RU2271583C1 - Cryogenic scanning probing microscope - Google Patents

Abstract

FIELD: measuring equipment engineering, in particular, engineering of devices for researching samples at atomic level under conditions of extremely low temperatures.

SUBSTANCE: cryogenic scanning probing microscope has first flange, on which rotation drive with rod is mounted, and also linear drive with first holder, directing device, second flange, vibration protection system, probe holder with probe and sample holder with sample. Directing device is made in form of rods. Rods have spherical end pieces and are held on first flange and connected to second flange. Rods are mated with catchers. Catchers are held on first platform with possible mating with spherical end pieces vibration protection system is connected to analyzing block. Analyzing block is made in form of first, second and third platforms. First platform is fixedly connected to second platform. Third platform is mounted on second platform by means of supports with spherical end pieces. Spherical end pieces are mated with V-shaped guides, positioned in third platform. Screw with spherical pusher by its smooth surface is mated with first platform.

EFFECT: improved precision of measurements and reliability of device operation.

6 cl, 6 dwg

Description

The invention relates to measuring equipment, and more particularly to devices for the study of samples at the atomic level in ultra-low temperatures.

Known cryogenic high-vacuum installation for conducting scanning tunneling microscopy [1]. The design of the STM involves the use of a stepper piezoelectric motor, which leads to insufficient reliability of the device, in addition, the described design contains an insufficient vibration protection system, which reduces the accuracy of the device.

Also known is a cryogenic scanning probe microscope [2] containing a first flange on which a rotation drive with a rod and a rotation transmission unit is mounted, as well as a linear drive with a first grip and a second flange connected to the first flange, an analysis unit coupled by means of vibration protection to the second flange. An orienting device in the form of rods with needle-shaped tips mounted on the analysis unit and paired with catchers installed on the second flange of the second grip mounted on the analysis unit and mated to the first grip, the analysis unit containing a probe holder with probes, a sample holder with a sample , made in the form of a first platform, motionlessly connected to the second platform by means of two supports with spherical tips mounted on the third platform and mated to the second platform, pos COROLLARY screw with ball pusher movably mounted on the second platform and mating with the rotation transfer unit, and second springs connected to the second and third platforms.

The disadvantages of the described device

The execution of the rods of the orienting device with needle tips and fixing them to the analysis unit worsens the orientation of the analysis unit when the probe comes closer to the sample, which can cause transfer and jamming in the circuit from the rotation drive to the screw. The use of vibration protection between the second flange and the analysis unit due to its insufficient length degrades its characteristics and measurement accuracy.

The installation of two supports on the third flange affects the resonance characteristics of the device and also the accuracy of the measurements.

Installing the screw on the second platform and pairing it with the rotation transmission unit located on the first platform can cause the block to be transferred and the screw to jam when it moves.

The technical result of the invention is to improve the accuracy of measurements and the reliability of the device.

The indicated technical result consists in the fact that in a cryogenic scanning probe microscope containing a first flange on which a rotation drive with a rod is mounted, as well as a linear drive with a first grip, an orienting device in the form of rods paired with catchers, a second flange, a vibration protection system, connected by the first ends of the first springs to the analysis unit, paired with a second grip with a first grip comprising a probe holder with a probe and a sample holder with a sample and made in the form of a first platform movably connected to the second platform, and the third platform, movably connected to the second platform by means of two bearings with spherical tips, a screw with a slot connected to the rotation transmission unit with a ball pusher mounted movably on the second platform and interfaced with the third platform, as well as the second springs connected to the second and third platforms, the rods of the orienting device have spherical tips, are fixed on the first flange and connected to the second flange, cone-type catchers are fixed on the first the second platform of the analysis unit with the possibility of interfacing with spherical tips, the vibration protection system with the second ends of the first springs is connected to the first flange, two supports are mounted on the second flange and are interfaced with spherical tips with a V-shaped guide located in the third platform, and the screw with a ball pusher has a smooth surface paired with the first platform.

