Dr. Moïra Hocevar, Institut Néel CNRS, France (CMU MSE Seminar)
Growth of Nanowires Heterostructures for Quantum Devices and Nanotechnology
Abstract: Nanowires are crystals with the morphology of a hair but ten thousand times smaller. They measure several microns in length and tens of nanometers in diameter. For the past twenty years, nanowires have been at the root of important breakthrough in both basic science and nanotechnology in a multitude of scientific areas. They are now commonly developed for transistor and sensor applications, light emitting diodes or solar cells. In quantum technologies, their unique properties enabled the development of bright single photon sources, spin quantum bits and nanomechanical resonators. We fabricate nanowires with crystalline semiconductor materials such as silicon which is the backbone of electronics or gallium arsenide, which emits light and is used to manufacture light emitting diodes. For a certain number of applications, it is necessary to juxtapose different semiconductors to form a heterostructure. Yet, creating heterostructures is not an easy task, especially in thin films. As different crystalline materials have different lattice parameters (distance between atoms), the lattice is strained at the junction (or interface) between two materials. This induces the formation of defects, among them dislocations which deteriorate the targeted physical properties. Thanks to their morphology, nanowires have more flexibility to release strain, preventing the formation of defects. Nanowires have the potential to host heterostructures that cannot be fabricated in standard technologies, enabling the discovery of new physical phenomena and the improvement of existing devices. During the seminar, I will present an overview of my ongoing research on nanowire heterostructures. The first part will be dedicated to embedding light emitters in silicon technology. Different semiconductor families or high-mismatch semiconductors are combined in nanowires. I will show how interfaces are built without structural defects, a prerequisite for optoelectronic devices . Then, I will present superconductor-semiconductor nanowire hybrids. A particular focus will be on the development and study of Sn/InSb interfaces which have recently shown high potential for superconducting and topological quantum circuits . Finally, I will present the development of an ultrasensitive tool to study the mechanical properties of nanowires using a focused electron beam .
 Beznasyuk et al (2020)
 Pendharkar et al (2020)
 Pairis et al (2019)
Biography: Moïra Hocevar is a researcher at CNRS Néel Institute in Grenoble since January 2015. She received an Engineering degree in Materials Science from INSA de Lyon in France (2004), a master degree in Environmental Science from Université Denis Diderot in Paris (2005) and her PhD in Electronics from INSA de Lyon in 2008. Prior to joining Néel Institute in Grenoble, she was a Marie Curie postdoctoral fellow at the Technical University of Delft in the Netherlands and a Nanoscience Foundation postdoctoral fellow in Grenoble. Her research focuses on creating novel nanowire heterostructures by molecular beam epitaxy and uncovering their unique physical properties using Mhigh-end characterization tools.