Changes in the electronic structure of pyrite irradiated surfaces explored by UPS, ISS and DFT

GUSTAVO RUANO; FERNANDO POMIRO; LUCILA JOSEFINA CRISTINA; EDUARDO ALBANESI; CARLOS ZANDALAZINI; JULIO FERRÓN

Santa Fe

Conferencia; VI San Luis Conference on Surfaces, Interfaces and Catalysis; 2018

INTEC-UNL-CONICET

Pyrite has proven to be a versatile material. A commodity in the heavy industry, this inexpensive iron sulfide is an indirect-gap semiconductor. The fields of science in which its study is interesting ranges from biology; in regard to the origin of life1, to solid state technology with the search of advanced semiconductors2.Recently, we have characterized by surface science techniques the interaction of noble gases ions (with kinetic energies in the keV range) with (100) natural surfaces of pyrite. We have found out that 4 keV He+ ions induce a series of on-surface chemical reactions that lead to aggregates of iron3. The so obtained nanoparticles (Fe-np) have sizes and depth distributions highly dependent on the energy of the ions4. In this work we analyze further the alteration of the pyrite surface by ion bombardment focusing in the electronic properties of the system, i.e. imbedded Fe-np in the semiconductor matrix, by a combination of Ultraviolet Photoemission Spectroscopy (UPS) and Density Functional Theory (DFT). With the additional light shed by Ion Scattering Spectroscopy (ISS), which explores the atomic structure of the very surface, we have been able to assign the changes in the density of states (DOS) to both a change in atomic proportions (due to preferential sputtering) and to vacancies formation5 leading to iron agglomeration. Another interesting effect we report here is the reversibility of the damage (S atomicity restitution and DOS structure) upon a thermal annealing of the system.References1.Wächtershäuser G. ?On the chemistry and evolution of the pioneer organism?, Chem. Biodivers., Vol. 4, 584-603, 2007.2.Ding L., Fan X., Sun X., Du J., Liu Z.,Tao C.,?Direct preparation of semiconductor iron sulfide nanocrystals from natural pyrite?, RSC Adv, Vol. 3 , p. 4539-4546, 2013. 3.Ruano G., Pomiro F., Ferrón J. ?Surface chemical reactions induced on pyrite by ion bombardment?, Surf. Sci., Vol. 64, 138-147, 2018.4.Pomiro F., Candia A. E., Montoro S., Passeggi (Jr) M. C. G., Ruano G., Ferrón J., ?Iron Nanoparticle Generation by He+ Ion Bombardment?, J. Phys. Chem. C, Vol. 121, 26117-26124, 2018.5.Ruoshi Sun, Chan M. K. Y., Ceder G. ?First-principles electronic structure and relative stability of pyrite and marcasite: Implications for photovoltaic performance?, Phys. Rev. B, Vol. 83, 235311-12, 2011.