JPH0518706A - Probe cleaning device for tunnel microscope - Google Patents

Abstract

PURPOSE:To easily clean a probe without removing it by providing a heater for heating the probe at the position where it opposes to a probe for tunneling microscope and conducting electricity to the heater. CONSTITUTION:Wire material which melts at high temperature such as tungsten wire is used as a heater 3 and wound in the shape of a coil. A magnetic loader 12 is operated to mount a sample holder 1 to stage electrode sections 6, 7. Current introduction terminals 2a, 2b on the holder side contact the electrode sections 6, 7, and electricity is conducted to the heater 3 to heat it. Consequently, a probe 8 which is mounted on an opposing piezoelectric scanning device 10 is heated and cleaned by inserting it into a heater coil 3. Thus, it is possible to heat and clean the probe 8 without removing it by providing the heater 3 in the existing sample holder.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a cleaning device for a scanning tunneling microscope (STM) probe that drives a probe three-dimensionally to approach a sample on the order of nm and detects the tunnel current at that time. It is about.

[0002]

2. Description of the Related Art When the tip of the probe is brought close to the sample surface up to the nm order where the atom at the tip of the probe and the electron cloud of the atom of the sample overlap, when a bias voltage is applied between the probe and the sample in this state. , A tunnel current flows between the probe and the sample. Since this current particularly depends on the distance between the probe and the sample (height of the probe), the distance between the sample and the probe can be measured very accurately by measuring the magnitude of the tunnel current. Can be measured.

The STM controls the height of the probe so that the tunnel current is constant, while observing the uneven shape of the sample surface by the trajectory of the height of the probe when the probe is scanned in the horizontal direction. It is a device that is attracting attention in analyzing surface atomic arrangements. Further, STM is becoming established as a means of surface analysis, and its application field is expanding not only to the microscope method for examining atomic positions on the surface but also to the field of spectroscopy for locally examining the electronic state of the surface. ing. Moreover, the STM has been widely used by being applied to various fields in a short period of time because of its principle, simple mechanism, and small device size. For example, observation of uneven images including surface atomic and molecular levels. Atomic force microscopes that utilize atomic force, magnetic force microscopes that utilize magnetic force, and ballistic microscopes that can obtain information on the electronic structure of metal / semiconductor / semiconductor / semiconductor interfaces. There are also surface roughness meters in the field and applications to ultra-fine processing equipment. However, since the STM is a device that uses the current due to the tunnel effect, the surface state of the probe and the sample are important factors for obtaining a stable image. But,
For example, water vapor, hydrocarbon, etc. adhere to the tip of the probe, which deteriorates the quality of the uneven image on the sample surface.

Therefore, it is necessary to clean the probe. As a conventional probe cleaning method, a method of burning out the entire device with the probe set in the tunnel microscope device, that is, FIM (Field Ion Micro) is used.
oscopy) method, ion sputtering method, and the like.

[0005]

However, the method of baking out the entire apparatus cannot provide sufficient cleaning, and the FIM method or the ion sputtering method requires that the probe be once removed and cleaned. The probe tip may not be set perpendicularly to the sample surface when it is attached to the STM after cleaning or cleaning it and it may not be the observation surface of the sample accurately, and the size of the device may increase. There is also the problem of being lost.

As described above, if the surface unevenness image of the sample is observed by scanning the sample surface while controlling the probe so that the tunnel current becomes constant, the three-dimensional scanner follows a fixed sequence. However, if the STM is used as a scanning tunneling electron spectroscopy to obtain a spectrum, the surfaces of the sample and the probe facing each other must be clean at the atomic level. It is desired to develop a simple method for cleaning the probe.

The present invention has been made to solve the above-mentioned problems, and utilizes a terminal for heating a sample which is already incorporated,
It is an object of the present invention to provide a probe cleaning device for a tunnel microscope, which can be cleaned very easily in the same state without removing the probe.

[0008]

According to the present invention, in a scanning tunneling microscope in which a probe is three-dimensionally driven and the probe is brought close to the sample to detect a tunnel current, the sample is fixed at a position facing the probe. The cartridge-type sample holder is provided with a heater for heating a probe to form a heating holder, and the probe is heated and cleaned by energizing the heater.

Further, the present invention is characterized in that an electrode for applying a high voltage is arranged between the probe and the probe to heat while applying a high voltage.

[0010]

The function of the probe cleaning device for tunnel microscope of the present invention is as follows.
A heating heater is installed in a cartridge-type sample holder that has terminals for sample heating, bias voltage application, tunnel current detection, etc., to form a heating holder of the same shape as the sample holder. It is possible to indirectly perform heat cleaning by removing only the probe without removing the probe from the scanner head. By providing an electrode facing the probe and applying a high voltage, it is possible to clean the tip of the probe and remold it, and by heating the probe with a metal ion source attached. It is also possible to deposit a metal on the sample.

[0011]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 is a view showing an embodiment of a probe cleaning apparatus for tunnel microscope of the present invention. In the figure, 1 is a heating holder, 2a and 2b are current introducing terminals, 3 is a heater, 4 is an external holder, 5 is an insulator, 6 and 7 are stage electrode parts, 8 is a probe, 9 is a probe holder, and 10 is a probe holder. Is a piezoelectric scanning element, 11 is a fixed holder, and 12 is a magnetic loader.

