CN106849887B - High-bandwidth front-end of tunnel junction parallel resistance scanning tunnel microscope - Google Patents
High-bandwidth front-end of tunnel junction parallel resistance scanning tunnel microscope Download PDFInfo
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- CN106849887B CN106849887B CN201710114944.5A CN201710114944A CN106849887B CN 106849887 B CN106849887 B CN 106849887B CN 201710114944 A CN201710114944 A CN 201710114944A CN 106849887 B CN106849887 B CN 106849887B
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- 239000000523 sample Substances 0.000 claims abstract description 38
- 238000000034 method Methods 0.000 claims abstract description 14
- 230000005641 tunneling Effects 0.000 claims description 9
- 230000003321 amplification Effects 0.000 claims description 6
- 238000003199 nucleic acid amplification method Methods 0.000 claims description 6
- 238000013459 approach Methods 0.000 claims description 3
- 230000008859 change Effects 0.000 claims description 2
- 230000010355 oscillation Effects 0.000 abstract description 6
- 230000001105 regulatory effect Effects 0.000 abstract 1
- 238000010586 diagram Methods 0.000 description 3
- 238000012360 testing method Methods 0.000 description 3
- 230000000694 effects Effects 0.000 description 2
- 230000008569 process Effects 0.000 description 2
- 229920006395 saturated elastomer Polymers 0.000 description 2
- OKTJSMMVPCPJKN-UHFFFAOYSA-N Carbon Chemical compound [C] OKTJSMMVPCPJKN-UHFFFAOYSA-N 0.000 description 1
- 241000282376 Panthera tigris Species 0.000 description 1
- 230000009471 action Effects 0.000 description 1
- 230000000903 blocking effect Effects 0.000 description 1
- 229910002804 graphite Inorganic materials 0.000 description 1
- 239000010439 graphite Substances 0.000 description 1
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- 238000012986 modification Methods 0.000 description 1
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- 238000012545 processing Methods 0.000 description 1
Classifications
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- H—ELECTRICITY
- H03—ELECTRONIC CIRCUITRY
- H03F—AMPLIFIERS
- H03F1/00—Details of amplifiers with only discharge tubes, only semiconductor devices or only unspecified devices as amplifying elements
- H03F1/42—Modifications of amplifiers to extend the bandwidth
- H03F1/48—Modifications of amplifiers to extend the bandwidth of aperiodic amplifiers
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01Q—SCANNING-PROBE TECHNIQUES OR APPARATUS; APPLICATIONS OF SCANNING-PROBE TECHNIQUES, e.g. SCANNING PROBE MICROSCOPY [SPM]
- G01Q60/00—Particular types of SPM [Scanning Probe Microscopy] or microscopes; Essential components thereof
- G01Q60/10—STM [Scanning Tunnelling Microscopy] or apparatus therefor, e.g. STM probes
-
- H—ELECTRICITY
- H03—ELECTRONIC CIRCUITRY
- H03F—AMPLIFIERS
- H03F3/00—Amplifiers with only discharge tubes or only semiconductor devices as amplifying elements
- H03F3/04—Amplifiers with only discharge tubes or only semiconductor devices as amplifying elements with semiconductor devices only
- H03F3/08—Amplifiers with only discharge tubes or only semiconductor devices as amplifying elements with semiconductor devices only controlled by light
Abstract
The invention discloses a high-bandwidth front-end amplifier of a tunnel junction parallel resistance scanning tunnel microscope, and belongs to the technical field of high-bandwidth front-end amplifiers of scanning tunnel microscopes. The technical scheme of the invention is as follows: a high-bandwidth front-end amplifier of a scanning tunnel microscope by a tunnel junction parallel resistance method comprises a front-end amplifying circuit of the scanning tunnel microscope, and resistors are connected in parallel at two ends of a tunnel junction formed by a conductive sample and a conductive probe. The resistance of the resistor is regulated until the amplifying circuit can accurately amplify the input signal, so that the self-excitation oscillation of the front amplifier can be eliminated on the premise of not changing the tunnel junction information, the bandwidth of the front amplifier is larger, and a good atomic resolution image can be obtained.
Description
Technical Field
The invention belongs to the technical field of high-bandwidth front-end of a scanning tunnel microscope, and particularly relates to a high-bandwidth front-end of a tunnel junction parallel resistance scanning tunnel microscope.
Background
High bandwidth Scanning Tunneling Microscope (STM) pre-amplification circuits have long been the target of many team efforts. But when the bandwidth is large enough, noise within the bandwidth is amplified. At a certain noise frequencyf n At or near the resonant frequency of the amplifying circuit and where the circuit is not damped or damped relatively little, the noise at that frequency is amplified almost indefinitely until a saturated output of the circuit is reached, the so-called self-excited oscillation. At this time, the circuit outputs erroneously, and the STM front amplifier cannot work normally.
