rus
Issue #8/2016
G.Meshkov, O.Sinitsyna, I.Yaminsky
Combined scanning ion conductance, electrochemical and piezoelectrochemical microscopy of surfaces
Combined scanning ion conductance, electrochemical and piezoelectrochemical microscopy of surfaces
On the basis of scanning probe microscope an experimental facility to implement a scanning capillary microscopy, scanning electrochemical microscopy and scanning piezoelectric microscopy was developed.
The characteristic feature of the modern scanning probe microscopy is the ability to simultaneously study the surface of materials in a variety of ways.
A scanning ion conductance microscopy, which in its broader application is also called a scanning capillary microscopy, was first implemented by Paul Hansma in 1989 [1]. Works of research group of professor Yu.Korchev [2, 3] have provided her substantial further development. A scanning ion conductance microscope allows to observe objects in a liquid (the electrolyte) with micron and nanometer spatial resolution. The use of multi-channel capillaries greatly enhances the capabilities of this type of microscopy. One channel can be used to position the capillary above the surface of the sample, while the other channels can be used for directional mass transfer of substances, atomic or molecular 3D printing. After filling of the capillary channel with conductive material, it is possible by using such electrode to implement the mode of scanning electrochemical microscopy.
Scanning piezoelectric microscopy (SPM) is implemented in atomic force microscopy in the following way. A conductive cantilever that is in contact with the sample surface is used for the measurements. The applied potential difference between the conductive cantilever and the sample leads to the displacement of ions and deformation of the sample surface that is registered with nanometer spatial resolution by the deflection of cantilever. The resulting image reflects the nature of the ion fluxes in the surface layer of the sample. This method is highly informative in the study of surface properties of energy storage, lithium-ion batteries, capacitors, etc. For example, SPM allows to notice a change in the lattice parameter of the cathode material LixCоO2 along the normal to the surface on the magnitude of 40 pm in the process of charging/discharging of Li-ion power source [4].
If simultaneously to apply DC and AC voltage to a sample, measuring the position of the cantilever and the amount of current passing through the sample and the cantilever, as shown in Fig.1, it is possible to obtain information on both value of current and associated surface deformations.
Apparatus for implementing a scanning capillary microscopy, scanning electrochemical microscopy and scanning piezoelectric microscopy should enable the measurement of electrical currents in the pico- and subpicoampere ranges and the registration of the sample movement in picometer frequency range. For these purposes, the authors have developed an experimental system based on FemtoScan scanning probe microscope and FemtoScan X high-speed microscope, which is characterized by the following parameters:
• positioning accuracy along the normal to the sample is about 0.1 pm (RMS);
• measurement error of the input current is about 0.1 pA (RMS);
• the range of DC voltage applied between the probe and the sample is from 0 to 9 V with the accuracy of 16 bit;
• the range of AC voltage applied between the tip and the sample is from 0.001 Hz to 10 MHz with the accuracy of 32 bit;
• amplitude range of AC voltage is from 0 to 500 mV.
The programming for combined microscopy system is performed using Qt cross-platform software and C++ language. This solution allows to use the created software in most modern operating systems. And there is no need to change the code for a specific operating system.
To determine the accuracy of positioning at the level of 0.1 pm we have used previously developed standard of nanometer [5, 6] based on the reverse piezoelectric effect. At the application of potential difference U to the electrodes of piezo-plate its thickness is changed to the value Z in accordance with the ratio Z = d33 ∙ U, where d33 is the value of the piezomodule. At low operating voltages this relation is linear. It allows to carry out displacement by an amount which is substantially less than a nanometer. For example, if voltage applied to the electrodes of the plate (standard) is reduced by 1000 times, we obtain displacement of 1 pm.
Measurement of all input signals, as well as control of all output signals in FemtoScan X scanning probe microscope is carried out at a frequency of 1 MHz. High-speed multiplexer that is used at the input, allows to measure simultaneously up to 16 incoming signals, which is especially important in such applications as the integrated measurement of characteristics of materials.
