Dear Dr.

To analyze the stable peeling behavior of an infinite film, the length is bound to a solid substrate, if the film is thin with a finite length that sticks to a solid substrate and we perform an analysis of the effect of the film's initial adhesion length, film stiffness, and film length a typical relationship between peel strength and separation distance at the loading point is obtained. As well as the morphology of the deformed membranes. As we find that the length of the initial adhesion has a significant effect on the peeling behavior. Different from the case of infinite thin films, whether the peeling process can be achieved in the steady state or not depends on the adhesion length of the film. If the film is long enough, the entire peeling process can be divided into an initial peeling phase, a transition phase, a stationary phase and an unstable peeling phase. The peak peeling strength of the facade does not necessarily occur in the steady state stage,



Dear Hazem Mahmoud Ali ,

The adhesion of the film on the substrate depends on the physical and chemical properties of both the thin film and the substrate. Here, in the two articles below you find some of these properties that could help you:

Regards

Dear Hazem Mahmoud Ali,

Thin film grown on polished substrate are subject to peel off mainly due to i) high substrate temperature (~400degC) and ii) higher growth rate (~20nm/s).

This happens due to high tensile stress along the lateral direction during growth.

To understand the adhesive force between the film and the substrate one can use peel tester which uses a metal dolly glued to the film and remove the dolly using force meter. The meter provides the amount of force when the dolly is lifted along with the film.

Also you can use nano indentation (a stylus is use to produce scratch on the top of the film) to analyze both the cohesive and adhesive force.

To avoid the film to be lifted off, you can decrease the rate of the growth with higher dilution of source chemicals/gas. Avoid rapid cooling of the substrate.

More later

Abul

Hazem Mahmoud Ali there are 3 main reasons thin films peel off from substrates. (1) chemical incompatibility - try sputtering or plasma coating which has higher energy coating than evaporation or use thin seed layers. (2) impurities on the substrate and (3) stress build up in thicker films - both can be addressed with substrate heating and vacuum conditions prior to and during coating. Hope this helps. Martin

Usually:

1- dirty substrate

2- high difference in thermal expansion coefficients of film and substrate (peel off during cooling down after deposition)

3- high stress in the film (e.g. sputtering at low distance with high power)

4- strong hygroscopy of film

5- chemical incompatibility (polar/non polar materials may have low sticking coefficient)

6- substrate morphology can play a role