IRTG 2022 "ATUMS" - Project 2-4

2-4: Optical, structural and electronic Characterization of functionalized Si Surfaces and Clusters


TUM: Ulrich Heiz, Bernhard Rieger, Martin Stutzmann, Marc Tornow
UofA: Jonathan Veinot
Doctorial Candidates: Hannah Schamon, Matthias Jakob


The aim of this project is to develop a fundamental understanding of the optical, electronic and chemical properties of functionalized Si clusters and nanoparticles. This includes the influence of deposition conditions (temperature, purity, doping), structural properties affecting the overall crystallinity such as surface faceting and extended defects (dislocations, stacking faults), and different forms of surface treatments and functionalization after deposition (Veinot, Stutzmann). Covering the full range of particle sizes between a few nm and several tenth of nm plus a precise control of the chemical and ligand environment is required to this end, which can only be achieved by the combined expertise and experimental capabilities of the collaborating partners.

 

Average counts of dangling bond defects per nanoparticle in plasma-deposited Si nano­particles versus particle diameter, d, for different thermal and chemical treatments. The defect density was determined by electron spin resonance measurements. As-deposited and vacuum annealed (200 °C) particles have the highest defect densities related to Pb-defects at the Si/SiO2 surface, which therefore scale with the square of the particle diameter, d. Chemically passivated particles after HF-etching of the surface oxide plus annealing or hydrosilylation exhibit extremely low bulk defect densities scaling with the particle volume proportional to d3.

The aim of this project is to develop a fundamental understanding of the optical, electronic and chemical properties of functionalized Si clusters and nanoparticles. This includes the influence of deposition conditions (temperature, purity, doping), structural properties affecting the overall crystallinity such as surface faceting and extended defects (dislocations, stacking faults), and different forms of surface treatments and functionalization after deposition. Covering the full range of particle sizes between a few nm and several tenth of nm plus a precise control of the chemical and ligand environment is required to this end. Well-defined surfaces of monocrystalline Si wafers will serve as model and reference systems.

The groups participating in this project have access to and long-standing expertise in a large variety of complementary and highly sophisticated experimental techniques to investigate and characterize the structural, chemical, optical and electronic properties of functionalized Si surfaces and clusters prepared in different ways. This will provide a rich and versatile training ground for the education of PhD students in a highly relevant research area targeting the physico-chemical properties of silicon-based functional hybrid system.