Mesoscopic thermophysical Measurment of single Sb2Se3 nanowire with high resistivity

• Main Authors: Ko, Ting-Yu, 柯廷育
• Other Authors: Sun, Kien-Wen
• Format: Others
• Language: zh-TW
• Published: 2013
• Online Access: http://ndltd.ncl.edu.tw/handle/477s5u

博士 === 國立交通大學 === 應用化學系碩博士班 === 102 === The works presented in this thesis focus on measurements on three kinds of physical properties from single antimony triselenide(Sb2Se3) nanowires. The content is divided into three parts：(1)optoelectrical measurements, (2)thermal-electric：Seebeck coefficient measurements, and (3)thermoconductivity measurements. Part one： A dynamic scanning photocurrent microscopy (SPCM) technique was applied to Sb2Se3 single nanowires. In this experiment, an electrical transient was observed for the first time when the single nanowires were illuminated laser pulses. It was considered as a new phenomenon from the pyroelectric effect uncovered in single Sb2Se3 nanowires. By using the Chynoweth method, we were able to successfully retrieve the pyroelectric coefficient 60.09uC/m2K of a single nanowire. Although the Sb2Se3 nanowire is classified as non-ferroelectric materials, but it exhibit a high pyroelectric coefficient. Therefore, we believe that the pyroelectric transient observed in the single nanowires is due to the defects produced under optical excitation which result to space charges generated in nanowires. Part two： Through the semiconductor manufacturing processes, a micro-device was fabricated to measure the Seebeck coefficient of single Sb2Se3 nanowires. A Seebeck coefficient of 661.1uV/k was obtained by data fitting and processing. The measured thermopower with a positive value indicates that the thermal transport is dominated by holes. In addition, we also observed increase in Seebeck coefficients when the bias voltage was increased. Due to the high resistivity of the Sb2Se3 nanowires, we believe that this phenomenon can only be interpreted by the phonon drag effect, but not by the Mott formula. Part three： In order to measure the thermal conductivity of single nanowires, micro-devices consisted of two adjacent suspended silicon nitride membranes were fabricated. A single Sb2Se3 nanowire was carefully placed on the device to bridge the two membranes. By accurately determining the relationship of temperature difference on each heating/sensing suspension membranes with the joule heating, we successfully deduced a thermal conductivity value of k=0.0172W/mK