Direct determination of the local Hamaker constant of inorganic surfaces based on scanning force microscopy

Abstract

The energetics involved in the bonding fluctuations between nanometer-sized silicon dioxide (SiO2) probes and highly oriented pyrolytic graphite (HOPG) and molybdenum disulfide (MoS2) could be quantified directly and locally on the submicron scale via a time-temperature superposition analysis of the lateral forces between scanning force microscopy silicon dioxide probes and inorganic sample surfaces. The so-called "intrinsic friction analysis" (IFA) provided direct access to the Hamaker constants for HOPG and MoS2, as well as the control sample, calcium fluoride (CaF2). The use of scanning probe enables nanoscopic analysis of bonding fluctuations, thereby overcoming challenges associated with larger scale inhomogeneity and surface roughness common to conventional techniques used to determine surface free energies and dielectric properties. A complementary numerical analysis based on optical and electron energy loss spectroscopy and the Lifshitz quantum electrodynamic theory of van der Waals interactions is provided and confirms quantitatively the IFA results.

Simultaneous Deconvolution of In‐Plane and Out‐of‐Plane Forces of HOPG at the Atomic Scale under Ambient Conditions by Multifrequency Atomic Force Microscopy

“…We assume that using diamond‐like carbon (DLC) tips instead of the mostly used silicon tips might cause the higher tip–sample attraction originating from a larger Hamaker constant of DLC compared to that of silicon oxide. [ 51 ] The short‐range flexural force ( F flex,3 ) shows a similar trend to that of the third‐eigenmode flexural frequency shift, although note a major difference in the region between the blue and orange dashed lines (tip–sample distance of 2–1.5 nm), where the short‐range flexural force shows a small attractive region. During approach, starting from the orange dashed line, the repulsive force increases initially with a very small gradient.…”

The role of interactions between abrasive particles and the substrate surface in chemical-mechanical planarization of Si-face 6H-SiC

“…where 3 (¼78.5) is the relative dielectric constant of water, 3 0 (¼8.854 Â 10 À12 C V À1 m À1 ) is the permittivity of vacuum, R is the particle diameter, j 1 or j 2 is the surface potential, D is the separation distance, k is the inverse Debye length. 36 The energies of van der Waals interaction (W A ) can be calculated according to 37,38 W A ¼ ÀA 132 R/6D…”

Self-assembly of CdS nanocrystals obtained by Langmuir-Blodgett technique on the SiO<inf>2</inf> surface

“…Also, in previous investigation [13] of selfassembly process of CdS NC obtained by LB method on the surface of highly oriented pyrolytic graphite (HOPG) substrate we observed that during matrix annealing the NC tend to evenly cover HOPG surface. Hamaker constant of CdS-HOPG interaction equal to 17.86 10 -20 J [14] indicates predominance of the NC-substrate interaction. Both of the results show that at the low temperatures region selfassembly pattern mainly determined by van der Waals forces.…”