Seminar Speaker

Prof. Jerry Moloney 

Venue

Room G06, Kane Science Building, UCC

Time/Date 

4pm / Monday, 12 October, 2026

Title

 Extreme Ultrafast Nonlinear Optics: Short and long wave laser Filamentation

Abstract

Ultrashort femtosecond duration laser pulses undergo extreme self-focusing when propagating in various transparent materials such as glasses, liquids and even in the atmosphere. The physical consequences of such extreme behavior (mathematical blowup singularity) can depend sensitively on the nature of the medium in which the pulse propagates and the central wavelength of the propagating pulse. I will review two physical scenarios: (1) where the linear material dispersion dominates over the (Kerr) nonlinearity leading to the generation of exotic superbroadened spectral features (X-waves) and, (2) the opposite case where the optical carrier wave itself self steepens (shocks) while filamenting, generating subwavelength attosecond duration temporal substructures.

Seminar Speaker

Dr. Hubert Klahr

Venue

Room G06, Kane Science Building, UCC

Time/Date 

4pm / Monday, 5 October, 2026

Title

 A Chapter from the Book of Planet Formation: Pebbles, Planetesimals, and Turbulence

Abstract

The small bodies of the Solar System — asteroids, Trojans, comets, and Kuiper Belt objects — are surviving remnants of the earliest stages of planet formation. These planetesimals were the building blocks from which planets emerged 4.5 billion years ago, through mutual collisions and the accretion of millimetre- to centimetre-sized solids known as pebbles. Yet the fundamental question of where and when planetesimals formed within the solar nebula remains unresolved.

In this talk, I will present recent models exploring how hydrodynamic instabilities, such as the Vertical Shear Instability and Convective Overstability, together with particle-feedback-driven processes such as the Streaming Instability, generate turbulence in magnetically inactive regions of protoplanetary disks. This turbulence governs the evolution of solid particles: it regulates the growth of dust grains into pebbles, drives their vertical stirring, and promotes their concentration into dense pebble clouds. Under the right conditions, these clouds can become gravitationally unstable and collapse into planetesimals.

Using numerical simulations with a Lagrangian hydrodynamics code, we find that the collapse of a single pebble cloud does not produce a single object, but rather a cluster of many planetesimals. The resulting size distribution is consistent with observations of asteroids, comets, and Kuiper Belt objects. In this way, the minor bodies of the Solar System provide a fossil record of the turbulent environments in which they were born — allowing us to read, in today’s small bodies, a chapter from the book of planet formation

Seminar Speaker

Dr. Michael Nolan

Venue

Room G06, Kane Science Building, UCC

Time/Date 

4pm / Monday, 28 September, 2026

Title

 Multiscale simulation of materials processing

Abstract

In modern semiconductor device fabrication, the dimensions involved require atomic level control over materials deposition and etch. Atomic layer deposition (ALD) and thermal atomic layer etch (tALE), is therefore critical deposition and etch of relevant materials. Further scaling and use of complex three-dimensional structures means that tALE will take centre stage in etching. The key chemistry takes place at surfaces which drives the self-limiting characteristics and other advantages of these atomic level processing approaches. In this presentation I will discuss how atomistic simulations based on first principles density functional theory (DFT), ab initio molecular dynamics and kinetic Monte Carlo methods can be used to predict the chemistry of atomic level deposition and etch processes. I will first discuss the key chemistries involved in atomic level processing chemistries and the challenges that we have identified in this exciting area. The first scientific topic is the simulation of plasma enhanced deposition (PE-ALD) of metals, using the example of cobalt (Co) for next generation interconnects. This is the first example of an atomistic study of the full PE-ALD cycle for Co metal and show that the process requires use of ammonia or mixed NH2/N2 plasma. Calculated energy barriers for key steps give guidance regarding the temperatures required for the process. We show how substrate pretreatment can reduce nucleation delay and therefore allow selectivity in deposition of the target film. Finally we show how kinetic Monte Carlo can be used to predict the structure of deposited metal films on different nitride substrates using data from DFT level simulations. The second example is molecular layer deposition of hybrid materials, using alucone as the prototypical example. Incorporation of aliphatic with functionalized aromatic molecules allows differences in film properties to be understood. A further application of this involves selective, templated deposition of target films using block co-polymer infiltration where differences in reactivity of a precursor in two polymers promotes selective deposition of the target films. Finally, I present our work on self-limiting thermal atomic layer etching (ALE), highlighting how simulations can (1) predict the window of self-limiting etch (2) unravel the difference between amorphous and crystalline substrates and (3) probe the impact of surface orientation on tALE chemistry, all of which are important for future, selective tALE processing on complex 3D substrates.