(Invited) Operando Scanning Electron and Photoelectron Spectromicroscopy to Study the Nucleation and Growth Phenomena in Liquid and Reactive Solid Electrolytes: The Technique Development

Abstract

Nucleation and growth (NG) phenomena play a central role in a variety of applications spanning from the back end of line (BEOL) microfabrication to environmental remediation and energy devices performance. Therefore, the development of analytical metrologies, capable to access these phenomena with the high chemical, spatial and temporal resolution is amongst the key tasks of the research community. Probing nucleation and growth phenomena in situ, using traditional high analytical power tools such as SEM, XPS, AES, SPEM, and PEEM, under realistic sample environments, is a great aim but also an experimental challenge due to the apparent sample-to-detector “pressure gap”. Implementation of the electron transparent membranes that separate the reactive, liquid, or dense gaseous sample environments from the high vacuum instrumentation, in principle, resolves this impediment thus the standard analytical surface science equipment can be used. The sample and or device, therefore, need to be covered or encapsulated with a mechanically robust electron transparent impermeable membrane. The thickness of such a membrane defines the energy range and broadening of the transmitted electrons and, therefore, the thinnest membranes such as those made of 2D materials are desirable. Here, using variable pressure SEM, we exemplify the sensitivity of electrochemically driven NG processes to the composition of the ambient environment. Using model liquid electrolytes, we review the capabilities, advantages, and limitations of the graphene membrane-based liquid cells to probe NG processes with electron spectromicroscopy. In particular, we discuss graphene-cupped single orifice and microchannel arrays (MCA), and their applications for electrochemical polarization, nucleation, and growth studies using SEM, AES, SPEM, and PEEM. In addition to local spectromicroscopy, MCA-like designs enable application of high throughput combinatorial data mining algorithms to collect multi-dimensional/ hyperspectral datasets. The experimental artifacts and major limitation of the technique related to radiation damage of the sample will be discussed.