Synthesis of Germanium Nanocrystals and its Possible Application in Memory Devices

Abstract

A novel method of synthesizing and controlling the size of germanium nanocrystals was developed. A tri-layer structure comprising of a thin (~5nm) SiO₂ layer grown using rapid thermal oxidation (RTO), followed by a layer of Ge+SiO₂ of varying thickness (6 - 20 nm) deposited using the radio frequency (r.f.) co-sputtering technique and a SiO₂ cap layer (50nm) deposited using r.f. sputtering, was investigated. It was verified using TEM that germanium nanocrystals of sizes ranging from 6 – 20 nm were successfully fabricated after thermal annealing of the tri-layer structure under suitable conditions. The nanocrystals were found to be well confined by the RTO SiO₂ and the cap SiO₂ under specific annealing conditions. The electrical properties of the tri-layer structure have been characterized using MOS capacitor test devices. A significant hysteresis can be observed from the C-V measurements and this suggests the charge storage capability of the nanocrystals. The proposed technique has the potential for fabricating memory devices with controllable nanocrystals sizes.