title: Influence of size, shape and core-shell interface on surface plasmon resonance in Ag and Ag@MgO nanoparticle films deposited on Si/SiO x.
abstract: Ag and Ag@MgO core-shell nanoparticles (NPs) with a diameter of d = 3-10 nm were obtained by physical synthesis methods and deposited on Si with its native ultrathin oxide layer SiO x (Si/SiO x ). Scanning electron microscopy and transmission electron microscopy (TEM) images of bare Ag NPs revealed the presence of small NP aggregates caused by diffusion on the surface and agglomeration. Atomic resolution TEM gave evidence of the presence of crystalline multidomains in the NPs, which were due to aggregation and multitwinning occurring during NP growth in the nanocluster source. Co-deposition of Ag NPs and Mg atoms in an oxygen atmosphere gave rise to formation of a MgO shell matrix surrounding the Ag NPs. The behaviour of the surface plasmon resonance (SPR) excitation in surface differential reflectivity (SDR) spectra with p-polarised light was investigated for bare Ag and Ag@MgO NPs. It was shown that the presence of MgO around the Ag NPs caused a red shift of the plasmon excitation, and served to preserve its existence after prolonged (five months) exposure to air, realizing the possibility of technological applications in plasmonic devices. The Ag NP and Ag@MgO NP film features in the SDR spectra could be reproduced by classical electrodynamics simulations by treating the NP-containing layer as an effective Maxwell Garnett medium. The simulations gave results in agreement with the experiments when accounting for the experimentally observed aggregation.
authors.affiliation: CNR-NANO, S3, via G. Campi 213/a, 41125 Modena, Italy ; Dipartimento FIM, Università di Modena e Reggio Emilia, via G. Campi 213/a, 41125 Modena, Italy ; Centro Interdipartimentale En&TECH, Università di Modena e Reggio Emilia, via G. Campi 213/a, 41125 Modena, Italy.
authors.forename: Sergio
authors.initials: S
authors.lastname: D'Addato
authors.affiliation: Dipartimento FIM, Università di Modena e Reggio Emilia, via G. Campi 213/a, 41125 Modena, Italy.
authors.forename: Daniele
authors.initials: D
authors.lastname: Pinotti
authors.affiliation: CNR-NANO, S3, via G. Campi 213/a, 41125 Modena, Italy ; Dipartimento FIM, Università di Modena e Reggio Emilia, via G. Campi 213/a, 41125 Modena, Italy.
authors.forename: Maria Chiara
authors.initials: MC
authors.lastname: Spadaro
authors.affiliation: CNR-NANO, S3, via G. Campi 213/a, 41125 Modena, Italy.
authors.forename: Guido
authors.initials: G
authors.lastname: Paolicelli
authors.affiliation: CNR-NANO, S3, via G. Campi 213/a, 41125 Modena, Italy ; CNR-IMEM, Parco Area delle Scienze 37/A, 43100 Parma, Italy.
authors.forename: Vincenzo
authors.initials: V
authors.lastname: Grillo
authors.affiliation: CNR-NANO, S3, via G. Campi 213/a, 41125 Modena, Italy ; Dipartimento FIM, Università di Modena e Reggio Emilia, via G. Campi 213/a, 41125 Modena, Italy.
authors.forename: Sergio
authors.initials: S
authors.lastname: Valeri
authors.affiliation: Dipartimento di Ingegneria "Enzo Ferrari", Università di Modena e Reggio Emilia, via Vignolese 905, 41125 Modena, Italy.
authors.forename: Luca
authors.initials: L
authors.lastname: Pasquali
authors.affiliation: CNR-NANO, S3, via G. Campi 213/a, 41125 Modena, Italy ; Dipartimento FIM, Università di Modena e Reggio Emilia, via G. Campi 213/a, 41125 Modena, Italy ; Department of Electricity and Electronics, Faculty of Science and Technology, UPV/EHU, 48080 Bilbao, Spain ; Materials Physics Center CSIC-UPV/EHU and Donostia International Physics Center DIPC, Paseo Manuel Lardizabal 4, 20018 Donostia-San Sebastian, Spain.
authors.forename: Luca
authors.initials: L
authors.lastname: Bergamini
authors.affiliation: CNR-NANO, S3, via G. Campi 213/a, 41125 Modena, Italy.
authors.forename: Stefano
authors.initials: S
authors.lastname: Corni
keywords: Ag; MgO; core–shell nanoparticles; electron microscopy; surface differential reflectivity; surface plasmon resonance
references.citation: Phys Rev Lett. 2001 Dec 31;87(27 Pt 1):276801
references.pmid: 11800905
references.citation: Nanotechnology. 2013 Dec 13;24(49):495703
references.pmid: 24231177
references.citation: J Phys Condens Matter. 2011 May 4;23(17):175003
references.pmid: 21493971
references.citation: Nature. 2003 Jun 19;423(6942):850-3
references.pmid: 12815426
references.citation: Phys Rev Lett. 2000 Apr 24;84(17):3994-7
references.pmid: 11019258
references.citation: Nanotechnology. 2011 Nov 4;22(44):445703
references.pmid: 21975584