New Structural Model for theSi(331)−(12×1)Surface Reconstruction

Abstract

A new structural model for the Si(331)-(12×1) reconstruction is proposed. Based on scanning tunneling microscopy images of unprecedented resolution, low-energy electron diffraction data, and firstprinciples total-energy calculations, we demonstrate that the reconstructed Si(331) surface shares the same elementary building blocks as the Si (110)-(16×2) surface, establishing the pentamer as a universal building block for complex silicon surface reconstructions.The study of semiconductor surface reconstructions has been an area of active research for many years and has gained tremendous importance with the advent of low-dimensional heteroepitaxial semiconductor nanostructures such as quantum dots and quantum wires [1]. The creation of a surface results in broken bonds, called dangling bonds. Dangling bonds are energetically unfavorable causing surface atoms to rearrange or reconstruct. This often results in highly complex atomic structures, whose determination remains a formidable challenge and requires the complementary role of different experimental and theoretical methods. In order to lower the surface energy, silicon surfaces adopt a variety of strategies allowing to reduce the number of dangling bonds. Despite the large number of known surface reconstructions, one frequently encounters common elementary structural building blocks [2,3]. Identifying these building blocks is important not only for a better understanding of these surfaces, but also serves as a guide for the elaboration of new structural models. Two of the most important strategies, encountered for instance on Si(100) [4] and Si(111) [5], are respectively the formation of dimers, where two surface atoms pair up to eliminate their dangling bonds, and the appearance of adatoms, which bond to three surface atoms thus saturating three dangling bonds. An important step towards the understanding of high-index group IV surfaces with a surface normal in between the (111) and (100) direction was the introduction of an additional reconstruction element by Dabrowski et al. [6]. They proposed a six-fold coordinated surface self-interstitial which is captured by a conglomerate of surface atoms [7,8]. This concept was subsequently adapted by An [9] and theoretically analyzed by Stekolnikov [10,11] to explain the pairs of pentagons observed in scanning tunneling microscopy (STM) images of the reconstructed Si(110) surface.In this letter we focus on the atomic structure of the Si(331)-(12×1) reconstruction. We present highresolution STM images resolving for the first time rows of * Electronic address: corsin.battaglia@unine.ch; URL: http://www.unine.ch/phys/spectro 1a)), is an important surface, since it is the only confirmed planar silicon surface with a stable reconstruction located between (111) and (110). Since the discovery of the Si(331)-(12×1) reconstruction more than 17 years ago [12] several structural models containing dimers and adatoms have been proposed [13,14]. However, none of these models is able to explain the pentagons observed in our STM image...

Valence band structure of the Si(331)-(12 × 1) surface reconstruction

“…Note also the shaded gray areas within the (12 × 1) unit cells of figure 1(b), which indicate the glide plane symmetry in real space, which reduces to a mirror symmetry in reciprocal space as discussed in [15]. We now turn to our experimental ARPES data.…”

“…5 Present address: Via Monte Velino 17, 20137 Milano, Italy. surface. Using scanning tunneling microscopy (STM) we were able to resolve for the first time rows of pentagon pairs running across the Si(331) surface [15]. Inspired by the adatom-tetramer-interstitial (ATI) model for the Si(110)-(16 × 2) surface [16,17], we proposed a structural model containing silicon pentamers and adatoms as elementary structural building blocks [11,15].…”

Scanning tunneling microscopy at multiple voltage biases of stable “ring-like” Ag clusters on Si(111)–(7×7)

“…First, the sample was heated up to 1300 K with a base pressure below 5 ⋅ 10 −10 mbar, then it was flashed repeatedly over 1500 K to clean the surface and then slowly cooled down across the (7 × 7) transition range of temperature (around 1130 K [19]). Typically, more than 10 h is spent to ensure that the sample remains enough time close to the transition temperature [20]. Sample temperature was monitored using a pyrometer.…”

Atomically precise Si(331)-(12×1) surfaces

“…Based on scanning tunneling microscopy (STM) images of unprecedented resolution, we were recently able to resolve for the first time double rows of silicon pentamers on this surface (see Fig. 1) [5]. Combining our STM images with low energy electron diffraction data and first-principles total energy calculations allowed us to propose a new structural model.…”

“…However, the uniformity often suffers from relatively large variations and the spatial arrangements are hard to control. A prototypical example for atomically precise selfassembled nanostructures are semiconductor surface reconstructions, which form not only on clean surfaces [1], but may also be stabilized by foreign adsorbate species [2,3]. They are ideal templates for the growth of more complex atomically precise structures such as magic clusters exhibiting enhanced stability at certain magic sizes.…”