Optical and Electric Properties of Aligned-Growing Ta₂O₅ Nanorods

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These vertically aligned Ta₂O₅ nanorods were deposited on Si (100) substrates by thermal deposition in a vacuum of the order of 10⁻² Torr at about 600°C. When excited by 514 nm Ar⁺ laser, they showed a strong photoluminescence at ∼622 nm, which was attributed to the oxygen vacancies. In addition, their dielectric constant is ∼20 in the frequency range from 1 kHz to 10 MHz, far larger than that of SiO₂ and Si₃N₄. Due to this cone-shaped morphology, the Ta₂O₅ nanorods exhibited a threshold field of ∼8.5 V/μm in field emission and a field enhancement factor of 764 that are sufficiently high for field emission application.