Scanning thermal microscopy (SThM)
is a type of scanning probe microscopy
Scanning Probe Microscopy is a branch of microscopy that forms images of surfaces using a physical probe that scans the specimen. An image of the surface is obtained by mechanically moving the probe in a raster scan of the specimen, line by line, and recording the probe-surface interaction as a...
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 nanoscale thermometer. Thermal measurements at the nanometer scale are of both scientific and industrial interest.
SThM allows thermal measurements at the nanoscale. These measurements can include: temperature, thermal properties of materials, thermal conductivity
In physics, thermal conductivity, k, is the property of a material's ability to conduct heat. It appears primarily in Fourier's Law for heat conduction....
, heat capacity
Heat capacity , or thermal capacity, is the measurable physical quantity that characterizes the amount of heat required to change a substance's temperature by a given amount...
, glass transition temperature, latent heat
Latent heat is the heat released or absorbed by a chemical substance or a thermodynamic system during a process that occurs without a change in temperature. A typical example is a change of state of matter, meaning a phase transition such as the melting of ice or the boiling of water. The term was...
Enthalpy is a measure of the total energy of a thermodynamic system. It includes the internal energy, which is the energy required to create a system, and the amount of energy required to make room for it by displacing its environment and establishing its volume and pressure.Enthalpy is a...
, etc. The applications include:
- Ultralarge-scale integration (ULSI) lithography
Lithography is a method for printing using a stone or a metal plate with a completely smooth surface...
research and cellular diagnostics in biochemistry.
- Detecting such parameters as phase changes in polymer blends.
- Joule heating
Joule heating, also known as ohmic heating and resistive heating, is the process by which the passage of an electric current through a conductor releases heat. It was first studied by James Prescott Joule in 1841. Joule immersed a length of wire in a fixed mass of water and measured the temperature...
- Measuring material variations in semiconductor devices
- Subsurface imaging
- Near-field photothermal microspectroscopy
Photothermal microspectroscopy , alternatively known as photothermal temperature fluctuation , is derived from two parent instrumental techniques: infrared spectroscopy and atomic force microscopy...
- Data storage
thumb|200px|right|A reel-to-reel tape recorder .The magnetic tape is a data storage medium. The recorder is data storage equipment using a portable medium to store the data....
Calorimetry is the science of measuring the heat of chemical reactions or physical changes. Calorimetry is performed with a calorimeter. The word calorimetry is derived from the Latin word calor, meaning heat...
- 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
Scanning thermal microscopy (SThM) was invented by Williams
-People:* Williams , a surname English in origin, but popular in Wales, 3rd most common in the United Kingdom* "Williams", the pseudonym of racing driver and SOE agent William Grover-Williams-United States:Communities*Williams, Arizona...
Wickramasinghe is a surname, and may refer to:* Chandra Wickramasinghe , Sri Lankan professor of applied mathematics and astronomy* Jagath Wickramasinghe , Sri Lankan musician* Martin Wickramasinghe , Sri Lankan novelist...
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
A bolometer is a device for measuring the power of incident electromagnetic radiation via the heating of a material with a temperature-dependent electrical resistance. It was invented in 1878 by the American astronomer Samuel Pierpont Langley...
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 micromachining 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, we can create a thermal map of 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.