Why Does XPS Need UHV?

• Contamination of surface

• XPS is a surface sensitive technique.

• Contaminates will produce an XPS signal and lead to incorrect analysis of the surface of composition.

• The pressure of the vacuum system is ≤ 10^-9 Torr

• Removing contamination

• To remove the contamination the sample surface is bombarded with argon ions ( Ar⁺ = 3KeV).

• heat and oxygen can be used to remove hydrocarbons

• The XPS technique could cause damage to the surface, but it is negligible.