Effect of doping on the modification of polycrystalline silicon by spontaneous reduction of diazonium salts

Highlights: • Spontaneous grafting of aryl diazonium salts on polycrystalline silicon surfaces. • Effect of the nature and level of doping on the efficiency of the functionalization. • The grafting process was more efficient on PolySi substrates than on monosilicon. • Influence of the crystal structure and grain boundaries on the modification procedure. • Role of the reducing power of the substrate on the grafting procedure. - Abstract: The chemical modification of doped polycrystalline silicon materials (N+, N++ and P++) and silicon (1 0 0) and (1 1 1) used as references is investigated by spontaneous reduction of diazonium salts. The effectiveness of the grafting process on all polySi surfaces is shown by AFM and XPS analyses. The effect of substrate doping on the efficiency of the electrografting process is compared by using the thicknesses of the deposited organic films. For a better accuracy, two methods are used to estimate the thicknesses: XPS and the coupling of a O₂ plasma etching with AFM measurement. Structural characteristics of the poly-Si films were investigated by Scanning Electron Microscopy and X-ray diffraction to find a correlation between the structure of the material and its reactivity. Different parameters that could have an impact on the efficiency of the grafting procedure are discussed. The observed differences between differently doped silicon surfaces is rather limited, this is in agreement with the radical character of the reacting species