Carbon spark evaporation
The invention relates to a method for operating a pulsed discontinuous spark discharge. The spark is fed via a capacitor. Between the pulses there are switched-off time intervals during which no spark current flows. Within the pulses, that is to say during the switched-on time intervals, the supply of charge is stopped upon a current threshold being reached and is restarted, with the result that subpulses occur within the pulses. The time intervals and subpulses are chosen according to the invention such that when the capacitor is switched on again, the spark discharge readily ignites again.
1. Method for depositing a layer on a substrate, comprising the steps of:
providing substrates;
placing the substrates in a vacuum chamber;
pumping out the vacuum chamber;
providing two separate current supplies, namely a direct current supply and a pulse current supply that discharge to achieve a pulsed discontinuous spark discharge,
with the pulse current supply comprising at least one capacitor and where the corresponding discharge current of the pulse current supply is controlled by periodical switching on and off of the capacitor to form switched-on time intervals and switched-off time intervals,
wherein the capacitor is switched off during the switched-off time intervals, during which no current is supplied from the direct current supply and no current is supplied from the pulse current supply,
wherein within the switched-on time intervals, no current is supplied from the direct current supply and the discharge current of the pulse current supply is momentarily interrupted upon reaching a previously determined threshold, with the result that subpulses occur within a current pulse from the pulse current supply; and
depositing the layer on the substrate by performing a cathodic spark evaporation by means of the pulsed discontinuous spark discharge,
wherein the layer comprises carbon.
2. Method according to claim 1 , wherein at least a first plurality of the switched-off time intervals is chosen so to be short enough that after expiration of each one of the plurality of the switched-off time intervals, the switching on of the capacitor automatically causes the renewed ignition of the spark discharge.
3. Method according to claim 1 , wherein the first ignition of the spark discharge is achieved by means of an ignition device, and after the first ignition of the spark the capacitor is switched on for the first time and has a first charge state at the time of the first ignition,
and the pulsed discontinuous spark discharge method is subsequently further operated with the direct current supply switched off.
4. Method according to claim 3 , wherein a length of a second plurality of switched-off time intervals is chosen depending on the charging means of the at least one capacitor, such that after expiration of each of the second plurality of switched-off time intervals, the capacitor has essentially reached the first charge state.
5. Method according to claim 1 , wherein the layer is one or more carbon layers that are hydrogen-free and/or contain hydrogen and/or metal-free and/or contain metal and is coated on the substrate.
6. Method for depositing a layer on a substrate, comprising the steps of:
providing substrates;
placing the substrates in a vacuum chamber;
pumping out the vacuum chamber;
providing two separate current supplies, namely a direct current supply and a pulse current supply that discharge to achieve the pulsed discontinuous spark discharge,
with the pulse current supply comprising only one discharging capacitor and where the corresponding discharge current of the pulse current supply is controlled by periodical switching on and off of the capacitor to form switched-on time intervals and switched-off time intervals,
wherein the capacitor is switched off during the switched-off time intervals, during which no current is supplied from the direct current supply and no current is supplied from the pulse current supply,
wherein within the switched-on time intervals, no current is supplied from the direct current supply and the discharge current of the pulse current supply is momentarily interrupted upon reaching a previously determined threshold, with the result that subpulses occur within the a current pulse from the pulse current supply; and
depositing the layer on the substrate by performing a cathodic spark evaporation by means of the pulsed discontinuous spark discharge,
wherein the layer comprises carbon.
7. Method according to claim 3 , wherein the ignition device that causes the first ignition of the spark discharge is a DC direct voltage source.
8. Method according to claim 1 , wherein the direct current supply provides current for the first ignition of the spark discharge during a first switched-on time interval.
9. Method according to claim 8 , wherein during switched-on time intervals after the first switched-on time interval, no current is supplied from the direct current supply.
10. Method according to claim 1 , wherein the switched-on time intervals and switched-off time intervals alternate with each other.