From Point Defects in Graphene to Two-Dimensional Amorphous Carbon

While crystalline two-dimensional materials have become an experimental reality during the past few years, an amorphous 2-D material has not been reported before. Here, using electron irradiation we create an sp2-hybridized one-atom-thick flat carbon membrane with a random arrangement of polygons, including four-membered carbon rings. We show how the transformation occurs step-by-step by nucleation and growth of low-energy multi-vacancy structures constructed of rotated hexagons and other polygons. Our observations, along with first-principles calculations, provide new insights to the bonding behavior of carbon and dynamics of defects in graphene. The created domains possess a band gap, which may open new possibilities for engineering graphene-based electronic devices.Comment: 10 pages, 10 figures including supplementary informatio

Atomistic simulations of the implantation of low energy boron and nitrogen ions into graphene

By combining classical molecular dynamics simulations and density functional theory total energy calculations, we study the possibility of doping graphene with B/N atoms using low-energy ion irradiation. Our simulations show that the optimum irradiation energy is 50 eV with substitution probabilities of 55% for N and 40% for B. We further estimate probabilities for different defect configurations to appear under B/N ion irradiation. We analyze the processes responsible for defect production and report an effective swift chemical sputtering mechanism for N irradiation at low energies (~125 eV) which leads to production of single vacancies. Our results show that ion irradiation is a promising method for creating hybrid C-B/N structures for future applications in the realm of nanoelectronics

Cutting and controlled modification of graphene with ion beams

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 0\circ and 88\circ 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

Binding a carbon nanotube to the Si(100) surface using ion irradiation-an atomistic simulation study

"Using carbon nanotubes (CNTs) as building blocks in silicon-based electronics requires good electric contacts between the tubes and other devices. Recent experimental and theoretical works have shown that irradiation can be used to modify both the structure and the electrical properties of nanotubes, and also to create new covalent bonds to different nanotube structures. In this study, we have used atomistic computer simulations with analytical, empirically fitted interaction models, to examine the possibility to enhance binding between a CNT and a silicon substrate with C, Si and Ne ion irradiation. Low irradiation doses (< 2.8 x 10(14) ions/cm(2)) and energies (0.2 - 2.0 keV) were used, to ensure that the irradiated nanotube will not be destroyed. Our results indicate, that ion irradiation can be used to create new covalent bonds, and also to increase the binding energy between these structures, when the irradiation doses and energies are carefully chosen. We found that a typical number of created new covalent C - Si bonds is 0.5 - 0.9 (10(14) ions/cm(2))(-1), and a typical increase in the binding energy between the structures is 100 - 400% for moderate irradiation doses.""Using carbon nanotubes (CNTs) as building blocks in silicon-based electronics requires good electric contacts between the tubes and other devices. Recent experimental and theoretical works have shown that irradiation can be used to modify both the structure and the electrical properties of nanotubes, and also to create new covalent bonds to different nanotube structures. In this study, we have used atomistic computer simulations with analytical, empirically fitted interaction models, to examine the possibility to enhance binding between a CNT and a silicon substrate with C, Si and Ne ion irradiation. Low irradiation doses (< 2.8 x 10(14) ions/cm(2)) and energies (0.2 - 2.0 keV) were used, to ensure that the irradiated nanotube will not be destroyed. Our results indicate, that ion irradiation can be used to create new covalent bonds, and also to increase the binding energy between these structures, when the irradiation doses and energies are carefully chosen. We found that a typical number of created new covalent C - Si bonds is 0.5 - 0.9 (10(14) ions/cm(2))(-1), and a typical increase in the binding energy between the structures is 100 - 400% for moderate irradiation doses.""Using carbon nanotubes (CNTs) as building blocks in silicon-based electronics requires good electric contacts between the tubes and other devices. Recent experimental and theoretical works have shown that irradiation can be used to modify both the structure and the electrical properties of nanotubes, and also to create new covalent bonds to different nanotube structures. In this study, we have used atomistic computer simulations with analytical, empirically fitted interaction models, to examine the possibility to enhance binding between a CNT and a silicon substrate with C, Si and Ne ion irradiation. Low irradiation doses (< 2.8 x 10(14) ions/cm(2)) and energies (0.2 - 2.0 keV) were used, to ensure that the irradiated nanotube will not be destroyed. Our results indicate, that ion irradiation can be used to create new covalent bonds, and also to increase the binding energy between these structures, when the irradiation doses and energies are carefully chosen. We found that a typical number of created new covalent C - Si bonds is 0.5 - 0.9 (10(14) ions/cm(2))(-1), and a typical increase in the binding energy between the structures is 100 - 400% for moderate irradiation doses."Peer reviewe