Nanostructured Silicon Containing Materials Derived from Solid State Pyrolysis of Sililated Polyphosphazene Derivatives

Pyrolysis of the silicon-containing polymer {(NP[O₂C₁₂H₈])_0.5[NP(OC₆H₄·SiMe₃)₂]_0.5−x [NP(OC₆H₅)·(OC₆H₄SiMe₃)] _x } _n (1) (x = 0.13), (2) (x = 0.3), and (3) {(NP[O₂C₁₂H₈])_0.5[NP(OC₆H₄SiMe₂Ph)₂]_0.2·[NP(OC₆H₅)(OC₆H₄SiMe₂Ph)]_0.3} _n in air at 600 °C, 800 °C and 1000 °C results in the formation of nanostructured SiP₂O₇, along with P₄O₇. The morphology as well as the size and shape of the nanostructures is observed to depend on both the mole fraction of silicon, the polymer precursor and the temperature of the pyrolysis. The first observation of nanotube formation using polyphosphazenes as a template, was noted during pyrolysis of the precursor (1) at 600 °C. The surface morphology of the Si or SiO₂, studied by AFM, depends strongly on the crystallinity of the wafer surface used during deposition. Regular lance or point-like structures were obtained from SiP₂O₇ deposited on SiO₂ from its precursor (2). The unique formation of micro and nanostructured SiP₂O₇ is discussed and a mechanism of the formation of the nanostructured materials is proposed.