Transmission electron microscopy study of semiconductor nanowires and nanostructured materials

INVITATION

Program:
Lucia Nasi, IMEM CNR, Parma, Italy
Transmission electron microscopy study of semiconductor nanowires and nanostructured materials

Abstract:
Semiconductor heterostructures provide unique tailored properties for electronic, optoelectonic, photovoltaic and sensing applications. As the semiconductor size approaches the nanoscale, parameters such as size, shape, crystalline structure, composition and strain become crucial, and their control come to be indispensable at atomic level, in order to precisely engineer their properties for advanced functional materials. In lattice mismatched systems, additionally, defects formation and inter-mixing at the interfaces still represents a critical issue which ultimately limits the exploitation of a variety of materials in semiconductor heterostructures.
Transmission Electron Microscopy (TEM) is a powerful and versatile technique which provides information on material morphology, structure, crystal defects, and chemical composition at both nanoscale and atomic scale. The advantage of using conventional diffraction contrast, high resolution TEM and Scanning TEM Z-contrast imaging modes as well as analytical TEM techniques will be demonstrated for selected emblematic examples, from thin films to nanostructured systems. In particular, the study of self-assembled In(Ga)As/GaAs quantum dots, core-shell and axial heterostructured nanowires InAs/InP/InAsSb-based nanowires and wurtzite ZnS and ZnO porous nanostructures will be presented and discussed. Finally, the usefulness of the TEM techniques is shown for the investigation of structural and magnetic properties of nanostructured NiMnGa shape memory materials. For these systems, a better understanding of the growth mechanisms and in turn, in the control of the functional properties of the nanostructures, has been achieved.