Journal
ACS APPLIED MATERIALS & INTERFACES
Volume 6, Issue 4, Pages 2255-2261Publisher
AMER CHEMICAL SOC
DOI: 10.1021/am4055589
Keywords
Al2O3 thin films; magnetron sputtering; leakage current; breakdown mechanism; oxygen vacancy; subband electronic structure
Funding
- Chinese National Program on Key Basic Research Project [2012CB933003]
- National Natural Science Foundation of China [11104289, 61274095]
- Science and Technology Innovative Research Team of Ningbo Municipality [2009B21005]
- Key Program for Science and Technology Innovative Team of Zhejiang Province [2010R50020]
- Analysis Research for Public Welfare Project of Zhejiang Province [2012C37047]
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High dielectric constant (high-k) Al2O3 thin films were prepared on ITO glasses by reactive RF-magnetron sputtering at room temperature. The effect of substrate bias on the subband structural, morphological, electrode/Al2O3 interfacial and electrical properties of the Al2O3 films is systematically investigated. An optical method based on spectroscopic ellipsometry measurement and modeling is adopted to probe the subband electronic structure, which facilitates us to vividly understand the band-tail and deep-level (4.8-5.0 eV above the valence band maximum) trap states. Well-selected substrate biases can suppress both the trap states due to promoted migration of sputtered particles, which optimizes the leakage current density, breakdown strength, and quadratic voltage coefficient of capacitance. Moreover, high porosity in the unbiased Al2O3 film is considered to induce the absorption of atmospheric moisture and the consequent occurrence of electrolysis reactions at electrode/Al2O3 interface, as a result ruining the electrical properties.
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