JP4697709B2 - Electrochemical measuring device - Google Patents

Description

  The present invention relates to an electrochemical measuring apparatus for observing the surface of a reaction process while controlling the electrochemical reaction of a sample generated in an electrolytic solution.

When elucidating various reaction processes that proceed at the electrode / solution interface, particularly electrochemical reaction processes, it is essential to know the structure of the sample surface that provides the reaction field. Several methods for observing the electrochemical reaction processes occurring in various electrolytes have already been considered and put into practical use. Among them, an electrochemical STM (ECSTM: Electrochemical STM) using a scanning tunneling microscope (STM) that observes a sample surface in real space at an atomic or molecular level is known (for example, see Patent Document 1). .
In this ECSTM, a sample, a counter electrode, a reference electrode, and a probe tip are arranged in at least an electrolyte solution, and after setting a certain potential with respect to the sample, a tunnel current flowing between the sample and the probe is scanned while the probe is scanned. It is a method of detecting and observing an electrochemical reaction. According to ECSTM, a change in the surface of a sample due to an electrochemical reaction can be immediately observed on the spot, and thus is widely studied and used.

  However, this ECSTM is a device for observing the surface shape of a sample using a tunnel current as a parameter on the principle of STM, and therefore a nonconductor that does not pass current is not suitable as a sample. Therefore, when a nonconductor is generated on the sample surface as a result of the electrochemical reaction or the semiconductor becomes nonconductor due to a potential, there is a disadvantage that the measurement cannot be performed.

  On the other hand, similarly to ECSTM, an apparatus such as an electrochemical atomic force microscope (ECAFM) is known as an apparatus that can measure an electrochemical reaction process in an electrolytic solution (see, for example, Patent Document 2). Since this ECAFM is an apparatus for observing a sample using a physical quantity that does not depend on the conductivity of the sample as an atomic force as a parameter, unlike the ECSTM, it is possible to measure the surface shape of a non-conductor surface. Therefore, it can respond to a wide variety of samples. Therefore, in recent years, it has expanded more rapidly than ECSTM.

The ECAFM will be briefly described with reference to FIG.
The ECAFM 80 is attached in a state in which the sample cell 82 that accommodates the sample 81 in the state of being immersed in the electrolytic solution W, the cantilever 83 that is disposed opposite to the sample 81 in the electrolytic solution W, and the state of immersion in the electrolytic solution W. The counter electrode 84 and the reference electrode 85 are provided.
The sample cell 82 includes a sample cell lower portion 82a on which the sample 81 is placed, and a sample cell upper portion 82b that is combined with the sample cell lower portion 82a and presses the sample 81 against the sample cell lower portion 82a through an O-ring 86. ing.
In addition, a cantilever holder 87 for fixing the cantilever 83 is combined with the sample cell upper part 82 b through an O-ring 88. The electrolyte solution W is filled in a space surrounded by the cantilever holder 87, the sample cell upper part 82b, and the sample 81. Thereby, the sample 81 and the cantilever 83 are immersed in the electrolytic solution W.

A conductive member 90 electrically connected to the bipotentiostat 89 is provided on the upper surface of the sample cell lower portion 82a. Further, since the sample 81 is pressed by the O-ring 86 of the sample cell upper part 82b, the sample 81 is brought into contact with the conductive member 90 to be conductive. Therefore, the sample 81 functions as a first working electrode whose potential is controlled by the bipotentiostat 89.
The cantilever 83 is fixed to the cantilever holder 87 by a clip 91 electrically connected to a bipotentiostat 89. Therefore, the cantilever 83 acts as a second working electrode whose potential is controlled by the bipotentiostat 89.
Further, the counter electrode 84 and the reference electrode 85 capable of independently controlling the potential are electrically connected to the bipotentiostat 89.

In the ECAFM 80 configured as described above, a three-electrode system that controls the potential of the first working electrode (sample 81) based on the potential of the reference electrode 85, or the first working electrode (sample 81) and the first electrode. By controlling the electrochemical reaction using a four-electrode system that controls the potential with the two working electrodes (cantilever 83), various electrochemical treatments such as plating, corrosion, and electrodetachment are possible. It can be observed in real time by AFM.
JP-A-1-141302 JP-A-9-143799

However, the following problems still remain in the above-described ECAFM80.
That is, the sample 81 that is the first working electrode, the cantilever 83 that is the second working electrode, the counter electrode 84, and the reference electrode 85 are simply immersed in the electrolytic solution W, and the positions of each other. There is no consideration for the relationship. Therefore, the following various problems have occurred.

  First, since the counter electrode 84 is simply attached in a state of being immersed in the electrolyte W at a position away from the cantilever 83, when the cantilever 83 scans the sample 81, the counter electrode and the observation position on the sample 81 are countered. The relative positional relationship with 84 changes. For this reason, even if the potential of the sample 81 is adjusted by the bipotentiostat 89, the potential at each position on the surface of the sample 81 is not uniform and is not uniform.

  Even if the potential of the sample 81 can be accurately set, the positional relationship between the sample 81 and the counter electrode 84 changes, so that the current density depending on the distance from the counter electrode 84 changes. For this reason, the electrochemical reaction rate could not be kept constant.

