JP2610913B2 - Scanning tunneling microscope with gain control means - Google Patents
Scanning tunneling microscope with gain control meansInfo
- Publication number
- JP2610913B2 JP2610913B2 JP31325887A JP31325887A JP2610913B2 JP 2610913 B2 JP2610913 B2 JP 2610913B2 JP 31325887 A JP31325887 A JP 31325887A JP 31325887 A JP31325887 A JP 31325887A JP 2610913 B2 JP2610913 B2 JP 2610913B2
- Authority
- JP
- Japan
- Prior art keywords
- scanning
- sample
- axis
- amplifier
- probe
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Expired - Lifetime
Links
Description
【発明の詳細な説明】 〔産業上の利用分野〕 本発明は走査トンネル顕微鏡等に係わり、特に走査幅
に応じてゲインコントロールを行うことにより操作性を
向上させるようにした走査型顕微鏡に関するものであ
る。Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a scanning tunneling microscope and the like, and more particularly to a scanning microscope in which operability is improved by performing gain control according to a scanning width. is there.
一般に、探針先端の原子と試料の原子の電子雲とが重
なり合う1nm程度まで探針を試料に近づけ、この状態で
探針と試料との間に電圧をかけると電流が流れる。この
電流はトンネル電流と呼ばれ、電圧が1mV〜1Vのとき、
１〜10mA程度である。このトンネル電流Ｊの大きさは、
ｄを試料と探針との間の距離、φを試料の仕事関数、
Ａ、Ｂを比例定数としたとき、 Ｊ＝Aexp（−Bdφ1/2） ……（１） と表わされる。このトンネル電流の大きさを測定するこ
とにより試料と探針との間の距離を超精密測定すること
ができ、探針位置が既知であれば試料の表面形状を原子
レベルで求めることができる。またトンネル電流が一定
になるように探針位置を制御すれば探針位置軌跡により
同様に試料の表面形状を測定することができ、走査トン
ネル顕微鏡（STM）として近年注目されている。In general, when the probe is brought close to the sample until the atom at the tip of the probe and the electron cloud of the atoms of the sample overlap by about 1 nm, and a voltage is applied between the probe and the sample in this state, a current flows. This current is called tunnel current, and when the voltage is between 1mV and 1V,
It is about 1 to 10 mA. The magnitude of this tunnel current J is
d is the distance between the sample and the probe, φ is the work function of the sample,
When A and B are proportional constants, J = Aexp (−Bdφ 1/2 ) (1) By measuring the magnitude of the tunnel current, the distance between the sample and the probe can be measured ultra-precisely. If the position of the probe is known, the surface shape of the sample can be obtained at the atomic level. In addition, if the probe position is controlled so that the tunnel current becomes constant, the surface shape of the sample can be measured in the same manner based on the probe position trajectory, and has been attracting attention as a scanning tunneling microscope (STM) in recent years.
STMにおいては（１）式に示すような電流出力が得ら
れ、非常に高い感度をもっている。このことにより原子
レベルの極めて微細な凹凸まで観察可能である。ところ
で、STMはその走査範囲が数nm〜数μｍと非常に広く、
このため凹凸像もサブnm〜数十nmと幅広くならざるを得
ない。従って、同一面積のディスプレイ上に観察像を表
示する場合、広い走査幅での観察像、狭い走査幅での観
察像、或いは凹凸が微細な位置と大きい位置の観察像を
表示しようとすると、ゲインをコントロールしないと十
分な像観察を行うことができない。そのためゲインを変
える必要があるが、このゲインコントロールは、従来、
手動で行われていたが、前述したような高い感度の中で
の調整は極めて困難な作業である。In the STM, a current output as shown in the equation (1) is obtained, and the STM has a very high sensitivity. As a result, it is possible to observe extremely fine irregularities at the atomic level. By the way, STM has a very wide scanning range of several nm to several μm,
For this reason, the concavo-convex image must be as wide as sub-nm to several tens of nm. Therefore, when an observation image is displayed on a display having the same area, when an observation image with a wide scanning width, an observation image with a narrow scanning width, or an observation image with a fine and uneven position is displayed, the gain is increased. If it is not controlled, sufficient image observation cannot be performed. Therefore, it is necessary to change the gain.
