Nanopatterning of Si(110) surface by ion sputtering: An experimental and simulation study

Abstract

Nanopatterning of Si(110) surface by the normal incident ${\mathrm{Ar}}^{+}$ ion sputtering has been conducted as a function of sample temperature (room temperature---$800\phantom{\rule{0.2em}{0ex}}\ifmmode^\circ\else\textdegree\fi{}\mathrm{C}$) and ion energy $(1--5\phantom{\rule{0.3em}{0ex}}\mathrm{keV})$ with the ion flux of $20\phantom{\rule{0.3em}{0ex}}\ensuremath{\mu}\mathrm{A}∕{\mathrm{cm}}^{2}$. The surface morphology was characterized by an atomic force microscope. For ion energy of $1.5\phantom{\rule{0.3em}{0ex}}\mathrm{keV}$, the sputtered surface morphology changes from a dim dot/hole pattern to a distinct dot one with the increasing temperature. On the other hand, at the temperature of $800\phantom{\rule{0.2em}{0ex}}\ifmmode^\circ\else\textdegree\fi{}\mathrm{C}$, the nanodot shape of the dot pattern evolves from being $\text{circular}\ensuremath{\rightarrow}\text{elliptical}\ensuremath{\rightarrow}\text{circular}\ensuremath{\rightarrow}\text{elliptical}$ with the increasing ion energy in general. A dynamic continuum model is adopted to describe the experimental results, which includes both the Bradley--Harper (BH) mechanism good for the amorphous surface under ion sputtering and the Ehrlich--Schwoebel (ES) one for the crystalline surface. By adjusting the effective surface tension following its temperature- or ion energy-dependence relationship in the BH or ES mechanism-relevant regime, the processes of surface morphology evolution have been simulated, which agrees with the experimental ones.