Fabrication of 3D quantum dot array by fusion of bio-template and neutral beam etching I: Basic technologies

The direct formation of a uniform, closely packed, and high density two-dimensional array of ferritin molecules is realized on Si and GaAs substrates using our developed neutral beam oxidation (NBO) technique to prepare the surface oxide. The NBO process is applied to form thin films by slight surface oxidations, which have negative zeta potential and highly hydrophilic surfaces. It is experimentally proven that surface hydrophilicity is essential for the mechanism of uniform and high density ferritin arrangement. Uniform and defect-free 2D and 3D array of Si-NDs with ND density of more than 7 × 10¹¹ cm^-2 were realized as Si-QDSLs using combination of bio-templates and NBE processes. The diameter of Si-ND can be controlled by changing the conditions under which surface-oxide removal was conducted. 2D array of GaAs-NDs with ND density of 7 × 10¹¹ cm^-2 has been also developed successfully. Each step of the process, i.e., ferritin protein shell removal, NBE, and iron core removal, has been investigated and several novel solutions have been developed that do not damage the GaAs substrate. O-radicals are first found to eliminate the protein shell effectively at a low temperature of 280 °C without deteriorating surface roughness or moving the iron oxide cores. NBE with a 22 % chlorine and 78 % argon gas mixture and 16 W RF bias power can etch a GaAs nanostructure with a diameter of about 10 nm, atomic-level surface roughness of less than 1 nm and vertical taper angle of 88°.