Thermal evolution of Co on the coexisting Ag/Ge(111)- $$ \sqrt 3 \times \sqrt 3 $$ and Ag/Ge(111)-4 × 4 phases

Huang, Xiao Lan; Tomaszewska, Agnieszka; Chou, Chi Hao; Hsu, Chung Yu; Lin, Chun Liang; Fu, Tsu Yi

doi:10.1007/s11051-012-1257-y

Cited by 3 publications

(1 citation statement)

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“…[45][46][47] However, the precise formation process of the complex Co/Ag/Ge(111) reconstruction and the role played by the Ag buffer layer is not fully understood. 48 A supporting theoretical model for the atomic and electronic structure of the √ 13R14 • reconstruction still needs to be developed. Unambiguous interpretation of the reported experimental results for the Co/Ag/Ge(111) system obviously requires detailed understanding of the more simple growth process of Co on bare Ge(111) surfaces.…”

Section: Introductionmentioning

confidence: 99%

Electronic and atomic structure of Co/Ge nanoislands on the Ge(111) surface

2013

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We report on a detailed investigation of the electronic and atomic structure of nanometer-size Co/Ge islands obtained by solid-state reactive deposition of Co atoms on a Ge(111)c(2 × 8) surface. Relying on scanning tunneling microscopy (STM) and spectroscopy (STS) measurements combined with density functional theory based calculations, the atomic structure of the Co/Ge(111) √ 13 × √ 13 R13.9 • surface reconstruction is determined. Real-space STM imaging combined with Fourier-transform analysis reveals the coexistence of two inequivalent phases of √ 13 × √ 13 R13.9 • reconstructed Co/Ge nanoislands that are rotated by +13.9 • and −13.9 • with respect to the [211] direction. STS spectra probe a small band gap that varies within the √ 13 × √ 13 R13.9 • surface unit cell between 10 and 250 meV, suggesting local metallic behavior. According to the proposed atomic-structure model, each Co/Ge(111) √ 13 × √ 13 R13.9 • surface unit cell contains one Ge adatom and six Co atoms that are located at hollow sites below the top surface Ge layer and that are stacked in the form of an equilateral triangle. The Ge adatom is located asymmetrically with respect to the Co triangle and occupies two different, yet physically equivalent, positions, giving rise to two chiral phases of Co/Ge nanoislands. The Co/Ge valence band is dominated by Co atom derived 3d states, while states in the conduction band stem from Ge adatom and Ge rest-atom derived states. Analysis of the bonding properties confirms the stability of the proposed Co/Ge atomic structure and reveals significant charge transfer from Co atoms to Ge rest atoms, suggesting ionic or metallic-covalent interaction.

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Section: Introductionmentioning

confidence: 99%

Electronic and atomic structure of Co/Ge nanoislands on the Ge(111) surface

2013

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The role of Ag buffer layer in Fe islands growth on Ge (111) surfaces

Jhou

et al. 2015

Journal of Applied Physics

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Sub-monolayer iron atoms were deposited at room temperature on Ge (111)-c(2 × 8) substrates with and without Ag buffer layers. The behavior of Fe islands growth was investigated by using scanning tunneling microscope (STM) after different annealing temperatures. STM images show that iron atoms will cause defects and holes on substrates at room temperature. As the annealing temperature rises, iron atoms pull out germanium to form various kinds of alloyed islands. However, the silver layer can protect the Ag/Ge(111)-(√3×√3) reconstruction from forming defects. The phase diagram shows that ring, dot, and triangular defects were only found on Ge (111)-c(2 × 8) substrates. The kinds of islands found in Fe/Ge system are similar to Fe/Ag/Ge system. It indicates that Ge atoms were pulled out to form islands at high annealing temperatures whether there was a Ag layer or not. But a few differences in big pyramidal or strip islands show that the silver layer affects the development of islands by changing the surface symmetry and diffusion coefficient. The structure characters of various islands are also discussed.

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