In situ observation of the tip shape of Co-Ge liquid alloy ion sources in a high-voltage transmission electron microscope

For in situ observation in a 1 MeV TEM Co-Ge liquid alloy ion soures (LAISs) were mountet to a special specimen holder revealing the formation of the field-stabilizes Co-Ge liquid alloy cone, the change in the tip shape as a function of the ion emission current, spatial shifts of the liquid alloy cone, and microdroplet emission from Co-Ge LAISs. This has facilitated the better understanding of the ion and microdroplet emission process from Co-Ge LAISs in a large range of ion current. Below the onset voltage the shape of the tip covered with the liquid Co-Ge alloy is spherical. At the onset voltage the Tayler cone is formed. A jetlike protrusion at the cone vertex. The cone half-angle a decreases and the jet length l increases with increasing emission current le. Linear dependences of a and l on Ie are found. Emission of microdroplets is observed at the shanks behind the Tayler cone. The radius of microdroplets varied between 0.035 and 10 µm. These microdroplets are emitted in time intervals of about 0.1 s and more.