Interface roughness of plasma deposited polymer layers

The interface roughness of adjacent films which were made by plasma polymerization of hexamethyldisiloxane were investigated. Multilayered structures were made by using different plasma conditions in alteration resulting in different mechanical properties within each layer. Scanning force microscopy on the face side of fractured pieces of the multilayer structures revealed a significant phase contrast between the layers. The direct visualization of the interface using the mechanical contrast between layers allowed the estimation of the interfacial roughness. We found that the interfaces between hexamethyldisiloxane films deposited at a radio frequency (RF) input power of 90 W in the presence of oxygen on top of films made by 48 W without oxygen resulted in an interface roughness of ≈10 nm. In the reverse case, a significantly lower interface roughness of ≈3 nm was determined. We attribute the increase of the interfacial roughness compared to the surface roughness being <1 nm to partial etching of the films by the subsequent deposition process. A key role in the appearance of higher interface roughness plays the RF-input power that determines the cross linking density and the hydrocarbon content in layers.

Graphical abstractScanning force microscopy revealed an asymmetric interface roughness in films which were made by plasma polymerization of hexamethyldisiloxane.Figure optionsDownload full-size imageDownload high-quality image (49 K)Download as PowerPoint slideResearch highlights► Scanning force microscopy revealed an asymmetric interface roughness of stacked layers of plasma polymerized films made from HMDSO. ► A key role in interface roughness plays the RF-input power and the presence of oxygen. ► Film defects have been imaged using the phase contrast mode.