page_title: Electrochemical AFM
section_title: Principles and experimental precautions
hierarchical_section_title: Electrochemical AFM / Principles and experimental precautions
caption_attribution_description: English: Ec AFM
context_page_description: Electrochemical AFM is a particular type of Scanning probe microscopy, which combines the classical Atomic force microscopy together with electrochemical measurements. EC-AFM allows to perform in-situ AFM measurements in an electrochemical cell, in order to investigate the actual changes in the electrode surface morphology during electrochemical reactions. The solid-liquid interface is thus investigated.
  This technique was developed for the first time in 1996 by Kouzeki et al., who studied amorphous and polycrystalline thin films of Naphthalocyanine on Indium tin oxide in a solution of 0.1 M Potassium chloride. Unlike the Electrochemical scanning tunneling microscope, previously developed by Itaya and Tomita in 1988, the tip is non-conductive and it is easily steered in a liquid environment.
context_section_description: The technique consists in an AFM apparatus integrated with a three electrode electrochemical cell.
   The sample works as working electrode (WE) and must be conductive.  The AFM probe is a "passive" element, as it is unbiased and it monitors the surface changes as a function of time, when a potential is applied to the sample. Several electrochemical experiments can be performed on the sample, such as cyclic voltammetry, pulse voltammetry etc. During the potential sweeping, the current flows through the sample and the morphology is monitored.
  The electrochemical cell is made of a plastic material resistant to various chemical solvents (e.g. sulfuric acid, perchloric acid etc.), with a good mechanical resistance and low fabrication costs. In order to satisfy these requirements, various materials can be employed, such as polytetrafluoroethylene (PTFE) or teflon.  Platinum and AgCl wires are widely employed as reference electrode and platinum wires as counter electrode.
  Since the measurement is performed in a liquid environment, some precautions must be taken. The chosen electrolyte must be transparent, in order to allow the laser beam to reach the sample and be deflected. For the right electrolyte opacity, depending on the solute concentration, very diluted solutions should be selected. The choice of a suitable electrolyte for the measurement must be taken considering also possible corrosion effects on the AFM scanner, which can be affected by strong acid solutions. The same problem affects the AFM cantilever. It is preferable to select an AFM tip with a specific coating resistant to acids, for example gold. The liquid environment adds one more constraint related to the choice of the tip material, as the laser sum registered on the photodiode must be scarcely affected. The change in the refractive index of the solution with respect to air leads to a change in the position of the laser spot, necessitating a repositioning of the photodiode.
caption: Electrochemical AFM section.
  (a) Cantilever and tip
   (b) electrochemical cell
   (c) Liquid (electrolyte)
   (d) sample
   (e) Sample holder. The electrochemical connections are usually placed under the sample holder.
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