Ab initiostudy of the surface properties and ideal strength of (100) silicon thin films

Abstract

Studying the ideal strength of nanostructured materials is important for understanding of their mechanical properties. We have performed ab initio modeling of nanoscale Si films with ͑100͒ surfaces and computed the surface energy and surface stress as well as the ideal tensile strength of the structure. The strength of the thin film is not significantly decreased down to a thickness of less than 1 nm. Surprisingly, there is also no considerable effect of the surface reconstruction. This suggests that the lower stresses found for surface crack nucleation in an experiment are due to substantial flaws and not an intrinsic effect of the ideal surface. The band gap energy of the thin film is lower than that of the bulk, but a band gap remains up to high strain in the thin film.

First-principles calculation of mechanical properties of Si⟨001⟩ nanowires and comparison to nanomechanical theory

“…42 Despite considerable attention to Si surfaces, the mechanics of hydrogen-passivated surfaces has not been studied in detail.…”

“…39 One quantum study based on an empirical tight-binding technique has been published. 28,40 Recently the size dependence of the Young's modulus of thin slabs has been reported calculated from first-principles, 41,42 results that are quite relevant but not equivalent to nanowire calculations due to the absence of edges. We are not aware of any ab initio calculations of nanowire moduli in the literature apart from the brief article, Ref.…”

Effects of size and defects on the elasticity of silicon nanocantilevers

“…For all these examples, use was made of the mechanical response of a nanostructure, which highly depends on the effective elasticity. In the past two decades, experimental measurements [4][5][6][7][8] and theoretical investigations, including ab initio and density functional theory (DFT) [9][10][11], molecular dynamics (MD) [12][13][14][15] and modifications to continuum theory [16][17][18][19], have been conducted toward characterizing the mechanical properties of nanostructures. The studies revealed a strong size dependence of the mechanical properties as the characteristic [11,12] and experiments [4,7,20,28].…”

Mechanics of Nanoelectromechanical Systems: Bridging the Gap Between Experiment and Theory

“…The existence of scale-dependent behavior has been confirmed by experimental measurements, including resonance frequency tests [6], tensile testing in scanning electron microscope (SEM) [7], transmission electron microscope (TEM) [8,9], atomic force microscope (AFM) [10,11] and nanoindenter [12] and also theoretical investigations, including ab initio and density functional theory (DFT) [13,14,15], molecular dynamics (MD) [16,17,18,19] and modifications to continuum theory [20,21,22,23]. Although scale-dependence has been observed by both theory and experiment, a considerable discrepancy still remains between the experiments and models.…”