  Similarly to the counter electrode 84, the reference electrode 85 is simply attached in a state of being immersed in the electrolytic solution W at a position away from the cantilever 83. Therefore, when the cantilever 83 scans the sample 81, The relative positional relationship between the observation position on 81 and the reference electrode 85 changes. Therefore, it has been difficult to maintain a constant potential gradient. For example, even if the reference electrode 85 is set to 0V and the sample 81 is set to 1V, it is difficult to uniformly set the sample 81 to 1V. As a result, it was difficult to accurately control the potential of the sample 81 as the first working electrode.

  When the cantilever 83 is used as the second working electrode, that is, when observation is performed using the four-electrode method, the relative positional relationship with the counter electrode 84 and the reference electrode 85 changes when the sample 81 is scanned. As a result, the same problem described above has occurred.

  As described above, the conventional ECAFM 80 does not consider the positional relationship between the sample 81 that is the first working electrode, the cantilever 83 that is the second working electrode, the counter electrode 84, and the reference electrode 85. Various problems occur, and it is difficult to control an accurate electrochemical reaction. In particular, when the concentration of the electrolytic solution W in which the sample 81 is immersed is low and the electric resistance is high, or when the current flowing through the electrolytic solution W is large, the voltage drop becomes large. It became prominent.

  In addition, since the conventional ECAFM 80 uses the entire sample 81 as the first working electrode, when the surface state of the sample 81 is observed with the cantilever 83, an electrochemical reaction always occurs in a portion other than the observation region. Therefore, depending on the location, the surface state may change before surface observation with the cantilever 83. As a result, there was a problem that an accurate shape image could not be obtained and the shape observation of the electrochemical reaction process could not be performed accurately.

The present invention has been made in consideration of such circumstances, and its purpose is to observe the position on the sample without being affected by the observation position or the position of the sample when the surface of the sample is scanned with a cantilever. It is to provide an electrochemical measuring apparatus that can observe an accurate electrochemical reaction process by constantly controlling the potential and current density of the liquid crystal.
Furthermore, it is to provide an electrochemical measurement apparatus capable of performing an accurate surface shape observation by locally performing an electrochemical reaction near the observation position.

In order to achieve the above object, the present invention provides the following means.
The electrochemical measurement apparatus of the present invention is an electrochemical measurement apparatus for observing a reaction process of a sample while controlling an electrochemical reaction in the electrolytic solution, and is a solution that accommodates the sample immersed in the electrolytic solution A cell, a lever portion having a probe at the tip, and a support portion that supports the base end side of the lever portion in a cantilevered manner, and is disposed to face the sample while being immersed in the electrolytic solution. The cantilever, the probe and the sample are scanned relatively in a direction parallel to the sample surface, and a moving means for moving the cantilever relatively in a direction perpendicular to the sample surface, and the deflection of the lever part is measured. Based on the measurement result of the displacement measuring means and the displacement measuring means, the distance between the probe and the sample surface during the scanning is controlled, and the moving means is controlled so that the deflection of the lever portion is constant, Sample surface shape data And control means for a sample electrode in electrical contact with the sample, provided on the distal end of the lever portion with the probe, the reference electrode and a counter electrode disposed in a state of being immersed in the electrolyte within the A potential measuring device configured to control the potential of the sample electrode with reference to the potential of the reference electrode, and to measure a current flowing between the sample electrode and the counter electrode; and the cantilever includes the reference electrode and the counter electrode A reference electrode and a counter electrode are arranged in the vicinity of the probe, and two conductive films extending in the longitudinal direction from the support part side to the tip side are formed on the same plane on the lever part, One end of the conductive film located on the tip side of the lever portion is used as the reference electrode, and the other end of the conductive film located on the tip side of the lever portion is the counter electrode. characterized in that it is a It is intended to.

  In the electrochemical measurement apparatus according to the present invention, first, a sample that is a measurement object (for example, highly oriented pyrolytic graphite) is accommodated in a solution cell in which an electrolyte such as a sulfuric acid aqueous solution is stored, Immerse in the electrolyte. Next, a cantilever having a reference electrode and a counter electrode is disposed so as to face the sample while being immersed in the electrolytic solution. In this state, the current measuring means controls the potential of the sample electrode, that is, the sample, based on the potential of the reference electrode. With this three-electrode system, a current flows between the counter electrode and the sample, and an electrochemical reaction occurs on the sample surface, for example, platinum or the like is deposited. The current measuring means measures a current flowing between the sample electrode and the counter electrode.

  On the other hand, simultaneously with this electrochemical reaction, the probe and the sample are scanned in a direction parallel to the sample surface by the moving means, and scanning is performed on the sample surface where the electrochemical reaction is occurring with the probe. At this time, the control means feedback-controls the distance (height) between the probe and the sample surface based on the measurement result by the displacement measuring means so that the bending of the lever portion becomes constant. Thereby, the surface shape data of the sample can be acquired. As a result, the shape of the sample surface on which platinum or the like is deposited can be observed by an electrochemical reaction. The surface shape data of the sample and the measurement result measured by the current measuring means can be correlated with each other, and the reaction process of the sample by the electrochemical reaction can be observed.

