MSE Department Seminar

Since the beginning of the microelectronics era ongoing miniaturization of transistors has been accompanied by the development of ever more intricate interconnects. Presently these range from nanoscale on-chip wiring to 3D TSV for chip stacking along with related structures for advanced packaging and printed circuit board applications. Electrodeposition has been a key process in the void-free fabrication of recessed patterned Cu interconnects by virtue of surfactant-mediated superconformal film growth.

The unique ability of carbon to bond with itself forming extended chains and networks underlies the structural complexity of organic matter. This complexity extends to elemental carbon. Several hundred crystalline carbon phases have been theoretically predicted to date. However, few of these materials have been realized experimentally. Advances in the synthesis of nonbenzenoid and sp1-containing allotropes have been especially limited.

The advancement of quantum photonic technologies relies on the ability to precisely control the degrees of freedom of optically active states. First, motivated by recent evidence showing that nanowrinkles generate strain-localized room-temperature emitters, we demonstrate a method to intentionally induce wrinkles with collections of stressors. We show that long-range wrinkle direction and position are controllable with patterned array design, forming quantum emitters as evidenced by cryogenic anti-bunched emission.

The ever-growing demand for sustainable transportation and renewable energy sources has placed a critical spotlight on lithium batteries, which are key to unlocking a cleaner future. However, current lithium-ion battery technology has reached its theoretical energy density limit and cannot meet these demands. Developing new battery chemistries with high energy density has been challenging due to the intrinsic complexity of batteries. This complexity includes defects in materials, inhomogeneity in manufacturing, and phase transitions and interphase formation under electrochemical dynamics.

Nature provides extraordinary examples of high-performance polymers with properties often surpassing those of man-made plastics. Protein-based materials are particularly interesting because their palette of amino acid “monomers” and their precisely controlled sequence can give rise to complex properties based on the synergy of diverse intermolecular interactions. Silk fibroin, a class of proteins produced by many insects and arachnids, is an archetypal elastomer with an unrivaled combination of strength and toughness.

An ability to first visualize and then shape the nanoworld is of great scientific and technological interest. In this talk, we present two unusual approaches that both allow the formation of structures with atomic precision. In the first approach, we are capitalizing on the fact that with the continued development of scanning probe microscopy techniques, atomic structure imaging and manipulation of single molecules has become possible, providing unprecedented insight into chemistry at the single-molecule level.

Organic inorganic hybrid semiconductors exhibit a rich interplay between organic and inorganic components, resulting in unique tunable electronic, optical, and structural properties. Central to their functionality is the control of dynamic structural phenomena, such as phase transitions, lattice distortions, and structural reorganization, which are influenced by external stimuli like temperature, light, or electric fields. I will present strategies to manipulate these dynamic structures, including compositional tuning, external field application, and molecular design.

Interfaces of two dimensional (2D) van der Waals (vdW) crystals constitute the most versatile material platforms for the exploration of new physical phenomena, particularly emergent quantum phases. Here we apply femtosecond pump-probe spectroscopy/microscopy to develop a time-domain view of quantum phases at 2D vdW interfaces of semiconducting, ferro/antiferro-magnetic, and ferroelectric materials. For transitional metal dichalcogenide (TMDC) moiré interfaces, we show the robustness of correlated electron phases and their coupling to phonons.

Multi-dimensional Coherent Terahertz Spectroscopy (THz-MDCS) is a new tool for studying with unprecedented resolution and for controlling quantum materials, by using a pair of phase-locked, intense Terahertz (THz) laser pulses. Establishing this experimental technique in superconductors and topological materials requires solving a non-equilibrium many-body problem that spans across several fields of current interest, including light-induced superconductivity, parametric driving of metastable phases, and quantum entanglement of supercurrent qubits.

In this talk, I will discuss several symmetries in quantum physics that have recently led to the observations of intriguing optical phenomena and the realizations of novel photonic functionalities. Different from canonical quantum mechanics, these symmetries imply non-Hermiticity that is difficult to realize in high-energy physics or condensed matter systems in a controlled fashion.