Formation of the ordered array of Al magic clusters on Si„111…7Ã7 V. G. Kotlyar, 1 A. V. Zotov, 1,2 A. A. Saranin, 1,3 T. V. Kasyanova, 1 M. A. Cherevik, 3 I. V. Pisarenko, 1 and V. G. Lifshits 1,2,3 1 Institute of Automation and Control Processes, 690041 Vladivostok, Russia 2 Department of Electronics, Vladivostok State University of Economics and Service, 690600 Vladivostok, Russia 3 Faculty of Physics and Engineering, Far Eastern State University, 690000 Vladivostok, Russia Received 28 April 2002; published 2 October 2002 Deposition of Al onto the Si11177 surface held at temperatures ranging from 475 to 600 °C has been found to result in the formation of a superlattice of the identical-size nanoclusters magic clusters. The Al magic clusters appear to have the structure similar to that reported recently for the magic clusters of Ga and In on Si111: each cluster contains six metal atoms linked by three Si atoms. The present results reveal that at the early stages of deposition all the group III metals demonstrate a distinct tendency for the formation of the magic clusters on Si surfaces. DOI: 10.1103/PhysRevB.66.165401 PACS numbers: 68.35.Bs, 68.55.Jk Self-organized formation of the ordered arrays of the identical-size nanoclusters i.e., magic clusters on the solid surfaces is a fabulous challenge of scientific and technologi- cal research. Recently the goal has been achieved by using the metal deposition onto the Si11177 surface. 1–3 Vitali, Ramsey, and Netzer 1 have found that upon room-temperature RT deposition of about 0.2 monolayer ML (1 ML=7.8 10 14 cm -2 ) of thallium Tl onto Si111, Tl adatoms ag- glomerate into the nanoclusters of 9 adatoms located in the faulted halves of the 77 unit cells HUC’s thus forming a superlattice of Tl nanoclusters. Lai and Wang 2 reported ‘‘an unprecedented two-dimensional lattice of magic clusters’’ each built of exactly six gallium Ga atoms linked by three Si atoms and residing at the centers of both faulted and un- faulted 77 HUC’s. Li et al. 3 have grown an ordered array of the identical-size indium In clusters ‘‘by delicate regu- lation of the growth kinetics.’’ It is particularly remarkable that magic clusters of In and Ga appear to have an identical structure. One can notice that in all three cases the adsorbates were group-III metals. Two species are left, boron B and alumi- num Al. While B demonstrates adsorption properties very different from those of other group-III metals, Al behavior at the early stages of adsorption is very similar to that of In and Ga e.g., formation of the same  3  3 structure on Si111, 4,5 as well as the similar 23, 25, and 22 struc- tures on Si100Ref. 6. Thus one can expect the formation of the ordered arrays of the magic clusters in the Al/Si111 system also. The early scanning tunneling microscopy STM observations of the so-called -77 Al/Si111 phase by Yoshimura et al. 7,8 provide additional promise to reach the goal. Indeed, the results of the present study reveals the formation of the ordered arrays of Al magic clusters on Si11177. The Al magic clusters have been shown to be identical to the In and Ga ones, indicating that their forma- tion is a general phenomenon for group-III metals. Our experiments were performed with Omicron STM op- erated in an ultrahigh vacuum ( 1.510 -10 Torr). Atomi- cally clean Si11177 surfaces were prepared in situ by flashing to 1250 °C after the samples were first outgassed at 600 °C for several hours. Aluminum was deposited from a heated Al-cowered W wire at a typical deposition rate of 0.3 ML/min. The samples were heated by passing dc cur- rent through them. For STM observations, electrochemically etched tungsten tips cleaned by in situ heating were em- ployed. The STM images were acquired in a constant-current mode after cooling the sample to room temperature. Formation of the highly ordered superlattice of the Al nanoclusters on the Si11177 surface is illustrated by Fig. 1, showing the surface after deposition of 0.35 ML of Al at 575 °C. One can see that every 77 HUC is occupied by the identical-size triangle-shaped cluster. The cluster shows up as a group of three protrusions in the filled states Fig. 2a and as a group of six protrusions in the empty states Fig. 2b. This STM appearance of Al clusters coincides exactly with the STM appearance reported for the magic clusters of Ga and In adatoms. 2,3 The atomic structure of the magic clusters as elucidated by means of first-principles total en- ergy calculations 3 is shown in Fig. 2c. The structure was originally proposed for the Ga magic clusters formed on Si(111)  3  3-Ga reconstruction 9 and it consists of six metal atoms linked through three Si atoms to form a triangle- shaped configuration with satisfied bonding. The six protru- FIG. 1. Filled state +2.0 V STM image 470320 Å 2  of the ordered array of the Al identical-size nanoclusters magic clusters formed by depositing 0.35 ML onto the Si11177 surface held at 575 °C. PHYSICAL REVIEW B 66, 165401 2002 0163-1829/2002/6616/1654014/$20.00 ©2002 The American Physical Society 66 165401-1