Swift heavy ions for materials engineering and nanostructuring

Ion beams have been used for decades for characterizing and analyzing materials. Now energetic ion beams are providing ways to modify the materials in unprecedented ways. This book highlights the emergence of high-energy swift heavy ions as a tool for tailoring the properties of materials with nanoscale structures. Swift heavy ions interact with materials by exciting/ionizing electrons without directly moving the atoms. This opens a new horizon towards the 'so-called' soft engineering. The book discusses the ion beam technology emerging from the non-equilibrium conditions and emphasizes the power of controlled irradiation to tailor the properties of various types of materials for specific needs

Defect Induced Intrinsic Ferromagnetism in Fullerene Thin Films

The occurrence of intrinsic ferromagnetism in energetic ion irradiated fullerene films is reported. The magnetic properties of irradiated fullerene films are studied by superconducting quantum interference device and electron spin resonance. Raman spectroscopy measurement has been performed to investigate the structural transformation at high fluence. The role of electronic energy density deposition by the ions on their magnetic properties is investigated. The origin of magnetic signal in irradiated films is due to the generation of an amorphous carbon network consisting sp(2)/sp(3) bonded carbon atoms. (C) 2008 The Japan Society of Applied Physic

Structural changes induced in graphene oxide film by low energy ion beam irradiation

Graphene oxide consists of sp$^3$ hybridization due to the presence of different oxygen containing functional groups on its edges and basal planes. However, its sp$^3$/sp$^2$ hybridization can be tuned by various methods. Ion beam irradiation can also be one of the methods to optimize sp$^2$/sp$^3$ hybridization for its desirable properties. In this work, graphene oxide films were irradiated with 100 keV Argon ions at different fluences varying from 10$^{13}$ to 10$^{16}$ ions/cm$^2$. Synchrotron X-ray diffraction (XRD) measurements showed an increase in crystallinity at low fluence of 10$^{13}$ ions/cm$^2$. Raman spectroscopy qualitatively determines the defects induced by ion beam in graphene oxide. Also, identification of different groups and their removal at different ion fluences was done using Fourier transform infra-red spectroscopy technique

Improved photoelectrochemical properties of TiO₂-graphene nanocomposites: Effect of defect induced visible light absorption and graphene conducting channel for carrier transport

Use of heterojunctions between two materials having favorable optical and electronic properties can lead to increased photon absorption and charge separation resulting in enhanced photo-electro-chemical energy conversion. In the present study, graphene monolayer nano-flakes are mixed with TiO2 nanoparticles to form nanocomposites having different weight percentages of graphene. The microstructural, morphological and structural properties of the composite samples are investigated using X-ray diffraction, Raman spectroscopy and transmission electron microscopy techniques. Raman studies carried out on samples annealed at different temperatures show the interfacial interaction between TiO2 and graphene, although Anatase TiO2 and graphene maintain their phase integrity. PEC measurements show higher photo-electro-chemical activity in TiO2-graphene nanocomposite at an optimized concentration (2.0 weight percent) due to increased surface area, higher optical absorption in the visible part of the solar spectrum and favorable carrier transport due to increased concentration of defect states and graphene acting as a charge carrier medium

Conducting carbon nanopatterns (nanowire) by energetic ion irradiation

This work reports the formation of conducting carbon nanopatterns (nano-wires) in a semi-inorganic polymer by irradiation with energetic ions. The conducting nano-patterns/wires are evidenced by conducting atomic force microscopy. The typical diameter of the conducting wires is observed to be about similar to 50-200 nm. The density (spacing), growth direction and length of these carbon nanowires can be changed simply by ion fluence, angle of irradiation and the film thickness, respectively. The formation of conducting nanopatterns in an insulating matrix (polymers/gels) is correlated with the structural transformation of films, investigated by means of Raman spectroscopy

Engineering bright fluorescent nitrogen-vacancy (NV) nano-diamonds: Role of low-energy ion-irradiation parameters

Bright emission from fluorescent nanodiamonds (FNDs) is highly desirable for optical bio-imaging applications. Here we report about optimized ion-irradiation and heat treatment conditions for efficient creation of Nitrogen-vacancy (NV) centers in high pressure high temperature (HPHT) grown type Ib Nanodiamond samples irradiated in energy range (20-50 KeV) and at varying fluence (10(12)-10(16) ions/cm(2)). Different low energy ion irradiations are not detrimental for the crystallinity of nanodiamonds as confirmed by X-ray diffraction and HRTEM. The concentration of defects near the outer surface (non-diamond carbon) has been increased for highest ion dose (50 KeV, 10(16) ions/cm(2)) as compared to lower ion dose (50 KeV, 10(13) ions/cm(2)). The relative emission intensity of characteristic Zero-phonon lines of NV degrees, NV- centers as compared to broad emission in the range 550-750 nm was monitored with varying NV creation conditions. Sample irradiated at 50 KeV and with fluence of 10(13) ions/cm(2) show maximum emission in the phonon side band (550-750 nm) with maxima at 680 nm. These optimized ion irradiation conditions leads to the fabrication of 12.5 +/- 0.8 ppm concentration of NV- centers in nanodiamonds. This is desirable for their use as biomarker. This work provides a recipe for creating bright nanodiamonds for optical imaging applications

In-situ structural investigations on monazite-type La0.2Gd0.8PO4-ceramics under heavy ion irradiation

Phosphate based ceramics with monazite structure are considered as promising nuclear waste forms for the conditioning of special Actinide-bearing waste streams. The incorporation of these elements on lattice sites in the monazite structure allows for high waste loadings and offers certain advantages over other waste forms (e.g. borosilicate glasses) regarding their long-term durability with respect to chemical stability and irradiation resistance [1]. The phase transformations in La0.2Gd0.8PO4 with monazite structure as consequence of irradiation with 100 MeV Au ions at different ion fluences varying from 1x1012 ions/cm2 to 1x1014 ions/cm2 are investigated using in-situ grazing-incidence X-ray diffraction spectrometry (XRD). In the in-situ XRD experiment, La0.2Gd0.8PO4 samples are irradiated with swift heavy ions and a sequential in-situ diffraction pattern is recorded. After that, the ion fluence is successively increased until amorphisation of the sample is discernable in the diffraction patterns [2, 3]. The experimental results related to irradiation-induced structural processes during amorphisation and recrystallisation of La0.2Gd0.8PO4 will be discussed in detail and compared to complementary computational studies. References [1] W.J. Weber, A. Navrotsky, S. Stefanovsky, E. Vance, E. Vernaz, MRS Bulletin 34 (2009) 46-53[2] P.K. Kulriya, F. Singh, A. Tripathi, R. Ahuja, A. Kothari, R. N. Dutt, Y.K. Mishra, A. Kumar, D.K. Avasthi, Rev. Sci. Instrument 78 (2007) 113901[3] P.K. Kulriya, R. Kumari, R. Kumar; V. Grover, R. Shukla, A.K. Tyagi, D.K. Avasthi, Nucl. Instr. Methods Phys. Res. B342 (2015) 98-10