Terahertz Dielectric Properties and Low-Frequency Phonon Resonances of ZnO Nanostructures

Han, Jiaguang; Zhang, Weili; Chen, Wei; Ray, Sanith; Zhang, Jun; He, Ming; Azad, and Abul K.; Zhang, Zhu

doi:10.1021/jp073343t

Cited by 32 publications

(28 citation statements)

References 35 publications

(77 reference statements)

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“…The commonly used EMTs include the Maxwell-Garnett (MG) model, the Bruggeman (BR) model and the simple effective medium model. 19 These EMT models have been widely used to characterize many composite systems and presented good agreement with the measured results. The detailed discussions about these EMT models, for instance the validity or applications, have been well described previously.…”

Section: Theoretical Methodsmentioning

confidence: 70%

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Terahertz Response of Ferroelectric Nanofibers

Xin¹,

Wang²,

Han³

et al. 2011

j nanosci nanotechnol

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Far-infrared optical and dielectric properties of ferroelectric SrTiO3 and BaTiO3 nanofibers, prepared by hydrothermal syntheses, were studied using terahertz time-domain spectroscopy. The power absorption, refractive index, and complex dielectric function were characterized in the frequency range from 0.2 to 1.0 THz. The measured results are well reproduced by theoretical fittings based on the dielectric models and the effective medium model. The study reveals that the low-frequency dielectric properties of the ferroelectric SrTiO3 nanofibers are associated with the lowest transverse optical (TO) soft mode TO1 at 2.70 THz (90.0 cm(-1)), and that of the ferroelectric BaTiO3 nanofibers are related to the lowest pair of transverse optical (TO) and longitudinal optical (LO) modes near 5.35 THz, which are both consistent with their bulk single-crystal and thin-film counterparts.

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Section: Theoretical Methodsmentioning

confidence: 70%

“…The detailed discussions about these EMT models, for instance the validity or applications, have been well described previously. [19][20][21][22] For the SrTiO 3 and BaTiO 3 nanofibers studied here, the simple effective medium model is well suited to describe our experimental results.…”

Section: Theoretical Methodsmentioning

confidence: 99%

Terahertz Response of Ferroelectric Nanofibers

Xin¹,

Wang²,

Han³

et al. 2011

j nanosci nanotechnol

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“…These behaviors are quite consistent with what have been observed in the bulk and nanostructured crystalline ZnO and ZnS, but with relatively low absorption comparable to ZnO tetrapods. 5,16,17 The observed discrepancies in dielectric response between bulk singlecrystalline and nanocrystalline MgO may not be attributed to different crystal orientations because the far-infrared phonon spectra of MgO, similar to crystalline ZnS, do not exhibit remarkable orientation dependence. 18,19 Absorption spectra of MgO small particles have been widely studied in the infrared regime due to a great interest in understanding the infrared surface modes.…”

Section: Resultsmentioning

confidence: 99%

Terahertz Dielectric Properties of MgO Nanocrystals

et al. 2008

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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 ω 1 /(2π) ) 4.26 THz, ω 2 /(2π) ) 7.68 THz, and ω 3 /(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.

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“…THz, experimentally obtained power absorption and refractive index for single crystal ZnO are fitted quite accurately and compared with ZnO nanowire's results [19][20][21] . Unlike other ZnO nanomaterials, such as nanowires, tetrapods and prismlike structures, the annealed ZnO nanoparticles show a strong absorption at higher frequencies starting from 0.9 THz.…”

mentioning

confidence: 88%

Study of optical and dielectric properties of annealed ZnO nanoparticles in the terahertz regime

Wang

Woo

Tian

et al. 2009

Optoelectron. Lett.

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The frequency-dependent optical and dielectric properties of annealed ZnO nanoparticles in the range of 0.1 to 0.9 THz are studied by using terahertz time-domain spectroscopy (THz-TDS). The refractive index, power absorption and complex dielectric constants are obtained and the experimental results are well fit with a simple effective medium theory in conjunction with a pseudo-harmonic model. This study reveals that annealed ZnO nanoparticles exhibit the similar phonon response characteristics to the single ZnO crystal and other ZnO nanostructures, such as tetrapods and nanowires.In recent years, ZnO has attracted great research interest because of its unique properties and a variety of potential applications in electro-optic, acousto-optic, optoelectronic devices, chemical sensors and piezoelectrics [1][2][3] . ZnO can be a highly potential choice for ultraviolet light emitters and low voltage applications [4,5] , and it also could be used in integrated active optic devices and generation of high power terahertz pulses [6] . Some ZnO nanoparticles have shown exciting applications in the field of optoelectronics due to its unique capability of being integrated into nano-devices with very low power consumption [7] . Recent advancement in nanomaterial research has revealed that a new type of ZnOorganic coated nanoparticles has luminescence properties [8] .In this paper, we present a study of far-infrared optical and dielectric properties of annealed ZnO nanoparticles made from the luminescence coated ZnO nanopowders in the regime of 0.1-0.9 THz using the terahertz time-domain spectroscopy system (THz-TDS).The THz-TDS system is a photoconductive switch-based spectrometer with four parabolic mirrors arranged in an 8-F confocal geometry [9] . This confocal configuration enables excellent beam coupling between the transmitter and the receiver. A frequency-independent 3.5 mm-diameter terahertz beam waist is achieved for sample characterization. The THz-TDS system is optically excited using a Kerr-lens modelocked Ti:sapphire laser of 26 fs pulse width and 88 MHz repetition rate and has an useful bandwidth of 0.1-4.5 THz (3 mm-67 m) and a signal-to-noise ratio (S/N) greater than 1.0 10 4 :1.The annealed ZnO nanopowder is prepared in the following two steps. First, wet chemistry method called reverse micelle technique is used to make the luminescence coated ZnO nanopowders [10] . The zinc acetylacetonate hydrate powder (1.4122 gm, 5.36 mmole) is dissolved in 35 ml ethanol and put into a flask that is connected with a water condenser. 1 ml DI water and stabilizer polyethylene glycol biscarboxymethyl ether (0.85 gm, 3.3 mmole) is then mixed with the prepared murky solution. The murky solution is then heated up to boiling point under vigorous magnetic stirring. Another cooled solution is prepared using sodium hydroxide pellets (0.4 gm, 10 mmole) which is dissolved in 35 ml ethanol. The cooled solution with temperature around 0 o C is then added slowly using a transfer pipet into the boiling solution. After that, a white preci...

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Terahertz Dielectric Properties and Low-Frequency Phonon Resonances of ZnO Nanostructures

Cited by 32 publications

References 35 publications

Terahertz Response of Ferroelectric Nanofibers

Terahertz Response of Ferroelectric Nanofibers

Terahertz Dielectric Properties of MgO Nanocrystals

Study of optical and dielectric properties of annealed ZnO nanoparticles in the terahertz regime

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