Analysis of Adhesion Strength Between Silver Film and Substrate in Plain Silver Surface Plasmon Resonance Sensor

Recently, plain silver surface plasmon resonance (SPR) sensor has been studied extensively due to its high sensitivity and desirable chemical stability in types of liquid environments. However, its physical stability was not reported yet. In this work, we explored the physical stability of the plain silver SPR sensor by analyzing its adhesion strength between the outmost silver film and substrate. After being divided into 1 x 1 mm grids by an adhesion cross-cut tester, the adhesion of the silver film was tested by Scotch adhesion testing tape. Under Zeiss optical microscope, no grid with a peeled-off area is found in the film, which proves adhesion between the silver film and substrate is firm. In contrast, a single silver film deposited on a substrate with chromium as the adhesion layer can be peeled off in all the grids. The comparative study shows that the gold layer can both promote the chemical and physical stability of the plain silver SPR sensor.