Hi,   tell me more...  a parallel plate 13.5MHz reactor and how about the microwave?

Or just a sample holder put on rf+mw frequencies?   What about gas pressures? H2 gas is not my speciality.. 

any reference to see your machine?

but a good machine for sure, do not give up.. nanodiamonds on WC tools..

lukas

hi Lukas. I have just a sample holder that works on rf+mw frequencies with a power of 100W each. H2 flux=100sccm. pressure= 5-7mbar. Bias=200-210 V. Once I start the process Bias voltage stops at 4 V. It seems to be a short circuit, but I do not know.

thnx

there are some photos of our set-up.

to my understanding your microwave is not directly coupled to your sample holder?

the microwave is injected through a dielectric window on the top cover of the chamber.

your bias voltage is firstly created by the rf self-bias. (without microwave?) there you reach -100 to -200 V.    Switching on the microwave this voltage drops to 4V ?

how do you control your matching of your rf..  whenever you start the microwave this tuning of rf will be strongly modified?

Yes, microwave is not directly coupled to sample holder. I switch both (rf+microwave) since at the beginning. Sometimes, it works but immediately it drops to 4V and nothing. I do not think it is a problem of microwave because I tried many times switchting one of them.

Thnx

Start without microwave.. there you should be able to tune your rf self-bias to high voltages..  (using the matching box and changing the rf power or gas pressure).

Once this is running fine,  you may switch on the mirowave..  then big changes applies to your plasma.. you have some more e-density provided by the mw power..

now this increase of plasma density will shift tremendously the matching point of your rf-matchbox..  so start with low mw power, and adapt little by little the rf matching.. progressively increase the mw power..

observe the increase of plasma intensity above your substrat holder..  whenever this plasma intensity is decreasing or disappearing then your main plasma has moved to the quartz windows of your mw-inlet port..   then again your rf matching will be completely disturbed... 

it is a really progressive setting... once you know the right settings you may later jump to these working points.. but first get them patiently..

microwave plasmas like mode jumps.. once the stick to your quartz input port, no chance to get them back to your rf-holder..

only by starting your rf first, burning a rf plasma first, gives the microwave some plasma to put the wave energy. so you can decide where the plasma is sustained.

if not the plasma region will be determined by the microwave fields maximum, which may not be at the sample holder.. especially the quartz surface is convenient place for the microwave plasma since it is directly at the source of energy.

At high pressures it is difficult to maintain the plasma somewhere else than at the source of microwave energy.

good luck

thank you, i will try. it really helps

all the best