Скачать или смотреть Strain engineering across phase change materials | Prof. Viswanath Balakrishnan, IIT Mandi

Abstract

The interaction between lattice strain and phase transition leading to modulation of physical properties is of high importance in materials engineering. Phase transformations like martensite-to-austenite transformations in nickel titanium alloys, the amorphous-to-crystalline transformation in germanium antimony telluride alloys and lithium intercalation in battery electrodes has vital applications in actuators, non-volatile memory and in energy storage. Vanadium dioxide is a well-known functional material for its reversible first-order metal-insulator transition (MIT) accompanied by a structural phase transition from monoclinic to tetragonal at 68 ◦ C. This phase transition can also be triggered by strain, electric field and light and has gained significant attention in the field of actuators, microcantilevers, thermochromic windows, sensors and thermistors etc. While most of the studies reported in the literature are dedicated to the physics of metal-insulator transition and its applications, the mechanical behavior/failure across the phase transition is not well investigated. Further insights into transformation stress and strain manipulation of phase transition towards engineering application continued to gain interest among researchers. In this talk, the following questions related to the phase transition and associated mechanics will be discussed by taking VO2 (Vanadium Di-oxide) as a model system.

How do we visualize the phase change induced actuation
in nanoscale cantilevers and experimentally measure the
transformation stress in thin films, nanostructures, and
single crystals?

Can we manipulate the phase transition with aid of strain
and decrease the transition temperature and threshold
voltage?

How do we reliably measure the mechanical properties
across the phase change?

At the end, the role of strain engineering in atomically thin 2D
allotropes of transition metal dichalcogenides and growth of vertically aligned 1D carbon nanotubes from gas phase will be presented to highlight the strong linkage between the strain and phase change among various materials at different length scales.