Adhesion of thin films is a macroscopic indicator, and usually referring to the degree of binding between the film and the substrate. During the plating process of the DLC film, it was found that the film was peeling off the substrate, and the most common types are: One is that the film is not well bonded to the substrate, and there is no transition region between the film and the substrate. When the external force is greater, the film completely peeled off the substrate. The second type is that a transition region has been formed between the film and the substrate, and has a high bonding strength. However, due to a certain reason, the internal stress of the film is too large, the film is damaged, and then demolding.
The factors associated with the first type of film release are: the type of substrate material, the cleanness of the substrate surface, and the energy of charged particles. For different types of substrates, DLC films have different energy requirements for the transition zone between them, and the binding forms between the molecules are different, so the stability is different. When the surface of the substrate is not sufficiently clean, and some impurity molecules are adsorbed on the surface of the substrate or the energy of the charged particles is too low, the bonding force between the DLC film and the substrate is reduced, and the film is peeled off from the substrate as a whole. When the deposition device is determined, the energy of the deposited particles is only related to the voltage of the main discharge circuit, and the energy of the charged particles can be obtained by selecting the main circuit voltage reasonably.
Of the several substrates tested, the adhesion of the titanium substrate was the best, followed by the silicon substrate, followed by the germanium substrate, and the worst for the C-containing metal substrate, and the transition layer is needed. The phenomenon of film release due to film stress factors, the hardness and temperature of the substrate material are different, and the phenomenon is also different. And the three common phenomena are:
(1) When the hardness of the substrate material is low, and the film is peeled off from the substrate, the transition layer between the film and the substrate has been formed and has a higher adhesion, so that the surface of the substrate film is peeled off. For example, when a DLC film is plated on a Ge or Si substrate, such a phenomenon often occurs, and the surface of the substrate is damaged, and the uniform distribution diameter of spot is less than 0.1mm. The spot size is inverse relationship to the hardness of the substrate diameter, high hardness, while spot diameter decreases obviously.
(2) When the hardness of the substrate material is high, the film is stripped from the substrate and there is a residual film on the base surface, and it cannot be removed by the conventional cleaning method. This also indicates that the transition layer between the film and the substrate has formed and has high adhesion, because the stress of the film causes the film to be removed.
(3) When the temperature of the substrate is too high, the rupture of the film does not occur between the interface of the film and the substrate, but in the film, and the peeled thin film is square and not on the same surface.
From the above three common phenomena, the DLC film is plated by pulsed vacuum arc ion plating, and the transition layer can be formed between the film and the substrate, and it has high adhesion, which is the advantage of the ion plating.