Article

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

Carbon (Impact Factor: 6.16). 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.

1 Bookmark
 · 
134 Views
  • [Show abstract] [Hide abstract]
    ABSTRACT: Quantitative, three-dimensional surface imaging is one of the most significant advantages of atomic force microscopy (AFM). The imaging speed, however, is its major issue, due to the limited response time of the feedback loop. We present a dynamically adjusted scanning speed feature implemented on a commercial AFM instrument. The signals available in the system are utilized for that purpose. The auxiliary module controls the scanning speed in order to provide the necessary time to restore the tip–sample distance, which may deviate due to insufficient settling time. The solution allows the measurement to be performed with a relatively fast scanning rate and the desired imaging quality. Quantitative analysis of the results shows the relation between the imaging error and the settings of the system. It is shown that the image is acquired faster and with better imaging quality than using the constant speed method. Also, the data are presented showing a reduction of the topographical crosstalk in the phase imaging feature, as an example of the utilization of this feature in advanced AFM modes.
    Measurement Science and Technology 03/2014; 25(4):044005. · 1.44 Impact Factor
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: Single-layered graphene has unique electronic, chemical, and electromechanical properties. Recently, graphite exfoliation in N-methylpyrrolidone and molten salt has been demonstrated to generate monolayer exfoliated graphene sheets (EGS). However, these solvents are either high-priced or require special care and have high boiling points and viscosities, making it difficult to deposit the dispersed graphene onto substrates. Here we show a universal principle for the exfoliation of graphite in water to single-layered and several-layered graphene sheets via the direct exfoliation of highly oriented pyrolytic graphite (HOPG) using pyridinium tribromide (Py(+)Br3(-)). Electrical conductivity >5100 S/cm was observed for filtered graphene paper, and the EGS exhibited superior performance as a hole transport layer compared to the conventional material N,N-di(naphthalene-1-yl)-N,N-diphenylbenzidine at low voltage. The overall results demonstrate that this method is a scalable process for the preparation of highly conductive graphene for use in the commercial manufacture of high-performance electronic devices.
    Scientific Reports 01/2014; 4:3928. · 5.08 Impact Factor
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: Single-layer chemical vapor deposition (CVD)-grown graphene was transferred onto a ZnO (0001) substrate forming a large-area, low-defect density, protective layer. The quality of the graphene layer and its effect on the interaction between the ZnO support and vapor-deposited cobalt particles was investigated by spectroscopic and microscopic techniques. We demonstrate that the in-between graphene layer influences both the oxidation state and the morphology of cobalt upon annealing in vacuum. In particular, cobalt strongly interacts with the bare ZnO substrate forming flat particles, which are readily oxidized and redispersed upon annealing in ultrahigh vacuum conditions. In contrast, in the presence of the graphene interlayer, cobalt forms highly dispersed nanoparticles, which are resistant to oxidation, but prone to surface diffusion and agglomeration. The graphene layer exhibits remarkable stability upon cobalt deposition and vacuum annealing, while interaction with reactive gases can facilitate the formation of defects.
    Journal of Physical Chemistry Letters 01/2014; 5:1837-1844. · 6.59 Impact Factor

Full-text (2 Sources)

View
44 Downloads
Available from
May 23, 2014