+7 ions for various ion fluence in the range 1012–1013 ions/cm2. The modifications in the composition, structure and surface morphology have been studied as a function of ion fluence. The Energy Dispersive X-ray Analysis (EDS) shows slightly Te-rich composition for both as-grown and irradiated films with no significant change after irradiation. X-ray diffraction (XRD) analysis indicates a consistent shift in the (111) peak position towards higher diffraction angle and an increase in the full width at half maximum (FWHM) with increase in ion fluence. The change in the residual stress during irradiation has been evaluated and is related to the corresponding microstructural changes in the films. The initial tensile stress is found to be relaxed after irradiation. Atomic Force Microscopy (AFM) studies revealed significant grain splitting after irradiation and formation of hillocks at higher ion fluence. The surface roughness was significantly increased at higher ion fluence. [ABSTRACT FROM AUTHOR]

Gold nanoparticles embedded in silica matrix were prepared by co-evaporation. After deposition, the samples were annealed at different temperatures in inert environment for 30 min. No signature of nanoparticle formation was found in case of as-deposited samples, while the annealed samples showed a clear signature of a surface plasmon resonance absorption peak around 520 nm, which indicated the formation of Au nanoparticles. The samples annealed at 900 °C were irradiated with 100 MeV Ag ions at fluences 2.5×1012 and 1×1013 ions/cm2. UV-visible absorption measurements of pristine and irradiated films showed a clear signature of dissolution of Au nanoparticles with ion beam fluence. X-ray diffraction studies of pristine and irradiated samples also supported the dissolution of Au nanoparticles with ion beam fluence. Rutherford backscattering spectrometry was used for quantification of gold. [ABSTRACT FROM AUTHOR]

Thin silica films containing Au nanoparticles were prepared by cosputtering. The kinetics of the growth of nanoparticles under 90 MeV Ni ion irradiation was studied by in situ x-ray diffraction. The growth of nanoparticles from 4 (for pristine) to 9 nm at a fluence of 1×1014 ions/cm2 was observed, in accordance with the observations made by transmission electron microscopy analyses. The present study shows that the ion irradiation is an effective tool for tailoring the size of nanoparticles. The results are discussed in the framework of thermal spike model. [ABSTRACT FROM AUTHOR]

Thin Ca F 2 targets with carbon backing are fabricated for the first time using physical vapour deposition technique at the target laboratory of IUAC, New Delhi to perform a multi nucleon transfer reaction on 10 , 11 B＋40Ca systems using General Purpose Scattering Chamber (GPSC) facility. Ca being an oxidizing material, we have used molecular Ca F 2 as the target material instead of Ca. Using turbo-molecular pump based coating unit (TMPU), carbon is deposited on cleaned glass slide and then Ca F 2 is deposited on diffusion pump based coating unit (DPU). We are successful in fabricating Ca F 2 targets of thickness ≈ 264. 4 μ g/cm 2 on carbon backing of thickness ≈ 21. 5 μ g/cm 2 . The thickness and purity measured by the crystal thickness monitor equipped with the vacuum chamber is verified by different techniques like alpha energy loss, Rutherford Back Scattering (RBS), Electron Diffraction Spectroscopy (EDS) and X-ray Diffraction (XRD). Small impurity level were smeared during the observation and the target is successfully used for nuclear reaction experiment. The fabrication of molecular Ca target is found to be more conducive to experimentation since they exhibit less oxidation and herewith we discuss about fabrication technique, experimentation and characterization. [ABSTRACT FROM AUTHOR]

AuFe alloy nanoparticles embedded in silica matrix are synthesized using atom beam sputtering technique and subsequently irradiated with 100 MeV Au ions at various fluences ranging from 1 × 10 13 to 6 × 10 13 ions/cm 2 . The X-ray diffraction, absorption spectroscopy, X-ray photo electron spectroscopy and transmission electron microscopy results show that swift heavy ion irradiation leads to decomposition of AuFe alloy nanoparticles from surface region and subsequent reprecipitation of Au and Fe nanoparticles occur. The process of phase decomposition and reprecipitation of individual element nanoparticles is explained on the basis of inelastic thermal spike model. [ABSTRACT FROM AUTHOR]

Highlights: [•] We report the strain engineering in graphene layers by means of Au adsorbates. [•] Raman studies show that disorder in graphene increases with increase in content of Au adsorbates. [•] We observed splitting and blueshift in G band by Raman spectroscopy signifying compressive strain in graphene. [•] X ray diffraction measurements corroborate the Raman finding of Au adsorbates induced compressive strain in graphene. [ABSTRACT FROM AUTHOR]

Abstract: The formation of strained layers and a non-monotonic evolution of strain in high energy (100MeV) silver ion (Ag7+) irradiated undoped semi-insulating GaAs are observed and analyzed using Raman scattering and high resolution X-ray diffraction (HRXRD) measurements. At low fluence, compressively strained layers are formed, whereas, with increase in fluence both compressive and tensile strains appear as observed from HRXRD measurements. Further, at low fluence, the change in compressive strain with increase in fluence is found to be sharper than what is observed at higher fluence, thereby suggesting a critical fluence value, beyond which there is a simultaneous generation and annihilation of vacancy type defects. The initial blue shift and subsequent relative red shift beyond above critical fluence in the Raman peak also qualitatively reveal non-monotonic evolution of strain in this case. Finally, we demonstrate the sensitivity of Raman spectroscopy in detecting the decrease in lattice ordering in the crystal in the low fluence regime, below the detection limit of Rutherford back-scattering channeling (c-RBS) measurements. [Copyright &y& Elsevier]

