JP2006349459A - Scanning probe microscope - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To solve the problem wherein a feed mechanism or a taking-up mechanism is required in order to prevent the entanglement and damage of connected optical fibers when an SPM cell unit is moved between chambers and assembly, disassembly and maintenance are difficult as a result because the complication and scaling-up of an apparatus can not be avoided. <P>SOLUTION: This scanning prove microscope is constituted so that a unit connector is attached to the outer surface of the SPM unit, a receiving connector is attached to the part opposed to the unit connector of an SPM unit receiver, the other end parts of the optical fibers supported on an optical fiber support are attached to the unit connector and the respective connectors are connected so as to enable the giving and receiving of light between the respective fibers when the unit is mounted on the unit receiver. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention is a scanning probe microscope (hereinafter referred to as a generic name of a scanning tunnel microscope, an atomic force microscope, a magnetic force microscope, a friction force microscope, a micro viscoelastic microscope, a surface potential difference microscope, a scanning near field microscope, and the like). SPM).

  In recent years, the atomic force acting between the probe and the sample can be achieved by scanning the surface of the sample with the probe by placing the cantilever with the probe and the sample facing each other, setting the distance between the probe and the sample to be a few nanometers or less. Attention has been focused on a scanning probe microscope that measures physical quantities such as those and obtains a concavo-convex image of the sample surface based on the measurement. As a method of measuring the physical quantity acting on the probe, there is a method of irradiating the back surface of the cantilever having the probe with a laser beam, receiving the reflected laser beam, and measuring the displacement of the position or the frequency displacement of the laser beam. Be taken.

  When observing, it may be necessary to observe in an environment of different atmospheres such as vacuum, ultra-low temperature, and magnetic field depending on the purpose. For this reason, the sample stage, the cantilever provided facing the sample, the scanner that scans the sample and the cantilever relatively, etc. are made into cell units, and the SPM cell unit is moved between the chambers of each environment by the SPM cell transfer rod. And observed.

  An optical fiber is connected to the SPM cell unit and a detection signal is sent to the outside of the apparatus. However, when the SPM cell unit is transported, it is transported with the optical fiber connected. In this case, slack is prevented by using a string-wound spring-like optical fiber or a winding / feeding mechanism.

  However, in order to prevent the optical fiber from being damaged, a winding / feeding mechanism larger than the radius of curvature is required, resulting in an increase in size and complexity of the apparatus. Also, the assembly, adjustment and maintenance of the device was difficult. Since the optical fiber is movable, the operability is poor due to entanglement or damage. In particular, at a liquid helium temperature of about 4K, the optical fiber is hardened and difficult to move, and it has been necessary to move it after raising the temperature to near room temperature.

  Further, when the SPM cell unit is transported in a vacuum environment, when the string-wound spring-shaped optical fiber expands and contracts, a very small amount of gas is emitted from the coating agent of the optical fiber, which affects the ultra-high vacuum environment. Particles also came out from the moving part of the winding / feeding mechanism and contaminated the ultra-high vacuum environment.

  Conventional optical fiber connectors were not intended for use in environments such as ultra-high vacuum, liquid nitrogen temperature and liquid helium. For this reason, in such an environment where direct attachment / detachment by a human hand cannot be performed, positional accuracy cannot be obtained, and attachment / detachment is difficult. Further, thermal contraction or the like occurred, and the connector was sometimes damaged. Most optical fiber connectors are made of resin, so they melted and deformed during baking to create an ultra-high vacuum, or were unsuitable for vacuum by releasing gas.

  As a conventional technique, there is a scanning probe microscope that is unitized and connected to a main body via an electrical connector (for example, Patent Document 1).

JP-A-8-75757

  The problem to be solved by the present invention is that when the SPM cell unit is moved between chambers, a connected optical fiber is not entangled and a feeding mechanism and a winding mechanism are required to prevent damage. It is. For this reason, complication and enlargement of the apparatus cannot be avoided, and as a result, assembly, disassembly, and maintenance have been difficult. It also had a negative effect on clean ultra-high vacuum.

  According to the first aspect of the present invention, a cantilever having a probe, a scanner for scanning the probe and the sample relatively with the probe approaching or contacting the sample surface, and an optical fiber support are unitized. And a unit receiver that detachably receives the unit, irradiates the cantilever with light from a light source provided outside the unit through an optical fiber supported by the optical fiber support, and reflects light from the cantilever. In the scanning probe microscope configured to receive the light by the optical fiber, a unit connector is attached to the outer surface of the unit, and a receiving connector is attached to a portion of the unit receiver facing the unit connector. Attach the other end of the optical fiber supported by the optical fiber support The receiving connector is configured to attach the other end of an optical fiber substantially connected to the light source, and when the unit is attached to the unit receiver, the light can be exchanged between the fibers. This is a scanning probe microscope in which each connector is connected.

