JP2875066B2 - Probe cleaning device for tunnel microscope - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

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

[0002]

2. Description of the Related Art When the tip of a probe is brought close to the surface of the sample until the electron cloud of the atoms at the tip of the probe and the atoms of the sample overlap with each other, a bias voltage is applied between the probe and the sample in this state. Then, a tunnel current flows between the probe and the sample. Since this current depends particularly on the distance between the probe and the sample (height of the probe), the distance between the sample and the probe can be determined very precisely by measuring the magnitude of the tunnel current. Can be measured.

In the STM, while controlling the height of the probe so that the tunnel current is constant, the unevenness of the surface of the sample is observed based on the locus of the height of the probe when the probe is scanned in the horizontal direction. This is a device that has attracted attention in analyzing surface atomic arrangements. In addition, STM is becoming established as a means of surface analysis, and its application field is expanding not only to microscopy for examining the atomic position of a surface but also to spectroscopy for locally examining the electronic state of a surface. ing. In addition, STM has been widely applied in 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 microscope using atomic force, magnetic force microscope using magnetic force, ballistic microscope that can obtain information on the electronic structure of the interface of metal / semiconductor / semiconductor / semiconductor, etc. There are also applications to surface roughness meters and ultra-fine processing equipment in the field. However, since the STM is an apparatus using a current by the tunnel effect, the surface condition of the probe and the sample is an important factor for obtaining a stable image. But,
For example, water vapor, hydrocarbon, and the like adhere to the tip of the probe, and the quality of the uneven image on the sample surface deteriorates.

Therefore, it is necessary to clean the probe. Conventional methods for cleaning the probe include a method in which the probe is set in a tunnel microscope device and the entire device is burned out, and a FIM (Field Ion Micr).
oscopy) method, ion sputtering method, and the like.

[0005]

However, the method of baking out the entire apparatus cannot perform sufficient cleaning, and the FIM method or the ion sputtering method requires that the probe be once removed and cleaned. When the probe is contaminated or cleaned and the probe is attached to the STM, the tip of the probe may not be set perpendicular to the sample surface, and may not accurately become the sample observation surface. There is also a problem that.

As described above, if the surface of the sample is to be observed by scanning the surface of the sample while controlling the probe so that the tunnel current is constant, the three-dimensional scanner is required to follow a predetermined sequence. It is only necessary to control each of the piezoelectric elements, but if it is necessary to take a spectrum using STM as scanning tunneling electron spectroscopy, the opposing surfaces of the sample and the probe 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 an already incorporated terminal for heating a sample,
An object of the present invention is to provide a probe cleaning device for a tunnel microscope which can extremely easily clean the probe without removing the probe.

[0008]

SUMMARY OF THE INVENTION According to the present invention, in a scanning tunneling microscope for driving a probe three-dimensionally, approaching the probe to the sample and detecting tunnel current, the sample is fixed at a position facing the probe. A heater for probe heating is provided on a cartridge-type sample holder to be formed to constitute 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, and the probe is heated while applying a high voltage to the probe.

[0010]

The probe cleaning device for a tunnel microscope according to the present invention comprises:
A cartridge-type sample holder having terminals for heating a sample, applying a bias voltage, detecting a tunnel current, and the like is provided with a heater for heating to form a heating holder having the same shape as the sample holder. By only exchanging the probe, the probe can be indirectly heated and cleaned without removing the probe from the scanner head. In addition, by applying a high voltage by providing an electrode facing the probe, it is possible to remold the shape while cleaning the tip of the probe, and by heating the probe with a metal ion source attached. It is also possible to deposit a metal on the sample.

[0011]

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

The heating holder 1 is provided with current introduction terminals 2a and 2b at the ends of an insulator 5 attached to an outer holder 4. Usually, a sample is mounted on the insulator 5 and a cartridge type sample is provided. It functions as a holder. This heating holder 1 is a magnetic loader 1
The external holder 4 is screwed to the base 2 and can be moved by operating the magnetic loader 12 by a magnet (not shown) from outside the vacuum, and attached to the electrode portions 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 bias voltage application 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 a heater. The 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 contact the stage electrode portion.
Electricity can be passed through the stage electrode portion to heat it. Therefore, heat cleaning can be performed by inserting the probe 3 attached to the opposing piezoelectric scanning element 10 into the coil. Thus, by simply providing a heater on the existing sample holder, heating cleaning can be performed without removing the probe by a method such as ordinary sample heating.

FIG. 2 shows an example of a heating holder. In the heating holder shown in FIG. 2, the heater 3 has a coil shape, and an external 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 or outside the external holder 4. The heater is attached to the electrode stage by pressing it outward, and the heating holder is mounted on the electrode stage by a magnet (not shown) outside the vacuum. 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 shape, and can be cleaned by placing the tip of the probe in a heater cup and heating the same as in the case of FIG.
FIG. 4 is a diagram showing another embodiment of the present invention. In this embodiment, when the 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 supply is arranged at a position facing the probe. By applying a 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 a probe is inserted into the heater 3,
An example is shown in which a metal plate 14 is used as a counter electrode at a position facing the probe.

In this embodiment, the probe is connected to the metal plate 14 by n.
The probe can be cleaned while approaching in the order of m, detecting the tunnel current between the metal plate and the probe, and observing the STM image on the surface of the metal plate 14. In addition, by attaching a metal ion source 15 such as gallium or germanium to the probe, it is possible to observe how the metal is deposited on the sample.

Although the above embodiment has been described with respect to an example in which cleaning is performed while maintaining an ultra-high vacuum, a mechanism for introducing gas only around the probe is provided to cause plasma discharge to etch the tip of the probe. By doing so, the cleaning may be performed.

[0019]

As described above, according to the present invention, a probe holder heater is mounted using an existing sample holder to constitute a heating holder, and cleaning can be easily performed by heating the probe. Also, by attaching a metal ion source or the like to the probe and heating it, the metal can be deposited on the sample, so that it is possible to observe the state of the deposition, etc., and to probe while applying a high voltage. By heating the needle, the tip of the probe can be cleaned using electric field evaporation.

[Brief description of the drawings]

FIG. 1 is a view showing one 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 illustrating cleaning using electrolytic evaporation.

FIG. 5 is a diagram illustrating 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.

Continuation of front page (58) Field surveyed (Int.Cl. ⁶ , DB name) G01B 7/34

Claims (2)

(57) [Claims] In a scanning tunneling microscope in which a probe is three-dimensionally driven to bring a probe close to a sample and a tunnel current is detected, a probe is mounted on a cartridge type sample holder for fixing the sample at a position facing the probe. A probe cleaning device for a tunnel microscope, comprising a heater for heating provided with a needle heater, and heating and cleaning the probe by energizing the heater. 2. The probe according to claim 1, wherein an electrode for applying a high voltage is arranged between the probe and the probe, and the probe is heated while applying a high voltage to the probe. Purification equipment.