INVESTIGADORES
VIDAL ricardo Alberto
congresos y reuniones científicas
Título:
Electronic characterization of CuxN/Cu(001) self assembled nanostructures
Autor/es:
L.J.CRISTINA; S.SFERCO; R. A. VIDAL; J.FERRÓN
Lugar:
Valparaiso (Chile)
Reunión:
Jornada; Reunión Internacional SOLIDOS 2009; 2009
Institución organizadora:
Departamento de Física, Universidad Técnica Federico Santa María
Resumen:
Copper nitrides have been widely studied due to their possible applications in the developing of write-once optical recording media (WORM) or electron induced lithography because Cu3N changes into Cu and N2 under thermal decomposition or electron bombardment [1]. Cu3N is a low reflectivity and high resistivity semiconductor material that crystallizes in a cubic anti-ReO3 type structure. It can be grown over different substrates and its electrical and optical properties are strongly dependent on the growing characteristics. A renewed interest has been recently triggered by the possibility of using copper nitrides in the bottom up design of nanostructure devices [2].In a recent work, combining several surface techniques we studied the process of low energy N2+ implantation and annealing of a Cu(001) surface as a way of obtaining self assembled Cu3N/ Cu(001) nanostructures [3]. We found that the N binding energy shifts non-monotonously along the whole process pointing out that the charge transfer between N and Cu depends on the atomic rearrangement and on the N amount at the surface. Our LEIS results are compatible with a c(2x2) ordering, but some N atoms may be either located in c(1x1) sites or substituting Cu atoms.This work is devoted to the electronic characterization of the CuxN/Cu(001) structure. Ultraviolet Photoelectron Spectroscopy (UPS), Angle Resolved UPS (ARUPS), Low Energy Ion Spectrometry LEIS and Electron Energy Loss Spectroscopy (ELS) were used to determine the modification of the band structure along the nitride compound formation.  DFT calculations based on the Wien2k program, and slabs of 11-layer atoms were used to characterize theoretically these systems. The pure and N adsorbed surfaces were simulated using  Cu(001)-c(2x2) slabs, without and with N atoms on the surfaces, letting relaxing them in the perpendicular direction, obtaining the theoretical interlayer distance at the surface, and the corresponding N 1s core level shifts. All results are compared with those obtained for Cu and Cu3N bulk calculations,  to identify features in the nitride formation. In particular, detailed band structure calculations will be presented for the Cu(001) clean and N-relaxed surfaces, in order to understand the experimental results.The experimental and theoretical results allow us to determine: i) the differential response to N incorporation of the band structure along different azimuths; ii) the metalic to semiconductor character transition under N incorporation; iii) the location of the N atom. both, in the surface network (fourfold hollow site within a c(2x2) structure), and normal to the surface (0.3Å over the Cu(001) surface).   We acknowledge financial support from ANPCyT (grant PICT 2006-1138) and UNL through CAID programs. References[1] T. Nosaka, M. Yoshitake, A. Okamoto, S. Ogawa, Y. Nakayama, Appl. Surf. Sci. 169-170 358 (2001).[2] F. M. Leibsle, Surf. Sci. 514, 33 (2002).[3]  L.J.Cristina, R.A.Vidal and J.Ferrón, Surf. Sci. 602, 3454 (2008).