The possibility to grow long (up to several microns) GaAs nanoscale whiskers on the GaAs(111)B surface activated by Au by magnetron sputtering deposition is demonstrated. It is shown that the length/diameter dependence of GaAs nanowhiskers is decreasing, while the dependence of whisker length at given diameter on the effective thickness of deposited GaAs is linear. The length of thinnest (40 nm in diameter) whiskers is 16 times higher than the effective thickness of deposited GaAs. A semi-quantitative model of whisker formation is developed that explains the experimentally observed facts. In particular, it allows LIS to estimate the adatom diffusion flux from the surface to the whisker tips, the surface growth rate and the desorption rate of Ga atoms from the drops. It is shown that the nanoscale whisker formation is mainly controlled by the adatom diffusion. (c) 2005 Elsevier B.V. All rights reserved.