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J. Phys. Chem. C 2008, 112, 17512–17516
Terahertz Dielectric Properties of MgO Nanocrystals Jiaguang Han,†,‡ Boon Kuan Woo,§ Wei Chen,§ Mei Sang,†,# Xinchao Lu,† and Weili Zhang*,† School of Electrical and Computer Engineering, Oklahoma State UniVersity, Stillwater, Oklahoma 74078, Department of Physics, National UniVersity of Singapore, 2 Science DriVe 3, Singapore 117542, Department of Physics, The UniVersity of Texas at Arlington, Arlington, Texas 76019, and Center for Terahertz waVes, College of Precision Instrument and Optoelectronics Engineering, Tianjin UniVersity, Tianjin 300072, People’s Republic of China ReceiVed: July 3, 2008; ReVised Manuscript ReceiVed: September 3, 2008
Terahertz properties of chemically synthesized MgO nanocrystals are studied by terahertz time-domain spectroscopy in the frequency range extending up to 3.7 THz. The experimentally determined optical and dielectric properties of the nanocrystalline MgO are compared with those of a bulk MgO single crystal. Three prominent resonance modes, which are essentially responsible for the dielectric properties of the nanostructured MgO in the terahertz regime, are characterized at ω1/(2π) ) 4.26 THz, ω2/(2π) ) 7.68 THz, and ω3/(2π) ) 12.18 THz and are well-described by a multiple-oscillator model through theoretical fitting. The MgO nanocrystals may find intriguing applications in developing terahertz quasi-optic components and terahertz spectroscopy. I. Introduction Magnesium oxide (MgO) is an attractive wide bandgap semiconductor due to promising applications in a broad range of disciplines. As a well-known substrate, MgO is widely involved in new material growth, for instance, high-Tc superconductor processing, and it is therefore utilized in a wide variety of microwave and infrared components.1 In the terahertz regime, MgO plays an essential role in developing quasi-optic and nonlinear parametric components for terahertz generation and detection.2 Also, being known as a good transparent material at low terahertz frequencies (
