I want to make PLD targets for thin film deposition and i have made some using Sol-Gel method but not getting good results so i want to know that Sol-Gel method is good for this as i have seen in the literature that most of the targets formed using solid state method so should I also follow the same or my method is correct........?
Yes, you can make PLD targets by reacting powders using the simplest solid state reaction method. I have always made my targets using this process.
One important thing the sintered target should show a single phase formation, and this can be examined using XRD.
Secondly, you should achieve a high density.
Using sol gel process derived powders can be used. But normally the yield of a sol gel process and amount of powders is less. In case the complicated composition you are developing is achievable by sol gel process. I do not see any problem in using those powders. But the sintered ceramic disc to be formed using sthe sol gel powders should have a single phase, and the highest possible density.
K. Sreenivas
Sol gel method is not bad as such, you can obtain ceramic powders perhaps at very low annealing/sintering temperatures. After ensuring single phase formation with appropriate annealing/sintering of powders;
For PLD target preparation you have to compact the sol gel derived powders into a hard dense ceramic.
K. Sreenivas
I couldn't agree more with the comment above. Let me just rephrase and put it in a format which you may comprehend.
1. Make the necessary composition by sol-gel if it is required. Otherwise, its common to weigh the ingredients carefully in a micro-balance and mix them thoroughly using agate mortar and pestle or better yet ball-milling.
2. Make a green compact by pressing the powder using a die and a hydraulic press. The required shape and size would depend on the die, typically a pellet with a dimension of 15-20 mm diameter with 4-5 mm thick should hopefully work fine for PLD. If necessary, you might use binder like poly-vinyl-alcohol.
3. Sinter the green compact at the required temperature,duration and ambient. The green compact will shrink upon sintering and densify. Make sure that the pellet has as high density as possible and there are no cracks.
For further details, you might have a look at the link below.
http://link.springer.com/article/10.1007%2Fs12034-011-0122-4
To make a target for PLD, generally people uses solid state reaction method but care must be taken regarding impurities issue.
Dear Vinay
Both methods, Sol-gel or Solid state reaction can be used to prepare ceramic powder. This powders is used to prepare PLD target. During the PLD process, target is subjected to a very high energy so it should have high density and low porosity. In my opinion target making process (powder to pellet) is more important with your optimized sintering time and temperature.
The sol-gel method may be a good starting point but subsequent sintering will be usually required.
I agree with Adam. Even if you prepare powder using sol-gel, you need sintering to make a dense target. Please add some PVA in the powder and mix it thoroughly and then make a target using press. Then sintered the target (in most case upto 1000C, but depends on sample to sample) at slow ramp rate. We have made hundreds of target using this technique.
To add to the good information above, a sure way to improve target density is to use a Cold Isostatic Press (CIP). This is where the preformed uniaxially pressed pellet is placed into a rubber bag (or latex balloon) and pressed in a fluid medium (typically water or hydraulic oil). High pressures can be achieved in the CIP which compacts the powder pellet equally in all directions, providing more homogeneous compaction before sintering.
This does not reduce the importance of the powder processing routes mentioned above; ball milling, sintering temperatures, ramp rates and dwell time are all very important to get a good target, CIP allows you to achieve densities beyond 90 % and reduces cracking formed from inhomegenous stresses from uniaxial pressing. >85% (ideally >90%) is really where you want it to be to reduce droplet formation in the growing film and this also elongates the life and "handlability" of your target significantly.
One drawback is that when the final dimensions of a target are critical, CIP may not work for you as it is difficult to exactly control the final dimesnions of the target. For PLD, this is not always a huge issue and is often the case anyhow after the target shinks a little during sintering.
If you are looking for a CIP close to you, they're often found in a the old powder processing / powder metallurgy rooms in Materials Science departments. You can also now also purchase CIP dies which fit within a normal uniaxial press which greatly reduces the capital outlay for new equipment. This would be for the group who is often making targets as opposed to someone making one or two on occasion.
Any questions feel free to get in contact!
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