We have developed a new thermal model for laser interference patterning. The results show laser interference patterning is feasible within the range of pulse energies available. From the MBE simulation, we determine the most likely mechanism to achieve nanopatterning is the surface diffusion of mobile species (eg: In on GaAs) and that this is achievable in a single pulse. For the CVD processes the reaction is directly initiated by the thermal or photochemical interaction with the laser pulse and the thermal response is somewhat slower. From the modelling of the thermal behaviour, we have determined two different laser protypes are needed, with a key difference in the pulse duration.
To address previous concerns over the shape and stability of the laser profile, a novel configuration of a VRM Resonator with an external pinhole for laser1. This laser has demonstrated a homogenous noise-free beam profile in near field. However, as part of this assessment, wave‐front aberrations have been identified as a critical risk and will be studied over the next few months
We have reviewed all the options for the interference lithography systems and have designed and tested prototype optical systems. The MBE system at USFD uses a system of beam splitters and mirrors and is based on a novel optical layout developed by BED. The more compact reactors at CEIT and TUT use a diffractive optical element arrangement in a custom configuration. All the optical systems contain significant novelty in design, component sourcing and mounting.
Three reaction chambers for in-situ laser interference patterning studies have been designed, built and in some cases are now operational. Each system has been specially designed to provide state of the art materials capability whilst allowing appropriate optical access. The CEIT approach of laser chemical vapour deposition (LCVD) using aerosol microdroplets is significantly novel in itself and ZnO nanoparticle growth has already been demonstrated using this process. The USFD uses a custom designed commercial MBE reactor, which has been adapted to allow optical access and reduced sensitivity to vibration. The TUT system studies the reaction of SCCo2 , injected up to 300bar and reacted with metal films in a laser assisted decomposition process. This is an emerging process which has already shown great potential. Patterning the surface using laser interference during this reaction is an entirely novel development
Potential impact
New optical systems and new reactor vessels have been developed and evaluated. Impact will be achieved from academic publication and potential technology transfer to industry
New patterned nanomaterials are expected to have significant impact within the fields of electronics, photonics, sensing and bio-engineering. Demonstration of methods and devices over the next year are expected to lead to opportunities for high quality scientific publications and potential uptake from industry
The build and evaluation of laser 1 has led to significant improvements which are marketable by Innolas and would be expected to generate future sales
