Terahertz time-domain measurement of non-Drude conductivity in silver nanowire thin films

Abstract

We investigate the complex conductivity of silver nanowire thin films using terahertz time-domain spectroscopy. The measured conductivity shows a characteristic non-Drude response unlike bulk metals. The interesting behavior is explained by the Gans approximation and the Drude-Smith model.A wide range of applications using transparent thin-film electrodes emerge in areas such as liquid crystal displays (LCDs), organic light-emitting diodes (OLEDs), touch screens, and solar cells. Metallic nanowires, especially silver nanowires (Ag NWs), are considered to be good candidates for these applications, since Ag NWs exhibit outstanding electrical conductivity as well as high mechanical flexibility due to the mesh-like network structures mixed with various composites [1][2][3]. Therefore, it is important to explore the electromagnetic response of the NWbased transparent thin films. Terahertz time domain spectroscopy (THz-TDS) is an excellent spectroscopic tool for measuring conductivity without requiring electrical contact or damage to the samples [3].In this work, we study spectroscopic measurements on the terahertz (THz) complex conductivity of transparent metal composites containing various filling fractions of Ag NWs (1-15%) (Figs. 1a and b). Atomic-force microscopy (AFM) confirms that the average diameter of the Ag NW is 90 nm with a standard deviation of 10 nm, and the average length is 5 μm with a standard deviation of 2 μm. Figure 1c shows the time-domain THz signals where the phase shifts of E sam (t) are negligibly small with some amplitude decreases. The frequency-domain analysis shown in Fig. 1b depicts decreases in amplitude transmission with increasing Ag NW filling fractions. Fig. 1. a, Optical transmittance and b, optical microscope (the scale bar is 10 μm) and atomic force microscope (the scale bar is 5 μm) images of AgNW films with varying filling fraction. c, The measured THz time-domain signals and sample modulation scheme (inset) d, The obtained THz frequency-domain signals.

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“…Consequently, it would be desirable to integrate novel functional nanomaterials that having inherent nanoscale sizes for example nanowires having one-dimensional. Recently, network-like films made up of nano-scale materials for example reduced graphene oxide, single-walled nanotubes, and silver nanowires have appeared as a potential alternatives for developing THz optoelectronic devices ( De et al, 2009 ; Kim et al, 2013 ). Furthermore, solution-based procedures involve to practice relatively low-cost spin-coating approaches, in particular, AgNWs exhibit also exhibits superior optical and electrical properties, which makes them interesting to develop applications in THz based optoelectronic devices (2017); however, biomedical sensing applications with improves sensitivity are yet to be addressed.…”