Topological investigation of electronic silicon nanoparticulate aggregates using ultra-small-angle X-ray scattering
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The network topology of two types of silicon nanoparticles, produced by high energy milling and pyrolysis of silane, in layers deposited from inks on permeable and impermeable substrates has been quantitatively characterized using ultra-small-angle X-ray scattering, supported by scanning electron microscopy observations. The milled particles with a highly polydisperse size distribution form agglomerates, which in turn cluster to form larger aggregates with a very high degree of aggregation. Smaller nanoparticles with less polydisperse size distribution synthesized by thermal catalytic pyrolysis of silane form small open clusters. The Sauter mean diameters of the primary particles of the two types of nanoparticles were obtained from USAXS particle volume to surface ratio, with values of ~41 and ~21 nm obtained for the high energy milled and pyrolysis samples, respectively. Assuming a log-normal distribution of the particles, the geometric standard deviation of the particles was calculated to be ~1.48 for all the samples, using parameters derived from the unified fit to the USAXS data. The flow properties of the inks and substrate combination lead to quantitative changes in the mean particle separation, with slowly curing systems with good capillary flow resulting in denser networks with smaller aggregates and better contact between particles.
KeywordsUltra-small-angle X-ray scattering Semiconductor nanocomposites Network structures Fractals Printed electronics
This work was in part supported by the NanoPower Africa Project funded by United States Agency for International Development (USAID) through the Higher Education for Development (HED) office. The contents are the responsibility of the authors and do not necessarily reflect the views of HED, USAID, or the United States Government. GB, SC, and DKR acknowledge the financial support of LyondellBasell, LP, the National Science Foundation (CTS # 0626063 to Beaucage), and P&G Corporation. Additional funding to the UCT NanoSciences Innovation Centre was provided by the US Airforce Office of Scientific Research through the project “Nanoparticle Solutions for Printed Electronic Applications”, by the University of Cape Town Vice Chancellor’s Strategic Fund, and by the South African National Research Foundation (NRF) under focus area grant FA20064160004. The development of the printed silicon materials was supported by the South African Department of Science and Technology through its business unit the Innovation Fund under Technology Advancement Project T50055. ChemMatCARS Sector 15 is principally supported by the National Science Foundation/Department of Energy under grant number NSF/CHE-0822838. Use of the Advanced Photon Source was supported by the U. S. Department of Energy, Office of Science, Office of Basic Energy Sciences, under Contract No. DE-AC02-06CH11357.
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