In particular, the cantilever has a counter electrode and a reference electrode, and has a single structure in which both the reference electrode and the counter electrode are arranged in the vicinity of the probe. Therefore, when the cantilever is scanned to observe the surface shape of the sample, the reference electrode and the counter electrode also move together with the probe. That is, observation can be performed without changing the relative positional relationship between the probe, the reference electrode, and the counter electrode.
Therefore, unlike the conventional case, the potential and current density at the observation position on the sample can always be made constant without being affected by the observation position or the position of the sample when the sample surface is scanned with a cantilever. Similarly, the potential of the sample surface at the observation position can always be constant with the reference electrode potential as a reference.

As a result, the electrochemical reaction can be accurately controlled. Accordingly, the sample surface can be observed with high accuracy during the electrochemical reaction process, and the reliability of the observation result can be improved.
In addition, since the reference electrode, the counter electrode, and the probe are all provided in the same lever portion, the probe, the reference electrode, and the counter electrode can be arranged in a closer state. Therefore, the electrochemical reaction can be controlled more reliably, and the reliability of the observation result can be improved. In addition, since the probe, the reference electrode, and the counter electrode can be formed at the same time in the same lever portion, it is easy to manufacture the cantilever.

  Further, the electrochemical measurement device of the present invention is the electrochemical measurement device of the present invention, wherein the cantilever is supported by the support portion in a cantilever manner so that the cantilever is parallel to the lever portion. And a deflection measuring portion for measuring the deflection of the second lever portion, and the tip of the second lever portion with the sample electrode protruding to the sample side from the probe Is provided.

In the electrochemical measurement apparatus according to the present invention, since the sample electrode is provided on the cantilever, the sample electrode can be arranged in the vicinity of the probe in addition to the reference electrode and the counter electrode.
Further, since the sample electrode protrudes to the sample side with respect to the probe, when the cantilever is brought close to the sample by the moving means, the sample electrode can be brought into contact with the sample earlier than the probe to be conductive. . At this time, it is possible to reliably determine whether or not the sample electrode is in contact with the sample by confirming the bending state of the second lever portion. Therefore, the current measuring means can reliably control the potential of the sample via the sample electrode.

  In particular, since the sample electrode is disposed in the vicinity of the probe, an electrochemical reaction can be performed only in the vicinity of the probe for observing the sample surface. Therefore, unlike the conventional case, it is possible to prevent the surface state of the sample other than the observation position from being changed by an electrochemical reaction before the observation with the probe. As a result, the surface shape of the sample in the electrochemical reaction process can be accurately observed.

  Further, the electrochemical measurement apparatus of the present invention is the electrochemical measurement apparatus of the present invention, wherein the probe is electrically connected to the current measuring means and the potential of the reference electrode is used as a reference. The potential can be controlled separately from the sample electrode.

  In the electrochemical measurement apparatus according to the present invention, the electrochemical measurement can be performed by the four-electrode system while the current measuring means controls the potential of the probe in addition to the sample electrode. As a result, for example, when observing a sample whose potential is not controlled (such as when there is a metal plate in an acidic solution), an unintended electrochemical reaction may occur on the sample surface when the probe approaches. Can be prevented. In this way, by controlling the probe potential, it is possible to perform highly accurate shape observation without affecting the sample surface. Furthermore, during observation, the electrical potential of the probe can be changed at a desired position on the sample surface to measure local changes in the electrical properties of the sample.

  In this way, by controlling the potential of the probe, the shape of the sample surface can be observed with higher accuracy, and more diverse observations can be performed. When the probe is used as the second working electrode, the sample is observed in a non-contact state with respect to the sample. Thereby, it can prevent that the potential of a sample electrode and a probe becomes the same.

  The electrochemical measurement apparatus of the present invention is the electrochemical measurement apparatus of any one of the present inventions described above, further comprising vibration means for vibrating the lever portion in a direction perpendicular to the sample surface at a predetermined frequency. The displacement measuring means measures the vibration state of the lever portion, and the control means determines the distance between the probe and the sample during the scanning based on the measurement result by the displacement measuring means. The moving means is controlled so that the vibration state is constant.

In the electrochemical measurement apparatus according to the present invention, when observing, the vibration means vibrates the lever portion having the probe at the tip at a predetermined frequency in the direction perpendicular to the sample surface. Further, the displacement measuring means measures the vibration state of the lever portion at this time. The control means controls the distance between the probe and the sample by the moving means so that the vibration state (for example, vibration amplitude) of the lever portion is constant based on the measurement result by the displacement measurement means. Based on the control amount, the shape of the sample surface is observed.
Thus, by observing the shape of the sample surface by a dynamic method, the accuracy of the measurement result can be further improved as compared with the static method.

  According to the electrochemical measurement apparatus according to the present invention, the electrochemical reaction can be accurately controlled without being affected by the observation position or the position of the sample when the sample surface is scanned with the cantilever. The sample surface can be observed with high accuracy during the process. Therefore, the reliability of the observation result can be improved.

Hereinafter, a first embodiment of an electrochemical measurement apparatus according to the present invention will be described with reference to FIGS. 1 to 4. In the present embodiment, a case where an Au substrate is used as a sample and a CuSO ₄ aqueous solution is used as an electrolytic solution will be described as an example.
The electrochemical measurement apparatus 1 of the present embodiment is an apparatus (electrochemical ECAFM) that observes the reaction process of the sample S while controlling the electrochemical reaction in the electrolytic solution W.

