title: Purification/annealing of graphene with 100-MeV Ag ion irradiation.
abstract: Studies on interaction of graphene with radiation are important because of nanolithographic processes in graphene-based electronic devices and for space applications. Since the electronic properties of graphene are highly sensitive to the defects and number of layers in graphene sample, it is desirable to develop tools to engineer these two parameters. We report swift heavy ion (SHI) irradiation-induced annealing and purification effects in graphene films, similar to that observed in our studies on fullerenes and carbon nanotubes (CNTs). Raman studies after irradiation with 100-MeV Ag ions (fluences from 3 × 10(10) to 1 × 10(14) ions/cm(2)) show that the disorder parameter α, defined by I D/I G ratio, decreases at lower fluences but increases at higher fluences beyond 1 × 10(12) ions/cm(2). This indicates that SHI induces annealing effects at lower fluences. We also observe that the number of graphene layers is reduced at fluences higher than 1 × 10(13) ions/cm(2). Using inelastic thermal spike model calculations, we estimate a radius of 2.6 nm for ion track core surrounded by a halo extending up to 11.6 nm. The transient temperature above the melting point in the track core results in damage, whereas lower temperature in the track halo is responsible for annealing. The results suggest that SHI irradiation fluence may be used as one of the tools for defect annealing and manipulation of the number of graphene layers.
  60.80.x; 81.05.ue.
authors.affiliation: Materials Science Group, Inter University Accelerator Centre, Aruna Asaf Ali Marg, New Delhi 110067, India.
authors.forename: Sunil
authors.initials: S
authors.lastname: Kumar
authors.affiliation: Materials Science Group, Inter University Accelerator Centre, Aruna Asaf Ali Marg, New Delhi 110067, India.
authors.forename: Ambuj
authors.initials: A
authors.lastname: Tripathi
authors.affiliation: Materials Science Group, Inter University Accelerator Centre, Aruna Asaf Ali Marg, New Delhi 110067, India.
authors.forename: Fouran
authors.initials: F
authors.lastname: Singh
authors.affiliation: Materials Science Group, Inter University Accelerator Centre, Aruna Asaf Ali Marg, New Delhi 110067, India.
authors.forename: Saif Ahmad
authors.initials: SA
authors.lastname: Khan
authors.affiliation: Nanotechnology Application Centre, University of Allahabad, Allahabad 211002, India.
authors.forename: Vikas
authors.initials: V
authors.lastname: Baranwal
authors.affiliation: Materials Science Group, Inter University Accelerator Centre, Aruna Asaf Ali Marg, New Delhi 110067, India.
authors.forename: Devesh Kumar
authors.initials: DK
authors.lastname: Avasthi
keywords: Annealing; Disorder parameter; Graphene; Inelastic thermal spike model; Ion irradiation