Fabrication of germanium nanodisk array by neutral beam etching with protein as etching mask

A uniform 10 nm diameter Ge two-dimensional (2D) nanodisk array structure was fabricated using iron oxide cores in a 2D closed-packed array of cage shaped proteins, ferritins, as an etching mask. Thin Ge layer on Si substrate was protected by a-Si capping layer and etched, which eliminated an uncontrollable factor of Ge native oxide. The density of Ge nanodisks was as high as 5.8 × 10¹¹cm⁻², and the center-to-center distance was estimated to be 14 nm. It was demonstrated that a quantum confinement effect can be obtained with our fabricated Ge nanodisk array by controlling the nanodisk thickness. The obtained high density Ge nanodisk is promising for Ge/Si quantum dot intermediate band solar cells and other photonics devices.