High spatial density nanocrystal formation using thin layer of amorphous Si_0.7Ge_0.3 deposited on SiO₂

The process to make nanocrystals with an average size <5 nm and a spatial density > 10¹²/cm² was proposed using agglomeration and partial oxidation of thin amorphous Si_0.7Ge_0.3 layer deposited in between the SiO₂ layers by low pressure chemical vapor deposition. The reason to use an amorphous layer is to make it possible to deposit a thin continuous layer with a thickness of less than 5 nm. Si_0.7Ge_0.3 alloy layer was used to control the spatial density of the nanocrystals by using selective oxidation of Si in Si_0.7Ge_0.3 alloy layer. The single electron memory, similar to a flash type memory device was fabricated using these Si_0.7Ge_0.3 nanocrystals. The Coulomb blockade effect could be clearly observed at room temperature with a threshold voltage shift of about 2.4 V, which demonstrated the formation of nanocrystals with a high spatial density.