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Scanning thermal microscopy

Scanning thermal microscopy is a engineering topic covered in the lgStudy science library. This page brings together a partial reference excerpt, illustrations, worked examples, real-world applications and a short study plan, so you can understand Scanning thermal microscopy rather than just read about it. In short: Scanning thermal microscopy (SThM) is a type of scanning probe microscopy that maps the local temperature and thermal conductivity of an interface. The probe in a scanning thermal microscope is sensitive to local temperatures – providing a nano-scale thermometer.

Scanning thermal microscopy — main illustration
Scanning thermal microscopy — illustration

Key takeaways

  • Scanning thermal microscopy belongs to engineering; place it in that map before memorising details.
  • Learn the definition first, then one example that makes the definition concrete.
  • Connect Scanning thermal microscopy to a quantity you can measure, compute or draw — that is where exam questions come from.
  • Reproduce the core statement of Scanning thermal microscopy from memory before moving on to harder problems.

Reference excerpt

Scanning thermal microscopy (SThM) is a type of scanning probe microscopy that maps the local temperature and thermal conductivity of an interface. The probe in a scanning thermal microscope is sensitive to local temperatures – providing a nano-scale thermometer. Thermal measurements at the nanometer scale are of both scientific and industrial interest. The technique was invented by Clayton C. Williams and H. Kumar Wickramasinghe in 1986.

Applications SThM allows thermal measurements at the nano-scale. These measurements can include: temperature, thermal properties of materials, thermal conductivity, heat capacity, glass transition temperature, latent heat, enthalpy, etc. The applications include:

Ultra large-scale integration (ULSI) lithography research and cellular diagnostics in biochemistry. Detecting such parameters as phase changes in polymer blends. Joule heating Measuring material variations in semiconductor devices Subsurface imaging Near-field photo thermal micro-spectroscopy Calorimetry applications Hot-spots in integrated circuits Low temperature scanning thermal microscopy Magnetic spectroscopy in combination with the ferromagnetic resonance realized in the SThM-FMR technique Other applications

Technique SThM requires the use of specialized probes. There are two types of thermal probes: Thermocouple probes where the probe temperature is monitored by a thermocouple junction at the probe tip and resistive or bolometer probes where the probe temperature is monitored by a thin-film resistor at probe tip. These probes are generally made from thin dielectric films on a silicon substrate and use a metal or semiconductor film bolometer to sense the tip temperature. Other approaches, using more involved micro machining methods, have also been reported. In a bolometer probe the resistor is used as a local heater and the fractional change in probe resistance is used to detect the temperature and/or the thermal conductance of the sample. When the tip is placed in contact with the sample, heat flows from the tip to sample. As the probe is scanned, the amount of heat flow changes. By monitoring the heat flow, one can create a thermal map of the sample, revealing spatial variations in thermal conductivity in a sample. Through a calibration process, the SThM can reveal the quantitative values of thermal conductivity. Alternately the sample may be actively heated, for example a powered circuit, to visualize the distribution of temperatures on the sample. Tip-sample heat transfer can include

Solid-solid conduction. Probe tip to sample. This is the transfer mechanism which yields the thermal scan. Liquid-liquid conduction. When scanning in non-zero humidity, a liquid meniscus forms between the tip and sample. Conduction can occur through this liquid drop. Gas conduction. Heat can be transferred through the edges of the probe tip to the sample.

