Intelligent Real-time MAnipulation of metal nanostructure growth – IRMA

IRMA seeks to develop efficient and non-invasive strategies for manipulating the morphology and the opto-electronic properties of vapor-deposited Ag nanostructures grown by magnetron sputtering at room temperature (i.e., 3D islands and ultrathin continuous layers). This will be achieved via selective deployment of additives (i.e., gaseous species and solute metals), either at the growth front (acting like surfactants) or using a seed layer, to improve wetting of Ag layers with the ultimate goal to produce conductive layers at sufficiently low thickness to ensure optical transparency. In order to capture the structural, morphological, and chemical evolutions at the nano- and atomic-scales while the materials are ‘alive’, IRMA proposes a novel and challenging experimental approach combining:
- A detailed, real-time lab-based study providing simultaneous information on the optical, electrical, and stress evolution during growth and establishing a knowledge base for the impact of different surfactant approaches on the growth of ultrathin Ag films (work package 1).
- An in situ ultra-high vacuum surface-characterization study providing complementary information about chemical state and local morphology of the as-grown films (work package 2).
- A synchrotron-based study giving real-time information about the growth dynamics, structure evolution, and stress development, through X-ray diffraction, X-ray reflectivity and grazing incidence small-angle X-ray scattering combined with wafer curvature measurements (work package 3).
- The determination of optical and electrical properties in situ and ex situ, including ageing effects on the structural and functional properties (work package 4).
More specifically, different sputter-deposited Ag layers will be critically examined and benchmarked against reference Ag films grown in pure argon on silicon oxide surfaces: 1) the use of gas additives by performing Ag growth in argon/nitrogen plasma discharge, and 2) the growth of Ag on amorphous Ge seed layers, as these two approaches are the most efficient in promoting metal wetting, according to the literature. Additionally, we will explore the intelligent deployment of these surfactants, such as the use of Ag(1-x)-Ge(x) seed layers grown by co-deposition or the addition of nitrogen at specific nanostructure-formation key stages.
Three main research objectives are foreseen:
- To gain fundamental understanding on the impact of additives on the early-growth stages of Ag ultrathin films, in terms of interface chemistry, growth morphology, crystal structure, stress development, and surface roughness.
- To study relaxation processes after short-time growth interruptions as well as long-term and thermal stability of the investigated systems.
- To propose guidelines for efficient design strategies with the aim of achieving ultrathin metal layers with optimal optical transmittance, electrical conductivity, and improved durability for use as transparent conductive electrodes.
The IRMA project leverages on the complementary expertise and existing collaboration of three academic partners, Pprime Institute and SOLEIL in France, and Karlsruhe Institute of Technology in Germany, which offer unique research facilities to reach these objectives. On a grander scale, the fundamental knowledge generated by the IRMA project paves the way toward intelligent in-line control of industrial nanostructure synthesis processes.