Growth of Si whiskers by MBE: Mechanism and peculiarities

We analyzed the stress-driven mechanism of MBE Si whisker growth. It is shown that the driving force for MBE whisker growth is determined by the relaxation of elastic energy stored in the overgrown layer L_s due to gold intrusion. In this case the supersaturation is determined by the interplay between elastic stresses and surface energy. The latter is considerably decreased due to decoration of the Si surface by gold resulting in formation of thin liquid Si/Au eutectic layer. This suggests that in our case the Si supersaturation is not an independent growth parameter as it is in the chemical vapor deposition growth method. Instead it is determined by stress in the overgrown Si layer. This approach allows us to explain quite well the growth kinetic and the relationship between the radius and the length of the whiskers. The whisker growth in our case can be considered as a stress relaxation mechanism, where the stress relaxation occurs due to transition from the two-dimensional system to the three-dimensional one.