The image of the mechanical systems of scanning probe microscopes is presented in Fig.2. ■
The present project is supported by RFBR (project No. 16-29-06290 ОФИ-М).
A scanning ion conductance microscopy, which in its broader application is also called a scanning capillary microscopy, was first implemented by Paul Hansma in 1989 [1]. Works of research group of professor Yu.Korchev [2, 3] have provided her substantial further development. A scanning ion conductance microscope allows to observe objects in a liquid (the electrolyte) with micron and nanometer spatial resolution. The use of multi-channel capillaries greatly enhances the capabilities of this type of microscopy. One channel can be used to position the capillary above the surface of the sample, while the other channels can be used for directional mass transfer of substances, atomic or molecular 3D printing. After filling of the capillary channel with conductive material, it is possible by using such electrode to implement the mode of scanning electrochemical microscopy.
Scanning piezoelectric microscopy (SPM) is implemented in atomic force microscopy in the following way. A conductive cantilever that is in contact with the sample surface is used for the measurements. The applied potential difference between the conductive cantilever and the sample leads to the displacement of ions and deformation of the sample surface that is registered with nanometer spatial resolution by the deflection of cantilever. The resulting image reflects the nature of the ion fluxes in the surface layer of the sample. This method is highly informative in the study of surface properties of energy storage, lithium-ion batteries, capacitors, etc. For example, SPM allows to notice a change in the lattice parameter of the cathode material LixCоO2 along the normal to the surface on the magnitude of 40 pm in the process of charging/discharging of Li-ion power source [4].
If simultaneously to apply DC and AC voltage to a sample, measuring the position of the cantilever and the amount of current passing through the sample and the cantilever, as shown in Fig.1, it is possible to obtain information on both value of current and associated surface deformations.
Apparatus for implementing a scanning capillary microscopy, scanning electrochemical microscopy and scanning piezoelectric microscopy should enable the measurement of electrical currents in the pico- and subpicoampere ranges and the registration of the sample movement in picometer frequency range. For these purposes, the authors have developed an experimental system based on FemtoScan scanning probe microscope and FemtoScan X high-speed microscope, which is characterized by the following parameters:
• positioning accuracy along the normal to the sample is about 0.1 pm (RMS);
• measurement error of the input current is about 0.1 pA (RMS);
• the range of DC voltage applied between the probe and the sample is from 0 to 9 V with the accuracy of 16 bit;
• the range of AC voltage applied between the tip and the sample is from 0.001 Hz to 10 MHz with the accuracy of 32 bit;
• amplitude range of AC voltage is from 0 to 500 mV.
The programming for combined microscopy system is performed using Qt cross-platform software and C++ language. This solution allows to use the created software in most modern operating systems. And there is no need to change the code for a specific operating system.
To determine the accuracy of positioning at the level of 0.1 pm we have used previously developed standard of nanometer [5, 6] based on the reverse piezoelectric effect. At the application of potential difference U to the electrodes of piezo-plate its thickness is changed to the value Z in accordance with the ratio Z = d33 ∙ U, where d33 is the value of the piezomodule. At low operating voltages this relation is linear. It allows to carry out displacement by an amount which is substantially less than a nanometer. For example, if voltage applied to the electrodes of the plate (standard) is reduced by 1000 times, we obtain displacement of 1 pm.
Measurement of all input signals, as well as control of all output signals in FemtoScan X scanning probe microscope is carried out at a frequency of 1 MHz. High-speed multiplexer that is used at the input, allows to measure simultaneously up to 16 incoming signals, which is especially important in such applications as the integrated measurement of characteristics of materials.
The image of the mechanical systems of scanning probe microscopes is presented in Fig.2. ■
The present project is supported by RFBR (project No. 16-29-06290 ОФИ-М).
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