Article

Anomalies in thickness measurements of graphene and few layer graphite crystals by tapping mode atomic force microscopy

Carbon (Impact Factor: 6.2). 12/2008; 46:1435-1442. DOI: 10.1016/j.carbon.2008.06.022
Source: arXiv

ABSTRACT

Atomic Force Microscopy (AFM) in the tapping (intermittent contact) mode is a commonly
used tool to measure the thickness of graphene and few layer graphene (FLG) flakes on silicon oxide surfaces. It is a convenient tool to quickly determine the thickness of individual FLG films. However, reports from literature show a large variation of the measured thickness of graphene layers. This paper is focused on the imaging mechanism of tapping mode AFM (TAFM) when measuring graphene and FLG thickness, and we show that at certain measurement parameters significant deviations can be introduced in the measured thickness of FLG flakes. An increase of as much as 1 nm can be observed in the measured height of FLG crystallites, when using an improperly chosen range of free amplitude values of the tapping cantilever.We present comparative Raman spectroscopy and TAFM measurements on selected single and multilayer graphene films, based on which we suggest ways to correctly measure graphene and FLG thickness using TAFM.

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Available from: Zoltán Osváth
    • "The edge length of the structures shown in the middle of Fig. 2(a) is approximately 6 µm.The height profile measured across the flake reveals a thickness of (0.8 ± 0.1) nm, representing a monolayer [cf. Figure 2(b)]. This result slightly differs from the expected theoretical thickness of 0.615 nm[53], which is commonly ascribed to a combination of different hygroscopicity/water accumulation on the SiO 2 substrate and the MoS 2 film as well as the AFM tapping mode, which has been reported to produce lower accuracy than in contact mode measurements, which has also been derived from the characterization of graphene samples[54]. The CVD MoS 2 islands contain occasionally bilayer growth seeds near their center. "

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    • "It was reported that large variations in the GN thickness values for similar substrates determined by different groups are result of exact setting of the scanning parameters. Error in determination of the GN thickness for the SiO2 substrate was reported as 1 nm [58]. Hence we assigned the flat GN parts as delaminated from the substrate for dGN_substrate > 2.6 nm (the GN_5, GN_6, GN_8, GN_10 samples, Table 1). "
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    ABSTRACT: Wrinkles in monolayer graphene (GN) affect the GN electronic and transport properties. Defined network of wrinkles can be reached by placing the GN on a substrate decorated with nanoparticles (NPs). In order to explain mechanism behind the topographically induced changes of the electronic structure of the GN and to correlate it with the wrinkling, correct description of the GN morphology is of high demand. We propose a methodology based on advanced analysis of atomic force microscopy (AFM) images, which enables determination of the contact/delamination of the GN from the substrate and correlation of the NP density with the character of the wrinkling. Also the relevance of detection of the NPs hidden beneath the GN layer is discussed. The study was carried out on the samples of the GN transferred on the top of SiO2/Si substrate decorated with metal-oxide NPs with nominal diameter of 6 and 10 nm. The NP density varied in the range of ∼20–450 NPs/μm2. The projected area of wrinkles increased linearly with the increasing NP density, independently on the NP diameter.
    Preview · Article · Dec 2015 · Carbon
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    • "While investigating properties and phenomena related to MLG, an accurate, easy and preferably nondestructive method that can characterize its thickness (or number of layers) is very much required. The currently available techniques are accompanied by certain drawbacks and limitations [2] [3]. In general, optical techniques offer faster and simpler avenues to tackle this problem. "
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    ABSTRACT: Abstract A simple method based on relative luminance is proposed for the rapid counting of layers in multilayer graphene. The number of graphene layers can be immediately identified by processing the acquired standard RGB images, once the one-time calibration of the entire optical system has been performed. The estimated number of layers was corroborated using the common counting methods of Raman spectroscopy and atomic force microscopy. The relative luminance method was successfully applied on both pristine and chemical vapor deposited graphene, regardless of the microscopes or even the substrates utilized, as long as there are some noticeable contrast differences.
    Full-text · Article · Nov 2015 · Carbon
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