Figure 6
Cross-sectional SEM image of the emitter structures after annealing at 1300 °C for 6 h (a) and 1400 °C for 1 h (b) under 2×10−2 mbar vacuum pressure and encapsulated by the Ar atmosphere. Note that a thin Au/C layer is sputter deposited on the sample prior to the FIB milling to prevent charging of the substrate during imaging. White dotted boxes indicate visible cross-sectional areas of voids formed after annealing.
