Hydrogen termination following Cu deposition on Si(001)

Abstract

We describe the surface structures following submonolayer Cu deposition on Si͑001͒ and subsequent hydrogen termination as characterized by scanning tunneling microscopy. Cu adsorption at 870 K results in a characteristic ͑2 ϫ 8͒ island+ vacancy structure, as previously reported. In addition, occasional structures are observed attributed to Cu in surface interstitial sites. After H termination, the dominant features of the island+ vacancy structure remain, but the size and distribution of the structures are significantly altered. Based on the atomic-scale appearance of both the clean and H-terminated structures, we propose that within the ͑2 ϫ 8͒ island+ vacancy structure all surface atoms are Si, with all Cu subsurface, contrary to previous structural models.

First-principles calculations of Cu adsorption on an H-terminated Si surface

“…32 Core electrons are represented by normconserving pseudopotentials using the Troullier-Martins parametrization and including scalar relativistic corrections. The pseudopotential for the silicon atom was generated in the electron configuration ͓Ne͔3s 2 3p 2 , for oxygen in ͓1s 2 ͔2s 2 2p 4 , for copper in ͓Ar͔4s 1 3d 10 , and for hydrogen in 1s 1 , with the square brackets denoting the core electron configurations. After extensive testing of different basis sets, we used double zeta with a single shell of polarization orbitals for Si and H, double zeta with two shells of polarization orbitals for oxygen, and triple zeta with two shells of polarization orbitals for copper.…”

“…5 Similarly, solutions used to etch silicon itself contain significant metal impurities, including copper, and the role of copper in etched morphologies is a significant issue in micro-and nanoelectromechanical-system fabrications. 6 Due to its high diffusion 3 and reactivity in silicon, copper has also attracted interest in the design of nanostructured surfaces and deposition of nanowires, [7][8][9][10] in analogy with the surface templating demonstrated with Ga. 11 The deposition and growth of copper on the clean silicon surface have been experimentally studied by a variety of techniques, especially scanning tunneling microscopy. 10,[12][13][14][15][16][17] Despite the large number of experimental studies, most of the previous theoretical studies, for example, [18][19][20][21] have focused on the properties of copper impurities in bulk silicon, and very few have approached copper adsorption on the surface.…”

“…Furthermore, in many applications, the surface is hydrogen-terminated due to the cleaning process, and studies of the interaction of copper and silicon in the presence of hydrogen have been even more limited. 10,20,22,23 A comparative study of copper deposition on the clean and hydrogenterminated silicon ͑111͒ surface showed that the growth modes are quite similar at room temperature, but that at higher temperatures ͑570-770 K͒ copper is much more mobile on the hydrogen-terminated surface. 22 Theoretical predictions support the mobility of copper on a hydrogenterminated surface, 23 but the very low calculated adsorption energies are difficult to reconcile with etching experiments.…”

Ab initiostudy of subsurface diffusion of Cu on the H-passivated Si(001) surface

“…When adsorbed on clean Si(001), Cu forms a distinctive threelobed linear feature perpendicular to the dimer rows which orders to form a c(8x8) reconstruction at high coverages [3]. On addition of hydrogen to a Cu-dosed surface, the feature sizes and appearance change, suggesting that the Cu may be subsurface [4], though the structure of these features is still unknown. The adsorption of hydrogen onto Si(001) follows various stages [5]: very low coverages lead to single hydrogen atoms adsorbed on one side of a dimer, giving a hemihydride [6]; however, when the coverage goes beyond more than about 0.1 ML, these single hydrogens rapidly pair up to form saturated dimers [7] with one hydrogen for each dangling bond; adsorption of a full monolayer leads to the saturated, monohydride surface.…”

Evolution of Interdiffused Gaussian-Shape Nanolayer in Au-Si(111) System at Ambient Condition

“…Au-Si is one such interface, which has longstanding interest for device fabrications [1,2]. It is known that the presence of a native oxide layer at the interface strongly suppresses the interdiffusion behavior across a metal-semiconductor interface [3,4]. Oxide growth, at ambient conditions, could be hindered by passivation of surface dangling bonds [5,6].…”