Electrical study of DC positive corona discharge in dry and humid air containing carbon dioxide

Electrical Discharge in a Nanometer-Sized Air/Water Gap Observed by Atomic Force Microscopy

“…For such a nanogap, the discharge behavior deviates significantly from the traditional Paschen law valid for large scale discharges . The growth of discharge probability with bias voltage observed in Figure e is related to the enhancement of ionization by higher field in the Townsend electron avalanche process. − A higher field would significantly increase the primary and secondary ionization coefficients α and γ, and larger α and γ values favor a higher discharge probability W according to the relation of W = 1 − {γ exp[(α d ) − 1]} -1 , where d is the separation between cathode and anode . It is further seen in Figure e that humidity conditions strongly affect the discharge probability.…”

“…For both Si and PS, the probability decreased by ∼33% when the RH was reduced from 75% to 40%. The impact of water on the discharge occurrence is 3-fold: (i) O 2 is a strong electronegative molecule which lowers the secondary ionization coefficient γ through the electron attachment reaction of O 2 + e = O - + O; , partial replacement of O 2 by the less electronegative H 2 O molecule would reduce the degree of electron attachment; (ii) the incorporation of H 2 O can reduce the size of the ionization zone, thus facilitating the secondary avalanche in the air/water gap; (iii) it has been proven by Lyuksyutov and co-workers that water ionic dissociation can generate substantial electron flux in the tip−surface junction . On one hand, these electrons could act as seed electrons to initiate the primary ionization in ambient air.…”

“…The discharge of gases is usually triggered by ionizations under conditions of high temperature, high electrical field, or strong optical radiation. − In dry gases, the primary ionization is initiated by seed electrons, and subsequent ionizations are self-sustained by avalanching electron−molecule collisions. The current and charge distribution in the discharge is governed by Laplacian and space charge fields. − Controlled gas discharges have wide applications in micromachining, − thin film growth, , gas-filled switching devices, pollutant removal , and microsurgery. , In laser-induced gas breakdown, the energy liberated from the plasma was exploited to modify semiconductors 6-8 and decompose energetic polymers .…”

“…The discharge of gases is usually triggered by ionizations under conditions of high temperature, high electrical field, or strong optical radiation. − In dry gases, the primary ionization is initiated by seed electrons, and subsequent ionizations are self-sustained by avalanching electron−molecule collisions. The current and charge distribution in the discharge is governed by Laplacian and space charge fields. − Controlled gas discharges have wide applications in micromachining, − thin film growth, , gas-filled switching devices, pollutant removal , and microsurgery. , In laser-induced gas breakdown, the energy liberated from the plasma was exploited to modify semiconductors 6-8 and decompose energetic polymers . Yet, our understanding of gas breakdown has been restricted to bulky gas discharges which often spread over large areas. − The emerging nanotechnology demands functional structures to be defined with nanometer accuracy for miniaturized devices and improved performance. − For example, memory bits with diameter of ∼40 nm and bit spacing of <100 nm have to be fabricated to achieve a potential storage density of 400 Gbyte/in 2 on polymer. , Highly localized gas discharges are also desirable for site-specific deposition of single nanostructures in chemical vapor deposition .…”

Water surface deformation in strong electrical fields and its influence on electrical breakdown in a metal pin–water electrode system

“…The broadening of the conductive channel in the case when the pin is the cathode starts about 1.5 mm above the water surface indicating that bulk effects cause this phenomenon. As is known from corona discharges in air, the presence of water vapour affects not only the initiation field strength but also the mobility of the charge carriers due to cluster formation of ions with polar water molecules ( [22,24] and references therein). The water vapour content near the water surface in comparison with the rest is larger and charge carriers in this region have smaller mobility.…”