Fig. 1.

The 4D EM for imaging phase reactions in a free-standing NW. (A) Green optical pulse enables the eutectic-related reaction of Au/GaAs NWs to be probed by a delayed electron pulse (generated by a nanosecond UV laser pulse) at a given time delay. (B) Scheme of free-standing NWs on substrate integrated in 4D EM (SI Appendix, Fig. S1). The laser heating pulse is incident upon the NW at a nearly vertical angle, while a series of eutectic-related events are captured by single-pulse methodology. (C) Projections of the NWs. The NWs were intentionally grown far apart from each other to exclude mutual perturbation during the measurement.