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Journal of Nanomaterials
Volume 2011, Article ID 810879, 12 pages
Research Article

Temperature-Dependent Physical and Memory Characteristics of Atomic-Layer-Deposited RuO𝑥 Metal Nanocrystal Capacitors

1Thin Film Nano Tech Lab., Department of Electronic Engineering, Chang Gung University, 259 Wen-Hwa 1st Road, Kwei-Shan,Tao-Yuan 333, Taiwan
2Material and Chemical Research Laboratories, Industrial Technology Research Institute, Hsinchu 310, Taiwan
3Australian Key Centre for Microscopy and Microanalysis, University of Sydney, NSW 2006, Australia
4Department of Materials Science Engineering, National Taiwan University, Taipei 106, Taiwan

Received 26 February 2011; Revised 16 April 2011; Accepted 6 June 2011

Academic Editor: Edward Andrew Payzant

Copyright © 2011 S. Maikap et al. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.


Physical and memory characteristics of the atomic-layer-deposited RuO𝑥 metal nanocrystal capacitors in an n-Si/SiO2/HfO2/RuO𝑥/Al2O3/Pt structure with different postdeposition annealing temperatures from 850–1000°C have been investigated. The RuO𝑥 metal nanocrystals with an average diameter of 7 nm and a highdensity of 0.7 × 1012/cm2 are observed by high-resolution transmission electron microscopy after a postdeposition annealing temperature at 1000°C. The density of RuO𝑥 nanocrystal is decreased (slightly) by increasing the annealing temperatures, due to agglomeration of multiple nanocrystals. The RuO3 nanocrystals and Hf-silicate layer at the SiO2/HfO2 interface are confirmed by X-ray photoelectron spectroscopy. For post-deposition annealing temperature of 1000°C, the memory capacitors with a small equivalent oxide thickness of ~9 nm possess a large hysteresis memory window of >5 V at a small sweeping gate voltage of ±5 V. A promising memory window under a small sweeping gate voltage of ~3 V is also observed due to charge trapping in the RuO𝑥 metal nanocrystals. The program/erase mechanism is modified Fowler-Nordheim (F-N) tunneling of the electrons and holes from Si substrate. The electrons and holes are trapped in the RuO𝑥 nanocrystals. Excellent program/erase endurance of 106 cycles and a large memory window of 4.3 V with a small charge loss of ~23% at 85°C are observed after 10 years of data retention time, due to the deep-level traps in the RuO𝑥 nanocrystals. The memory structure is very promising for future nanoscale nonvolatile memory applications.