Formation of Ge nanocrystals by utilizing nanocluster source

A novel method has been introduced in the fabrication process of semiconductor nanocrystal (NC). It consists of a magnetron sputtering system connects with an ultra-high vacuum (UHV) chamber. By varying aggregation lengths, sputtering gas (Ar) pressure and ionization power, nanoclusters of semiconductor material with different sizes can be formed. Multi-layered thin film structure with the embedment of Ge nanocrystals (Ge-NC) has been achieved by utilizing this new type of combination of two vacuum coating systems. High-resolution transmission electron microscopy study revealed that the average size of the Ge-NCs formed is about 10–30 nm in diameter and uniformly distributed for various growth conditions. The trilayer structure (HfAlO/Ge-NC/HfAlO/Si) was fabricated by pulsed-laser deposition and NC200U nanocluster source at a relatively low growth temperature with different growth time of Ge-NCs. The memory effect manifested by the counterclockwise hysteresis loop in the C–V measurement showed that a charge density of 3×1010 cm−2 and a flat band voltage shift of 1.5 V have been achieved.