For metals, it depends on material and parameters of the oxide layer (composition, thickness, structure, etc.). It can occur (theoretically) for noble metals, but nevel for aluminium, as I know.

Thanks Mikhail Slobodyan

Do you have any idea about MoS2. The thickness is one mono-layer (0.8nm)?

Unfortunatly, I am not a specialist in this area. I work in the field of welding of metals and alloys

Oxidation is a chemical reaction. A vacuum will remove O2 from the space around the target, but it won't un-do the reaction. That will require another chemical reaction with a deoxidizer or antioxidant.

Will depend on the material. A reducing agent will remove surface oxide (so PdO is reduced to the metal by H2) as will an argon ion etch (as found in XPS). For aluminum, amalgamating it with mercury removes the oxide layer and the Al reacts with water in the same manner that sodium does.

Strictly speaking, oxidation is a reversible process. However, there is no guarantee that the shape of the material after reduction will remain the same as it was before oxidation. For example, the oxidation of MoS2 leads to the formation of volatile molybdenum oxides. It is clear that they can evaporate and, after reduction, condense in another geometrical place.

Oxidation depends on the nature of the material. I attached two pdf files.

The first one is talking about the irreversible oxidation of organic compounds and the other one tells about the chain of oxidation and reduction process is reversible for graphene quantum dots.

I hope this might be useful for you..

Good Luck..

For me, we are in the Semiconductor industry and it could not get the oxidized film back unless to use etching not in a vaccum system.

I would agree with Alexander N Titov answer. And I have to note that the reversibility of oxidation process is used in metal-oxide semiconductor gas sensors. For example, high lattice-oxigen mobility in TiO2 at high temperature was used for air/fuel ratio measurements at automobile exhost. And as I remember, ZnO can be reduced to Zn for several surface monolayers by reducing gas at temperature about 500 C.

Thank you all for your concern and giving thoughtful comments.

We can't get back the oxidation from the sample once the reaction has done. Unless otherwise we do some other methods. but we can remove from the deposition chamber.

2D-MoS2 atomic layers have a strong potential[1] to be used as 2D electronic (reversible chemi-resistive[2,3], room temperature, gas) sensors[1-4].

1. Charge-transfer-based Gas Sensing Using Atomic-layer MoS2 https://www.nature.com/articles/srep08052.pdf

2. A review on chemiresistive room temperature gas sensors based on metal oxide nanostructures, graphene and 2D transition metal dichalcogenides https://link.springer.com/content/pdf/10.1007%2Fs00604-018-2750-5.pdf

3. Adsorption of O3, SO2 and SO3 gas molecules on MoS2 monolayers: A computational investigation https://www.sciencedirect.com/science/article/pii/S0169433218331076?via%3Dihub

4. Highly selective and reversible NO2 gas sensor using vertically aligned MoS2 flake networks http://iopscience.iop.org/article/10.1088/1361-6528/aade20/meta

Metal oxides are a product of a chemical reaction in which an oxygen atom is attached to a metal atom. The binding energy of these atoms depends on the "affinity" of the metal to oxygen. To break such a bond, the vacuum (if this vacuum is “pure”) cannot even “sublimate” oxygen from oxide. In any case, the prerequisites for this, I do not see.

To Igor Taran.

Dear Igor,

The energy of each chemical compound is the final value. This means that at a nonzero temperature, there is a nonzero probability of its decay. This probability leads to the presence of the so-called dissociation pressure — the equilibrium pressure of the volatile component, in our case oxygen, above the surface of the material. If the content of the component (oxygen) in a vacuum is below the equilibrium dissociation pressure, then exposure in such a vacuum will lead to the oxide reduction reaction. Since the dissociation pressure is determined by the thermodynamic probability of a decay reaction, it increases exponentially with heating. For example, if you take copper and heat it to a temperature of about 150-170 C, then in equilibrium it will provide you with oxygen pressure not higher than 10 ^ -20 Torr. If you put copper oxide in the same volume, and heat it to a temperature of, say, 500 C, you will see that your copper will oxidize at 150 C, and copper oxide at 500 C will be reduced.