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Low pressure plasmas have found numerous applications in material processing and manufacturing semiconductor industries. The advantages of these plasmas are well known as they produce high density of reactive species advantageous for fast etch/deposition rates while maintaining the gas at near room temperature. This enables the surface treatment of thermally sensitive materials. On the other hand, operating plasma at low pressure has several downsides; vacuum systems are expensive and they require frequent maintenance. The size of the vacuum chamber also restricts the size of the object to be treated.
Atmospheric pressure plasmas overcome these vacuum requirements of low pressure plasmas, however generating plasma at atmospheric pressure (760 Torr) can have its own challenges. These plasmas have high reactivity due to the formation of multiple excited and ionized species and as such have an important role in many current and emerging fields, including plasma medicine, agriculture, plasma processing of materials and surfaces, catalysis, and aerospace engineering. Recent advancements in this area have emerged in the development of Plasma Jet and Dielectric Barrier Discharges.
In its simplest design, a plasma jet consists of a cylindrical shaped cathode, and an outer glass/dielectric shield wrapped by the anode. By feeding any carrier gas or air between the cathode and shield, and by applying DC/RF power, an arc between the electrodes may be ignited and sustained. Higher voltages (kV) are required for gas breakdown at atmospheric pressure as described by Paschen’s law.
Find out more about Plasma Jets here.
Dielectric barrier discharge consists of two metal electrodes, in which at least one is coated with a dielectric layer. Plasma gas flows in the gap, and the discharge is ignited by means of a sinusoidal or pulsed power source. The gap is on the order of several mm and the plasma is generated through a succession of micro arcs, lasting for 10 – 100 ns and distributed randomly. These systems are used for many applications, for example surface cleaning and material functionalization.
Find out more about Dielectric Barrier Discharge here.
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