Adjustment at high sensitivity as described above is a very difficult task, which has been done manually.
本発明は上記問題点を解決するためのもので、走査幅
が広くダイナミックレンジが大きい走査型顕微鏡におい
て、走査領域に応じてゲインコントロールすることによ
り、常に像観察を適切に行うことができ、操作性を向上
させることができるゲインコントロール手段を有する走
査型顕微鏡を提供することを目的とする。The present invention has been made to solve the above problems, and in a scanning microscope having a wide scanning width and a large dynamic range, image control can always be appropriately performed by controlling gain according to a scanning region, so that operation can be performed. It is an object of the present invention to provide a scanning microscope having a gain control means capable of improving performance.
そのため本発明のゲインコントロール手段を有する走
査トンネル顕微鏡は、試料との間に電圧が印加され、試
料に対向して設けられた探針と、探針を試料に対してＸ
軸、Ｙ軸方向に走査する走査手段と、探針と試料との距
離を可変するためのＺ軸方向駆動手段と、トンネル電流
検出信号に基づく凹凸信号を取り出して増幅する増幅器
と、該増幅器の出力が入力されて試料の観察像を表示す
る表示手段と、探針による試料上のＸ軸走査幅、または
Ｙ軸走査幅を表す信号に基づいて、走査幅が大きい場合
には小さい場合より前記増幅器のゲインを小さく設定す
るゲインコントロール手段とを備えたことを特徴とす
る。Therefore, in the scanning tunneling microscope having the gain control means of the present invention, a voltage is applied between the sample and the sample, and the probe provided opposite the sample and the probe are moved with respect to the sample.
Scanning means for scanning in the axial and Y-axis directions; Z-axis driving means for varying the distance between the probe and the sample; an amplifier for extracting and amplifying a concavo-convex signal based on a tunnel current detection signal; A display unit to which an output is inputted to display an observation image of the sample, and a signal representing the X-axis scanning width or the Y-axis scanning width of the probe by the probe, wherein the scanning width is larger than the smaller scanning width. Gain control means for setting the gain of the amplifier small.
本発明のゲインコントロール手段を有する走査トンネ
ル顕微鏡は、走査領域に応じてトンネル電流検出信号に
基づく凹凸信号を取り出して増幅する増幅器のゲインを
制御し、走査幅に応じた感度で像表示しており、そのた
め広い走査幅に対応して適正に像表示することができ、
十分な像観察を行うことができるので、操作性を向上さ
せることが可能となる。The scanning tunneling microscope having the gain control means of the present invention controls the gain of an amplifier that takes out and amplifies a concavo-convex signal based on a tunnel current detection signal according to a scanning region, and displays an image with sensitivity according to a scanning width. Therefore, an image can be properly displayed corresponding to a wide scanning width,
Since sufficient image observation can be performed, operability can be improved.
以下、実施例を図面を参照して説明する。 Hereinafter, embodiments will be described with reference to the drawings.
第１図は本発明のゲインコントロール手段を有する走
査トンネル顕微鏡の一実施例で、トンネル電流を一定に
するように探針と試料の間隔を制御する場合を示す図、
第２図は像観察における走査幅を示す図、第３図は本発
明のゲインコントロール手段を有する走査トンネル顕微
鏡の他の実施例を示す図である。図中、１はＺ軸走査
部、２はＸ軸走査部、３はＹ軸走査部、４は探針、５は
試料、６はＺ軸駆動回路、７は増幅器、８は対数増幅
器、９は誤差増幅器、10は増幅器、11はディスプレイで
ある。FIG. 1 is a diagram showing an embodiment of a scanning tunnel microscope having a gain control means of the present invention, in which a distance between a probe and a sample is controlled so as to keep a tunnel current constant.
FIG. 2 is a diagram showing a scanning width in image observation, and FIG. 3 is a diagram showing another embodiment of a scanning tunnel microscope having gain control means of the present invention. In the figure, 1 is a Z-axis scanning unit, 2 is an X-axis scanning unit, 3 is a Y-axis scanning unit, 4 is a probe, 5 is a sample, 6 is a Z-axis driving circuit, 7 is an amplifier, 8 is a logarithmic amplifier, 9 Is an error amplifier, 10 is an amplifier, and 11 is a display.