  That is, as shown in FIG. 1, the electrochemical measurement apparatus 1 includes a liquid tank (solution cell) 2 that accommodates the sample S in a state of being immersed in the electrolyte W, a cantilever 3 having a probe 3a at the tip, A moving means 4 for relatively moving the probe 3a and the cantilever 3; a displacement measuring means 5 for measuring the deflection of the lever portion 21 of the cantilever 3; a control means 6 for controlling the moving means 4; The first working electrode (sample electrode) 7 that comes into contact with the electrode, the reference electrode 8 and the counter electrode 9 that are arranged so as to be immersed in the electrolyte W, and the potential of the first working electrode 7 are controlled. Current measuring means 10 for measuring a current flowing between one working electrode 7 and the counter electrode 9.

As shown in FIGS. 1 and 2, the liquid tank 2 is formed in a U-shaped cross section with an upper portion opened, and stores the electrolyte W therein. The sample S is accommodated in a state of being placed on the bottom surface of the liquid tank 2. At this time, the sample S is held in the liquid tank 2 so as not to move easily.
A first working electrode 7 formed in a plate shape with a conductive material is embedded in the bottom plate of the liquid tank 2. The first working electrode 7 is formed in a size that is hidden behind the lower surface of the sample S, so that the upper surface is exposed so as not to directly touch the electrolyte solution W. Moreover, the 1st working electrode 7 is electrically connected with respect to the bipotentiostat 11, and an electric potential is controlled arbitrarily. That is, the potential of the sample S can be controlled via the first working electrode 7.

  The liquid tank 2 configured in this way is fixed on the XYZ stage 12. The XYZ stage 12 is, for example, a piezoelectric element made of PZT (lead zirconate titanate) or the like. When a voltage is applied from the sample driving unit 13, the liquid tank 2 is set according to the voltage application amount and polarity. Thus, the sample S can be finely moved in the three directions of the XY direction parallel to the sample surface S1 and the Z direction perpendicular to the sample surface S1. Thereby, the probe 3a and the sample S can be relatively scanned in the XY directions and can be relatively moved in the Z direction. That is, the XYZ stage 12 and the sample driving unit 13 constitute the moving unit 4.

  Further, the XYZ stage 12 is attached in a recess of the housing 15 fixed on the vibration isolation table 14. A cantilever support 16 that supports the cantilever 3 is fixed to the casing 15, and a block 17 to which a laser light source 32 and a laser light receiving unit 33 to be described later are attached is fixed.

As shown in FIG. 3, the cantilever 3 is formed from an SOI substrate in which, for example, three layers of a silicon support layer 20a, an oxide layer 20b made of SiO ₂ and a silicon active layer 20c are thermally bonded together, and the probe is formed at the tip. The lever part 21 which has the needle | hook 3a and the base (support part) 22 which supports the base end side of this lever part 21 in a cantilever form are provided.
Further, the cantilever 3 of the present embodiment includes the reference electrode 8 and the counter electrode 9 at the tip of the lever portion 21 together with the probe 3a. Thereby, the reference electrode 8 and the counter electrode 9 are arrange | positioned in the vicinity of the probe 3a.

More specifically, as shown in FIG. 4, the entire upper surface of the lever portion 21 on which the probe 3a is formed is coated with an insulating film 23 made of SiO ₂ like the oxide layer 20b. A conductive film 24 made of various metal materials is patterned on the insulating film 23. As shown in FIG. 3, two conductive films 24 are formed in the longitudinal direction from the base 22 side to the distal end side of the lever portion 21, and one end on the base 22 side serves as an external connection terminal 25. The other end on the part 21 side functions as the reference electrode 8 and the counter electrode 9.
Further, an insulating film 26 made of SiO _{2 is} further coated on the conductive film 24 in a region excluding the external connection terminal 25, the reference electrode 8 and the counter electrode 9. As a result, portions other than the external connection terminal 25, the reference electrode 8, and the counter electrode 9 are prevented from directly touching the electrolytic solution W.

  In FIG. 3, the insulating films 23 and 26 are not shown. In addition, as the reference electrode 8, for example, an Au, Ag, or Pt electrode often used in ECAFM, and as the counter electrode 9, a material of the conductive film 24 is selected so as to be, for example, a Pt electrode.

  As shown in FIGS. 1 and 2, the cantilever 3 configured in this manner is placed on the cantilever support 16 via the cantilever holder 30 so as to be opposed to the sample S while being immersed in the electrolytic solution W. It is fixed. Further, the cantilever support 16 is formed of an optically transparent material, and transmits light that guides laser light L emitted from a laser light source 32 described later to a reflection surface (not shown) formed on the back side of the cantilever 3. Part 31 is attached. In addition, the light transmitting portion 31 not only guides the laser light L to the reflecting surface but also guides the laser light L reflected by the reflecting surface to the laser light receiving portion 33.

A laser light source 32 for irradiating the reflecting surface of the cantilever 3 with the laser light L via the light transmitting portion 31 is attached to the upper surface of the block 17 at a position substantially directly above the light transmitting portion 31. A laser receiving unit 33 that receives the laser light L reflected by the reflecting surface and passed through the light transmitting unit 31 is attached.
The laser light receiving unit 33 is, for example, a photodetector, and detects a change in the bending of the lever unit 21 based on the incident position of the laser light L. Then, the laser light receiving unit 33 outputs the detected change in the bending of the lever unit 21 to the preamplifier 34 as a DIF signal.
That is, the light transmitting part 31, the laser light source 32, and the laser light receiving part 33 constitute the displacement measuring means 5.

