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

TL;DR

This study compares rubidium and cesium ion sources to gallium in scanning ion microscopy, showing Rb$^+$ and Cs$^+$ produce higher secondary electron yields and different ion signal characteristics, promising improved imaging performance.

Contribution

It introduces ultracold Rb$^+$ and Cs$^+$ ion sources for scanning ion microscopy and compares their performance with traditional Ga$^+$ systems.

Findings

Rb$^+$ and Cs$^+$ yield higher secondary electrons than Ga$^+$.

Cs$^+$ ion signals are dominated by secondary ions.

Rb$^+$ and Cs$^+$ produce different ion signal profiles.

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.