Phases of Ba adsorption on Si(100)-(2 x 1) studied by LEED and AES

Phase transitions of Ba adsorption on a clean Si(001)-(2 x 1) studied by low energy electron diffraction (LEED) and Auger electron spectroscopy (AES) are reported. The depositions of the Ba were performed with (a) the substrate held at room temperature followed by annealing at elevated temperatures, and (b) the substrate held at 900 degrees C. While confirming earlier established phases, the existence of 4 x streaks in the (3 x 2) + c(6 x 2) and (2 x 1) phases has been identified. Also found was a real-time phase transition from a (3 x 2) phase to a mixture of (3 x 2) and c(6 x 2) phases during sample cooling. Finally, it was found that AES of Ba;Si peak ratios exhibit plateaus in the phase vs. temperature diagram for the (3 x 2), (3 x 2)+c(6 x2), and (2 x 1)+4 x streak phases, indicating a temperature-dependent mechanism limiting the Pa coverage. (C) 1999 Elsevier Science B.V. All rights reserved.