The phonon scattering mechanism and its effect on the temperature dependent thermal and thermoelectric properties of a silver nanowire.

In this work, the electron-phonon, phonon-phonon, and phonon structure scattering mechanisms and their effect on the thermal and thermoelectric properties of a silver nanowire (AgNW) is investigated in the temperature range of 10 to 300 K. The electron-phonon scattering rate decreases with the increase of temperature. The phonon-phonon scattering rate increases with temperature and becomes greater than the electron-phonon scattering rate when the temperature is higher than the Debye temperature (223 K). The rate of phonon structure scattering is constant. The total phonon scattering rate decreases with temperature when the temperature is lower than about 150 K, and increases when the temperature is higher than 150 K. Correspondingly, the temperature dependent variation trend of the lattice thermal conductivity is opposite diametrically to that of the total phonon scattering rate. The thermoelectric properties of the AgNW are strongly coupled with the thermal conductivity via the phonon and electron transition. The thermoelectric properties of the material are quantified by the figure of merit (ZT). The ZT value of the AgNW is greater than that of bulk silver in the corresponding temperature range, and this difference increases with temperature. The order of the ZT of the AgNW is about 13 times greater than that of bulk silver at room temperature. The large increase of the ZT value of the AgNW is mainly due to the enhanced electron scattering and phonon scattering mechanisms in the AgNW.

Proposed a self-absorption internal standard model to detect element concentrations of complex constituent material with a single emission line of element in laser plasmas.

Laser induced plasmas (LIPs) method is a highly regarded approach to evaluate the chemical composition of materials. But the strong self-absorption of the radiation seriously affects its accuracy. Meanwhile, the model based on self-absorption phenomenon makes its application very difficult. In this work, a self-absorption internal standard (SAIS) model is proposed for detection of the multi-element concentrations of complex constituent material with a single emission line of the element in laser plasmas. A typical LIPs experiment system is set up to generate plasmas, and the soil is selected as a test sample. The average electron temperature (0.975 eV) and electron density (1.44×1018 cm-3) are determined by the Boltzmann plot and emission lines Stark broadening, respectively. The plasmas are diagnosed as in local thermodynamic equilibrium condition. The emission lines selected to calculate the concentration of sample contain a wide set of kt values (0.575×10-30∼37.2×10-30 m3). Then, the concentrations of some elements are calculated by the model using single emission line of each element. It is found that the concentrations of the five elements (Ti, Fe, Mg, Al, Si) calculated by SAIS model are relatively consistent with the results of the traditional chemical testing methods. This indicated that the SAIS model is an effective and neat method for multi-element concentrations detection of complex constituent materials.

Electrical and thermal properties of silver nanowire fabricated on a flexible substrate by two-beam laser direct writing for designing a thermometer.

Accurate knowledge of electrical conductivity and thermal conductivity temperature dependence plays a crucial role in the design of a thermometer. Here, by using a two-beam laser direct writing system, an individual silver nanowire (AgNW) with well-defined dimensions is fabricated on a polyethylene terephthalate (PET) substrate. The temperature dependence of the resistivity of the fabricated AgNW is measured ranging from 10 to 300 K, and fitted with the Bloch-Grüneisen formula. The residual resistivity ((1.62 ± 0.20) × 10-7 Ω m) of the AgNW is larger than that of the bulk material (1 × 10-11 Ω m). The electron-phonon coupling constant of the AgNW is (1.08 ± 0.13) × 10-7 Ω m, which is larger than that of the bulk silver (5.24 × 10-8 Ω m). Moreover, the Debye temperature of the AgNW is 199.30 K and is lower than that of the bulk silver (235 K). The Lorenz number of the fabricated AgNW is found to decrease as the temperature increases. Besides, the Lorenz number (2.66 × 10-7 W Ω K-2) is larger than the Sommerfeld value (2.44 × 10-8 W Ω K-2) at room temperature. The measurement results allow one to design a thermometer in the temperature range 40-300 K. The flexibility of the AgNW is also excellent, and the resistance increase of the AgNW is only 2.58% when the AgNW bending about 1000 times with a bending radius of 1 mm.

The Conductive Silver Nanowires Fabricated by Two-beam Laser Direct Writing on the Flexible Sheet.

Flexible electrically conductive nanowires are now a key component in the fields of flexible devices. The achievement of metal nanowire with good flexibility, conductivity, compact and smooth morphology is recognized as one critical milestone for the flexible devices. In this study, a two-beam laser direct writing system is designed to fabricate AgNW on PET sheet. The minimum width of the AgNW fabricated by this method is 187 ± 34 nm with the height of 84 ± 4 nm. We have investigated the electrical resistance under different voltages and the applicable voltage per meter range is determined to be less than 7.5 × 103 V/m for the fabricated AgNW. The flexibility of the AgNW is very excellent, since the resistance only increases 6.63% even after the stretched bending of 2000 times at such a small bending radius of 1.0 mm. The proposed two-beam laser direct writing is an efficient method to fabricate AgNW on the flexible sheet, which could be applied in flexible micro/nano devices.