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

Abstract: 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.