  The DIF signal output to the preamplifier 34 is amplified by the preamplifier 34, then converted into DC by the AC-DC conversion circuit 35, and sent to the Z voltage feedback circuit 36. The Z voltage feedback circuit 36 feedback-controls the sample driving unit 13 so that the DC-converted DIF signal is always constant. Thereby, when scanning is performed by the moving means 4, the distance between the probe 3a and the sample surface S1 can be controlled so that the bending of the lever portion 21 is constant. The preamplifier 34, the AC-DC conversion circuit 35, and the Z voltage feedback circuit 36 constitute an AFM measurement system 37.

The AFM measurement system 37 is connected to a control unit 38 such as a personal computer, and the control unit 38 measures the surface shape of the sample S based on the feedback signal from the Z voltage feedback circuit 36. Various physical property information (for example, potential distribution) can be measured by detecting a change in phase. The control unit 38 outputs the measured surface shape observation result to a monitor (not shown) or the like.
The control unit 38 and the AFM measurement system 37 constitute the control means 6. The control means 6 has a function of comprehensively controlling all the components including the components described later.

Here, the external connection terminal 25 provided on the base 22 of the cantilever 3 is electrically connected to the bipotentiostat 11 in the same manner as the first working electrode 7. The bipotentiostat 11 controls the potential of the first working electrode 7 based on the potential of the reference electrode 8. The electrochemical measurement system 39 measures the current flowing between the first working electrode 7 and the counter electrode 9 with reference to the potential of the reference electrode 8. That is, the bipotentiostat 11 and the electrochemical measurement system 39 constitute the current measuring means 10.
The electrochemical measurement system 39 outputs the measured current value to the control unit 38. And the control part 38 is output to the monitor etc. which are not shown in figure as an electrochemical reaction measurement result from the sent electric current value.

Next, the reaction process of the sample S is controlled by controlling the electrochemical reaction by the three-point electrode method using the first working electrode 7, the reference electrode 8 and the counter electrode 9 by the electrochemical measuring apparatus 1 configured as above. The case of observing will be described.
First, after setting the sample S in the liquid tank 2 in which the electrolytic solution W is stored, the positions of the laser light source 32 and the laser light receiving unit 33 are adjusted. That is, the laser light L emitted from the laser light source 32 passes through the light transmission part 31, is reflected by the reflection surface of the cantilever 3, and again enters the laser light receiving part 33 through the light transmission part 31 without fail. Make adjustments.

  Next, the moving unit 4 minutely moves the sample S in the three-dimensional direction. At this time, the laser light L is irradiated from the laser light source 32 toward the reflection surface of the cantilever 3, and the laser light L reflected by the reflection surface is detected by the laser light receiving unit 33. When the sample surface S1 and the probe 3a come into contact with each other in this state, the probe 3a is pushed by the sample S and the lever portion 21 is slightly bent. As a result, the angle of the laser light L reflected by the reflecting surface changes, and the incident position of the laser light L incident on the laser light receiving unit 33 changes. Therefore, it can be reliably determined that the sample surface S1 and the probe 3a are in contact with each other.

Next, the bipotentiostat 11 controls the potential of the first working electrode 7, that is, the sample S, based on the potential of the reference electrode 8. As a result, an electric current flows between the sample surface S1 and the counter electrode 9 to cause an electrochemical reaction on the sample surface S1. For example, Cu or the like is deposited on the sample S. The electrochemical measurement system 39 measures the current at this time.
On the other hand, simultaneously with this electrochemical reaction, the probe 3a and the sample S are scanned in the X and Y directions by the moving means 4, and scanning is performed on the sample surface S1 where the electrochemical reaction is occurring with the probe 3a. That is, scanning is performed in a state where feedback control is performed so that the bending of the lever portion 21 is constant. At this time, since the lever portion 21 tends to bend according to the unevenness of the sample surface S1 due to the electrochemical reaction, the amplitude of the laser light L (laser light reflected by the reflecting surface) incident on the laser light receiving portion 33 is increased. Different.

The laser light receiving unit 33 outputs a DIF signal corresponding to the amplitude to the preamplifier 34. The output DIF signal is amplified by the preamplifier 34 and DC-converted by the AC-DC converter circuit 35 and then sent to the Z voltage feedback circuit 36.
The Z voltage feedback circuit 36 slightly moves the XYZ stage 12 in the Z direction by the sample driving unit 13 so that the DC-converted DIF signal is always constant (that is, the bending of the lever unit 21 is constant). And perform feedback control. Thereby, as described above, the distance between the sample surface S1 and the probe 3a can be scanned while controlling the bending of the lever portion 21 to be constant. Further, the control unit 38 can acquire the surface shape data of the sample S based on a signal that is moved up and down by the Z voltage feedback circuit 36. As a result, the shape of the sample surface S1 on which Cu or the like is deposited can be observed by an electrochemical reaction.
Then, the surface shape data of the sample S and the measurement result measured by the current measuring means 10 can be correlated, and the reaction process of the sample S due to the electrochemical reaction can be observed.

