Figure 3

STM images of Ge WL on Si(001) at the outset of QD array formation: T _gr = 360°C, a h _Ge = 4.4 Å, U _s = -1.86 V, I _t = 100 pA, neither hut clusters nor their nuclei are observed; b h _Ge = 5.1 Å, U _s = +1.73 V, I _t = 150 pA; c U _s = +1.80 V, I _t = 100 pA; d U _s = +2.00 V, I _t = 100 pA. Examples of characteristic features are numbered as follows: nuclei of pyramids (1) and wedges (2) [1 ML high over WL patchs, Figure 1] [20, 32], small pyramids (3) and wedges (4) [2 ML high over WL patchs] [18, 20, 32, 49].