In the long run you'll be better off doing reactive co-sputtering using two targets (rather than making doped target material). Then you have two options: either have two metallic targets: Zn and the dopant material (if you're doing a single element doping) and add oxygen gas in the right ratio during deposition, or have a ZnO target and a dopant material. Then you can cover many different concentrations in the films with the same targets. I would suggest buying the targets rather than making yourself. These are rather inexpensive materials and purity is crucial for what you are trying to do. Plus ceramic targets are hard to make to the correct density. Good luck!
In the long run you'll be better off doing reactive co-sputtering using two targets (rather than making doped target material). Then you have two options: either have two metallic targets: Zn and the dopant material (if you're doing a single element doping) and add oxygen gas in the right ratio during deposition, or have a ZnO target and a dopant material. Then you can cover many different concentrations in the films with the same targets. I would suggest buying the targets rather than making yourself. These are rather inexpensive materials and purity is crucial for what you are trying to do. Plus ceramic targets are hard to make to the correct density. Good luck!
With separate targets you can get a concentration gradient across the substrate. For some work that is an advantage: You can do a whole concentration series with just one sample, even two-dimensional with two dopant targets. But if you want a uniform film on a whole wafer, I'd recommend to order doped targets of sufficient size. As Lyubov mentioned, making targets yourself is not a good idea, unless you have a well-equipped ceramics lab and lots of time. And purity is a concern - but also with commercial targets! I routinely do an elemental analysis with x-ray fluorescence on each new target before using it. I've had some big "surprises" with commercial targets already!
Thank you Lyubov and Dieter... But if i mixed the dopant materials with ZnO by ball milling and then make the target, how it will be useful to me?
In this case there are serious challenges you'll have to overcome. First of all, with mechanical alloying you need to be sure that the mixture is homogeneous and the dopants are distributed evenly, which is not so straightforward. Then it will be a real challenge to produce a dense enough pellet to use as target. In most cases doped ZnO cannot be heat-treated at high temperatures (e.g. above 400C-450C or so) as the dopant will most likely phase-separate and form own oxide. And making dense ceramics at low temperatures is not an easy task. What size targets do you use for sputtering? What size of the films are you aiming at?
@ Lyubov Belova: We generally use 2inch diameter target and the substrate is Al2O3 of 2*2 cm. I have to deposit a thin film with 1Kohm resistance (may be more than 1Kohm) for gas sensing application. After ball milling process I will keep the materials for heat treatment at 500C and then check the phase by XRD. If I achieve the single phase materials then I will make the target pellet.
Isn't reactive sputtering useful here? Be careful with the sinterization here because the most probably thing that would happen, as Lyubov Belova said, is a change in the phase or a mixing of oxides. Try to put graphite in the sinterization so not to oxide it, but not too much grphite so your ZnO converts to an alloy metal Zn and dopants. And tell us if you succeed!
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