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All-electronic Nanosecond-resolved Scanning Tunneling Microscopy: Facilitating the Investigation of Single Dopant Charge Dynamics
Published on: January 19, 2018
High-resolution dc-voltage-biased ac conductance bridge for tunnel junction measurements
M V Moody1, J L Paterson, R L Ciali
1Physics Dept., University of Virginia, Charlottesville, Virginia 22901, USA.
The Review of Scientific Instruments
|July 1, 1979
Summary
This study presents a low-cost conductance bridge circuit for high-resolution measurements of dI/dV and d 2I/dV2. The circuit achieves excellent resolution for tunnel junctions, with detailed noise analysis included.
Area of Science:
- Experimental Physics
- Electronic Instrumentation
Background:
- Accurate measurement of differential conductance (dI/dV) and its derivative (d 2I/dV2) is crucial for characterizing electronic devices.
- Existing methods may face limitations in resolution, cost, or complexity.
Purpose of the Study:
- To present a simple, low-cost conductance bridge circuit.
- To achieve high-resolution measurements of dI/dV and d 2I/dV2 for voltage-biased loads.
- To analyze the factors affecting measurement accuracy, including output impedance and noise.
Main Methods:
- Development of a novel conductance bridge circuit.
- Utilizing a low modulation voltage (35 microV-rms) and a 1-s postdetection time constant (Bn=0.25 Hz).
- Measurement of a 90-Ohm tunnel junction.
Main Results:
- Achieved a resolution in dI/dV of several parts in 10^5 for a 90-Ohm tunnel junction.
- The circuit exhibits a low output impedance of 0.02 Ohm with an AD119 operational amplifier.
- Detailed analysis of Johnson-Nyquist, tunnel junction, and amplifier noise contributions.
Conclusions:
- The presented circuit offers a high-resolution, cost-effective solution for dI/dV and d 2I/dV2 measurements.
- The low output impedance and comprehensive noise analysis contribute to reliable measurements.
- This circuit is suitable for various applications requiring precise characterization of electronic transport properties.
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