The heating holder 1 has current-introducing terminals 2a and 2b provided at the end of an insulator 5 attached to the outer holder 4. Normally, the sample is attached on the insulator 5 and is a cartridge type sample. It functions as a holder. This heating holder 1 is a magnetic loader 1.
The external holder 4 is screwed to the unit 2, and can be moved from outside the vacuum by operating the magnetic loader 12 with a magnet (not shown), and is attached to the electrode units 6 and 7 of the sample stage (not shown). The current introduction terminals 2a and 2b of the heating holder 1 heat the sample, detect the tunnel current,
It is used for applying a bias voltage and the like.

FIG. 1 shows a heating holder in which a heater 3 for heating a probe is attached to an existing sample holder. In this embodiment, a high melting point wire such as a tungsten wire is used as the heater. This tungsten wire is wound in a coil shape. When the magnetic loader 12 is operated to mount the sample holder 1 on the stage electrode portions 6 and 7, the current introduction terminals 2a and 2b on the holder side come into contact with the stage electrode portion.
Electricity can be supplied and heated through the stage electrode section. Therefore, heating cleaning becomes possible by inserting the probe 3 attached to the opposing piezoelectric scanning element 10 into the coil. In this way, by simply providing the heater on the existing sample holder, it is possible to perform the heating cleaning without removing the probe by a method such as normal sample heating.

FIG. 2 is a view showing an example of the heating holder. In the heating holder shown in FIG. 2, the heater 3 has a coil shape, and an outer holder 4 that fits with the magnetic loader is provided in an annular shape around the insulator 5, and the tip of the magnetic loader is placed inside the outer holder 4 or The heater 3 is pushed into the outside to be fitted, the heating holder is attached to the electrode stage by a magnet (not shown) outside the vacuum, the tip of the probe is set in the coil, and the probe is energized through the current introduction terminals 2a and 2b by the heater 3 Heat cleaning.

FIG. 3 is a view showing another example of the heating holder. In the holder shown in FIG. 3, the heater 3 has a cup-like shape and can be cleaned by putting the tip of the probe in the heater cup and heating it as in the case of FIG.
FIG. 4 is a diagram showing another embodiment of the present invention. In this embodiment, when a probe is inserted into a heater as shown in FIG. 1, a needle electrode 13 to which a high voltage can be applied from an external power source is arranged at a position facing the probe. By applying voltage, the tip of the probe can be cleaned by electric field evaporation, and the tip of the probe can be remolded into a stable shape.

FIG. 5 shows that when the probe is inserted into the heater 3,
An example is shown in which the metal plate 14 is used as a counter electrode at a position facing the probe.

In this embodiment, the probe is mounted on the metal plate 14
It is possible to clean the probe while approaching it on the order of m and detecting the tunnel current between the metal plate and the probe to observe the STM image on the surface of the metal plate 14. Further, by attaching a metal ion source 15 such as gallium or germanium to the probe, it is possible to observe how metal is vapor-deposited on the sample.

In the above-mentioned embodiment, an example in which cleaning is carried out in an ultrahigh vacuum state has been described. However, a mechanism for introducing gas only around the probe is provided to cause plasma discharge to etch the tip of the probe. You may make it clean by doing.

[0019]

As described above, according to the present invention, an existing sample holder can be used to attach a heater for heating a probe to form a heating holder, and heating can be performed easily by heating the probe. Also, by attaching a metal ion source, etc. to the probe and heating it, metal can be deposited on the sample, so it is possible to observe the state of deposition, etc. By heating the needle, the tip of the probe can be cleaned using electric field evaporation.

[Brief description of drawings]

FIG. 1 is a diagram showing an embodiment of a probe cleaning device for a tunnel microscope.

FIG. 2 is a diagram showing an example of a heating holder using a coil heater.

FIG. 3 is a diagram showing an example of a heating holder using a cup heater.

FIG. 4 is a diagram for explaining cleaning using electrolytic evaporation.

FIG. 5 is a diagram showing an example of cleaning while observing an STM image.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Heating holder, 2a, 2b ... Current introduction terminal, 3 ... Heater, 4 ... External holder, 5 ... Insulator, 6,7 ... Stage electrode part, 8 ... Probe, 9 ... Probe holder, 10 ... Piezoelectric scanning Element, 11 ... Fixed holder, 12 ... Magnetic loader.

Claims (2)

[Claims] 1. In a scanning tunneling microscope in which a probe is three-dimensionally driven to bring the probe close to the sample to detect a tunnel current, a probe is mounted on a cartridge-type sample holder that fixes the sample at a position facing the probe. A probe cleaning apparatus for a tunnel microscope, wherein a heater for heating a needle is provided to constitute a holder for heating, and the probe is heated and cleaned by energizing the heater. 2. The probe for a tunnel microscope according to claim 1, wherein an electrode for applying a high voltage is arranged between the probe and the probe, and heating is performed while applying a high voltage to the probe. Cleaning device.