Fabrication of SiGe quantum dots on a Si(100) surface

This paper reports a method to produce SiGe quantum dots on a Si(100) surface, which is based on the selective adsorption effect of hydride molecules on a partially hydrogen-terminated Si(100) surface. It is shown that etching of Si(100) surfaces for a limited time in ammonium fluoride $\left({\mathrm{NH}}_4\mathrm{F}\right)$ solution initially produces an atomically flat and dihydride-terminated surface and that further etching leads to the formation of microscopic (111) facets which are regularly distributed along the surface. Hydrogen atoms are found to desorb completely from dihydride sites at $\sim 400°\mathrm{C}$ while those from monohydrides remain stable up to $650°\mathrm{C}$. Hence, we show that in the temperature range of $400–650°\mathrm{C}$, SiGe growth occurs only on the sites that were previously terminated by dihydrides, i.e., free of hydrogen. We demonstrate that SiGe dots formed by using this approach are much smaller in size $\left(\sim 400\hspace{0.5em}\mathrm{\AA }\right)$ and more uniform than dots formed by the strain-induced growth mode transition.