Kinetic Instability in the Growth of CaF2on Si(111)

Even when thermodynamic driving forces favor a thin film to grow with a particular growth mode, this preferred growth mode may be kinetically inaccessible. While this is not uncommon at low temperature (short diffusion length), we show that in the Si(111)/Ca${\mathrm{F}}_2$ system, during the early stage of growth, the preferred growth mode may be inacessible at temperatures as high as 660 °C, where the surface diffusion length (several microns) exceeds the terrace spacing. Once the preferred growth mode is initiated the surface morphology becomes unstable, leading to a fast and striking change in layer occupancies.