Fabrication of ultra-sharp tips from carbon fiber for scanning tunneling microscopy investigations of epitaxial graphene on 6H-SiC(0 0 0 1) surface

• Autores: Morán Meza J.A., Lubin C., Thoyer F., Villegas Rosales K.A., Gutarra Espinoza A.A., Martin F., Cousty J.
• Formato: artículo
• Fecha de Publicación: 2015
• Institución: Consejo Nacional de Ciencia Tecnología e Innovación
• Repositorio: CONCYTEC-Institucional
• Lenguaje: inglés
• OAI Identifier: oai:repositorio.concytec.gob.pe:20.500.12390/657
• Enlace del recurso: https://hdl.handle.net/20.500.12390/657; https://doi.org/10.1016/j.carbon.2015.01.050
• Nivel de acceso: acceso abierto
• Materia: Thermoelectric equipment; Atomic force microscopy; Carbon; Carbon fibers; Frequency modulation; Graphene; Silicon carbide; Dynamic scanning; Electronic device; Epitaxial graphene; Force gradients; Fowler-Nordheim plots; https://purl.org/pe-repo/ocde/ford#2.10.00

The fabrication of ultra-sharp tips from carbon fiber (CF), which are mounted on a qPlus probe for combined dynamic scanning tunneling microscopy (STM) and frequency modulation atomic force microscopy (FM-AFM) experiments, is reported. The carbon fiber tips were electrochemically etched in a KOH or NaOH solution, using different electronic devices. CF tips with an apex radius ∼10 nm, as deduced from the measured slopes of the Fowler–Nordheim plots (kR < 70 nm for k ∼ 6), were routinely obtained with a homemade electronic device that controls the intensity of the etching current. Then, these conductive CF tips were also characterized by imaging the 6H-SiC(0 0 0 1) surface covered by an epitaxial graphene layer in ultra-high vacuum (UHV). The lattice of the R30° reconstruction was regularly imaged by STM working either in non-oscillating mode or in dynamic mode, which also maps the variations of the force gradient. From these measurements with a constant mean-tunneling-current of 20 pA, it was found that the STM tip suffered variations of the tip/surface force gradient in between 8.25 and 16.50 N/m when it scanned the epitaxial graphene layer on the reconstructed 6H-SiC(0 0 0 1) surface.