Plasma interaction with Zn nano layer on organic materials for analysis of early stage of inorganic/organic hybrid multi-layer formation

Interactions between Ar-O2 mixture plasmas and Zn thin film on Tris(8-hydroxyquinolinato) aluminium (Alq3) were investigated on the basis of nondestructive depth analyses of chemical bonding states at the Zn/Alq3 interface via hard x-ray photoelectron spectroscopy (HXPES). The HXPES Zn 2p3/2 spectrum measured at take-off angle (TOA) = 20° clearly shows significant increase of the Zn–O bond after Ar–O2 mixture plasma exposure. This result indicated that the Ar–O2 mixture plasma exposure has made it possible to form ZnO thin films on organic materials due to oxidation of Zn thin film. The HXPES C 1 s spectra measurement at TOA = 80° and 42° indicated that the Ar–O2 mixture plasma exposure does not give significant damage to the chemical bonding states in regions up to about 20 nm from the Zn/Alq3 interface. Whereas, the results of HXPES measurement at a TOA = 20° suggested that the oxygen radicals through the Zn thin film cause oxidation of Alq3 at shallower region up to about a few nm from the interface.

► Chemical bonding states of Ar–O2 plasma exposed Zn/Alq3 was investigated by HXPES.
► Oxygen radicals from Ar–O2 plasma can pass through Zn film (thickness 5 nm).
► Ar–O2 plasma exposure makes it possible to form ZnO on Alq3.
► The plasma exposure causes oxidation only in a few nm from the Zn/Alq3 interface.