Dusty Plasma

Dusty PlasmaDusty plasma, or complex plasma, contains particles sized between a millimetre and a nanometre, which can also combine to form larger particles known as “grain plasmas”. These particles are charged, and both the particles and the plasma behave as a plasma.

Measuring the dust directly is difficult because of the small size; in addition, measuring the charge on each dust particle is tricky because of the tiny charge. The most straightforward way to measure the dust density and charge is to measure the plasma density and temperature and calculate the dust parameters.

Semion Sensors

The Semion measures the ion energy and produces the ion energy distribution function (IEDF), ion flux, negative ions, temperature and Vdc at the substrate position inside a plasma reactor. The Semion can be used to determine ion energy and flux in dusty plasmas.

Vertex Sensors

The Vertex Sensor is placed inside a plasma reactor and measures the angle of ions hitting a surface. The Vertex Sensor can measure the deflection of ions off dust particles and the impact that dust has on the ion energy arriving at a surface in a dusty plasma. The angular spread of ion energies at a given pressure will depend on the dust particle density.

Quantum Sensors

The Quantum is a unique instrument to measure the ratio of ions to neutrals hitting a surface inside a plasma reactor. The Quantum is ideal for use in dusty plasmas to monitor the rate of deposition and its dependence on ion flux.

Species Sensors

The Species Sensor sits at any location inside a plasma reactor and measures the individual species (mass) of ions hitting a surface using a miniaturised single sensor. This sensor can be used to understand the chemistry of complex plasmas commonly found in dusty plasma applications.

Langmuir Probes

The Langmuir Probe is the key instrument used by scientists to measure the internal parameters of the bulk of the plasma. Among the key parameters measured are electron density, electron temperature. In a dusty plasma key parameters of interest are the density of the dust particles and the charge per dust particle. These parameters are extremely difficult to measure directly but can be derived from the measured electron density and electron temperature. Well known theories of orbital limited current collection on the dust particles can be solved when the basic plasma parameters have been measured by the Langmuir Probe.

LP02: Langmuir Probe used in an RF Dusty Plasma to measure the dust charge and density
Demonstration of a Langmuir Probe used in an RF dusty plasma with a mixture of gasses (SiH4 / C2H4 / Ar) to measure the dust charge and density in a capacitively coupled reactor.

Plato Probes

The Plato Probe scans across the bulk of a plasma and measures the parameters at different locations even when depositing an insulating layer up to 100 microns thick on the probe surface. This probe is ideally suited to depositing plasma such as silane where rapid deposition of insulating layers prevent standard Langmuir probes operating effectively. The Plato can measure electron density and temperature in real time in plasma depositing insulating layers.

Octiv Range

The Octiv is an in-line RF voltage, current and phase measurement system. It can measure fundamental frequencies simultaneously and harmonics with frequency agility at 1% accuracy and 1 micro second time resolution. The Octiv can be used to monitor dust formation rates by measuring changes in impedance real time in a plasma reactor. In some applications it has been shown empirically that the magnitude of the harmonics are directly correlated with particle size.

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