One way to eliminate self-oscillation is to increase the feedback capacitanceC f I.e. phase compensation. But so on, according to the bandwidth formula:f b =1/2pR f C f the bandwidth is significantly reduced and is therefore not the best choice.
Another method of eliminating self-oscillation is to reduce the feedback coefficient, which can be increased by (a) increasing the feedback resistanceR f Or (B) reduce the equivalent resistance of the tunnel junctionR ST Is realized by the method of (1). But there is hardly any current between the probe and the sample before they approach the tunneling region, i.e. the equivalent resistance is almostIs infinite. In this way, even if the resistance of the feedback resistor is 1gΩ, the feedback coefficient is still large, almost always constant 1, so that the method (a) has no effect. And because of the equivalent resistance of the tunnel junctionR ST Is the object to be measured, cannot be artificially lowered, and the method (B) has no effect. Finally, self-excitation oscillation is caused to become a high-bandwidth STM-forward-placed road blocking tiger.
In order to solve the problems, combining the working principle of STM, the project approval number is: the invention provides a high-bandwidth self-excitation-free pre-amplification circuit of a tunnel junction parallel resistance method under the support of 11304082 'improvement and application of an ultra-fast scanning tunnel microscope'.
Disclosure of Invention
The invention aims to provide a high-bandwidth front-end of a tunnel junction parallel resistance scanning tunnel microscope.
The invention adopts the following technical proposal to solve the technical problems, and the high-bandwidth front-end amplifier of the scanning tunnel microscope by a tunnel junction parallel resistance method comprises a front-end amplifier circuit of the scanning tunnel microscope, and is characterized in that: and resistors are connected in parallel at two ends of a tunnel junction formed by the conductive sample and the conductive probe.
Further preferably, a switch is arranged on the connecting branch of the resistor, the switch is closed when the tip of the conductive probe is close to the conductive sample, and the switch is opened when the resistance value of the equivalent resistor between the tip of the conductive probe and the conductive sample is not greater than the resistance value of the set resistor.
Further preferably, the resistance value of the resistor satisfies that the output of the scanning tunneling microscope pre-amplifying circuit can correctly respond to the change of the input signal.
Further preferably, the resistance value of the resistor is 0.01-0.2 times of the feedback resistance value of the pre-amplifying circuit of the scanning tunnel microscope.
Further preferably, the pre-amplifying circuit is a transimpedance amplifier structure, one end of a tunnel junction formed by the conductive sample and the conductive probe is grounded, the other end of the tunnel junction formed by the conductive sample and the conductive probe is connected with an inverting input end of the transimpedance amplifier, a non-inverting input end of the transimpedance amplifier is connected with one end of a bias voltage, the other end of the bias voltage is grounded, and a feedback resistor is connected between the inverting input end and the output end of the transimpedance amplifier.
Further preferably, the resistance of the resistor is 100kΩ, the resistance of the feedback resistor is 1mΩ, and the model of the integrated operational amplifier in the transimpedance amplifier is OPA627.
Further preferably, the resistor is a constant value resistor or an adjustable resistor.
The invention can eliminate self-excitation oscillation of the STM forward amplifier on the premise of not changing tunnel junction information, so that the bandwidth of the STM forward amplifier is larger.
Drawings
FIG. 1 is a schematic diagram of a high bandwidth non-self-excited pre-amplifier circuit of the tunnel junction parallel resistance method of the present invention;
FIG. 2 is a schematic circuit diagram of the present invention during actual testing;
FIG. 3 is an atomic resolution image of the invention measured using the STM preamble of the parameters in FIG. 2;
fig. 4 is a schematic diagram of a switching leg of the high bandwidth non-self-excited pre-amplifier circuit of the tunnel junction parallel resistance method of the present invention.
In the figure: 1. conductive probe, 2, conductive sample.
Detailed Description
The above-described matters of the present invention will be described in further detail by way of examples, but it should not be construed that the scope of the above-described subject matter of the present invention is limited to the following examples, and all techniques realized based on the above-described matters of the present invention are within the scope of the present invention.
The working principle and the technical mode of the STM determine that the equivalent resistance of the tunnel junction is almost infinite and the feedback coefficient is almost maximum in the process that the tip of the conductive probe 1 approaches the conductive sample 2, and is infinitely close to 1. However, when the tip enters the tunneling region and starts scanning the sample, the distance between the tip of the conductive probe 1 and the conductive sample 2 is almost less than 1nm, and thus the resistance becomes small. The feedback coefficient is very small, usually about 0.1, and the self-excitation oscillation is not usually caused under the feedback coefficient.
