Subscribe to the gold package and get unlimited access to Shamra Academy
Register a new userCutting and controlled modification of graphene with ion beams
131
0
0.0
(
0
)
Ask ChatGPT about the research
No Arabic abstract
Using atomistic computer simulations, we study how ion irradiation can be used to alter the morphology of a graphene monolayer by introducing defects of specific type, and to cut graphene sheets. Based on the results of our analytical potential molecular dynamics simulations, a kinetic Monte Carlo code is developed for modelling morphological changes in a graphene monolayer under irradiation at macroscopic time scales. Impacts of He, Ne, Ar, Kr, Xe and Ga ions with kinetic energies ranging from tens of eV to 10 MeV and angles of incidence between 0circ and 88circ are studied. Our results provide microscopic insights into the response of graphene to ion irradiation and can directly be used for the optimization of graphene cutting and patterning with focused ion beams.
rate research
Read More
We present experimental results and numerical simulations to investigate the modification of structural-mechanical properties of ion-implanted single-crystal diamond. A phenomenological model is used to derive an analytical expression for the variation of mass density and elastic properties as a function of damage density in the crystal. These relations are applied together with SRIM Monte Carlo simulations to set up Finite Element simulations for the determination of internal strains and surface deformation of MeV-ion-implanted diamond samples. The results are validated through comparison with high resolution X-ray diffraction and white-light interferometric profilometry experiments. The former are carried out on 180 keV B implanted diamond samples, to determine the induced structural variation, in terms of lattice spacing and disorder, whilst the latter are performed on 1.8 MeV He implanted diamond samples to measure surface swelling. The effect of thermal processing on the evolution of the structural-mechanical properties of damaged diamond is also evaluated by performing the same profilometric measurements after annealing at 1000 {deg}C, and modeling the obtained trends with a suitably modified analytical model. The results allow the development of a coherent model describing the effects of MeV-ion-induced damage on the structural-mechanical properties of single-crystal diamond. In particular, we suggest a more reliable method to determine the so-called diamond graphitization threshold for the considered implantation type.
The impact of 400 keV $Ar^+$ ion irradiation on the magnetic and electrical properties of in-plane magnetized magnetic tunnel junction (MTJ) stacks was investigated by ferromagnetic resonance, vibrating sample magnetometry and current-in-plane tunneling techniques. The irradiation-induced changes of the magnetic anisotropy, coupling energies and tunnel magnetoresistance (TMR) exhibited a correlated dependence on the ion fluence, which allowed us to distinguish between two irradiation regimes. In the low-fluence regime, ${Phi} < 10^{14} cm^{-2}$, the parameters required for having a functioning MTJ were preserved: the anisotropy of the FeCoB free layer (FL) was weakly modulated following a small decrease in the saturation magnetization $M_S$; the TMR decreased continuously; the interlayer exchange coupling (IEC) and the exchange bias (EB) decreased slightly. In the high-fluence regime, ${Phi} > 10^{14} cm^{-2}$, the MTJ was rendered inoperative: the modulation of the FL anisotropy was strong, caused by a strong decrease in $M_S$, ascribed to a high degree of interface intermixing between the FL and the Ta capping; the EB and IEC were also lost, likely due to intermixing of the layers composing the synthetic antiferromagnet; and the TMR vanished due to the irradiation-induced deterioration of the MgO barrier and MgO/FeCoB interfaces. We demonstrate that the layers surrounding the FL play a decisive role in determining the trend of the magnetic anisotropy evolution resulting from the irradiation, and that an ion-fluence window exists where such a modulation of magnetic anisotropy can occur, while not losing the TMR or the magnetic configuration of the MTJ.
Nanopores of nanometer-size holes are very promising devices for many applications: DNA sequencing, sensory, biosensoring and molecular detectors, catalysis and water desalination. These applications require accurate control over nanopores size. We report computer simulation studies of regrowth and healing of graphene nanopores of different sizes ranging from 30 to 5 {AA}. We study mechanism, speed of nanopores regrowth and structure of healed areas in the wide range of temperatures. We report existence of at least two distinct healing mechanisms, one so called edge attachment where carbons are attached to the edges of graphene sheet and another mechanism that involves atom insertion directly into a sheet of graphene even in the absence of the edges. These findings point a significantly more complicated pathways for graphene annealing. They also provide an important enabling step in development of graphene based devices for numerous nanotechnology applications.
The authors report micro-Raman investigation of changes in the single and bilayer graphene crystal lattice induced by the low and medium energy electron-beam irradiation (5 and 20 keV). It was found that the radiation exposures results in appearance of the strong disorder D band around 1345 1/cm indicating damage to the lattice. The D and G peak evolution with the increasing radiation dose follows the amorphization trajectory, which suggests graphenes transformation to the nanocrystalline, and then to amorphous form. The results have important implications for graphene characterization and device fabrication, which rely on the electron microscopy and focused ion beam processing.
In this paper we show how single layer graphene can be utilized to study swift heavy ion (SHI) modifications on various substrates. The samples were prepared by mechanical exfoliation of bulk graphite onto SrTiO$_3$, NaCl and Si(111), respectively. SHI irradiations were performed under glancing angles of incidence and the samples were analysed by means of atomic force microscopy in ambient conditions. We show that graphene can be used to check whether the irradiation was successful or not, to determine the nominal ion fluence and to locally mark SHI impacts. In case of samples prepared in situ, graphene is shown to be able to catch material which would otherwise escape from the surface.
Log in to be able to interact and post comments
comments
Fetching comments
Sign in to be able to follow your search criteria
