Young's modulus of PS/CeO2 composite with core/shell structure microspheres measured using atomic force microscopy

Organic-inorganic composite microspheres with PS as a core and CeO2 as a shell were synthesized by in situ chemical precipitation method. The size of PS core was 117, 163, 206, and 241 nm, respectively, and the shell thickness was about 10 nm. The CeO2 shell was composed of a large number of nanoparticles, of which the size was 4-6 nm. Atomic force microscopy was employed to probe the mechanical properties of core-shell structured ceria-coated polystyrene (PS/CeO2) composite microspheres. On the basis of Hertz's theory of contact mechanics, compressive moduli were measured by the analysis of force-displacement curves captured on themicrosphere samples. For a fixed CeO2 shell thickness, the Young's modulus of composite microspheres increased with an increase of PS core size. The calculated Young's moduli (E) values of composites for 136, 185, 242, and 261 nm in diameter were 5.78 +/- 0.9, 7.23 +/- 1.3, 11.46 +/- 1.7, and 14.54 +/- 1.4 GPa, respectively. The results revealed the effect of the CeO2 shell on the elastic deformation of the PS core. This approach will provide fundamental insights into the actual role of organic/inorganic core/shell composite abrasives in chemical mechanical polishing.