STM must howeverThe following scanning tunneling can be performed only after the approaching process. When the information of the tunnel junction cannot be changed, the processing can be performed outside the tunnel junction, i.e. a resistor is arranged in parallel at two ends of the tunnel junction, such as R in FIG. 1 in As shown.
TIA in FIG. 1 is a transimpedance amplifier, V b Is a bias voltage. At this time, even if the tip of the conductive probe 1 is far from the conductive sample 2, the equivalent resistanceR ST Infinity but parallel R in The total equivalent resistance value of the product does not exceed R in The feedback coefficient is thus reduced. R is R in The larger the value of R is, the better R is, but due to different oscillation environments of different circuits in Also different in specific values, the maximum allowable R that enables correct amplification of the STM pre-amplifier circuit is selected inmax The value is obtained. At this time, the information of the tunnel junction is not changed.
Example 1
In specific implementation, according to the formula for restricting bandwidth:f b =1/2pR f C f in order to obtain a larger bandwidth, R is required f And (3) withC f Are as small as possible. As shown in FIG. 2, R is selected in the present embodiment f External connection with no initiative and 1mΩC f (however, unavoidable stray capacitances may be present in the circuit); the integrated operational amplifier model was selected as OPA627 in view of weak signal amplification capability and operational stability. At this time, even if the input terminal is not connected to the input signal, the output terminal of the amplifying circuit will have a saturated output of square wave.
After a resistor of 0.1MΩ is arranged in parallel with the tunnel junction, the STM preamplifier can amplify correctly, and the working state is good. At this time, according to the formula of the bandwidth of the transimpedance amplifier (TIA, trans-impedance amplifier), when OPA627 is used, the estimation results:f b =(GBP/2pR f C S ) 1/2 =0.412 MHz. Then, according to the expected tunnel junction resistance value of about 0.1M omega, an alternating voltage signal is input by taking 0.1// 0.1=0.05 (MΩ) as the total equivalent input resistance, and the actually measured bandwidth is 550KHz and is similar to the estimated value.
This bandwidth is the highest bandwidth of STM preambles that is currently known to be able to obtain atomic resolution images. Furthermore, STM atomic resolution images have been measured using this method, the sample being high order graphite (HOPG), as shown in FIG. 3. Because of few pixel points, a mosaic phenomenon occurs to a certain extent in the graph; higher quality images are being integrated.
Example 2
In embodiment 1, in order not to make the parallel resistors on the tunnel junction reduce the contrast of the test signal, a switch may be connected in series on the branch of the parallel resistor, as shown in fig. 4. The specific usage is as follows: when the tip of the conductive probe 1 is close to the conductive sample 2, the switch is closed. When the equivalent resistance between the tip of the conductive probe 1 and the conductive sample 2 is not more than the resistance value of the set resistance, the switch is turned off. Since the output is no longer erroneous even if the parallel resistor Rin is disconnected.
By measuring V out And (3) reversely deducing whether the resistance of the tunnel junction is smaller than or equal to the resistance of the set resistor.
When the switch is a mechanical switch, the switch needs to be arranged at a place far away from the tunnel junction in order to avoid the interference of vibration caused by the action of the mechanical switch on the test.
While the basic principles of the invention have been shown and described, there are various changes and modifications to the invention, which fall within the scope of the invention as hereinafter claimed, without departing from the spirit and scope of the invention.
Claims (5)
1. The utility model provides a tunnel junction parallel resistance method scanning tunnel microscope high bandwidth front-end amplifier, includes scanning tunnel microscope front-end amplifier circuit, its characterized in that: the pre-amplification circuit is of a transimpedance amplifier structure, one end of a tunnel junction formed by a conductive sample and a conductive probe is grounded, the other end of the tunnel junction formed by the conductive sample and the conductive probe is connected with an inverting input end of the transimpedance amplifier, an in-phase input end of the transimpedance amplifier is connected with one end of a bias voltage, the other end of the bias voltage is grounded, a feedback resistor is connected between the inverting input end and the output end of the transimpedance amplifier, and resistors are connected in parallel with two ends of the tunnel junction formed by the conductive sample and the conductive probe, wherein the resistance value of the resistor is 0.01-0.2 times of that of the feedback resistor of the pre-amplification circuit of the scanning tunnel microscope.
2. The high bandwidth front-end of tunnel junction parallel resistance scanning tunneling microscope of claim 1, wherein: and a switch is arranged on the connecting branch of the resistor, when the tip of the conductive probe approaches the conductive sample, the switch is closed, and when the resistance value of the equivalent resistor between the tip of the conductive probe and the conductive sample is not greater than the resistance value of the set resistor, the switch is opened.