Abstract: Sub-stoichiometric indium oxide (In x O y ) films were fabricated by electron-beam evaporation method. One set of films was irradiated with 120MeV Ag9+ ions of varying fluences. Another set was thermally annealed and subsequently irradiated. Irradiation of the as-deposited In x O y films leads to a phase separation resulting in In and In2O3 and the formation of nanometer crystalline In clusters. The In cluster size is in the range of 35–45nm. Elastic recoil detection analysis indicates a decrease in the O/In ratio with an increase in ion fluence, suggesting oxygen loss during irradiation. On the other hand, thermal annealing of the as-deposited In x O y films leads to a complete conversion into stoichiometric In2O3. The structure of the stoichiometric films is further resistant to irradiation. Preliminary electrical investigations indicate a decrease in the resistivity of the as-deposited sub-stoichiometric In x O y films with irradiation, but a very large increase after irradiation of the stoichiometric thermally annealed films. Thus, structural and electrical modifications induced by swift heavy ions depend upon the stoichiometry of the film. [Copyright &y& Elsevier]

Abstract: Single crystals of ZnS x Se1− x were grown by chemical vapour transport method using iodine as a transporting agent in a closed evacuated quartz ampoule. The structure of the grown crystals was confirmed using powder X-ray diffractometer. Then they were annealed at different elemental (Zn, Se) atmospheres at 600°C for about 24h. As grown crystal platelets were irradiated with high-energy Si ion irradiation. The room temperature photoluminescence studies were carried out. The bands correspond to SA emission and defects were obtained. [Copyright &y& Elsevier]

Abstract: In the present study, we have investigated the swift heavy ion induced structural modification of ZnO thin film deposited by atom beam sputtering. The films were irradiated by 100 MeV Ag ions at different fluences from 5×1010 ions/cm2 to 3×1013 ions/cm2. The influence of the irradiation fluence on structural and optical properties of these thin films was investigated. The structural properties have been studied using X-ray diffraction. The Zn–O bonding was confirmed by Fourier transform infrared spectroscopy and surface morphology was investigated by atomic force microscopy. XRD confirmed that the grain size and texture of the ZnO thin film are increased after the irradiation. The absorption peak intensity corresponding to Zn–O bonding is also increased as a result of energy deposition by swift heavy ion as revealed by FTIR. The AFM study of the films implied that roughness remains almost constant. Power spectral density was also estimated from the AFM micrograph to extract the value of roughness exponent. [Copyright &y& Elsevier]

Abstract: We report the preparation of pure zinc oxide (ZnO) and nickel-doped zinc oxide thin films (∼100nm) by fast atom beam (FAB) sputtering technique and their characterisation in the perspective of transparent conducting oxide (TCO). Grazing angle X-ray diffraction (GAXRD) reveals that the films are polycrystalline, which has been further confirmed by selected area diffraction (SAD) studies. The nanogranular nature of the films is examined by transmission electron microscopy (TEM). A high optical transmittance (>87%) across UV–vis range and quite low electrical resistivity (∼1×10−3 Ωcm) have been observed in the undoped ZnO films. In Ni-doped ZnO (ZnO:Ni) films the optical transmittance decreases and resistivity increases, which subsequently further affected by an increase in Ni content. Charge carrier concentration, which is the highest in undoped film, reduces after Ni doping. The X-ray photoelectron spectroscopy (XPS) results show that zinc and nickel are in 2+ state. High electrical conductivity of undoped film is explained on the basis of presence of oxygen vacancies deduced from O1s spectra of the films. Decrease of electrical conductivity due to nickel doping is explained on the basis of compensation of oxygen vacancies. [Copyright &y& Elsevier]

Abstract: In/Se bilayer films, irradiated using 40MeV silicon ions, with a fluence of 1×1013 ions/cm2, were vacuum annealed at 50°C and 100°C for 1h. Optical and structural properties were studied using optical absorption and X-ray diffraction measurements respectively. Irradiated sample, annealed at 50°C had both InSe and In2Se3 phases. Annealing the sample at 100°C resulted in the elimination of In2Se3 phase and formation of InSe along (006) plane in the irradiated system. Absorption measurements also showed only one absorption edge, corresponding to InSe phase. In the case of un-irradiated In/Se system, annealing at 400°C for 1h was required to obtain single-phase indium selenide. Thus it was observed that single-phase indium selenide was formed at much lower annealing temperature in irradiated system in comparison with un-irradiated system. [Copyright &y& Elsevier]

Abstract: Thermally evaporated ZnO thin films have been irradiated with 100MeV Au8+ ions at different fluence from 5×1011 ions/cm2 to 5×1013 ions/cm2. The optical and structural properties of the irradiated and pristine films were studied using Fourier transform infrared spectroscopy (FTIR), UV–visible absorption spectroscopy, photoluminescence (PL), atomic force microscopy (AFM) and XRD. FTIR results showed that for low fluence, the transmittance of the film decreased and increased again at higher fluence but Zn–O bond remains unaffected by irradiation. As revealed from the absorption spectra, absorption edge is not changed by the irradiation but the optical absorption is increased. The AFM study of the films implied that roughness decreased at low fluence values up to 5×1012 ions/cm2 and at higher fluences the roughness increased. [Copyright &y& Elsevier]

Abstract: The effects of large electronic excitation resulting in silicide formation at the zirconium/silicon interface were studied using the swift heavy ions (SHI). In the present study Zr was deposited on Si () over Si [100] substrate at a pressure of . The final layer was Si to avoid oxidation of Zr. The Zr/Si system was irradiated by 350MeV ions at liquid nitrogen temperature at the fluences of and . Rutherford backscattering spectroscopy (RBS) was done for the compositional analysis of the different specimens. X-ray diffraction experiments were carried out on the as-deposited and irradiated samples to study the phase formation. RBS results indicated mixing at the interface and XRD revealed the silicide phase. [Copyright &y& Elsevier]