As you changed the targets...first are they having same quality....from same vendor and specifications?.....is there any preparatory steps taken before deposition ...like allowing removal of any deposits on the target surface....if deposition has transparent nature thickness variations will give you different colours....so check all this to repeat your results.

Dear Jignesh G. Hirpara

thanks for your response. cleaned the targets with isopropyl alcohol firstly and then during the process they were cleaned by arc plasma. what made me surprised is that changing gas pressure, bias, arc current and time deposition has no effect on the color .

Dear Saba,

have you checked the connections, clamping and cooling circuit of the target ? Maybe your target is overheating... Then, vacuum level is OK ? Argon or other gas you are using are OK and reproducible ? No air is inside ?

Are you working at fixed current ? Did you observe changes in the voltage ? Eventual surface pollution of the target during operation could be checked through drifts in electrical parameters.

Generally with new arc target, the evaporation rate is higher compared to old one. To resolve this, one can reduce arc current, or increase nitrogen pressure to maintain the stoichiometry.

Dear Simone Vezzù

thanks for your clear response. I followed your guidance and I noticed that Although all parameters were same in each cycle, some targets randomly became hot and the others were cold. I checked cooling water circuit and it works properly. I did not find the reason yet.

dear Rajesh Mundotia

thanks a lot for your tips. I increased nitrogen pressure and the color became darker.

best regards

Dear Saba Khoramkhorshid,

All the best...