図において、Ｘ軸、Ｙ軸走査信号により所定の領域の
走査が行われる。このときのトンネル電流出力（Ｚ軸出
力）を増幅器７で増幅する。前述の（１）式で示したよ
うに、この出力は探針と試料との間隔の指数関数となる
ので、対数増幅器８で増幅することにより間隔に比例し
た出力が得られる。この出力を誤差増幅器９に加えて基
準値との差を検出し、この差出力をＺ軸駆動回路６に加
えることによりＺ軸出力が一定になるように制御する。
このときのＺ軸駆動回路出力を凹凸信号として取り出
し、増幅器10を介してディスプレイ11に供給すれば試料
表面の凹凸像が得られる。In the figure, a predetermined area is scanned by X-axis and Y-axis scanning signals. The tunnel current output (Z-axis output) at this time is amplified by the amplifier 7. As shown in the above equation (1), this output is an exponential function of the interval between the probe and the sample, so that an output proportional to the interval is obtained by amplifying the logarithmic amplifier 8. The output is applied to an error amplifier 9 to detect a difference from a reference value, and the difference output is applied to a Z-axis drive circuit 6 to control the Z-axis output to be constant.
The output of the Z-axis drive circuit at this time is extracted as an unevenness signal and supplied to the display 11 via the amplifier 10, whereby an unevenness image of the sample surface can be obtained.
このとき、増幅器10はＹ軸走査信号によりゲインコン
トロールされ、走査幅が大きい場合はゲインを下げ、走
査幅が小さい場合はゲインを大きくしている。その結
果、例えば走査領域が広くて第２図（ロ）に示すによう
な像しか植られなかったものが、走査幅を狭めてゲイン
を上げることにより第２図（イ）に示すように凹凸像を
表示することが可能となる。また逆に、走査幅を大きく
し、全体像を観察したいような場合はゲインを下げると
小さな凹凸は観察しづらくなるが全体像を観察すること
が可能となる。At this time, the gain of the amplifier 10 is controlled by the Y-axis scanning signal. When the scanning width is large, the gain is reduced, and when the scanning width is small, the gain is increased. As a result, for example, an image as shown in FIG. 2 (b) having a large scanning area was implanted, but the scanning width was narrowed and the gain was increased, as shown in FIG. 2 (a). An image can be displayed. Conversely, when it is desired to increase the scanning width and observe the entire image, lowering the gain makes it difficult to observe small irregularities, but allows the entire image to be observed.
なお、第２図ではＹ軸変調による表示例について説明
したが、輝度変調表示にしてもよいことは言うまでもな
い。In FIG. 2, a display example based on Y-axis modulation has been described, but it goes without saying that luminance modulation display may be used.
第３図は本発明の他の実施例を示す図で、探針のＺ軸
位置を一定に制御する場合を示す図である。FIG. 3 is a view showing another embodiment of the present invention, showing a case where the Z-axis position of the probe is controlled to be constant.
本実施例においては、Ｚ軸駆動回路６の出力を誤差増
幅器９に帰還し、基準値と比較してＺ軸駆動回路出力が
常に一定になるように制御して、探針のＺ軸方向の位置
を固定している。そして、対数増幅器を介して取り出さ
れた探針と試料との間隔に対応した信号が凹凸信号とし
て増幅器10を介してディスプレイ11に供給されるため、
ディスプレイ11の画面には試料表面の凹凸像が得られ
る。その際、Ｙ軸走査幅を表す信号に基づいて、トンネ
ル電流検出信号に基づく凹凸信号を取り出して増幅する
増幅器10のゲインを制御していることは第１図の実施例
と同様である。In the present embodiment, the output of the Z-axis drive circuit 6 is fed back to the error amplifier 9 and compared with a reference value to control the output of the Z-axis drive circuit so as to be always constant. The position is fixed. Then, since a signal corresponding to the interval between the probe and the sample taken out through the logarithmic amplifier is supplied to the display 11 via the amplifier 10 as an uneven signal,
On the screen of the display 11, an uneven image of the sample surface is obtained. At this time, the gain of the amplifier 10 for extracting and amplifying the concavo-convex signal based on the tunnel current detection signal based on the signal representing the Y-axis scanning width is controlled as in the embodiment of FIG.
