title: Superhard nanobuttons: constraining crystal plasticity and dealing with extrinsic effects at the nanoscale.
abstract: The compressive plastic strength of nanosized single-crystal metallic pillars is known to depend on their diameter D. Herein, the role of pillar height h is analyzed instead, and the suppression of the generalized crystal plasticity below a critical value h(CR) is observed. Novel in situ compression tests on regular pillars as well as nanobuttons, that is, pillars with h < h(CR), show that the latter are much harder, withstanding stresses >2 GPa. A statistical model that holds for both pillars and buttons is formulated. Owing to their superhard nature, the nanobuttons examined here underline with unprecedented resolution the extrinsic effects-often overlooked-that naturally arise during testing when the Saint-Venant assumption ceases to be accurate. The bias related to such effects is identified in the test data and removed when possible. Finally, continuous hardening is observed to occur under increasing stress level, in analogy to reports on nanoparticles. From a metrological standpoint the results expose some difficulties in nanoscale testing related to current methodology and technology. The implications of the analysis of extrinsic effects go beyond nanobuttons and extend to nano-/microelectromechanical system design and nanomechanics in general.
authors.affiliation: Fulton Schools of Engineering, School of Mechanical, Aerospace, Chemical and Materials Engineering, Arizona State University, Tempe, AZ 85287-6106, USA. antonio.rinaldi@uniroma2.it
authors.forename: Antonio
authors.initials: A
authors.lastname: Rinaldi
authors.forename: Pedro
authors.initials: P
authors.lastname: Peralta
authors.forename: Cody
authors.initials: C
authors.lastname: Friesen
authors.forename: Dhiraj
authors.initials: D
authors.lastname: Nahar
authors.forename: Silvia
authors.initials: S
authors.lastname: Licoccia
authors.forename: Enrico
authors.initials: E
authors.lastname: Traversa
authors.forename: Karl
authors.initials: K
authors.lastname: Sieradzki
mesh_terms: D019245:Compressive Strength; D003460:Crystallization; D004548:Elasticity; D006244:Hardness; D008422:Materials Testing; D049329:Nanostructures / Q000737:chemistry* / Q000648:ultrastructure; D017711:Nonlinear Dynamics; D010316:Particle Size; D012996:Solutions
chemical_list: D012996:Solutions