Electron dynamics in films made of transition metal nanograins embedded in SiO[sub 2]: Infrared reflectivity and nanoplasma infrared resonance

Handle URI:
http://hdl.handle.net/10754/552737
Title:
Electron dynamics in films made of transition metal nanograins embedded in SiO[sub 2]: Infrared reflectivity and nanoplasma infrared resonance
Authors:
Massa, Néstor E.; Denardin, Juliano C.; Socolovsky, Leandro M.; Knobel, Marcelo; Zhang, Xixiang ( 0000-0002-3478-6414 )
Abstract:
We report on near normal infrared reflectivityspectra of ∼550 nm thick films made of cosputtered transition metal nanograins and SiO2 in a wide range of metal fractions. Co0.85(SiO2)0.15,with conductivity well above the percolation threshold has a frequency and temperature behavior according to what it is find in conductingmetal oxides. The electron scattering rate displays a unique relaxation time characteristic of single type of carriers experiencing strong electron-phonon interactions. Using small polaron fits we identify those phonons as glass vibrational modes. Ni0.61(SiO2)0.39, with a metal fraction closer to the percolation threshold, undergoes a metal-nonmetal transition at ∼77 K. Here, as it is suggested by the scattering rate nearly quadratic dependence, we broadly identify two relaxation times (two carrier contributions) associated to a Drude mode and a midinfrared overdamped band, respectively. Disorder induced, the midinfrared contribution drives the phase transition by thermal electron localization. Co0.51(SiO2)0.49 has the reflectivity of an insulator with a distinctive band at ∼1450 cm−1 originating in electron promotion, localization, and defect induced polaron formation. Angle dependent oblique reflectivity of globally insulating Co0.38(SiO2)0.62, Fe0.34(SiO2)0.66, and Ni0.28(SiO2)0.72, reveals a remarkable resonance at that band threshold. We understand this as due to the excitation by normal to the film electric fields of defect localized electrons in the metallic nanoparticles. At higher oblique angles, this localized nanoplasma couples to SiO2 longitudinal optical Berreman phonons resulting in band peak softening reminiscent to the phonon behavior undergoing strong electron-phonon interactions. Singular to a globally insulating phase, we believe that this resonance might be a useful tool for tracking metal-insulator phase transitions in inhomogeneous materials.
KAUST Department:
Research and Development
Citation:
Electron dynamics in films made of transition metal nanograins embedded in SiO[sub 2]: Infrared reflectivity and nanoplasma infrared resonance 2009, 105 (11):114306 Journal of Applied Physics
Publisher:
AIP Publishing
Journal:
Journal of Applied Physics
Issue Date:
4-Jun-2009
DOI:
10.1063/1.3126485
ARXIV:
arXiv:0906.1805
Type:
Article
ISSN:
00218979
Additional Links:
http://scitation.aip.org/content/aip/journal/jap/105/11/10.1063/1.3126485; http://arxiv.org/abs/0906.1805
Appears in Collections:
Articles

Full metadata record

DC FieldValue Language
dc.contributor.authorMassa, Néstor E.en
dc.contributor.authorDenardin, Juliano C.en
dc.contributor.authorSocolovsky, Leandro M.en
dc.contributor.authorKnobel, Marceloen
dc.contributor.authorZhang, Xixiangen
dc.date.accessioned2015-05-14T06:28:46Zen
dc.date.available2015-05-14T06:28:46Zen
dc.date.issued2009-06-04en
dc.identifier.citationElectron dynamics in films made of transition metal nanograins embedded in SiO[sub 2]: Infrared reflectivity and nanoplasma infrared resonance 2009, 105 (11):114306 Journal of Applied Physicsen
dc.identifier.issn00218979en
dc.identifier.doi10.1063/1.3126485en
dc.identifier.urihttp://hdl.handle.net/10754/552737en
dc.description.abstractWe report on near normal infrared reflectivityspectra of ∼550 nm thick films made of cosputtered transition metal nanograins and SiO2 in a wide range of metal fractions. Co0.85(SiO2)0.15,with conductivity well above the percolation threshold has a frequency and temperature behavior according to what it is find in conductingmetal oxides. The electron scattering rate displays a unique relaxation time characteristic of single type of carriers experiencing strong electron-phonon interactions. Using small polaron fits we identify those phonons as glass vibrational modes. Ni0.61(SiO2)0.39, with a metal fraction closer to the percolation threshold, undergoes a metal-nonmetal transition at ∼77 K. Here, as it is suggested by the scattering rate nearly quadratic dependence, we broadly identify two relaxation times (two carrier contributions) associated to a Drude mode and a midinfrared overdamped band, respectively. Disorder induced, the midinfrared contribution drives the phase transition by thermal electron localization. Co0.51(SiO2)0.49 has the reflectivity of an insulator with a distinctive band at ∼1450 cm−1 originating in electron promotion, localization, and defect induced polaron formation. Angle dependent oblique reflectivity of globally insulating Co0.38(SiO2)0.62, Fe0.34(SiO2)0.66, and Ni0.28(SiO2)0.72, reveals a remarkable resonance at that band threshold. We understand this as due to the excitation by normal to the film electric fields of defect localized electrons in the metallic nanoparticles. At higher oblique angles, this localized nanoplasma couples to SiO2 longitudinal optical Berreman phonons resulting in band peak softening reminiscent to the phonon behavior undergoing strong electron-phonon interactions. Singular to a globally insulating phase, we believe that this resonance might be a useful tool for tracking metal-insulator phase transitions in inhomogeneous materials.en
dc.publisherAIP Publishingen
dc.relation.urlhttp://scitation.aip.org/content/aip/journal/jap/105/11/10.1063/1.3126485en
dc.relation.urlhttp://arxiv.org/abs/0906.1805en
dc.rightsArchived with thanks to Journal of Applied Physicsen
dc.titleElectron dynamics in films made of transition metal nanograins embedded in SiO[sub 2]: Infrared reflectivity and nanoplasma infrared resonanceen
dc.typeArticleen
dc.contributor.departmentResearch and Developmenten
dc.identifier.journalJournal of Applied Physicsen
dc.eprint.versionPublisher's Version/PDFen
dc.contributor.institutionLaboratorio Nacional de Investigación y Servicios en Espectroscopía Optica-CEQUINOR, Universidad Nacional de La Plata, C.C. 962, 1900 La Plata, Argentinaen
dc.contributor.institutionDepartamento de Física, Universidad de Santiago de Chile, Av. Ecuador 3493, Santiago, Chileen
dc.contributor.institutionInstituto de Tecnologías y Ciencias de la Ingeniería, Universidad de Buenos Aires, Av. Paseo Colón 850, Buenos Aires, Argentinaen
dc.contributor.institutionInstituto de Física, “Gleb Wataghin,” Universidade Estadual de Campinas, 13083-970 Campinas, Sao Paulo, Brazilen
dc.identifier.arxividarXiv:0906.1805en
kaust.authorZhang, Xixiangen
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