In particular, in the electrochemical measurement apparatus 1 of the present embodiment, the cantilever 3 includes a counter electrode 9 and a reference electrode 8, and the reference electrode 8 and the counter electrode 9 are both disposed in the vicinity of the probe 3a. Yes. Therefore, when the cantilever 3 is scanned to observe the surface shape of the sample S, the reference electrode 8 and the counter electrode 9 also move together with the probe 3a. That is, it is possible to maintain a constant positional relationship without changing the relative positional relationship among the probe 3a, the reference electrode 8, and the counter electrode 9.
Therefore, unlike the conventional case, the potential and current density at the observation position on the sample S are always made constant without being affected by the observation position when the sample surface S1 is scanned with the cantilever 3 or the position of the sample S. Can do. Similarly, the potential of the sample surface S1 at the observation position can always be kept constant with the potential of the reference electrode 8 as a reference.

  As a result, the electrochemical reaction can be accurately controlled without being affected by the observation position when the sample surface S1 is scanned with the cantilever 3, the position of the sample S, and the like. Therefore, the sample surface S1 can be observed with high accuracy during the electrochemical reaction process, and the reliability of the observation result can be improved.

  In particular, in the present embodiment, since the probe 3a, the reference electrode 8 and the counter electrode 9 are all provided on the same lever portion 21, the probe 3a, the reference electrode 8 and the counter electrode 9 are surely in close proximity. ing. Therefore, the above-described operational effects become more prominent. Further, since the probe 3a, the reference electrode 8 and the counter electrode 9 can be formed on the same lever portion 21 at a time, the cantilever 3 can be easily manufactured.

Next, a second embodiment of the electrochemical measurement apparatus according to the present invention will be described with reference to FIGS. In the second embodiment, the same components as those in the first embodiment are denoted by the same reference numerals, and the description thereof is omitted.
The difference between the second embodiment and the first embodiment is that the first embodiment is a three-electrode system that performs an electrochemical reaction while controlling the potentials of the first working electrode 7, the reference electrode 8, and the counter electrode 9. However, in the electrochemical measuring apparatus 40 of the second embodiment, the probe 3a is electrically connected to the bipotentiostat 11, and the potential of the probe 3a is controlled in addition to the first working electrode 7. However, the electrochemical reaction is controlled by a four-electrode system.

That is, in the cantilever 41 of the electrochemical measuring device 40 of the present embodiment, the probe 3a extends to the base 22 side as well as the reference electrode 8 and the counter electrode 9, as shown in FIGS. It is electrically connected to a connectable conductive film 24. The conductive film 24 is formed along the center of the lever portion 21 so as to pass between the reference electrode 8 and the counter electrode 9, and one end side is electrically connected to the probe 3 a and the other end side is externally connected. The terminal 25 is electrically connected. In addition, the conductive film 24 is covered with an insulating film 26 around the probe 3 a and a portion excluding the external connection terminal 25.
In FIG. 6, the insulating films 23 and 26 are not shown.

  The external connection terminal 25 is electrically connected to the bipotentiostat 11 through a wire (not shown). The bipotentiostat 11 can control the potential of the probe 3 a separately from the first working electrode 7 on the basis of the potential of the reference electrode 8. That is, the probe 3a functions as a second working electrode.

According to the electrochemical measuring apparatus 40 configured in this manner, an electrochemical reaction can be performed in a four-electrode system while controlling the potential of the probe 3a. For example, the sample S in which the potential is not controlled. When the probe 3a is observed, it is possible to prevent an unintended electrochemical reaction from occurring on the sample surface S1 by approaching the probe 3a. In this way, by controlling the potential of the probe 3a, it is possible to perform highly accurate shape observation without affecting the sample surface S1. Furthermore, it is also possible to measure the local change in electrical properties of the sample S by changing the potential of the probe 3a at a desired position on the sample surface S1 during observation.
In this way, by controlling the potential of the probe 3a, the shape of the sample surface S1 can be observed with higher accuracy, or more diversified observations can be performed.

Next, a third embodiment of the electrochemical measurement apparatus according to the present invention will be described with reference to FIG. In the third embodiment, the same components as those in the first embodiment are denoted by the same reference numerals, and the description thereof is omitted.
The difference between the third embodiment and the first embodiment is that, in the first embodiment, the first working electrode 7 is provided in the housing 15 so as to be hidden under the sample S. The electrochemical measurement device of the embodiment is that the cantilever and the first working electrode are integrally configured.

That is, as shown in FIG. 8, the electrochemical measuring apparatus according to the present embodiment has a second lever portion whose cantilever 50 is supported by the base 22 in a cantilevered manner so that the cantilever 50 is parallel to the lever portion 21. 51 and a piezoresistive element (deflection measuring unit) 52 for measuring the bending of the second lever portion 51.
For example, the second lever portion 51 is formed so as to protrude by the same length and the same thickness as the lever portion 21. The piezoresistive element 52 is formed by implanting impurities into an SOI substrate by an ion implantation method, a diffusion method, or the like, and its resistance value changes according to the bending of the second lever portion 51. . The piezoresistive element 52 is electrically connected to the control unit 38 via a wiring (not shown), and a bias voltage is applied. Then, the piezoresistive element 52 outputs an electrical signal that changes in level according to the amount of deflection of the second lever portion 51 to the control unit 38 as an output signal. Thereby, the control part 38 can judge the bending condition of the 2nd lever part 51. FIG.

