One-Dimensional Surface Reconstruction as an Atomic-Scale Template for the Growth of Periodically Striped Ag Films

One-dimensional (1D) stripe structures with a periodicity of 1.3 nm are formed by introduction of stacking fault arrays into a Ag thin film. The surface states of such striped Ag thin films are studied using a low temperature scanning tunneling microscope. Standing waves running in the longitudinal direction and characteristic spectral peaks are observed by differential conductance (dI/dV ) measurements, revealing the presence of 1D states on the surface stripes. Their formation can be attributed to quantum confinement of Ag(111) surface states into a stripe by stacking faults. To quantify the degree of confinement, the effective potential barrier at the stacking fault for Ag(111) surface states is estimated from independent measurements. A single quantum well model with the effective potential barrier can reproduce the main features of dI/dV spectra on stripes, while a Kronig-Penney model fails to do so. Thus the present system should be viewed as decoupled 1D states on individual stripes rather than as anisotropic 2D Bloch states extending over a stripe array.

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“…1(b)) 13 . The film surface consists of Ag(111) nano-planes with periodic insertion of SF planes at every five layers.…”

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confidence: 99%

One-dimensional surface states on a striped Ag thin film with stacking fault arrays

et al. 2011

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“…Ag films with a high density of stacking fault planes were prepared by low-temperature (LT) ($ 100 K) deposition on Si(111)-(4 Â 1)-In substrates followed by a natural annealing to room temperature (RT). 16,21 Subsequently, the Au films were grown at 100 K on the Ag templates and kept at RT for 12 h to obtain large Au terraces. All the spectroscopic measurements were performed at the sample temperature below 8 K. W tips used in the experiment were prepared by flashing and Ar þ ion bombardment.…”

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Modification of the surface-state occupancy on noble metal films with stacking fault arrays

Mishra

Uchihashi

Nakayama

2012

Applied Physics Letters

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Low-temperature scanning tunneling spectroscopy reveals that striped Au films grown on Ag templates containing periodic arrays of stacking faults exhibit partially populated one-dimensional (1D) surface states, in contrast to the depopulated 1D surface states on the Ag template. Detailed spectroscopic analysis on Au stripes shows the presence of 1D states with onset slightly below the Fermi level, while two-dimensional surface states exist at lower energies. These findings indicate that the Au stripes, owing to their occupied 1D surface states, may provide an effective means for 1D transport of charge and spin information between magnetic adsorbates.

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“…Ag films about 20 monolayers (ML) in thickness were grown on In4×1 around 100 K followed by a natural annealing to room temperature. This results in penetration of high-density SF planes into the film, which are terminated by 'fractional' steps with a height of 0.078 nm (equivalent to 1/3 of the MA step height) [21]. Figure 1 (a)(b) show a typical STM image of a Ag(111) film with SF step arrays and a tilt-corrected height profile taken along the dashed line (z: height, x: lateral distance).…”

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“…To determine the reflection amplitude and the phase shift, sufficiently long and straight SF steps are needed. For this aim, Si(111)4×1-In surfaces (referred to as In4×1) were used as one-dimensional (1D) atomic-scale geometric templates [17,18,21]. Ag films about 20 monolayers (ML) in thickness were grown on In4×1 around 100 K followed by a natural annealing to room temperature.…”

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Strong electron confinement by stacking-fault-induced fractional steps on Ag(111) surfaces

2010

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The electron reflection amplitude R at stacking-fault (SF) induced fractional steps is determined for Ag(111) surface states using a low temperature scanning tunneling microscope. Unexpectedly, R remains as high as 0.6 ∼ 0.8 as energy increases from 0 to 0.5 eV, which is in clear contrast to its rapidly decreasing behavior for monatomic (MA) steps [L. Bürgi et al., Phys. Rev. Lett. 81, 5370 (1998)]. Tight-binding calculations based on ab-initio derived band structures confirm the experimental finding. Furthermore, the phase shifts at descending SF steps are found to be systematically larger than counterparts for ascending steps by ≈ 0.4π. These results indicate that the subsurface SF plane significantly contributes to the reflection of surface states. The Shockley surface states on a noble metal exemplify an ideal two-dimensional (2D) electron system, which works as a basis for demonstrating and utilizing quantum natures of electrons [1][2][3]. To realize quantum confinement of surface states, monatomic (MA) steps [4][5][6][7][8], artificially manipulated atoms [9,10], and self-assembled molecules [11] have successfully been used. However, the lifetimes of resultant quantized states are rather short especially at high energies, because of lossy scattering at the boundary caused by low reflection amplitude [6,[12][13][14][15]. This may pose a fundamental limitation on the usage of these quantum structures. Although the reflection at the boundary may be enhanced by multiplying potential barriers [16], a search for a new form of confinement is highly desirable. Recently, stacking-fault (SF) defects have been found to substantially modify surface and bulk electronic states of Ag thin films [17][18][19][20]. Nevertheless, basic properties concerning the reflection of surface states by a SF-induced step have so far remained elusive.In this Letter, we determine the reflection amplitude R at SF steps for Ag(111) surface states using a low temperature scanning tunneling microscope (STM). R retains high values of 0.6 ∼ 0.8 as energy increases from 0 to 0.5 eV, which is in striking contrast to the rapid decrease in R for MA steps reported in Ref. [6]. Tight-binding calculations based on ab-initio derived band structures confirm the experimental finding. The results demonstrate that SF steps offer a better method for realizing a strong quantum confinement on metal surfaces than MA steps. The phase shifts at descending and ascending SF steps are also determined for the same energy region, the former being systematically larger than the latter by ≈ 0.4π. The possibility of significant scattering of the surface state by the subsurface SF plane is proposed based on these measurements.The experiments were performed in an ultrahigh vacuum system equipped with a low temperature STM. To determine the reflection amplitude and the phase shift, sufficiently long and straight SF steps are needed. For this aim, Si(111)4×1-In surfaces (referred to as In4×1) were used as one-dimensional (1D) atomic-scale geometric templates [17,18,21]. A...

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One-Dimensional Surface Reconstruction as an Atomic-Scale Template for the Growth of Periodically Striped Ag Films

Cited by 22 publications

References 33 publications

One-dimensional surface states on a striped Ag thin film with stacking fault arrays

One-dimensional surface states on a striped Ag thin film with stacking fault arrays

Modification of the surface-state occupancy on noble metal films with stacking fault arrays

Strong electron confinement by stacking-fault-induced fractional steps on Ag(111) surfaces

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