Abstract
An introduction is given into scanning tunneling microscopy (STM), where a small tunneling current is measured between probing tip and sample. Various operation modes, such as constant tunneling and constant height modes as well as tunneling spectroscopy, are described and application examples are given.
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Notes
- 1.
I–V converters are used to convert the tunneling current into a voltage. A possible realisation consists of an operational amplifier (e.g., Burr Brown OPA 111) and a resistor R, where the output voltage is given by \(V_\mathrm{out}=R I_\mathrm{t}\). With a resistor of the order of \(R=100\,\text {M}\Omega -1\,\text {G}\Omega \), currents of the order of nanoamperes, \(I_\mathrm{t}\approx 1\,\mathrm{nA}\), are measurable. Smaller currents of the order of 0.1 pA are more difficult to measure. Field-effect transistors are needed very close to the tip.
- 2.
Selection of the number of data points is user-defined, e.g., \(400\times 400\), \(500\times 500\) or \(1000\times 1000\). If fast fourier algorithms are to be used, powers of two, \(2^{N}\), are favourable, e.g., \(256\times 256\), \(512\times 512\) or \(1024\times 1024\).
- 3.
In this context, the corrugation height corresponds to the height difference between the hollow site and the top site in constant current operation.
- 4.
The bias voltage is applied to the sample side. Therefore, positive bias voltage means positive voltage on the sample and 0 V on the tip side. The I–V converter keeps the tip virtually grounded. The high gain of the operational amplifier keeps the potential of the positive and negative input at the same voltage.
- 5.
Both liquid crystals and hydrocarbons are oriented flat on the surface.
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Meyer, E., Bennewitz, R., Hug, H.J. (2021). Introduction to Scanning Tunneling Microscopy. In: Scanning Probe Microscopy. Graduate Texts in Physics. Springer, Cham. https://doi.org/10.1007/978-3-030-37089-3_2
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DOI: https://doi.org/10.1007/978-3-030-37089-3_2
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