  In the invention of claim 2, the unit receiver is provided in a plurality of types of chambers, and when the unit is moved between the chambers by a unit transport means and attached to the unit receiver of the destination chamber, 2. The scanning probe microscope according to claim 1, wherein the connectors are connected so that light can be exchanged between the fibers.

  The invention of claim 3 is the scanning probe microscope according to claim 2, wherein the plurality of types of chambers are a chamber in a room temperature environment in a vacuum state and a chamber in a low temperature environment in a vacuum state.

  According to the present invention, since the SPM cell unit is connected to the chamber through the optical fiber connector, the optical fiber is not routed in the apparatus even if the SPM cell unit is moved, and the optical fiber is damaged. The possibility of trouble is low, and the inside of the chamber is not contaminated. In addition, an optical fiber feeding mechanism and a winding mechanism are not required, and the apparatus is prevented from becoming complicated and large. In addition, assembly, disassembly, and maintenance have become easier.

  The configuration of the present invention will be described with reference to FIGS. FIG. 4 is a sectional view of the entire apparatus. A vibration isolation table 25 is installed on the gantry 26, and the main chamber 20 is installed above the vibration isolation table 25 via a damper mechanism 24. A room temperature section SPM cell stage (not shown) is installed in the main chamber 20. A transfer rod storage chamber 23 is installed on the main chamber 20. An SPM cell transfer rod 22 for moving the SPM cell unit 7 is movably stored in the transfer rod storage chamber 23. On the other hand, a cryostat 21 is connected to the lower portion of the main chamber 20 so as to hang. The SPM cell unit 7 and the SPM cell stage 5 are stored inside the cryostat 21 and filled with liquid helium 27. The inside of the main chamber 20 and the cryostat 21 is maintained at an ultra high vacuum by a vacuum pump (not shown).

  FIG. 1 is a detailed view of the SPM cell unit 7 and the SPM cell stage 5 in FIG. An SPM cell unit 7 is accommodated in the recess of the SPM cell stage 5.

  An inertial drive type XYZ coarse movement mechanism 8 fixed to the SPM cell stage 5 is installed in the SPM cell unit 7, and a tube scanner 9 composed of a piezoelectric element that is displaceable in the XYZ directions is installed on the upper surface thereof. Yes. A sample holder 10 is installed on the upper surface of the scanner 9, and a sample 11 is placed on the upper surface of the sample holder 10 in a replaceable manner. A cantilever 13 having a probe 12 at one end is installed facing the sample 11, and the other end of the cantilever 13 is fixed to the SPM cell unit 7.

  The irradiation surface of the cell side optical fiber 15 is installed facing the probe position of the cantilever 13, and the optical fiber insertion side connector 6 is installed at the other end of the cell side optical fiber 15. The optical fiber insertion side connector 6 is installed outside the SPM cell unit 7. An SPM cell transport rod 22 is detachably installed on the upper part of the SPM cell unit 7. In addition, a spring probe electrode 14 electrically connected to the scanner 9, the XYZ coarse movement mechanism 8, the cantilever 13, and the like is installed outside the SPM cell unit 7.

  The SPM cell stage 5 is provided with an optical fiber receiving side connector 2, and the optical fiber insertion side connector 6 is fitted to the optical fiber receiving side connector 2. The SPM cell stage 5 is provided with a receiving electrode 3 that transmits an electrical signal to the SPM cell unit 7. The SPM cell unit 7 and the SPM cell stage 5 are installed in vacuum in the SPM, and the stage side optical fiber 1 and the lead wire 4 are connected to the outside of the vacuum.

3 is a detailed view of the optical fiber receiving connector 2 and the optical fiber insertion connector 6 in FIG.
In the optical fiber receiving connector 2, a housing 36 accommodates a ferrule guide 34 and a spring 37 that hold a receiving ferrule 32 that performs terminal processing of the optical fiber cable 1. The receiving-side ferrule 32 is a cylindrical rod-shaped part that supports the stage-side optical fiber 1. Since the optical fiber alone is thin and easy to break, the optical fiber is bonded by fixing the optical fiber to the center of the ferrule and the ferrules are brought into contact with each other. Connect with high accuracy. The connection surface of the receiving ferrule 32 is chamfered, and the stage side optical fiber 1 appears. The stage-side optical fiber 1 is coated with a material that can be used in baking such as Teflon (registered trademark), ultra-high vacuum (hereinafter referred to as UHV), and liquid helium temperature environment. Further, the ferrule guide 34 is held on the inner surface of the housing 36 by a spring 37. The spring 37 is a tapered chord spring. The shape of the spring 37 may be cylindrical, but it is more effective when it is tapered.

