Atomic-scale electric capacitive change detected with a charge amplifier installed in a non-contact atomic force microscope

Nogami, Makoto; Sasahara, Akira; Arai, Toyoko; Tomitori, Masahiko

doi:10.7567/apex.9.046601

Cited by 1 publication

(1 citation statement)

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“…A self‐sensing qPlus‐type force sensor, comprising a quartz tuning fork, was used for the nc‐AFM; a conductive tip made of electrochemically etched tungsten wire was attached at the end of one prong of the tuning fork as a cantilever with a spring constant k of 1800 Nm −1 , while the other prong was fixed to the substrate of a force sensor holder. The prong with the tip oscillated at its resonant frequency by applying an AC voltage signal to the electrode of the tuning fork, and the oscillation amplitude was held constant . The Δ f was measured with a phase‐locked loop (PLL) FM detector (Nanosurf AG, easy PLL plus).…”

Section: Methodsmentioning

confidence: 99%

Nanomechanical Properties of Epitaxial Silicene Revealed by Noncontact Atomic Force Microscopy

Nogami

Fleurence

Yamada‐Takamura

et al. 2018

Adv Materials Inter

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particularity to form in a spontaneous and self-terminating way. [16] The so-formed silicene appears as a ZrB 2 (0001)-(2 × 2) reconstruction due to the matching of this (2 × 2) unit cell with the (√3 × √3) unit cell of silicene. [16] The structure of the Si layer adopts a so-called planar-like structure in which all Si atoms but one in the unit cell are in the same plane, and the remaining atom which is sitting above a Zr atom of the ZrB 2 (0001) surface, is protruding (see Figure 1a,b). [18,19] Moreover, the silicene layer is textured into a periodic stripe domain structure whose origin was proposed based on computational calculation results, to prevent a phonon instability. [20] However, the large-scale periodicity of the domain structure suggests that a long-range ordering governed by the release of the epitaxial strain may take place, associated with the formation of stress domains. [21] To reveal the atomic structures and mechanical properties of solid surfaces on a nanoscale, noncontact atomic force microscopy (nc-AFM) with a frequency-modulation (FM) technique is one of the most efficient methods; the nc-AFM detects changes in the resonant frequency (f 0 ) of an AFM cantilever induced by a weak interaction between a tip apex and surface atoms. [22] The method was able of giving directly insights into the buckling of silicene phases on Ag(111) [23][24][25] and how the interaction of the tip can modify this buckling. [25] The tipsample interactions can be separated into conservative and nonconservative forces using in-phase and 90° out-of-phase responses of the cantilever oscillation. [26] The frequency shift (Δf) is associated to the conservative forces and it is used to generate topographic images by recording the position of the tip while scanning and keeping Δf constant. On the other hand, nonconservative forces can originate from a hysteresis loop in the force-distance curve. [27] The resulting energy loss at each cycle is compensated in such a way that the oscillation amplitude is kept constant by a feedback loop. The variation of excitation energy output from the feedback loop, with respect to that of the tip far from the surface, called the energy dissipation, is mapped and gives the dissipation image. [28][29][30][31][32][33][34] In the atomic-resolution nc-AFM measurement, topography, and dissipation images are simultaneously recorded which allows for analyzing the interaction at atomic scale and evaluating the mechanical response of surface atoms.In this study, we applied the nc-AFM to epitaxial silicene on ZrB 2 thin films. Doing so, we reveal the specific nanomechanical properties resulting from the flexible buckled structure of silicene and the epitaxial conditions. These experiments Silicene, the graphene-like allotrope of silicon, has a great potential for the development of novel silicon-based nanotechnologies. Its unique buckling makes the atomic structure of this silicon 2D material particularly flexible and tunable. The nanomechanical properties of silicene are investigated by probing ep...

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Section: Methodsmentioning

confidence: 99%