Suppression of silicide formation in Fe films grown on Si(001)

Thin ferromagnetic Fe films were grown at both room and low temperatures (1 50 K) on (2x1) and on Au-passivated Si(001). In the case of Fe grown on (2x 1) Si(001), the magnetization sets in at an Fe coverage of 3.6 monolayers ( ML) at room temperature and of 2.3 ML at 150 K, indicating a reduced magnet ization due to silicide formation. To suppress Fe-Si reactions we used a 2 ML thick Au buffer layer deposited in two steps. We performed a reconstruct ion by the deposition of about 0.5 ML of Au at similar to 1000 K followed b y the growth of another 1.5 ML at room temperature or at 150 K. Room temper ature growth results in rough Au films and no earlier onset of magnetizatio n in comparison to the case of unbuffered Fe films. However, a strong out-o f-plane magnetization is measured at the onset coverage. By contrast, at 15 0 K, smooth Au buffer films are observed, acting as protective layers again st Fe and Si intermixing. Growth on these buffer layers results in an early onset of the out-of-plane magnetization at 1.4 ML of Fe and a larger Kerr signal. Both these findings point at a significant reduction of silicide fo rmation. A 2.3 ML thick Fe film grown on Au passivated Si(001) shows a reve rsible magnetic behavior upon annealing to 280 K and cooling back to 150 K, indicating a thermally stable system. (C) 2000 American Institute of Physi cs. [S0021-8979(00)08121-4].