3. The high bandwidth front-end of tunnel junction parallel resistance scanning tunneling microscope of claim 1, wherein: the resistance of the resistor meets the requirement that the output of the pre-amplifying circuit of the scanning tunnel microscope can correctly respond to the change of an input signal.
4. The high bandwidth front-end of tunnel junction parallel resistance scanning tunneling microscope of claim 1, wherein: the resistance of the resistor is 100KΩ, the resistance of the feedback resistor is 1MΩ, and the model of the integrated operational amplifier in the transimpedance amplifier is OPA627.
5. The high bandwidth front end of a tunnel junction parallel resistance scanning tunneling microscope according to any one of claims 1-4, further characterized by: the resistor is a fixed value resistor or an adjustable resistor.
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| Application Number | Priority Date | Filing Date | Title |
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| CN201710114944.5A CN106849887B (en) | 2017-02-28 | 2017-02-28 | High-bandwidth front-end of tunnel junction parallel resistance scanning tunnel microscope |
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| CN201710114944.5A CN106849887B (en) | 2017-02-28 | 2017-02-28 | High-bandwidth front-end of tunnel junction parallel resistance scanning tunnel microscope |
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| CN106849887B true CN106849887B (en) | 2024-03-22 |
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| CN112910466A (en) * | 2021-01-27 | 2021-06-04 | 东南大学 | Modulator circuit with combination of magnetic tunnel junction and resistor to replace pure resistor |
Citations (8)
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|---|---|---|---|---|
| US5347231A (en) * | 1993-02-23 | 1994-09-13 | Associated Universities, Inc. | Low noise charge sensitive preamplifier DC stabilized without a physical resistor |
| CN1156825A (en) * | 1995-06-20 | 1997-08-13 | 松下电器产业株式会社 | Two-dimensional sensor using LAPS for measuring cell activity |
| CN101329158A (en) * | 2008-07-28 | 2008-12-24 | 哈尔滨工业大学 | Method for measuring solid film thickness of atomic force microscope |
| CN102820858A (en) * | 2012-07-31 | 2012-12-12 | 赵烨梁 | High-frequency signal amplifying circuit for scanning tunnel microscope |
| CN202696547U (en) * | 2012-07-31 | 2013-01-23 | 赵烨梁 | High-frequency signal amplification circuit used for scanning tunnel microscope |
| CN104883137A (en) * | 2015-06-15 | 2015-09-02 | 河南师范大学 | Integrated operational amplifying circuit capable of increasing bandwidth to short-wave frequency band and reducing noise |
| CN204669314U (en) * | 2015-06-15 | 2015-09-23 | 河南师范大学 | A kind ofly improve bandwidth and reduce the pre-amplification circuit based on integrated transporting discharging of noise |
| CN206650638U (en) * | 2017-02-28 | 2017-11-17 | 河南师范大学 | A kind of high broadband of tunnel knot paraller resistanc method is without self-excitation pre-amplification circuit |
-
2017
- 2017-02-28 CN CN201710114944.5A patent/CN106849887B/en active Active
Patent Citations (8)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US5347231A (en) * | 1993-02-23 | 1994-09-13 | Associated Universities, Inc. | Low noise charge sensitive preamplifier DC stabilized without a physical resistor |
| CN1156825A (en) * | 1995-06-20 | 1997-08-13 | 松下电器产业株式会社 | Two-dimensional sensor using LAPS for measuring cell activity |
| CN101329158A (en) * | 2008-07-28 | 2008-12-24 | 哈尔滨工业大学 | Method for measuring solid film thickness of atomic force microscope |
| CN102820858A (en) * | 2012-07-31 | 2012-12-12 | 赵烨梁 | High-frequency signal amplifying circuit for scanning tunnel microscope |
| CN202696547U (en) * | 2012-07-31 | 2013-01-23 | 赵烨梁 | High-frequency signal amplification circuit used for scanning tunnel microscope |
| CN104883137A (en) * | 2015-06-15 | 2015-09-02 | 河南师范大学 | Integrated operational amplifying circuit capable of increasing bandwidth to short-wave frequency band and reducing noise |
| CN204669314U (en) * | 2015-06-15 | 2015-09-23 | 河南师范大学 | A kind ofly improve bandwidth and reduce the pre-amplification circuit based on integrated transporting discharging of noise |
| CN206650638U (en) * | 2017-02-28 | 2017-11-17 | 河南师范大学 | A kind of high broadband of tunnel knot paraller resistanc method is without self-excitation pre-amplification circuit |
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