Low Temperature Scanning Force Microscopy of the<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:mi>Si</mml:mi><mml:mo>(</mml:mo><mml:mn>111</mml:mn><mml:mo>)</mml:mo><mml:mi>−</mml:mi><mml:mo>(</mml:mo><mml:mn>7</mml:mn><mml:mo>×</mml:mo><mml:mn>7</mml:mn><mml:mo>)</mml:mo></mml:math>Surface

Lantz, Mark A.; Hug, Hans J.; Schendel, P. J. A. van; Hoffmann, R.; Martin, S.; Baratoff, A.; Abdurixit, Abduxukur; Güntherodt, H.‐J.; Gerber, Ch.

doi:10.1103/physrevlett.84.2642

Cited by 154 publications

(107 citation statements)

References 14 publications

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“…The restatoms in the Si (111)-(7 × 7) reconstruction were first observed by Lantz et al approximately 40 pm below the adatoms [13]. The z-position of the restatoms according to our new AFM data is almost exactly the same as that for the LEED data.…”

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confidence: 71%

Imaging silicon by atomic force microscopy with crystallographically oriented tips

et al. 2001

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Abstract. The images obtained by atomic force microscopy (AFM) originate from a convolution of atomic tip and sample states. Since the vertical resolution of AFM is approaching the picometer level, the atomic and subatomic structure of the tip is becoming increasingly important. Here, we demonstrate the preparation of crystallographically oriented AFM tips by breaking a silicon wafer along its preferential cleavage planes. Assuming bulk termination, the front atom of this tip should expose a single dangling bond. Images derived with this tip are consistent with this speculated tip geometry and show unprecedented vertical distinction of the six different surface atom sites of the Si(111)-(7 × 7) structure. 07.79.Lh; 34.20.Cf; 68.37.E Recently, sub-atomic resolution on the surface of silicon (111)-(7 × 7) with frequency-modulation atomic force microscopy (FM-AFM) [1] has been demonstrated. The subatomic structure of the adatom images was attributed to a tip with a very special symmetry: a tip with a front atom exposing two unsaturated bonds. The experimental observation at subatomic resolution outlines the importance of both the chemical nature and the geometric orientation of the front atom with respect to its nearest neighbors in the tip. While the preparation of the silicon sample to obtain the 7 × 7 reconstruction is straightforward, the preparation of the tip is more challenging. Here, we report on the construction of a deliberately shaped tip with predetermined crystallographic orientation. PACS:Most force sensors for AFM are microfabricated, and the crystallographic orientation of the tip is determined by the manufacturing process of the whole cantilever. Typically, the tips of micromachined cantilevers point in the 100 direction of the crystallographic orientation between tip and sample is given by the tilt angle of the cantilever. To assure that the micromachined tip is closer to the flat sample than any other parts of the cantilever and mounting devices, tilt angles between 10 • and 25 • typically have to be applied. The angle between the orientations of tip and sample cannot be freely chosen. This constraint does not apply to force sensors based on a tuning fork ("qPlus" sensor, see Fig. 1 in [3]), since it is possible to attach large tips on these sensors with a deliberate crystallographic orientation.The natural cleavage planes of silicon are (111) planes, since the free surface energy is minimal for this orientation. Each Si-Si bond has a bonding energy of approximately 2.3 eV, and the density of unsaturated bonds (dangling bonds) is 7.8 nm −2 for the (111) orientation and 13.6 nm −2 for the (100) orientation. Therefore, silicon exhibits a very strong preference to form (111) limited planes as boundaries of mesoscopic structures. This is nicely evident in the work of Baumgärtner et al., where silicon has been deposited by molecular beam epitaxy onto a Si (100) wafer through a square shaped 350 nm × 350 nm aperture. The resulting structure was a pyramid with (111) plane boundaries, rather than a pi...

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confidence: 71%

Imaging silicon by atomic force microscopy with crystallographically oriented tips

et al. 2001

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“…However, for achieving atomic resolution it seems crucial that surfaces be smooth enough and that there be no strong, long-range, tip-surface forces, e.g., those due to charging. In recent years, the emphasis in both STM and SFM studies has gradually shifted from surface topography and surface reconstructions (Behm et al, 1990;Chen, 1993) to surface chemistry (Fukui et al, 1997b;Hla et al, 2000;Hahn and Ho, 2001a;Sasahara et al, 2001) and surface dynamics (Molinas-Mata et al, 1998;Nishiguchi et al, 1998;Bennewitz et al, 2000;Lauhon and Ho, 2000;Schulz et al, 2000;Hoffmann et al, 2001).…”

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confidence: 99%

Theories of scanning probe microscopes at the atomic scale

2003

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Significant progress has been made both in experimentation and in theoretical modeling of scanning probe microscopy. The theoretical models used to analyze and interpret experimental scanning probe microscope (SPM) images and spectroscopic data now provide information not only about the surface, but also the probe tip and physical changes occurring during the scanning process. The aim of this review is to discuss and compare the present status of computational modeling of two of the most popular SPM methods-scanning tunneling microscopy and scanning force microscopy-in conjunction with their applications to studies of surface structure and properties with atomic resolution. In the context of these atomic-scale applications, for the scanning force microscope (SFM), this review focuses primarily on recent noncontact SFM (NC-SFM) results. After a brief introduction to the experimental techniques and the main factors determining image formation, the authors consider the theoretical models developed for the scanning tunneling microscope (STM) and the SFM. Both techniques are treated from the same general perspective of a sharp tip interacting with the surface-the only difference being that the control parameter in the STM is the tunneling current and in the SFM it is the force. The existing methods for calculating STM and SFM images are described and illustrated using numerous examples, primarily from the authors' own simulations, but also from the literature. Theoretical and practical aspects of the techniques applied in STM and SFM modeling are compared. Finally, the authors discuss modeling as it relates to SPM applications in studying surface properties, such as adsorption, point defects, spin manipulation, and phonon excitation. CONTENTS

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“…The one-electron state of the dangling bond is split from other occupied states of the Si tip modeling the Si valence band. This tip performs well when the short-range tip-surface interaction is determined by the onset of covalent bond formation between the dangling bond at the end of the tip and surface dangling bonds [17]. During simulations, the top two layers of the tip and the bottom third of the surface were kept frozen, and all other ions were allowed to relax freely until the forces are less than 0:05 eV= A.…”

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confidence: 99%

Interaction of Silicon Dangling Bonds with Insulating Surfaces

et al. 2004

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We use first principles density functional theory calculations to study the interaction of a model dangling bond silicon tip with the surfaces of CaF 2 , Al 2 O 3 , TiO 2 , and MgO. In each case the strongest interaction is with the highest anions in the surface. We show that this is due to the onset of chemical bonding with the surface anions, which can be controlled by an electric field across the system. Combining our results and previous studies on semiconductor surfaces suggests that using dangling bond Si tips can provide immediate identification of surface species in atomically resolved noncontact atomic force microscopy and facilitate selective measurements of short-range interactions with surface sites.

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Low Temperature Scanning Force Microscopy of theSi(111)−(7×7)Surface

Cited by 154 publications

References 14 publications

Imaging silicon by atomic force microscopy with crystallographically oriented tips

Imaging silicon by atomic force microscopy with crystallographically oriented tips

Theories of scanning probe microscopes at the atomic scale

Interaction of Silicon Dangling Bonds with Insulating Surfaces

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