Scientists at University of Wisconsin−Madison have recently reported lead sulfide (PbS) nanowires with morphologies resembling “pine trees” synthesized via chemical vapor deposition (CVD) and reestablished the screw dislocation nanowire growth mechanism.
In contrast to previous PbS nanowire growth via CVD reactions with or without intentional metal catalysts, this tree morphology is formed by a combination of screw dislocation-driven nanowire growth that produced long and twisted “trunk” nanowires and a simultaneous self-catalytic vapor-liquid-solid (VLS) mechanism that resulted in epitaxial “branch” nanowires. Lead particles generated in situ are suggested to be a self-catalyst to enable VLS growth of the branches that grow epitaxially off the trunk.
The optimum conditions for synthesizing PbS nanowire pine trees have been investigated in this research with detailed studies of morphology changes under various hydrogen, temperature, pressure, and substrate conditions. The successful growth of nanowires driven by screw dislocations requires two basic ingredients: the creation (seeding) of dislocations and a suitably low supersaturation condition for promoting dislocation-driven growth over layer-by-layer growth and other growth modes.
The ability to control the formation of hierarchical nanostructures with increasing structural complexity, as seen in these pine tree nanowires, can potentially empower increasing functionalities and enhance applications such as solar energy conversion and 3-D nanoelectronics.
This paper can be found at J. Am. Chem. Soc., 2009, 131 (45), pp 16461–16471
In contrast to previous PbS nanowire growth via CVD reactions with or without intentional metal catalysts, this tree morphology is formed by a combination of screw dislocation-driven nanowire growth that produced long and twisted “trunk” nanowires and a simultaneous self-catalytic vapor-liquid-solid (VLS) mechanism that resulted in epitaxial “branch” nanowires. Lead particles generated in situ are suggested to be a self-catalyst to enable VLS growth of the branches that grow epitaxially off the trunk.
The optimum conditions for synthesizing PbS nanowire pine trees have been investigated in this research with detailed studies of morphology changes under various hydrogen, temperature, pressure, and substrate conditions. The successful growth of nanowires driven by screw dislocations requires two basic ingredients: the creation (seeding) of dislocations and a suitably low supersaturation condition for promoting dislocation-driven growth over layer-by-layer growth and other growth modes.
The ability to control the formation of hierarchical nanostructures with increasing structural complexity, as seen in these pine tree nanowires, can potentially empower increasing functionalities and enhance applications such as solar energy conversion and 3-D nanoelectronics.
This paper can be found at J. Am. Chem. Soc., 2009, 131 (45), pp 16461–16471
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