Building carbon-free colloidal nanocrystal assemblies with plasma processing

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2017-01-01
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Mohapatra, Pratyasha
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Ludovico Cademartiri
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Materials Science and Engineering
Materials engineers create new materials and improve existing materials. Everything is limited by the materials that are used to produce it. Materials engineers understand the relationship between the properties of a material and its internal structure — from the macro level down to the atomic level. The better the materials, the better the end result — it’s as simple as that.
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Abstract

Removing the organic fraction from hybrid nanostructures is a crucial step in most

bottom-up materials fabrication approaches. It is usually assumed that calcination is an

effective solution, especially for thin films. This assumption has led to its application in

thousands of papers. We here test this assumption using a relevant and highly controlled

model system consisting of thin films of ligand-capped ZrO2 nanocrystals. Consistently with

carbonization, while Raman characterization fails to detect the ligands after calcination, EBS

characterization demonstrates that ~20% of the original carbons are left behind even after

calcination at 800C for 12hrs. By comparison plasma processing successfully removes the

ligands. Our growth kinetic analysis shows that the leftover carbon can significantly affect

interfacial properties.

We then employ plasma processing to remove ligands from synthesized colloidal

silicon nanoparticle (nc-Si) assemblies to form crack free thin films. We also compare the

Reactive Ion etching characteristics of these plasma processed thin films with single

crystalline silicon (sc-Si). The ligand free nc-Si thin films etch a rate twice as fast as sc-Si.

The faster etch rates are expected owing to the porous structure of the colloidal nanostructure

assemblies compared to sc-Si.

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Sun Jan 01 00:00:00 UTC 2017