Formation of metastable two-dimensional structures during Ag growth on Ge(100)

Abstract

Silver growth on Ge͑100͒ between 330 and 570 K was studied using scanning tunneling microscopy. At 330 K, three-dimensional ͑3D͒ clusters along with two types of two-dimensional ͑2D͒ islands were observed: one elongated perpendicular to the substrate dimer rows, the other parallel to the dimer rows. The spacing and registry with the substrate of the former could be explained by Ag adatoms attaching across the substrate dimer bond, while the latter could be attributed to Ag ad-dimers. Annealing caused the larger 3D clusters to grow at the expense of the smaller 3D clusters and 2D islands; at 470 K the 2D islands were completely eliminated. Low-energy electron diffraction indicated that the 3D clusters were oriented with their ͑110͒ planes parallel to the surface. After annealing, the 3D clusters became elongated parallel to the Ge dimer rows indicating that the Ag͓1 10͔ direction aligns parallel to the Ge 1ϫ direction. Although this suggested that the 3D clusters were lower in energy, Ag growth at 470 K led to two types of 2D islands along with pitting of the Ge surface; the pitting was taken as an indication that the islands were intermixed. Images of the islands revealed 2ϫ3 and 3ϫ2 periodicities. Images of the 3ϫ2 structure showed a single maximum per unit cell, while images of domain boundaries showed that the 3ϫ2 structure changed the outermost Ge layer. A model based on Ag-Ge mixed ad-dimers and Ag substitution into the Ge surface can explain these features. The 2ϫ3 and 3ϫ2 structures could only be seen after Ag deposition at ϳ470 K; both annealing films deposited at lower temperatures and higher growth temperatures created only 3D clusters. Thus formation of these intermixed structures was attributed to growth of metastable Ag-Ge nuclei at 470 K that were kinetically inhibited from forming at lower temperatures and whose lifetimes were too short to grow at higher temperatures.

Surface restructuring process on a Ag/Ge(001) surface studied by photoelectron spectroscopy

“…1(c). It elongates in the dimer-row direction on three dimer rows and have faint $ 2Â periodicity along the dimer row [5][6][7]. With increasing the amount of Ag, the substrate is saturated only by the 2D islands, and then 3D islands start to grow on top of them [5,6].…”

“…The 2D islands are www.elsevier.com/locate/apsusc Available online at www.sciencedirect.com Applied Surface Science 254 (2008) 7638-7641 stable even at RT. After annealing the surface up to 470 K, these islands change into 3D islands [7].…”

Buffer effects of Ag layers on magneto-optical Co/Ge(1 0 0) ultrathin films

“…In this paper, one monolayer (ML) is defined by the amount of Ag to saturate the substrate only by 2D islands, i.e., 1 ML ¼ 1:4Å. The thickness representation is consistent with the research group [6]. The SMOKE measurements were carried out in situ by introducing 633 nm He-Ne laser light in and out of the optical view ports.…”

“…Papers discussing about the Ag/Ge(1 0 0) system have been published by variable factors of growth, morphology, electronic structure and temperature [6][7][8][9]. Therefore, we choose the system as our base to study the magnetic properties of the Co capping layers.…”

Initial stages ofPtgrowth onGe(001)studied by scanning tunneling microscopy and density functional theory

“…Recently the potential of metal/Ge interfaces is being explored such as Ag/ Ge͑001͒ system. 2,3 Platinum growth on Ge͑001͒ received brief attention in the past 4,5 due to the application of Pt/ Ge structures in solid state radiation detectors 4 as well as in high-speed integrated circuit applications. 6 However, this system has never been examined at the atomic level in submonolayer (ML) to a few ML Pt coverage regime, like almost none of the transition metal/Ge͑001͒ systems.…”