以上のように本発明によれば、走査領域に応じてゲイ
ンコントロールするようにしたので、常に適正な観察像
が得られ、この像を観察しながら操作することにより操
作性が向上し、期待される凹凸像の目安を得ながら像観
察を行うことができる。As described above, according to the present invention, since the gain is controlled in accordance with the scanning area, a proper observation image is always obtained, and the operability is improved by operating while observing this image, which is expected. Image observation can be performed while obtaining a rough image of the uneven image.
第１図は本発明のゲインコントロール手段を有する走査
トンネル顕微鏡の一実施例を示す図、第２図は観察像を
示す図、第３図は本発明の他の実施例を示す図である。 １……Ｚ軸走査部、２……Ｘ軸走査部、３……Ｙ軸走査
部、４……探針、５……試料、６……Ｚ軸駆動回路、７
……増幅器、８……対数増幅器、９……誤差増幅器、10
……増幅器、11……ディスプレイ。FIG. 1 is a view showing one embodiment of a scanning tunnel microscope having gain control means of the present invention, FIG. 2 is a view showing an observation image, and FIG. 3 is a view showing another embodiment of the present invention. 1 ... Z-axis scanning section, 2 ... X-axis scanning section, 3 ... Y-axis scanning section, 4 ... probe, 5 ... sample, 6 ... Z-axis drive circuit, 7
...... Amplifier, 8 ... Logarithmic amplifier, 9 ... Error amplifier, 10
... amplifier, 11 ... display.
Claims (1)
して設けられた探針と、探針を試料に対してＸ軸、Ｙ軸
方向に走査する走査手段と、探針と試料との距離を可変
するためのＺ軸方向駆動手段と、トンネル電流検出信号
に基づく凹凸信号を取り出して増幅する増幅器と、該増
幅器の出力が入力されて試料の観察像を表示する表示手
段と、探針による試料上のＸ軸走査幅、またはＹ軸走査
幅を表す信号に基づいて、走査幅が大きい場合には小さ
い場合より前記増幅器のゲインを小さく設定するゲイン
コントロール手段とを備えたことを特徴とするゲインコ
ントロール手段を有する走査トンネル顕微鏡。A probe applied with a voltage between the sample and the sample; scanning means for scanning the sample with respect to the sample in the X-axis and Y-axis directions; Z-axis direction driving means for varying the distance to the sample, an amplifier for extracting and amplifying the uneven signal based on the tunnel current detection signal, and display means for receiving the output of the amplifier and displaying an observation image of the sample Gain control means for setting the gain of the amplifier to be smaller when the scanning width is large than when the scanning width is small, based on a signal indicating the X-axis scanning width or the Y-axis scanning width on the sample by the probe. A scanning tunnel microscope having gain control means.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP31325887A JP2610913B2 (en) | 1987-12-11 | 1987-12-11 | Scanning tunneling microscope with gain control means |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP31325887A JP2610913B2 (en) | 1987-12-11 | 1987-12-11 | Scanning tunneling microscope with gain control means |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| JPH01157049A JPH01157049A (en) | 1989-06-20 |
| JP2610913B2 true JP2610913B2 (en) | 1997-05-14 |
Family
ID=18039037
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| JP31325887A Expired - Lifetime JP2610913B2 (en) | 1987-12-11 | 1987-12-11 | Scanning tunneling microscope with gain control means |
Country Status (1)
| Country | Link |
|---|---|
| JP (1) | JP2610913B2 (en) |
Families Citing this family (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US5466935A (en) * | 1995-01-20 | 1995-11-14 | Quesant Instrument Corporation | Programmable, scanned-probe microscope system and method |
-
1987
- 1987-12-11 JP JP31325887A patent/JP2610913B2/en not_active Expired - Lifetime
Non-Patent Citations (1)
| Title |
|---|
| 「パリティ」Ｖｏｌ．０１．Ｎｏ．７（昭６１−７月号）、丸善、Ｐ．５２−５４ |
Also Published As
| Publication number | Publication date |
|---|---|
| JPH01157049A (en) | 1989-06-20 |
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Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| EXPY | Cancellation because of completion of term |