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Four-Dimensional Probing of Phase-Reaction Dynamics in Au/GaAs Nanowires
Bin Chen1, Xuewen Fu2, Mykhaylo Lysevych
1Center for Ultrafast Science and Technology, School of Chemistry and Chemical Engineering , Shanghai Jiao Tong University , Shanghai 200240 , China.
Abstract:
Nanoeutectic phase reaction covers the fundamental study of a chemical and physical reaction of multiple phases at the nanoscale. Here, we report the direct visualization of phase-reaction dynamics in Au/GaAs nanowires (NWs) using four-dimensional (4D) electron microscopy. The NW phase reactions were initiated with a pump laser pulse, while the following dynamics in the Au/GaAs NW was probed by a precisely time-delayed electron pulse. Single-pulse imaging reveals that the cubic zinc-blende NW presents a transient length increase within the time duration of ∼150 ns, giving the appearance of intermediate phase reactions at an early stage. A final length reduction of the NW is observed after the phase reactions have fully ended. In contrast, only length reduction is seen throughout the entire process in GaAs/AlGaAs core-shell and hexagonal wurtzite GaAs NWs. The reasons for the above intriguing phenomena are discussed. The eutectic-related phenomena in both zinc-blende and wurtzite materials offer a comprehensive understanding of phase-reaction dynamics in polytypic structures commonly available in compound semiconductors.
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