References

External links

SThM tutorial SThM-FMR technique SThM designs

Illustrations

Scanning thermal microscopy: Schematic and SEM images of a conventional SThM tip based on an Au–Cr thermocouple.[1]
Schematic and SEM images of a conventional SThM tip based on an Au–Cr thermocouple.[1]
Scanning thermal microscopy: SThM using the N-V center in diamond.(a) Schematics of experimental setup. An electric current is applied to the arms of an AFM cantilever (phosphorus-doped Si, P:Si) and heats up the end section above the tip (intrinsic Si, i-Si). The bottom lens excites a diamond nanocrystal with a green laser light and collects photoluminescence (PL). The crystal hosts an N-V center and is attached to the AFM tip. A wire on the sample surface serves as the microwave source (mw). The temperature of the cantilever Th is determined from the applied current and voltage. (b) Optically detected magnetic resonance spectra of the N-V center at three temperatures. (c) Thermal conductivity image of a gold letter E on sapphire. White circles indicate features that do not correlate with the AFM topography. (d) PL image of the AFM cantilever end and tip where the diamond nanocrystal appears as the bright spot. (e) Zoomed PL image of the N-V center in d.[2]
SThM using the N-V center in diamond.(a) Schematics of experimental setup. An electric current is applied to the arms of an AFM cantilever (phosphorus-doped Si, P:Si) and heats up the end section above the tip (intrinsic Si, i-Si). The bottom lens excites a diamond nanocrystal with a green laser light and collects photoluminescence (PL). The crystal hosts an N-V center and is attached to the AFM tip. A wire on the sample surface serves as the microwave source (mw). The temperature of the cantilever Th is determined from the applied current and voltage. (b) Optically detected magnetic resonance spectra of the N-V center at three temperatures. (c) Thermal conductivity image of a gold letter E on sapphire. White circles indicate features that do not correlate with the AFM topography. (d) PL image of the AFM cantilever end and tip where the diamond nanocrystal appears as the bright spot. (e) Zoomed PL image of the N-V center in d.[2]

Worked examples

Example 1 — a first encounter with Scanning thermal microscopy

Start with the simplest possible case. Write down what Scanning thermal microscopy claims or describes in one sentence, then invent the smallest concrete situation in which that sentence is true. In engineering, the smallest case is usually a single object, a single equation or a single measurement. Check that every symbol or term in your sentence has a meaning in that case.

Example 2 — changing one variable

Take the situation from Example 1 and change exactly one quantity: double it, halve it, or set it to zero. Predict what should happen to Scanning thermal microscopy before you calculate. Comparing your prediction with the result is the fastest way to find out whether you understand the idea or only the words.

Example 3 — an exam-style question

Typical questions about Scanning thermal microscopy ask you to (a) state it precisely, (b) apply it to given data, and (c) explain a limitation. Practise writing all three answers in under five minutes; the third part is what separates a full-mark answer from an average one.

Applications of Scanning thermal microscopy

In research
Scanning thermal microscopy appears in engineering research whenever the underlying quantities have to be modelled precisely. Papers usually cite it as a starting assumption and then explore where it breaks down.
In technology and industry
Engineering practice reuses Scanning thermal microscopy in design rules, simulations and safety margins. Knowing the idea lets you read a specification sheet and understand why the numbers look the way they do.
In the classroom
Scanning thermal microscopy is common in secondary-school and first-year university syllabi. It links to neighbouring topics Scanning probe microscopy, so understanding it makes those chapters shorter.
In everyday life
Look for Scanning thermal microscopy outside the textbook — in sport, cooking, traffic, electronics or the sky above you. An example you found yourself is remembered far longer than one you were given.

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How to study Scanning thermal microscopy in 20 minutes

  1. Read the reference excerpt below once, without taking notes.
  2. Close the page and write down what Scanning thermal microscopy means in your own words.
  3. Compare your version with the excerpt and mark what you missed.
  4. Work through the three examples above with pen and paper.
  5. Explain Scanning thermal microscopy out loud to somebody else — or to Teacher Smith in the lgStudy chat.

Frequently asked questions

What is Scanning thermal microscopy in simple terms?

Scanning thermal microscopy (SThM) is a type of scanning probe microscopy that maps the local temperature and thermal conductivity of an interface. The probe in a scanning thermal microscope is sensitive to local temperatures – providing a nano-scale thermometer.

Why does Scanning thermal microscopy matter?

Because it connects several engineering ideas at once: it gives you a definition you can apply, a quantity you can calculate, and a way to check whether a result is plausible.

How should I study Scanning thermal microscopy?

Read the excerpt, restate it from memory, then work through the examples and applications listed on this page. The five-step study plan above takes about twenty minutes.

What does this page cover?

It gives you a compact reference excerpt plus original lgStudy explanations, examples, applications and study material on Scanning thermal microscopy.

Tags

  • Scanning probe microscopy

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