In this case, the shape of Fe clusters is controlled by the thermodynamic stability of the planes in growth. But if the growth is controlled by the growing rate of crystal planes, the morphology of particles are check details changed depending on the condition [18]. As mentioned

above, three Si ad-atoms are remained in each half unit cell on the Si(111)-7 × 7-C2H5OH surface, and the deposited Fe atom may be stabilized by the dangling bond with one electron. In fact, the single-Fe atoms are recognized on the surface at low Fe coverage as shown in Figure 2a. If the Fe atoms are increased in a half unit cell, some kinds of interaction between the Fe atoms stabilize a cluster such as a pentagonal-base pyramid structure observed in the insert of Figure 2a. It should be reminded that the internal bond of Fe clusters may be stronger than selleck compound the interaction of Fe cluster with the surface, so that small Fe clusters grow instead of the Fe layers [19]. Figure 4 shows the simplified periodic grid of clusters in Figure 2d and the sizes of clusters. From Figure 4, it is known that the linearly arrayed Fe clusters take a size of about 5.4 × 4.7 nm, which

is much smaller than the reported critical size of Fe single magnetic domain clusters (~101 nm) prepared by the chemical methods. The 5-nm Fe clusters formed on Si(111)-7 × 7-C2H5OH showed unusual one-dimensional self-assembly with a regular periodic arrangement as shown in Figure 2c,d, which indicate some kinds of attractive interaction of large Fe clusters along the strings. This fact suggests the possibility for the preparation ID-8 of ca. 5-nm-size single magnetic domain Fe clusters. It is worthy of note that the straightly

linked chain structures appears on larger Fe clusters, just as shown in Figure 2c,d, and the authors presumed the formation of single magnetic domain of 5-nm Fe clusters. In addition, if we could oxidize and/or azotize the 5-nm Fe cluster, we could prepare the strong magnetic materials of FeO x and/or FeN x with single magnetic domain. Figure 4 The size of Fe clusters with 4 ML. In general, the periodical arrangement of Si atoms on Si(111)-7 × 7-reconstructed surface could result in the periodical surface potential field [20–22]. Then, the periodical surface potential field could restrain the growth of Fe cluster with certain periodicity. Based on the dimer-ad-atom-stacking (DAS) model of Si(111)-7 × 7-reconstructed surface [23], the side length of unit cell was 2.668 nm, just as shown in Figure 5a and the rhombus A in Figure 5b. According to the periodicity of rhombus unit cell in DAS model, the smallest rectangle structure with periodicity could be designed as the rectangle B-E shown in Figure 5b. Through the simple calculation, the width and length of the designed rectangle was 4.66 and 5.376 nm, respectively, which was corresponded well with the values of Fe clusters in Figures 2d and 4.