Atomic force microscopy analysis of nanoparticles in non-ideal conditions
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NANO EXPRESS
Open Access
Atomic force microscopy analysis of nanoparticles in non-ideal conditions Petr Klapetek1*, Miroslav Valtr1, David Nečas2, Ota Salyk3 and Petr Dzik3
Abstract Nanoparticles are often measured using atomic force microscopy or other scanning probe microscopy methods. For isolated nanoparticles on flat substrates, this is a relatively easy task. However, in real situations, we often need to analyze nanoparticles on rough substrates or nanoparticles that are not isolated. In this article, we present a simple model for realistic simulations of nanoparticle deposition and we employ this model for modeling nanoparticles on rough substrates. Different modeling conditions (coverage, relaxation after deposition) and convolution with different tip shapes are used to obtain a wide spectrum of virtual AFM nanoparticle images similar to those known from practice. Statistical parameters of nanoparticles are then analyzed using different data processing algorithms in order to show their systematic errors and to estimate uncertainties for atomic force microscopy analysis of nanoparticles under non-ideal conditions. It is shown that the elimination of user influence on the data processing algorithm is a key step for obtaining accurate results while analyzing nanoparticles measured in non-ideal conditions. Introduction Nanoparticle analysis is an important challenge in the present nanoscale metrology. Nanoparticles are used in many fields of research and technology [1-5], and their proper characterization is, therefore, very important. Even if there are several general and well established experimental methods to nanoparticle analysis (optical methods [6-8], electrochemistry-based methods [9], electron microscopy [10,11], X-ray methods [10,12] and scanning probe microscopy [10,13]), their results differ mutually very often due to different effects of non-ideal measurement conditions [6,7,10,14]. In this article, we focus on nanoparticle analysis performed using atomic force microscopy (AFM) [15], which is one of the most popular scanning probe microscopy methods. The interaction of nanoparticles with the AFM probe was studied in the past quite extensively from the experimental point of view–from the point of nanoparticle measurement, AFM tip modification, or nanoparticle manipulation [10,13,16-18]. If the isolated nanoparticles of spherical shape are deposited on an ideally flat substrate, their size can be determined easily from the AFM image by measuring the nanoparticle * Correspondence: [email protected] 1 Czech Metrology Institute, Okružní 31, 638 00, Brno, Czech Republic Full list of author information is available at the end of the article
image height [13]. This quantity is not influenced by tip-sample convolution effects and can provide accurate nanoparticle size results. However, if the particles are deposited on rough substrates (or curved substrates generally), particle size analysis is not so straightforward and therefore many questions arise from the point of particle analysis implementation in
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