High-bandwidth STM (scanning tunneling microscope) preamplifier adopting tunnel junction and resistor parallel connection method

A scanning tunneling and microscope technology, used in scanning probe microscopy, scanning probe technology, improving amplifiers to expand bandwidth, etc., can solve the problems of artificial reduction, ineffective methods, etc. big effect

Pending Publication Date: 2017-06-13
HENAN NORMAL UNIV
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

AI Technical Summary

Problems solved by technology

And because the tunnel junction equivalent resistance R ST It is the object to be tested and cannot be artificially lowered, causing method (B) to have no effect
In the end, the self-excited oscillation became a stumbling block for high-bandwidth STM preamplifiers

Method used

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  • High-bandwidth STM (scanning tunneling microscope) preamplifier adopting tunnel junction and resistor parallel connection method
  • High-bandwidth STM (scanning tunneling microscope) preamplifier adopting tunnel junction and resistor parallel connection method
  • High-bandwidth STM (scanning tunneling microscope) preamplifier adopting tunnel junction and resistor parallel connection method

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Experimental program
Comparison scheme
Effect test

Embodiment 1

[0025] During specific implementation, according to the formula for restricting bandwidth: f b =1 / 2p R f C f , in order to obtain greater bandwidth, R f and C f all as small as possible. Such as figure 2 Shown, in this example choose R f =1MΩ, no active external connection C f (However, there will be unavoidable stray capacitance in the circuit); considering the weak signal amplification capability and working stability, the selected integrated operational amplifier model is OPA627. At this time, even if the input terminal is not connected to the input signal, the output terminal of the amplifier circuit will have a saturated output of square wave.

[0026] When a resistance of 0.1MΩ is set in parallel with the tunnel junction, the STM preamplifier can amplify correctly and work well. At this time, according to the formula of the bandwidth of the transimpedance amplifier (TIA, trans-impedance amplifier), when using the OPA627, it is estimated that: f ...

Embodiment 2

[0029] In Embodiment 1, in order not to reduce the contrast of the test signal by the resistance connected in parallel on the tunnel junction, a switch can be connected in series on the branch of the resistance connected in parallel, such as Figure 4 shown. The specific usage is: when the needle tip of the conductive probe 1 is close to the conductive sample 2, the switch is closed. When the equivalent resistance between the needle tip of the conductive probe 1 and the conductive sample 2 is not greater than the resistance value of the set resistance, the switch is turned off. Because at this time, even if the resistor Rin connected in parallel is disconnected, the output will no longer be wrong.

[0030] can be measured by V out value, to deduce whether the tunnel junction resistance is less than or equal to the resistance value of the set resistance.

[0031] When the switch is a mechanical switch, in order to avoid the interference of the vibration caused by the mechani...

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Abstract

The invention discloses a high-bandwidth STM (scanning tunneling microscope) preamplifier adopting a tunnel junction and resistor parallel connection method and belongs to the technical field of the high-bandwidth STM preamplifier circuit. According to the technical scheme, the high-bandwidth STM preamplifier adopting the tunnel junction and resistor parallel connection method comprises an STM preamplifier circuit, 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 resistors is adjusted until the amplifier circuit can correctly amplify an input signal, self-excitation oscillation of the preamplifier can be eliminated on the premise that the tunnel junction information is unchanged, the bandwidth of the preamplifier is larger, and better atom resolution images can be acquired.

Description

technical field [0001] The invention belongs to the technical field of high-bandwidth preamplifiers for scanning tunneling microscopes, and in particular relates to a high-bandwidth preamplifier for scanning tunneling microscopes using tunnel junction parallel resistance method. Background technique [0002] High-bandwidth scanning tunneling microscope (STM) preamplification circuits have been the goal of many teams' efforts. But when the bandwidth is large enough, the noise within the bandwidth will also be amplified. when the frequency of a noise f n At or near the resonant frequency of the amplifying circuit and the circuit has no damping or the damping is relatively small, the noise at this frequency will be amplified almost infinitely until it reaches the saturated output of the circuit, which is the so-called self-oscillation. At this time, the circuit output is wrong, and the STM preamplifier cannot work normally. [0003] One way to eliminate self-oscillation i...

Claims

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Application Information

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Patent Type & Authority Applications(China)
IPC IPC(8): H03F1/48H03F3/08G01Q60/10
CPCH03F1/48H03F3/08G01Q60/10
Inventor 李全锋王洋崔明焕
Owner HENAN NORMAL UNIV
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