EVALUATION OF ULTRATHIN SI GROWTH LAYER ON W, MO, AND TA SURFACES WITH IN-SITU FIELD-EMISSION AND FIELD-ION MICROSCOPIES

Ultrathin Si films vapor-deposited onto W, Mo and Ta surfaces and Si-metal interface properties have been evaluated with microscopic-capability in situ field emission and field ion microscopies (FEM-FIM). Work functions of W, Mo, and Ta substrates covered with a Si monolayer were found to be 4.8 eV, 4.6 eV and 4.5 eV, respectively. The Si monolayer adatoms deposited onto the W and Mo surfaces at around 50 K are field-desorbed at voltages greater than 0.9 V-0 (V-0: evaporation voltage of substrate). The clean surfaces of the W and Mo substrates finally appeared at V/V-0=0.96-0.98, and the Si films were found to be desorbed without defects or disturbance of the substrate atomic structure. Silicon-metal intermixing was therefore not detected in the case of Si vapor deposition at around 50 K. The dynamical behavior of Si atoms due to thermal annealing was also examined.