Dr Amanda Barnard: Semiconductor Nanoparticles

bentgalaxyΗμιαγωγοί

1 Νοε 2013 (πριν από 3 χρόνια και 9 μήνες)

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Dr Amanda Barnard:
Semiconductor
Nanoparticles
Semiconductor nanoparticles are an important
component in many emerging nanotechnologies,
and will become part of our lives in years to
come.
Many of these devices are will be exposed to the
environment, or eventually recycled.
Understanding the how exposure to different environmental conditions is likely to affect the
structure and properties of semiconductor nanoparticles (and ultimately their performance) will be
an important part of quantify assurance.

Silicon

Zinc Sulfide


Iron Sulfide


Silicon
Under the direction of Dr Amanda Barnard, the CSIRO VNLab is embarking on a new project to
develop environmentally sensitive structure/property relationships of silicon and silica
nanostructures.
While a number of materials have presented as candidates to replace silicon in modern electronics,
the enormous global investment in silicon-based semiconductor technologies means that each of
these emerging materials must interface with silicon for the foreseeable future.
Silicon nanoparticles and quantum dots are promising interface materials, particularly given that the
additional degrees of freedom associated with nanomorphology allow the nanostructures to be
made to specification.
Commencing in 2013, this project will explore the role of size, shape, composition and thermo-
chemical environment in tailoring the properties of silicon and silica nanoparticles and quantum
dots, using a range of advanced computational and theoretical techniques.
More details will be posted in the coming years.
[
related publications may be found here
]

Zinc Sulfide
Zinc sulfide (ZnS) nanoparticles are of interest for their
luminescent and catalytic properties which are useful in bio-
medical, electronic and photovoltaic devices.
However, ZnS nanoparticles may adopt either a cubic or
hexagonal crystal structure, and may undergo reversible and
irreversible phase transformations under ambient
conditions. This has implications for the material properties
and their biological and environmental significance.
These transformations are complicated as there are many
influential factors, and so this project, together with PhD
student Chris Feigl, was aimed at understanding how the size, temperature, pressure and chemical
regimes mediate the shape and phase of individual particles.
The results were used to show how the (temperature- and pressure-dependent) phase
transformation size was sensitive to the shape, and features such as the aspect ratio of nanorods or
the prevalence of polar facets. The introduction of polar facets has implications for the catalytic
activity, and the way that the particles interact with their surroundings.
The team also considered the relative stability of particles with mixed phases, such as non-
equilibrium structures such as tetrapods, and core/shell particles involving an amorphous
component. This was the first time that thermodynamic cartography had been used to study
composite or amorphous materials.
[
related publications may be found here
]

Iron Sulfide
The cubic pyrite polymorph of iron
disulfide (FeS
2
) has been attracting
considerable attention, as it shows
promise for solar energy conversion
devices, solid-state batteries, and
catalysis.
This project was one of the earliest
studies using thermodynamic
cartography, to understand how the
temperature and supersaturation of sulphur may be used to anticipate or control the morphology.
Since pyrite nanoparticles are also associated with biomineralization from a sulfate-reducing
subset of the proteobacteria, the study was also able to draw parallels with these naturally occurring
nanoparticles.
By adsorbing water on the surfaces, it was possible model the shape and stability as a function of
humidity, and gain some basic understanding of why biogenic pyrite nanoparticles have a different
morphology to nanomineral samples, or particles grown in the lab.
[
related publications may be found here
]

Relevant Publications
Silicon
• A.S. Barnard, S.P. Russo, Structure and energetics of single-walled armchair and zigzag silicon
nanotubes, J. Phys. Chem. B, 107 (2003) 7577
Zinc Sulfide
• C.A. Feigl, S.P. Russo, A.S. Barnard, Modelling nanoscale cubic ZnS morphology and
thermodynamic stability under sulphur-rich conditions, Cryst. Eng. Comm. (2012) DOI:
10.1039/C2CE25814E
• C.A. Feigl, S.P. Russo, A.S. Barnard, Modelling polar wurtzite ZnS nanoparticles: the effect of
sulphur supersaturation on size- and shape-dependent phase transformations, J. Mater.
Chem. 22 (2012) 18992–18998
• C.A. Feigl, A.S. Barnard, S.P. Russo, Size- and shape-dependent phase transformations in
wurtzite ZnS nanostructures, PhysChemChemPhys, 14 (2012) 9871–9879
• C.A. Feigl, A.S. Barnard, S.P. Russo, Comparative density functional theory investigation of
the mechanical and energetic properties of ZnS, Molec. Simulat. 37 (2011) 321
• A.S. Barnard, C.A. Feigl, S.P. Russo, Morphological and phase stability of zinc blende,
amorphous and mixed core-shell ZnS nanoparticles, Nanoscale, 2, (2010) 2294–2301
• C.A. Feigl, S.P. Russo, A.S. Barnard, Safe, stable and effective nanotechnology: Phase
mapping of zinc sulfide nanoparticles, J. Mater. Chem. 20 (2010) 4971–4980
Iron Disulfide (Pyrite)
• A.S. Barnard, S.P Russo, Modeling nanoscale FeS
2
formation in sulphur rich conditions, J.
Mater. Chem. 19 (2009) 3389–3394
• A.S. Barnard, S.P Russo, Morphological stability of pyrite FeS
2
nanocrystals in water, J. Phys.
Chem. C, 113 (2009) 5376
• A.S. Barnard, S.P Russo, Modeling the environmental stability of FeS
2
nanorods, using
lessons from biomineralization, Nanotech. 20 (2009) 115702
• A.S. Barnard, S.P. Russo, Shape and thermodynamic stability of pyrite FeS
2
nanocrystals and
nanorods, J. Phys. Chem. C, 111 (2007) 11742