Structural development and energy dissipation in simulated silicon apices.
In this paper we examine the stability of silicon tip apices by using density functional theory (DFT) calculations. We find that some tip structures - modelled as small, simple clusters - show variations in stability during manipulation dependent on their orientation with respect to the sample surface. Moreover, we observe that unstable structures can be revealed by a characteristic hysteretic behaviour present in the F(z) curves that were calculated with DFT, which corresponds to a tip-induced dissipation of hundreds of millielectronvolts resulting from reversible structural deformations. Additionally, in order to model the structural evolution of the tip apex within a low temperature NC-AFM experiment, we simulated a repeated tip-surface indentation until the tip structure converged to a stable termination and the characteristic hysteretic behaviour was no longer observed. Our calculations suggest that varying just a single rotational degree of freedom can have as measurable an impact on the tip-surface interaction as a completely different tip structure.
School of Physics and Astronomy, University of Nottingham, Nottingham NG7 2RD, United Kingdom.
Samuel Paul
SP
Jarvis
Department of Physics, King's College London, The Strand, London WC2R 2LS, United Kingdom.
Lev
L
Kantorovich
School of Physics and Astronomy, University of Nottingham, Nottingham NG7 2RD, United Kingdom.
Philip
P
Moriarty
DFT; NC-AFM; apex structure; atomic force microscopy; dissipation; hysteresis; silicon; spectroscopy; tip structure