There are options in which the rotation transmission unit is made in the form of an elastic pin fixed in the rod and mated with a screw slot, the first springs of the vibration protection system are connected to the first flange by means of the first hooks and a Viton adapter, with the first platform of the analysis unit by means of second hooks, while the second springs are connected to the second and third platforms by third and fourth hooks, V-shaped guides are made of solid inserts, the third platform contains a plate of solid material, conjugated with a ball push of the screw, the screw, the first, second, third and fourth hooks, solid inserts, and also a plate of solid material made of materials with low thermal conductivity.

There are also options where the rods are hollow, and the solid inserts of the V-shaped guides and the plate are made of sapphire.

Figure 1 shows a cryogenic scanning probe microscope.

Figure 2 is an embodiment of a linear actuator.

Figure 3 is an embodiment of the capture.

Figure 4 presents the layout of the KSZM in the filling cryostat.

Figure 5 - layout of the KSZM in a vacuum chamber.

Figure 6 - layout of the KSZM in pumping cryostat.

The cryogenic scanning probe microscope contains a first flange 1, on which an analysis unit 6 is installed by means of a vibration protection system containing first hooks 2, adapters 3, first springs 4 and second hooks 5. Viton rings can be used as adapters 5. The analysis unit 6 is made in the form of the first 7, second 8 and third 9 platforms. Moreover, the first 7 and second 8 platforms are connected by racks 10. Depending on the specific structural use, two or, for example, three racks 10 can be used. A scanner 11 with a probe holder 12 of the probe 13 is mounted on the second platform 8. The third platform 9 is mounted on the second platform 8 by means of supports 14 with spherical tips 15 and using a screw 16 with ball pushing 17, coupled with a nut 18. Support 14 and nut 18 are mounted on the platform 8.

On the third platform 9 can be located V-shaped guides 19 and the plate 20, made, for example, of polycor, hard alloy or sapphire. The third platform 9 is tightened to the second platform 8 by the second springs 21 using the third 22 and fourth hooks 23.

The sample holder 24 with the sample 25 can be installed on the third platform 9 by glue, spring tabs (not shown), etc.

A screw 16 with a nut 18 and a first rod 26, mounted to interact with the screw 16 and paired with a coupling 27 with a rotation drive 28, are a mechanism for preliminary approach of the probe 13 with the sample 25. As a rotation drive 28, a stepper motor can be used. The screw 16 with the rod 26 can be interfaced by means of a slot 29 and a rotation transmission unit 30. On the first flange 1, rods 31 are fixed with spherical tips 32 connected to the second flange 33 and arranged to interact with cone catchers 34, which are fixed with the possibility of quotation movement platform 7 (for example, in the gaps of the set screws (not shown)).

A linear actuator 35 is installed on the flange 1 with a rod 36 located in the hole 37 of the flange 33 and containing a first grip 38 detachably mated to a second grip 39 mounted on the first platform 7. The scanner 11, probe 13 and, in some cases, sample 25 are connected to connector 40.

The rod 26 and the rod 36 are sealed in the flange 1 by, for example, fluoroplastic seals.

The connector 40 and the rotation drive 28 are connected to a control unit (not shown).

SPM and its elements are described in more detail in [3-5].

An embodiment of a linear actuator 35 (FIG. 2) may comprise a housing 41 in which a rod 36 is mounted with a pin 42 arranged to interact with grooves 43 made in the housing 41. The screw 44 has a threaded connection with the rod 36.

An embodiment of the rotation transmission unit (FIG. 3) may include an elastic pin 45 fixed in the rod 26, arranged to interact with the groove 29 of the screw 16.

In the filler cryostat 46 (figure 4) KSZM 47 is placed directly in liquid helium or nitrogen, filled in a tank 48, connected to the supply system 49 and outlet 50.

In the vacuum chamber 51 (FIG. 5), the KSZM 47, located in the immediate vicinity of the cryogenic input 52 (see, for example, [6]), is connected to it by flexible cold leads 53 made, for example, from a bundle of copper wire. It should be noted that in the vacuum chamber 51, it is advisable to use a temperature meter 54 and a heater 55 connected to a control unit (not shown) in the CMS.

