title: On the Structural and Chemical Characteristics of Co/Al2O3/graphene Interfaces for Graphene Spintronic Devices.
abstract: We report a detailed investigation of the structural and chemical characteristics of thin evaporated Al2O3 tunnel barriers of variable thickness grown onto single-layer graphene sheets. Advanced electron microscopy and spectrum-imaging techniques were used to investigate the Co/Al2O3/graphene/SiO2 interfaces. Direct observation of pinhole contacts was achieved using FIB cross-sectional lamellas. Spatially resolved EDX spectrum profiles confirmed the presence of direct point contacts between the Co layer and the graphene. The high surface diffusion properties of graphene led to cluster-like Al2O3 film growth, limiting the minimal possible thickness for complete barrier coverage onto graphene surfaces using standard Al evaporation methods. The results indicate a minimum thickness of nominally 3 nm Al2O3, resulting in a 0.6 nm rms rough film with a maximum thickness reaching 5 nm.
authors.affiliation: Instituto de Física, PPGFis, PPGMicro, Universidade Federal do Rio Grande do Sul, Porto Alegre, 91501-970, RS, Brazil.
authors.forename: Bárbara
authors.initials: B
authors.lastname: Canto
authors.affiliation: Divisão de Metrologia de Materiais, INMETRO, Duque de Caxias, 25250-020, RJ, Brazil.
authors.forename: Cristol P
authors.initials: CP
authors.lastname: Gouvea
authors.affiliation: Divisão de Metrologia de Materiais, INMETRO, Duque de Caxias, 25250-020, RJ, Brazil.
authors.forename: Bráulio S
authors.initials: BS
authors.lastname: Archanjo
authors.affiliation: Instituto de Física, PPGFis, PPGMicro, Universidade Federal do Rio Grande do Sul, Porto Alegre, 91501-970, RS, Brazil.
authors.forename: João E
authors.initials: JE
authors.lastname: Schmidt
authors.affiliation: Instituto de Física, PPGFis, PPGMicro, Universidade Federal do Rio Grande do Sul, Porto Alegre, 91501-970, RS, Brazil.
authors.forename: Daniel L
authors.initials: DL
authors.lastname: Baptista