Laser joining and assembly of nanowires: processing, structure, properties and performance

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This proposed research program will study both fundamental and engineering issues in laser joining and assembly of nanowires, with combined experimental and numerical modeling methods. The goal is to, based on our previous work on laser joining of nanoparticles and nanowires, establish fundamental relationships between laser and other processing parameters, metallurgical characteristics of dissimilar joints of semiconductor nanowires and metal electrodes/substrates, interfacial structure, and electrical contact properties and performance of selected nanowire based electronic components and devices. *** There are three specific objectives, i.e., (1) to study relationships between processing parameters and joint formation in laser joining of nanowires, based on quantitative (or semi-quantitative) thermal history at interfacial regions; (2) to investigate the effect of laser processing parameters on interfacial structures, including crystallographic orientation relations at the interface, and electrical contact properties; and (3) to build prototype nanowire based electronic devices and explore their electrical performance as related to interfacial structure and electrical contact properties, and study the carrier transport mechanisms at the metal-semiconductor interfaces. *** The program will cover oxide semiconductor nanowires, such as TiO2, ZnO and CuO, and metal electrodes such as Au, Ag and Ti. Initial processing parameters will include laser fluences, pulse duration, spot size, etc. Advanced analytical equipment such as transmission electron microscopy and X-ray photoelectron emission microscopy will be used for detailed study of metallurgical defects and crystal orientation relations at interfaces, etc. Electrical properties such as contact resistance of Ohmic contacts and energy barrier height of Schottky contacts will be studied as functions of interfacial structures. Electrical performance of functional prototype components and devices such as field effect transistor and memristor will be investigated. The examples of numerical modeling include finite element analysis of thermal history and molecular dynamic simulation of interfacial structures. *** The successful execution of this program will not only provide valuable fundamental insights such as laser-nanowire interactions, but also develop know-how technologies in laser precision assembly of nanoscale devices. This program will also train 13 highly qualified personnel (HQP), including six doctoral and master's students, four undergraduate work-term students and three post-doctoral fellows with cutting edge knowledge and skills in the fields of materials science and engineering, laser processing and nanoscale device development. Canada's future competitiveness will also be enhanced through their future positions in Canadian academia, industries and research institutes.