Drilling holes in silver ionic conductor using the high current density STEM probe
Authors: Fan Chenggao , Howie A. , Yuan Jun , Walsh C.A. , Wang Xueqin , Meng Guangyao 
Published: June 2020

High current density STEM probe can be used to drill holes and to draw wonderful pictures through samples such as metal β-aluminas, feuoride and titaniun oxide etc. Resently, we have also found that the high current density subnanometer probe in the HB-5 and HB-501 STEM rapidly drills small holes in samples of Ag ionic conductor (Agl+XZr2Si2P3−xO12,x between 0 and 3) from which silver filaments can be easily extruded under the irradiation of electron beam. By means of electron diffraction, EDX, MAP pattern,HREM and EELS,we discovered that the filaments are absolute pure, and there are not any element distribution of Zr,Si,P and O on the filaments, except for a little carbon contamenation. Most of the Ag filaments were single crystal, and others were polycrystal with the length of crystal grains over 100nm. It would interrupt the extrusion to remove the electron beam, but if the irradiation restore in several seconds the Ag filament will be continued to extruse slowly, otherwise never again for the root of the filament has crystallized quite well and solidly connected with the sample grain. We suggest that there exist lot of miniature tunnels in the sample for the Ag filaments do not contain any other elements, and the filament must be formed by the collection of some tunnels. Whether the hole-drilling is easily and the dimension of holes are related to the thickness, drill tine and beam current intensity, but they mainly depend on the content of silver in the drilling region. The less the content of Ag, the easier the hole- drilling. We can not drill any hole in the silver filaments and Ag particles on the surface of sample grains. The holes are easily contaminted for the EELS we obtained was almost belong to carbon as the tine passed. A silver filament on the right had been extruded from a sample grain as shown in Fig.1a, and the root of the silver filament was connected with a pear-shaped Ag-rich region. When the electron beam gradually approached near the edge of the pear-shaped region from the edge of the grain, we found that the dimension of holes increased from 10nm to 30 nm. But we could not obtain holes with more than 10 nm in diameter after entering the pearshaped region. As soon as the electron probe entered the centre of the Ag-rich region, the pear-shaped region was broken into two parts and a hole with 26 nm in diameter appeared. Meanwhile, a new Ag filament with 24 nm in diameter was extruded from the left broken part shown in Fig.1b. It was proved by EDX that there was not any content of silver in this hole-drilling region. The Ag filament on the right was still connected with the right broken part, and it was not continued to extrude. The nearer to the root of the Ag filament, the more difficult to drill holes in the right part,e.g., it spent 180 seconds to drill a hole with only 5 nm in diameter where 40 nm to the root of the filament. Holes could not be drilled in such sample grains in which x is not between 0 and 3 and any Ag filaments can not be extruded.