  A sleeve guide 31 is installed on the upper surface of the ferrule guide 34, protrudes from an opening of the housing 36, and is locked by a flange portion of the ferrule guide 34. A sleeve 33 is housed inside the sleeve guide 31 with mechanical backlash. The insertion-side ferrule 35 and the fitting accuracy of micron order are provided. The housing 36, the receiving ferrule 32, and the sleeve 33 are made of a material such as ceramic or zirconium that does not emit gas or the like even when heated to a high temperature. Even liquid helium 27 of about 4K is not damaged due to thermal contraction. Thereby, it can be used in a bake, UHV, or liquid helium temperature environment. The inner diameter of the sleeve guide 31 is made slightly larger than the outer shape of the sleeve 33. Since the upper surface of the sleeve guide 31 is provided with a claw, the sleeve 33 is held with a slight backlash. The sleeve 33 is fixed to the receiving ferrule 32.

  Further, in the optical fiber insertion side connector 6, an insertion side ferrule 35 is installed on the end face of the cell side optical fiber 15 and is fixed to the SPM cell 7. The cell side optical fiber 16 is coated with a material such as Teflon (registered trademark).

  The optical fiber insertion side connector 6 is guided by the sleeve of the optical fiber receiving side connector 2 to align the optical axis of the optical fiber. Since the sleeve 33 supported by the spring 37 is movable, the shift of the optical fiber insertion side connector 6 can be absorbed and the optical axis of the optical fiber can be accurately aligned.

  The configuration of each unit in FIGS. 1 to 4 has been described above. Next, the operation will be described. FIG. 1 shows a state in which the SPM cell unit 7 is installed on the SPM cell stage 5. The optical fiber insertion side connector 6 is connected through the optical fiber receiving side connector 2 and further connected to the outside of the apparatus.

  The fixed end of the cantilever 13 is provided with a piezoelectric vibrator for vibrating. The cantilever 13 has a natural frequency of several tens of kHz to several hundreds of kHz depending on its length and thickness. When this natural vibration frequency is applied to the piezoelectric vibrator, the free end where the probe 12 is formed is unique. Moves up and down about several nanometers at the vibration frequency.

When the state at this time is set to a steady state and the probe 12 is brought close to the sample 11, an interatomic attractive force acts between the probe 12 and the sample 11 at the lowest point. When the probe 12 receives an atomic attractive force, the spring constant of the cantilever 13 is apparently changed, and the frequency is lower (the vibration period is longer) than the vibration frequency f ₀ in the steady state.

  The tip of the cantilever 13 is irradiated with laser light from the optical fiber, and the laser light reflected from the cantilever 13 is detected by the same optical fiber. Thereby, the displacement of the cantilever 13 can be detected using optical interference. In this optical interference system, among the frequency components included in the laser light reflected from the cantilever 13, any one of the frequency change Δf, amplitude change ΔA, and phase change caused by the attractive force is used as a feedback signal, and the scanner 9 is moved in the Z direction. The distance between the probe 12 and the sample 11 is kept constant. The voltage input to the scanner 9 at this time is imaged as unevenness information based on the data obtained by converting the distance. In the detection of the feedback signal, an FM detection method for directly detecting it in a vacuum is used. Observation in a vacuum is performed for the purpose of obtaining a high-resolution image by excluding the influence of surface tension due to moisture or the like on the surface of the sample 11 or for the purpose of cooling.

  The laser light received by the cell side optical fiber 15 is transmitted from the optical fiber insertion side connector 6 to the optical fiber receiving side connector 2 and is transmitted to the outside of the apparatus.

  The inside of the cryostat 21 in FIG. 4 is cooled by liquid helium 27 of about 4K. Cooling methods include a liquid flow method, a mechanical refrigeration method, a liquid storage method, and the like, but a liquid storage method is used that is simple and not affected by the sound of the liquid circulating or the operating sound of the machine. The SPM cell unit 7 is cooled inside the cryostat 21. A laser unit used in a normal optical lever system does not operate at an extremely low temperature of about 4K, but an optical fiber interference system can irradiate the cantilever 13 with a laser beam even at an extremely low temperature.

  When the SPM cell unit 7 is moved from the cryostat 21 to the main chamber 20 in the room temperature portion, the SPM cell unit 7 placed on the SPM cell stage 5 is pulled up to the main chamber 20 using the SPM cell transport rod 22. . When the SPM cell transport rod 22 is lifted, the SPM cell unit 7 engaged with the SPM cell transport rod 22 is also lifted together. At this time, the optical fiber insertion side connector 6 and the spring probe electrode 14 are disengaged, and the state shown in FIG. 2 is obtained.

