The hydrostatic pressure dependence of the diffusivity of B and Sb in Si and of B in Si89Ge11 was measured. The diffusivity of Sb in Si was retarded by pressure (figure 5), characterized by an apparent activation volume of VSb = 0.06 times the Si atomic volume, Ω. The diffusivity of B was enhanced by pressure (figure 6), characterized by an apparent activation volume, VB, of –0.16Ω. The diffusivity of B in strain-relaxed Si89Ge11 was imperceptibly pressure-dependent; characterized by an apparent activation volume of 0.03Ω. The VB in Si was close to the activation volume for the interstitialcy mechanism calculated for B in Si by using ab initio methods. The VSb value was close to values inferred from atomistic calculations for a vacancy mechanism. A phenomenological thermodynamic treatment of diffusion under hydrostatic and non-hydrostatic stress was developed for sample configurations in which virtually all point defect equilibration occurred at the free surface of a hydrostatically or biaxially strained thin film stack. Relationships were predicted between the effects of hydrostatic and biaxial stress on diffusion normal to the surface. The prediction for Sb diffusion agreed reasonably well with the measured behavior of Sb diffusion in biaxially strained Si and Si-Ge films, lending additional supported to the conclusion that the vacancy mechanism dominated Sb diffusion, and supporting the non-hydrostatic thermodynamic treatment. The same analysis was used to compare hydrostatic B results with ab initio calculations and with literature values for the biaxial strain effect on diffusion. Predictions of the effect of biaxial strain on diffusion parallel to the surface were made using the results.Pressure and Stress Effects on the Diffusion of B and Sb in Si and Si-Ge Alloys. M.J.Aziz, Y.Zhao, H.J.Gossmann, S.Mitha, S.P.Smith, D.Schiferl: Physical Review B, 2006, 73[5], 054101 (20pp)

Figure 6

Intrinsic Diffusivity of B in Si

(Annealed for 1h at 810C)