I am fabricating WO3-ZnO nano composite for electrochromic application via DC co-sputtering method but i am not able to maintain the desired stoichiometry of W and Zn. Can anyone suggest me the needful solution to get desired stoichiometry of metals in the nano-composite. Any help would be appreciated in advanced.
Hi Gaurav,
Could you give me more details on the process like DC power, base pressure, process pressure, electrode substrate distance, gas composition, etc? One major question I have is concerning the DC-plasma. Are you sputtering from W and Zn targets or are you sputtering from WO3 and ZnO targets?
Dear peter thanks for your interest and support,
I am writing you the details of my experimental procedure.
I am using DC reactive sputtering with W and Zn targets in presence of O2 as a reactive gas. The distance between target and substrate is 6 cm. Ar/O2 ratio is 20:10. I am working at low sputtering pressure (5 mtorr). When I use same power for both the targets, stoichiometry of the composite does not retain. W and Zn are not in proper ratio but literature suggest nearly same deposition rate??. As, Tungsten has slightly high deposition rate. If i use high power for Zn target than the composition changes but XRD spectra is not confirming the composite formation. it's appear to be a different material. So, this is a critical issue with the composite of these two material. Kindly suggest any helpful material.
Hi Gaurav,
I think your basic problem is the DC source. If you sputter reactively with O2 the sputter targets will get poisoned and will form ZnO and WO3 on the target. These materials can be either conductive, if they are substoichiometric (e.g ZnO1-d), but can also become stoichiometric during sputtering. In the latter case no or almost no current will flow through the target and deprates will fall and compositions will change. My advise would be you start sputtering with either RF or with pulsed DC bias. Expecially in the case of co-sputtering the processes influence each other and gas composition changes can lead to non-conductive poisoned layers on your target. If you use RF or pulsed DC you will not have these problems with the conductivity of you poisoned layer and you will be able to sputter stable compounds. In conclusion, sputtering oxides with a DC source is a bad choice.
Dear Peter thanks for your valuable suggestion,
I am agree with your argument, a thin oxide layer may get deposited over the target surface but still plasma sustain in my case?, . As per your recommendation i will try to grow composite with RF source. Still i have a question, if i am using DC source for both the targets than i get different material (ZnWO4) not a composite for every gas ratio. The XRD spectrum confirm this material with some unknown XRD peaks. Is it possible to grow a composite with Zn and W targets irrespective of sputtering source??.
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