  When the SPM cell unit 7 is pulled up to the main chamber 20, the SPM cell unit 7 is installed on a room temperature SPM cell stage (not shown). At this time, the optical fiber insertion side connector 6 is again connected to the optical fiber receiving side connector 2 to be in the state shown in FIG. The spring probe electrode 14 is also connected to the receiving electrode.

  Connection between optical fibers requires micron-order axial alignment, but the optical fiber receiving connector 2 absorbs mechanical misalignment. For this reason, the connection surface of the ferrule which connects optical fibers satisfies connection conditions, such as contact pressure and axial accuracy. Moreover, the optical fiber receiving side connector 2 also absorbs shrinkage due to a temperature difference.

  When the sample is cooled from room temperature to liquid nitrogen temperature or liquid helium temperature and observed, the phase transition of the substance can be examined.

  By the way, baking is necessary to obtain a good UHV environment. Baking is to bake out at about 200 ° C. in order to remove a very small amount of gas adhering to the inside of the apparatus, and is performed every time the vacuum is broken. Since the optical fiber, the optical fiber receiving side connector 2 and the optical fiber insertion side connector 6 do not use a resin material or the like, gas is not generated from the parts even when baking is performed, and a clean UHV environment is achieved. Can be held.

  Although the operation has been described above, according to the above configuration, even if the SPM cell unit 7 is moved, the optical fiber is not routed in the apparatus, and the possibility of troubles such as damage to the optical fiber is reduced. In addition, an optical fiber feed-out and winding mechanism are not required, and the complexity and size of the apparatus can be avoided. Furthermore, assembly, disassembly, and maintenance are easy.

  In addition, this invention is not limited to the said embodiment, A various deformation | transformation is possible. For example, various environments according to the sample to be measured can be considered outside the SPM cell unit 7, but the sample may be observed in a strong magnetic field of about 20 stellars. In this case, a superconducting magnet in which a superconducting material is wound in a coil shape is installed inside the cryostat. In a strong magnetic field of about 20 stellar, a laser unit and a detector used for a normal optical lever system do not operate, but an optical interference system using an optical fiber used in this application operates even in a strong magnetic field.

Moreover, you may use for not only a scanning probe microscope but another surface observation apparatus.

It is the figure which combined the SPM cell unit and SPM cell stage in this invention. It is the figure which removed the coupling | bonding of the SPM cell unit and SPM cell stage in this invention. It is an optical fiber connector detailed drawing in this invention. 1 is an overall view of an SPM device in the present invention. It is a figure which shows the coupling | bonding of the SPM cell unit and SPM cell stage in a prior art.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Stage side optical fiber 2 Optical fiber receiving side connector 3 Receiver electrode 4 Lead wire 5 SPM cell stage 6 Optical fiber insertion side connector 7 SPM cell unit 8 XYZ rough movement mechanism 9 Scanner 10 Sample holder 11 Sample 12 Probe 13 Cantilever 14 Spring probe electrode 15 Cell side optical fiber 20 Main chamber 21 Cryostat 22 SPM cell transfer rod 23 Transfer rod storage chamber 24 Damper mechanism 25 Vibration isolation table 26 Mount 27 Liquid helium 31 Sleeve guide 32 Receiving ferrule 33 Sleeve 34 Ferrule guide 35 Insertion Side ferrule 36 Housing 37 Spring 38 Plug-in side optical fiber connector 39 Inner chamber in cryostat

Claims (3)

  A cantilever with a probe, a scanner for scanning the probe and the sample relatively with the probe close to or in contact with the sample surface, and an optical fiber support as a unit, and detaching the unit A unit receiver that can be freely received is provided, light from a light source provided outside the unit is irradiated to the cantilever through an optical fiber supported by the optical fiber support, and reflected light from the cantilever is received by the optical fiber. In the scanning probe microscope according to the present invention, a unit connector is attached to the outer surface of the unit, and a receiving connector is attached to a portion of the unit receiver facing the unit connector. The unit connector is attached to the optical fiber support. Attach the other end of the supported optical fiber and connect the receiving connector The other end of the optical fiber substantially connected to the light source is attached, and when the unit is mounted on the unit receiver, the connection of the connectors is possible so that light can be exchanged between the fibers. Scanning probe microscope made to perform.   The unit receiver is provided in a plurality of types of chambers. When the unit is moved between the chambers by a unit transporting unit and mounted on the unit receiver of the destination chamber, light is transmitted and received between the fibers. The scanning probe microscope according to claim 1, wherein the connectors are connected to each other so as to be possible. The scanning probe microscope according to claim 2, wherein the plurality of types of chambers are a chamber in a room temperature environment in a vacuum state and a chamber in a low temperature environment in a vacuum state.

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