Abstract
There are two research topics in this work. The first one is the investigation on water layers on free-standing surfaces. Herein, it was observed that a 100–170 nm-thick water layer formed on the free-standing Si3N4 films in microchannel chips designed for observing liquid samples by transmission electron microscopy (TEM). This water layer is surprisingly stable against the surface tension of water, and its thickness is beyond expectation. In this work, the thickness and the structure of water layers were analyzed by electron energy loss spectroscopy (EELS) and the quantitative particle counting method. Results show that the thickness of water layers is insensitive to microchannel gap heights, particle concentrations, and particle sizes. Furthermore, the microchannel was opened after forming water layers. It was found that the water layers formed only on free-standing Si3N4 films, and there is no water layer formed on the Si3N4 deposited on a Si substrate. Consequently, the water layer and the free-standing Si3N4 film together sandwiched by the air were taken as a system remaining at a constant total thickness. The Casimir-Lifshitz effect may have played a role in forming and/or holding stable of these free-standing layer systems. The second topic in the work is focused on self-assembled tin dioxide for resistive-switching devices. Resistive random access memory is a promising device compared to current mainstream memories. In this study, a forming-free resistive switching structure, Ag/tin-doped indium oxide (ITO)/SnO2-x (defined as SnO2 with oxygen vacancies)/SnS/Mo was demonstrated with nonlinear current–voltage characteristics, low set/reset voltage, and high on-state to off-state ratio. The interface between ITO and self-assembled SnO2-x contributes to the resistive-switching behavior. Besides, a p-n junction of p-SnS/n-SnO2-x acts as a selector. Hence, it shows great potential for low-power devices and solving the sneak path problem in cross-bar memory arrays. Furthermore, a micro-/nano-structured resistive switching device was demonstrated successfully.