  A first working electrode (sample electrode) 53 is provided at the tip of the second lever portion 51 so as to protrude from the probe 3a. Similar to the reference electrode 8 and the counter electrode 9, the first working electrode 53 is electrically connected to a conductive film 54 that extends to the base 22 side and can be electrically connected to the outside. The conductive film 54 is formed along the center of the second lever portion 51, and one end side is electrically connected to the first working electrode 53 and the other end side is electrically connected to the external connection terminal 55. Has been. In addition, an insulating film (not shown) is coated on the periphery of the probe 3a and the region excluding the external connection terminal 55. The external connection terminal 55 is electrically connected to the bipotentiostat 11 via a wire (not shown). Thereby, the potential of the first working electrode 53 is controlled by the bipotentiostat 11.

  As described above, in the electrochemical measurement device of this embodiment, the cantilever 50 and the first working electrode 53 are integrally formed, so that the reference electrode 8 and the counter electrode 9 are added in the vicinity of the probe 3a. The first working electrode 53 is also disposed.

  In the electrochemical measuring apparatus having the cantilever 50 configured as described above, first, when the cantilever 50 and the sample S are brought close to each other by the moving means 4, the first working electrode 53 is closer to the sample S than the probe 3a. Therefore, the first working electrode 53 can be brought into contact with the sample S before the probe 3a to establish conduction. At this time, based on the electrical signal output from the piezoresistive element 52, it is possible to reliably determine whether or not the first working electrode 53 is in contact with the sample S and is bent. Therefore, the bipotentiostat 11 can reliably control the potential of the sample S via the first working electrode 53.

  Thereafter, similarly to the first embodiment, scanning is performed to observe the surface state of the sample S in the electrochemical reaction process. In particular, since the first working electrode 53 is disposed in the vicinity of the probe 3a, an electrochemical reaction can be performed only in the vicinity of the probe 3a for observing the sample surface S1. Therefore, unlike the conventional case, it is possible to prevent the surface state of the sample S other than the observation position from being changed by an electrochemical reaction before the observation with the probe 3a. As a result, the surface shape of the sample S in the electrochemical reaction process can be accurately observed.

Next, a fourth embodiment of the electrochemical measurement apparatus according to the present invention will be described with reference to FIG. In the fourth embodiment, the same components as those in the second embodiment are denoted by the same reference numerals, and the description thereof is omitted.
The difference between the fourth embodiment and the second embodiment is that, in the second embodiment, the first working electrode 7 is provided in the housing 15 so as to be hidden under the sample S. The electrochemical measurement device of the embodiment is that the cantilever and the first working electrode are integrally configured.

  That is, as shown in FIG. 9, the cantilever 60 of the electrochemical measuring device of this embodiment is supported in a cantilevered manner on the base 22 so that the base end side is parallel to the lever portion 21 as in the third embodiment. The second lever portion 51 is provided, and a piezoresistive element 52 that measures the deflection of the second lever portion 51. The second lever portion 51 is provided with a first working electrode 53, a conductive film 54, and an external connection terminal 55 as in the third embodiment.

  In the electrochemical measuring apparatus having the cantilever 60 configured as described above, when the electrochemical reaction is controlled by the four-point electrode method, first, the signal is output from the piezoresistive element 52 by the same method as in the third embodiment. Based on the electrical signal, the first working electrode 53 and the sample S are reliably brought into contact with each other. At this time, the probe 3a and the sample S are kept in a non-contact state. Thereby, it is possible to prevent the probe 3a and the first working electrode 53 from having the same potential through the sample S.

Thereafter, using the potential of the reference electrode 8 as a reference, the potentials of the probe 3a and the first working electrode are controlled to cause an electrochemical reaction by a four-electrode system. In particular, since the first working electrode 53 is disposed in the vicinity of the probe 3a, the electrochemical reaction can be performed only in the vicinity of the probe 3a for observing the sample surface S1, as in the third embodiment. it can. As a result, the surface shape of the sample S in the electrochemical reaction process can be observed more accurately.
When the potential control of the probe 3a is not performed, the sample S can be observed by the three-point electrode method by contacting the probe 3a and the sample S.

  The technical scope of the present invention is not limited to the above embodiment, and various modifications can be made without departing from the spirit of the present invention.

  For example, in each of the embodiments described above, the lever portion where the probe is formed is provided with the reference electrode and the counter electrode. However, the present invention is not limited to this case. For example, the reference electrode and the counter electrode are separately provided. A dedicated lever portion provided at the tip may be provided, and these lever portions may be supported in a cantilevered manner by a base. Even in this case, since the reference electrode and the counter electrode are disposed in the vicinity of the probe, the same operational effects can be achieved.

  In each of the above embodiments, the displacement measuring unit measures the deflection of the lever portion by an optical lever method using laser light, but the invention is not limited to the optical lever method. For example, you may comprise so that the bending of a lever part may be measured by the self-detection system which provided the displacement detection mechanism (for example, piezoresistive element etc.) in the lever part itself.

