Rubidium and cesium ion-induced electron and ion signals for scanning ion microscopy applications

Scanning ion microscopy applications of novel focused ion beam (FIB) systems based on ultracold rubidium (Rb) and cesium (Cs) atoms were investigated via ion-induced electron and ion yields. Results measured on the Rb$^+$ and Cs$^+$ FIB systems were compared with results from commercially available gallium (Ga$^+$) systems to verify the merits of applying Rb$^+$ and Cs$^+$ for imaging. The comparison shows that Rb$^+$ and Cs$^+$ have higher secondary electron (SE) yields on a variety of pure element targets than Ga$^+$, which implies a higher signal-to-noise ratio can be achieved for the same dose in SE imaging using Rb$^+$/Cs$^+$ than Ga$^+$. In addition, analysis of the ion-induced ion signals reveals that secondary ions dominate Cs$^+$ induced ion signals while the Rb$^+$/Ga$^+$ induced signals contain more backscattered ions.