| We present a detailed investigation on terahertz (THz) time-domain spectroscopy (TDS) measured from Micro/Nano-structured periodic Au/dielectric sphere arrays on Si substrate. It is found that the metal-insulator transmission is determined by not only the thickness of Au shell but also the diameter of Au/dielectric spheres. The Au/polystyrene sphere arrays with 500 nm diameter does not show the metallic THz response even when the Au shell thickness is larger than 15 nm, which deviates from the observation in flat Au film on Si substrate. More interestingly, the Au sphere arrays with 5 nm thickness shows extraordinary absorption bands in frequency dependent absorption spectra. Such effect may be associated to the effect of quantum confinement where the electrons are trapped in sphere potential well of gold shell in the array structure. |
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