Nonlinear Responses of Electronic-Excitation-Induced Phase Transformations in GaSb Nanoparticles

We studied electronic-excitation-induced phase transformations in nanoparticles using transmission electron microscopy. GaSb particles excited by 75 keV electrons transform to two phases consisting of an antimony core and a gallium shell or an amorphous phase, or remain in the original crystalline phase, depending on particle size and/or temperature. It is suggested that such nonlinear responses of the phase transformations may arise from synergistic effects of bond instability, localized excitations, enhanced diffusivity, or thermal equilibrium in reactions.

Figure 1

An example of the structural change by excitation in approximately 20 nm-sized particles kept at 423 K. (a) A BFI of particles, and (a′) the corresponding SAED before excitation. (b) The same area after excitation for 240 s, and (b′) the corresponding SAED.

Figure 2

The behavior by excitation in approximately 20 nm-sized particles kept at 443 K, (a) and (a′) before excitation, (b) and (b′) after excitation for 240 s.

Figure 3

A behavior by excitation in approximately 20 nm-sized particles at 293 K, (a) and (a′) before excitation, (b) and (b′) after excitation for 240 s.

Figure 4

A behavior by excitation in approximately 30 nm-sized particles at 423 K, (a) and (a′) before excitation, (b) and (b′) after excitation for 240 s.

Figure 5

An example of the structural change by excitation in approximately 10 nm-sized particles kept at 423 K, (a) and (a′) before excitation, (b) and (b′) after excitation for 240 s.

Figure 6

An example of the structural change by excitation in approximately 10 nm-sized particles kept at 293 K, (a) and (a′) before excitation, (b) and (b′) after excitation for 240 s.

Figure 7

Summary of the results on phase transformations induced by excitation as functions of temperature and size. The double circle, circle, and square indicate the two-phase separation consisting of a crystalline antimony core and a liquid gallium shell, the formation of an amorphous phase, and the original crystalline phase, respectively.