Further, in each of the above embodiments, when observing the surface shape of the sample, the measurement may be performed with a DFM which is one of the vibration modes SPM.
That is, in this case, as shown in FIG. 10, an excitation source that vibrates at a predetermined frequency between the cantilever holder 30 and the base 22 in the Z direction perpendicular to the sample surface S1. (Excitation means) 70 may be provided. Further, the displacement measuring means 5 measures the vibration state of the lever portion 21 from the incident position of the laser light L reflected by the reflecting surface. Based on the measurement result measured by the displacement measuring means 5, the control unit 38 sets the distance between the probe 3a and the sample S at the time of scanning so that the vibration state of the lever portion 21 becomes constant, that is, the vibration. What is necessary is just to comprise so that the movement means 4 may be controlled so that an amplitude may become fixed.
Thus, by observing the shape of the sample S by a dynamic method, the accuracy of the measurement result can be further improved as compared to the static method.

  Further, the sample, the electrolytic solution, the reference electrode, and the counter electrode are not limited to those described above, and may be appropriately changed. For example, HOPG (highly oriented pyrolytic graphite may be used as a sample. Silver, platinum, or the like may be used as a counter electrode. When using a mercury / mercuric sulfate electrode, a mercury / mercury oxide electrode may be used when a concentrated alkaline electrolyte is used, and a lithium / lithium ion electrode may be used when using an organic electrolyte. Au, Ag, or Pt electrodes often used in ECAFM may be used.

It is a lineblock diagram showing a 1st embodiment of an electrochemical measuring device concerning the present invention. It is an enlarged view of the cantilever and liquid tank periphery shown in FIG. It is a perspective view which shows the structure of the cantilever shown in FIG. FIG. 4 is a cross-sectional arrow view AA shown in FIG. 3. It is a block diagram which shows 2nd Embodiment of the electrochemical measuring apparatus which concerns on this invention. It is a perspective view which shows the structure of the cantilever shown in FIG. It is a cross-sectional arrow BB figure shown in FIG. It is a figure which shows 3rd Embodiment of the electrochemical measuring device which concerns on this invention, Comprising: It is a perspective view of the cantilever which an electrochemical measuring device has. It is a figure which shows 4th Embodiment of the electrochemical measuring device which concerns on this invention, Comprising: It is a perspective view of the cantilever which an electrochemical measuring device has. FIG. 4 is a view of a cantilever that is a modification of the cantilever shown in FIG. 3 and in which a lever portion vibrates at a predetermined frequency by an excitation source. It is an example which shows the structure of the conventional ECAFM.

Explanation of symbols

S sample S1 sample surface W electrolyte
1, 40 Electrochemical measurement device 2 Liquid tank (solution cell)
3, 41, 50, 60 Cantilever 3a Probe 4 Moving means 5 Displacement measuring means 6 Control means 7, 53 First working electrode (sample electrode)
8 Reference electrode 9 Counter electrode 10 Current measurement means 21 Lever part 22 Base (support part)
51 Second lever part 52 Piezoresistive element (deflection measuring part)
70 Excitation source (excitation means)

Claims (4)

An electrochemical measurement device that observes the reaction process of a sample while controlling the electrochemical reaction in an electrolyte solution,
A solution cell containing the sample immersed in an electrolytic solution;
A cantilever having a lever portion having a probe at the tip and a support portion for supporting the base end side of the lever portion in a cantilever manner, and disposed opposite to the sample while being immersed in the electrolytic solution;
Moving the probe and the sample relative to each other in a direction parallel to the sample surface and moving in a direction perpendicular to the sample surface;
A displacement measuring means for measuring the deflection of the lever portion;
Based on the measurement result by the displacement measuring means, the distance between the probe and the sample surface during the scanning is controlled, the moving means is controlled so that the deflection of the lever portion is constant, and the surface shape data of the sample Control means for obtaining
A sample electrode in electrical contact with the sample;
A reference electrode and a counter electrode provided at the tip of the lever portion together with the probe, and arranged in a state of being immersed in the electrolytic solution,
The electric potential of the sample electrode is controlled on the basis of the electric potential of the reference electrode, and current measuring means for measuring the current flowing between the sample electrode and the counter electrode is provided,
The cantilever includes the reference electrode and the counter electrode, and the reference electrode and the counter electrode are disposed in the vicinity of the probe ,
In the lever portion, two conductive films extending in the longitudinal direction from the support portion side to the distal end side are formed on the same plane,
Of the one conductive film, the end located on the tip side of the lever portion is the reference electrode,
An electrochemical measurement apparatus , wherein an end portion of the other conductive film located on a distal end side of the lever portion is the counter electrode . The electrochemical measurement device according to claim 1,
The cantilever includes a second lever portion whose base end side is supported by the support portion in a cantilever manner so as to be parallel to the lever portion, and a deflection measuring portion that measures the deflection of the second lever portion. Prepared,
The electrochemical measurement apparatus, wherein the sample electrode is provided at a tip of the second lever portion in a state of protruding to the sample side from the probe. The electrochemical measurement device according to claim 1 or 2 ,
The probe is electrically connected to the current measuring means, and the potential can be controlled separately from the sample electrode based on the potential of the reference electrode. Electrochemical measuring device. In the electrochemical measuring device according to any one of claims 1 to 3 ,
A vibration means for vibrating the lever portion at a predetermined frequency in a direction perpendicular to the sample surface;
The displacement measuring means measures a vibration state of the lever portion;
The control unit controls the distance between the probe and the sample during the scanning based on the measurement result by the displacement measuring unit, and controls the moving unit so that the vibration state of the cantilever is constant. An electrochemical measuring device.

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