In the pumping cryostat 56 (Fig.6) KSZM 47 is located in a tank 57 with, for example, helium connected to the supply system 58 and pumping 59 of the refrigerant. In this case, it is also possible meter 54 and heater 55.

Cryostat designs are described in more detail in [7–10].

The device operates as follows. Fix the sample 25 on the holder 24 and, accordingly, the holder 24 on the platform 9. Install the probe 13 in the holder 12 of the scanner 11. After that, the flange 1 with the analysis unit 6 is placed in a cryostat and the required temperature of the measurement zone is formed. Using a linear actuator 35 and the grippers 38 and 39, raise the block 6 and carry out its orientation by the catchers 34 on the rods 31. In this case, the slot 29 of the screw 16 mates with the transmission transmission unit 30 of the rod 26. The drive 28 is turned on and the screw 16 is moved relative to the platform 8. The platform 9, moving on the supports 14, makes the sample 25 approach the probe 13. After that, using the drive 35, the grippers 38 and 39 are disconnected, while, respectively, the catchers 34 and the rods 31, as well as the slot 29 and the block 30 are opened. As a result block 6 is suspended from a spring nach 4. Thereafter, the probe 13 scans the sample 25, and accordingly, the analysis of its surface (more work SPM see Ref. [3-5]).

There are several options for the execution of individual elements KSZM, depending on the type of cryostat used.

In the first case, the sample 25 (figure 4) and the probe 13 can be located in the filling cryostat 46 directly in liquid helium or nitrogen. In this case, it is advisable to minimize heat dissipation in the direction of flange 1. For this, the first 2, second 5, third 22 and fourth 23 (Fig. 1) hooks, catchers 34, as well as guides 19 and plates 20 should be made of a material with low thermal conductivity. For hooks this can be ceramic, and for catchers 34, guides 19 and plates 20, polycor. In addition, the rod 26, the rod 36, the rack 10, as well as the screw 16 and the supports 14 can be made of thin-walled stainless tubes. Ball bearings 15 and 32 in this case can be made of balls. The thermal conductivity of the balls can be neglected and made of steel in order to increase the durability of the polycor-steel contacts. It should be noted that the specified performance of the parts is also advisable in the case of placement of the SCPS in the vacuum chamber 51 (Fig. 5) and cooling of the platform 9 with the sample 25 with flexible cold leads 53 connected to the cryogenic input 52. The heater 55 allows you to adjust the temperature of the measured object, which is fixed by the meter 54.

If KSZM placed in the pumping cryostat 56 (Fig.6) and the cooling of the measurement zone is carried out in pairs, for example helium, undesirable heat removal from the platform 9 is possible. In this case, it is more reasonable to carry out heat removal from the platform 9 to the center of the KSZM. In this case, the supports 14 (Fig. 1) and the screw 16 may not be hollow, and the guides 19 and the plate 20 are made of sapphire having high thermal conductivity at low temperatures.

The execution of the rods of the orienting device with spherical tips, their fastening on the first flange and their connection with the second flange, the execution of conical catchers and their fastening on the first platform with the possibility of pairing with spherical tips increases the orientation accuracy of the analysis unit for the preliminary approach of the probe and the sample and, accordingly , the reliability of the device. An optimal preliminary approach to the middle of the scanner range increases the accuracy of measurements (see details [3, 4]).

The connection of the analysis unit with the first flange by the springs allows to increase their length, reduces stiffness, reduces the resonant frequency of the device and, accordingly, increases the accuracy and reliability of the device. (For more details on the effect of the resonant frequency on the measurement accuracy, see [5]).

The installation of two supports on the second flange and pairing them with spherical tips with a V-shaped guide increases the resonant frequency of the device and, accordingly, increases the accuracy and reliability of its operation. At the same time, the V-shaped guide allows precise single-axis movement by an external device of the third platform relative to the second, which extends the functionality of the device.

