Charge storage in a metal–oxide–semiconductor capacitor containing cobalt nanocrystals

Self-assembled cobalt (Co) nanocrystals on ultra-thin silicon dioxide layer were fabricated by in situ annealing Co ultrathin films deposited with Co effusion cell in a molecular-beam-epitaxy chamber. The resultant nanocrystals obtained at the optimized annealing temperature are around 3–4 nm in diameter with dot density of about 1 · 10 cm . The metal–oxide–semiconductor capacitors containing Co nanocrystals exhibit much longer retention times than a Si nanocrystal memory with the same tunneling oxide thickness. This study suggests that Co nanocrystal should be an excellent alternative to replace Si nanocrystal as floating gates for future nonvolatile flash-type memory application. 2006 Elsevier Ltd. All rights reserved. PACS: 72.20.Jv; 73.63.Kv; 81.07.Ta; 85.35.Be