Effect of doping with niobium on the bond strength of silicon

Thermal expansion of undoped and Nb-doped silicon was measured between room temperature and 600 K. Doping with niobium was found to notably reduce the thermal expansion coefficient of Si throughout the temperature range examined. The thermal-expansion data were used to calculate the Debye characteristic temperature and mean-square dynamic displacements of atoms from the equilibrium position. The results demonstrate that Nb consolidates the crystal lattice of silicon-raises the Debye temperature and reduces dynamic atomic displacements over the entire temperature range examined. The conclusion is drawn that doping with Nb, increasing bond strength and, hence, suppressing possible structural transformations, must enhance the thermal stability of Si.