The pairing of the smooth surface of the screw with the first platform improves its orientation during preliminary approach of the probe to the sample and increases the reliability of approach.

The execution of the rotation transmission unit in the form of an elastic pin increases the reliability of the proximity of the probe with the sample.

The implementation of the KSZM elements with low thermal conductivity reduces the heat sink from the measurement zone and stabilizes its temperature.

Low thermal conductivity of the material is most often associated with its porosity, and this, accordingly, changes the passband of the frequencies of external vibrations, which improves the vibration protection of the device.

The use of Viton adapters can also simultaneously reduce the tempo transmission and change the bandwidth of external frequencies.

The execution of the rods hollow allows in some cases to work without the use of vibration protection. This may be necessary in the case of using the proposed device for photostimulation of the measurement zone by an external radiation source, which will require an oriented installation of a CPSM.

The manufacture of solid inserts of V-shaped guides and a sapphire plate having a coefficient of thermal conductivity at low temperatures, comparable with copper, makes it possible to optimally use the proposed device in pumping cryostats, which expands its functionality.

Literature

1. Cryogenic high-vacuum installation for scanning tunneling microscopy. I.N. Khlyustikov, B.C. Edelman.

2. Patent US 5410910, G 01 B 5/28, 1995.

PTE, 1996, No. 1 p. 158-165.

3. Probe microscopy for biology and medicine. V.A. Bykov Sensory systems vol. 12, 31, 1998, pp. 99-121.

4. Scanning tunneling and atomic force microscopy in surface electrochemistry A.I. Danilov, Advances in Chemistry 64 (8), 1995, p. 818-833.

5. Scanning tunneling microscope instrumentation. Y. Kyk, P. Sulverman. Rev. Sci. Instrum. 60 (1989), No.2, 165-180.

6. Patent US 4162401, G 01 N 23/00, 1979.

7. Patent US 3747365, F 25 B 19/00, 1973.

8. Patents US 4689970, F 25 B 19/00, 1987

9. Patents US 5735127, F 25 B 9/00, 1988

10. Patent US4 689970, F 25 B 19/00, 1987

Claims (6)

1. A cryogenic scanning probe microscope containing a first flange on which a rotation drive with a rod is mounted, as well as a linear drive with a first grip, an orienting device in the form of rods paired with catchers, a second flange, a vibration protection system connected by the first ends of the first springs to the block analysis, which is associated with the second capture with the first capture, contains a probe holder with a probe, a sample holder with a sample and is made in the form of a first platform fixedly connected to the second platform, and a third platform we are movably connected to the second platform by means of two bearings with spherical tips, a screw with a slot connected to the rotation transmission unit with a ball pusher mounted movably on the second platform, and interfaced with the third platform, as well as second springs connected to the second and third platforms characterized in that the rods of the orienting device have spherical tips fixed on the first flange and connected to the second flange, cone-type catchers are fixed on the first platform with the possibility of pairing with ball tips, the vibration protection system with the second ends of the first springs is connected to the first flange, the third platform is mounted on the second platform by bearings with ball tips paired with V-shaped guides located in the third platform, and a screw with a ball pusher with a smooth surface is mated to the first platform. 2. The device according to claim 1, characterized in that the rotation transfer unit is made in the form of an elastic pin fixed in the rod and mated with a slot of a screw with low thermal conductivity. 3. The device according to claim 1, characterized in that the first springs of the vibration protection system are connected to the first flange by means of first hooks and a screw adapter, and to the first platform of the analysis unit by means of second hooks, the first and second hooks being made of material with low thermal conductivity. 4. The device according to claim 1, characterized in that the second springs are connected to the second and third platforms by third and fourth hooks with low thermal conductivity, V-shaped guides are made of solid inserts with low thermal conductivity, the third platform contains a plate of solid material with low thermal conductivity coupled to the ball propeller. 5. The device according to claim 1, characterized in that the rods are hollow. 6. The device according to claim 4, characterized in that the solid insert V-shaped guides and the plate are made of sapphire.

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