MyScope
training for advanced research

Glossary

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Amplitude
The size of the oscillation in the cantilever during dynamic modes (tapping and non-contact modes).
Atomic Force Microscopy (AFM)
One of the scanning probe microscopes. This approach measures the force between a sharp probe and the sample. Many types of forces can be measured.
Backscattered Electrons (BSE )
Produced through an elastic scattering interaction with the atoms in the sample that results in the primary electron being re-emitted from the specimen. The electron is said to have backscattered (or reflected back) from the sample. In backscattering, the electron trajectory is changed by more than 90 deg from the forward direction of motion. This results in the scattered electron propagating back in the general direction of the original beam. Note that between the multiple elastic events (that form Backscattered electrons), the beam electrons may also be involved in inelastic events, and thus reduce the electron’s energy. Backscattered electrons usually have energy in the kV range.
Calibration Grid
A sample with known feature sizes which is used to calibrate the piezo scanner.
Cantilever
The spring on which the tip is mounted. It is often diving board or v-shaped.
Cantilever Deflection
The distance the cantilever is pushed or pulled away from its rest position. The deflection is a measure of the force the cantilever is experiencing and is core to the experiment.
Conductive
The ability of a material to transmit an electric current.
Contact Mode
One of the ways to carry out an AFM experiment. In this case the probe is very close to the surface and works in the repulsive regime. This mode can cause surface damage if the force used is excessive.
Control
The act of maintaining an experimental parameter at a certain level.
Current
Measured flow of electrons between the STM tip and the sample.
Feedback
The difference between the set point and the experimental value which is used to maintain the system in a stable state.
Force
Can be attractive or repulsive between the probe and the sample.
Force Image
Image obtained keeping the measured force between the probe and the sample constant.
Gain
The parameter in the control software that determines the size of the system response to the difference between the desired set point for a given quantity and the experimentally determined value of the same quantity.
Height Image
Image obtained keeping the separation between the sample and probe constant.
Hooke's Law

The relationship between the force applied to a spring and its elasticity. The force (F) needed to extend or compress a spring by a distance (X) is proportional to that distance: F = k X, where k is a constant characteristic of the spring, its stiffness.

Hysteresis
An image artefact caused because the piezoelectric elements of the scanner do not move uniformly in response to changes in direction (of applied voltage). The forward trace is different to the backward re-trace over the sample.
Image
A "picture" of the surface being examined. Generally presented in false colour with bright areas representing higher areas of the quantity being measured.
Image Artefacts
Features observed in an image that are not due to features on the sample. These images features can be due to tip effects or scanning effects.
Integral Gain
Gain is the parameter in the control software that determines the size of the system response to the difference between the desired set point for a given quantity and the experimentally determined value of the same quantity. For integral gain the size of the response is added up over time and averaged.
Laser Alignment
The act of getting the laser on the back of the cantilever near the end of the cantilever for maximum sensitivity and ensuring it reflects onto the photodiode.
Microns
10-6 metres
Nanometer
10-9 metres
Nonlinearity
Nonlinearity is when the piezoelectric scanner moves in a nonlinear manner depending on the size of the applied voltage. Generally, sensitivity (movement per applied volt) increases with increasing voltage.
Photodiode
The detector used to measure the position of the laser and hence measure the cantilever deflection.
Piezoelectric
Piezoelectricity is the electric charge that accumulates in certain solid materials in response to applied mechanical stress. The reverse also applies: piezoelectric materials internally generate mechanical movement in response to an applied electrical impulse.
Probe Microscopes
Set of microscopy approaches which use a sharp probe held within nanometres of a sample. The microscopes can determine what the samples look like and also measure interaction forces.
Probes
The tip that interacts with the sample in scanning probe microscopy.
Process lag
The time for the comparison to take place (slows down the control).
Proportional Gain
Gain is the parameter in the control software that determines the size of the system response to the difference between the desired set point for a given quantity and the experimentally determined value of the same quantity. For proportion gain the size of the response is directed related to the error signal.
Resolution
The fineness of detail that can be distinguished in an image; that is, the shortest distance between two points/ features, where the points/ features can be seen as separate.
Resonant Frequency
When the cantilever is oscillated, the frequency that provides the large amplitude of oscillation is the resonant frequency.
Sample
The specimen being examined by the probe microscope. Generally a solid.
Scan
The experiment carried out in scanning probe microscopy.
Scan Rate
The speed at which the tip is scanned over the surface. If the scan rate is too high it will led to image artefacts.
Scanner
The part of the microscope used to move the probe. Often a piezoelectric element which must control position at the nanometre level.
Scanning
The act of moving the probe over the sample to collect an image.
Scanning Tunnelling Microscope (STM)
One of the scanning probe microscopes. This approach measures the tunnelling current between an atomically sharp tip and the sample and is routinely capable of atomic resolution.
Set Point
The value of a parameter desired during the experiment. During a scan, the instrument tries to maintain this value throughout the experiment.
Spring Constant
The stiffness of the cantilever. A higher spring constant means the cantilever is harder to bend.
Surface
The specimen being examined by the probe microscope. Generally a solid.
Tapping Mode
One of the ways to carry out an AFM experiment. In this case the probe is far from the surface and works in the attractive regime. This mode lifts the probe before moving it to minimise sample damage. The cantilever is being oscillated during the experiment.
Topography
The variation in the height of the sample as a function of position.
Tunnelling
A quantum mechanical phenomenon that sees electrons moves from one electrode to another through a barrier.