Browsing by Author "Jhang, Jia-Sin"

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Effects of cross-sectional area on the tunneling-junction array in octahedral PbSe colloidal-nanocrystal solids
(2013)
Chiu, Shao-Chien
;
Jhang, Jia-Sin
;
Chen, Jenn-Fang
;
Fang, Jiye
;
Jian, Wen-Bin
Octahedral PbSe colloidal nanocrystals (NCs) are used to assemble a solid. Because of the special feature of the apexes of the octahedrons, the cross-sectional area of the inter-dot tunneling junctions is much smaller than that formed between spherical NCs. The inter-dot separation between NCs is easily adjusted by mild thermal treatment. Like a spherical NC-solid, the resistance of the octahedral NC-solid is exponentially dependent on the inter-dot separation. On the contrary, due to the difference in the cross-sectional area between the NCs, electron transport in the octahedral NC-solid does not follow the same model used for the explanation of electron transport in a spherical NC-solid. Through analyses of current-voltage and resistance-temperature behaviors, we have confirmed that the model of fluctuation-induced tunneling conduction fits very well with all of the data and explains the variation in the electrical properties of octahedral PbSe colloidal NC-solids after thermal annealing.
Nanocrystal shape and nanojunction effects on electron transport in nanocrystal-assembled bulks
(2013)
Chiu, Shao-Chien
;
Jhang, Jia-Sin
;
Lin, Yen-Fu
;
Hsu, Shih-Ying
;
Fang, Jiye
Bulk nanostructured materials are made from the assembly of octahedral PbSe nanocrystals. After thermal annealing, the artificial bulk demonstrates a large difference in behavior depending on the temperature, and a large variation of room-temperature resistivity of up to seven orders of magnitude. This variation originates from the high-indexed sharp edges of the octahedral nanocrystals. As the nanocrystals are arranged in the edge-to-edge configuration, which was observed in scanning electron microscopy images, the inter-nanocrystal capacitance is small due to the small parallel area between the nanocrystals. The small capacitance results in a high thermal fluctuation voltage and drives electron transport. The temperature-dependent resistivity and the electric field-dependent current are highly in agreement with the model of fluctuation-induced tunneling conduction. Thermal annealing reduces the inter-nanocrystal separation distance, creating a large variation in the electrical properties. Specifically, octahedral-shaped PbSe nanocrystals are employed in tailoring the electron transport in bulk nanostructured materials.