Ni Clusters Embedded in Multivacancy Graphene Substrates

AMBRUSI, RUBÉN E.; ORAZI, VALERIA; MARCHETTI, JORGE M.; PRONSATO, M. ESTELA

JOURNAL OF PHYSICS AND CHEMISTRY OF SOLIDS

PERGAMON-ELSEVIER SCIENCE LTD

Lugar: Amsterdam; Año: 2020 vol. 138

0022-3697

In the present work, density functional theory (DFT) calculations have been performed in order to study the structureand stability of small Ni clusters embedded in graphene multivacancy systems. Bader charges, band structure, totaldensity of states (DOS) and partial density of states (PDOS) in conjunction with spin density magnetization wereobtained, with the aim to understand the influence of cluster size in electronic and magnetic properties and detectpotential applications for spintronic devices. Ni cluster absorption, modified graphene multivacancy substratesbehavior, and a conversion from conductor to semiconductor could be achieved when the cluster size is changed.Linear dispersion relation around the reciprocal point K is conserved for almost the systems with the inclusion of aband gap between Dirac cones, which is important to obtain semiconductors with massless fermions. A comparisonwith Ni clusters adsorbed on pristine graphene, show that combinations of vacancy defects and Ni allow to obtainhigher band gaps. An analysis of the interactions between Ni clusters and vacancy defects were also performed basedon PDOS results. Ni clusters with different sizes, are able to generate ferromagnetic and ferrimagnetic coupling forgraphene with three, four and six (D2h and D6h symmetry) vacancies. The fact that the ferromagnetism generated onNi3 and Ni4 absorbed in graphene (with four and six vacancies respectively) have shown both, ferromagnetic andsemiconductor behavior, makes them good candidates for dilute magnetic semiconductors. Ni clusters do notmagnetize or present a slight magnetization on pristine graphene, and the ferromagnetic coupling was only achievedwith the introduction of vacancy defects.