ASE deposition is a technology that builds up atoms layer by layer.
This technology is based on the RF sputter method. Electrical and mechanical vibrations are blocked externally, and single crystal targets are used internally to allow atoms to be stacked on the substrate one layer at a time.
Using this technology, it is possible to produce high-quality copper thin films on various substrates including PTFE, sapphire, and glass.
Oxidation can deteriorate the properties of copper that are critical for its use, particularlyinthesemiconductorindustryandelectro-opticsapplications1–7.Thishas prompted numerous studies exploring copper oxidation and possible passivation strategies 8.
In situ observations have, for example, shown that oxidation involves stepped surfaces: Cu2O growth occurs on flat surfaces as a result of Cu adatoms detaching from steps and diffusing across terraces9–11.
But even though this mechanismexplainswhysingle-crystallinecopperismoreresistanttooxidationthan polycrystalline copper,the factthatflat copper surfaces can be free of oxidation has not been exploredfurther. Here we reportthe fabricationof copperthinfilms that are
semi-permanentlyoxidationresistantbecause theyconsistofflat surfaceswithonly occasional mono-atomic steps.
First-principles calculations confirmthat mono-atomic stepedges are as impervious to oxygenas flat surfaces and that surface
adsorption ofO atoms is suppressed once anoxygenface-centred cubic (fcc) surface site coverage of 50% has been reached.
These combined effects explain the exceptional oxidationresistance of ultraflat Cu surfaces.