Electrical properties of Ge nanocrystals grown in a SiO 2 matrix using MeV electron beam irradiation

The structural and electrical properties of Ge nanocrystals (Ge‐NCs) grown in a SiO 2 matrix using high energy electron beam irradiation are investigated. The Ge‐NCs in a SiO 2 were formed by irradiation of the electron beam on a tri‐layers (SiO 2 (20 nm)/Ge(5 nm)/SiO 2 (10 nm)) grown on a Si(001) substrate and followed by annealing. For a sample exposed in the atmosphere by electron beam with energy of 1 MeV and a dose of ∼5 × 10 16 e/cm 2 , and then annealed at 700 °C for 10 min, transmission electron microscopy (TEM) measurement revealed the formation of Ge‐NCs with average size of ∼20 nm in a SiO 2 matrix. For a metal–oxide–semiconductor (MOS) structure synthesized by Al deposition on the top of the sample, the capacitance–voltage ( C – V ) measurements showed the hysteresis loops with a flatband voltage shift (Δ V FB ) of ∼5.0 V, which would originate mainly from Ge‐NCs as the charge storage nodes. In contrast, for a sample annealed at above 900 °C for 10 min without electron beam irradiation, we could obtain a similar hysteresis loop of ∼4.0 V. This indicates that the e‐beam irradiation process can lead to temperature reduction of ∼200 °C for Ge‐NCs formation by annealing process. We propose that the temperature reduction would result from crystallity enhancement of Ge layers in the initial stage of Ge‐NCs formation due to Ge atomic displacements induced by the high energy electron beam. (© 2009 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)