Metal Contact
The Metal Contact is applied to exterior boundaries which are adjacent to the Plasma Model feature. This corresponds to a powered electrode, where the source voltage, power, or external circuit can be specified. The following options are available:
For the Terminal type, choose either Voltage, Power, or Circuit. When Circuit is selected, refer to the Circuit Options section. In nearly all cases, the Power option is a more stable way of driving the plasma, as multiple physically significant solutions can exist when a voltage source is used. When driving with a fixed power, there can only be one solution to the problem.
For the Source, select one of the following options:
RF. In this case, the excitation is periodic and the maximum and minimum amplitude of the applied voltage are equal. The following options are available.
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Select whether the Periodic function should be Cosine, Sine, Pulsed or Dual Pulsed. The first two options simply determine whether the excitation waveform should be a cosine or sine over the period. The last two apply a sinusoidal excitation at a given frequency for a specified number of periods. The usage of the pulsed options is discussed in Pulsed Discharges.
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If the Terminal type is Voltage, enter the Voltage amplitude Va (SI unit: V) at the electrode. If the Terminal type is Power, enter the RF Power Prf (SI unit: W) to be deposited into the plasma.
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Enter the Frequency fp (SI unit: Hz) for the applied voltage or power. This value must be consistent with the value given for the Period property of the physics interface. See Using Consistent Source Frequencies and Period Settings for further information.
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Enter the Source phase α (SI unit: dimensionless) of the generator. The default is zero and this rarely needs to be changed.
RF and DC. This option allows an additional bias power or voltage to be applied, or the DC self–bias to be computed. In addition to the options for the RF case above, the following options are available:
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Compute DC self–bias. In asymmetric discharges, where the grounded surface area of the discharge is different from the powered electrode surface area, the powered electrode will form a negative DC self–bias. This requires that the period averaged current arriving on the electrode surface is zero. By checking this option, the software will automatically compute the DC self–bias on the electrode. When this option is selected, no other options in the DC Source section are available.
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When the Terminal type is Voltage, and Compute DC self–bias is off, enter a DC bias voltage Vdc,b (SI unit: V). This can be used to increase the ion or electron fluxes to the electrode which may result in a net current flow into the electrode. When the Terminal type is Power, and Compute DC self–bias is off, enter a DC bias power Pdc,b (SI unit: W). There is an additional option to specify whether the Bias should be Negative or Positive.
DC. This option can be used to add a pure DC bias somewhere in the system, but there has to be at least one feature adding an RF excitation elsewhere. Adding a pure DC source generally makes it more difficult to obtain a converged solution. The following options are available:
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When the Terminal type is Voltage, enter a DC voltage Vdc (SI unit: V). When the Terminal type is Power, enter a DC power Pdc (SI unit: W). There is an additional option to specify whether the Electrode type should be Cathode or Anode, depending on whether the power should be deposited using a negative or positive potential.
When the Pulsed option is used the following options are available:
Number of periods on Non: Set the number of periods applied during the phase that the pulse is on.
Number of periods off Noff: Set the number of periods applied during the phase that the pulse is off.
Number of periods to ramp to high power Nlow, high: Set the number of periods used to ramp up to the on phase.
Number of periods to ramp to lower power Nhigh, low: Set the number of periods used to ramp down to the off phase.
If Create a mesh suggestion for the extra dimension is selected an automatic mesh along the extra dimension that represents the period is created. The following options are also available:
Number of elements per on period Nel, on: Set the number elements used per period when the pulse is on.
Total number of elements when excitation is off Nel, off: Set the total number elements used when the pulse is off
When the Dual pulsed option is used the following options are available:
Low power pulse Plow, rf: set the power of the low power phase of the pulse.
Number of periods on, low power Nlow, on: Set the number of periods applied during the low power phase of the pulse.
High power pulse Phigh, rf: set the power of the high power phase of the pulse.
Number of periods on, high power Nhigh, on: Set the number of periods applied during the high power phase of the pulse.
Number of periods to ramp to high power Nlow, high: Set the number of periods used to ramp up to the high power phase.
Number of periods to ramp to lower power Nhigh, low: Set the number of periods used to ramp down to the low power phase.
If Create a mesh suggestion for the extra dimension is selected an automatic mesh along the extra dimension that represents the period is created. The following options are also available:
Number of elements per period, low power Nel, low: Set the number of elements used per period for the low power phase.
Number of elements per period, high power Nel, high: Set the number of elements used per period for the high power phase