Or more interestingly having a metal like upper surface (blackish, resistance 1-10 ohm?)I have made sputtering target (dia 2inch, 1/4 inch thickness) centered at 400 C with TiO2 powder.I have got similar problem with CuAlO2. Though I can deposit doped and undoped ZnO in the same instrument without any such problems.
It may have to do with the fact that Zn has only one valence state (Zn(II)), while Ti may exist in trivalend and in tetravalent states. Copper may also exhibit univalend an bivalent states. In the oxides of metals haivn more than velence it frequently occurs that the crystal is non-stoichimetric and electrons may jump from one ion to the other. This sometimes results in dark, semiconducting or even conductng oxides. In the case of TiO2 an post-oxidation might help to remove Ti3+ ions from the lattice. But this is aguess only, I hope that people with proper experience may help more effectively.
Gyorgy is right about mixed valence oxides with different electrical properties. Additionally to post annealing, Sputrering from oxide targets has to be usually performed with an oxygen overpressure to avoid these non-stoichimetric oxides. You have to try to do the oxygen injection as close as possible to the sputtering target to make the oxygen positive ions react in the target.
If you want to get a insulating oxide with sputtering,adding oxygen is a good way like F. Caballero-Briones already said. Be aware that you still need the Ar for the sputtering process. You can try something like 20 sccm of Ar and 5 sccm of O2 for a start. Additionally, when you add the oxygen, the deposition rate will drop significantly.
Deposition rate for TiOx is usually low (typically 60nm/hour or less using a RF power of 1 w/cm² with Ar pressure around 10-2 mbar)). Did you wait enough time to see some deposition ?
Perhaps you should try to depose it starting from a metallic target of Ti instead of TiO2 powder.
I did not understand whether you were observing a metallic surface of your target after sintering or of the thin films you were depositing. Any way, sputtering partially reactive using an Ar/O2 mix should help, as was mentioned before...
In our lab we sputter Ti targets in Ar/O2 rf plasma since many years. Based on what observed, the deposition rate of Ti is about 8 times higher than TiO2, but its depends on pressure and rf power.
An important question : do you have a MAGNETRON cathode ? because without any magnetic field, the plasma density is very low .... so the deposition rate is also very low. This may explain why you observed no coating...
I had no problems with TiO2 RF magnetron sputtering. I use a commercial TiO2 target with 6 inch diameter which is bonded to a copper back plate for better cooling. To the oil-free vacuum system with a base pressure 5x10exp(-6) mbar I add oxygen up to a pressure between 5x10exp(-5) mbar and 1x10exp(-4)mbar. Than Ar is admitted to hold the working pressure at about 8x10exp(-3) mbar. RF power is controlled to hold a constant deposition rate at a chosen value between 0.04 to 0.08 nm/s. The TiO2 thin films have excellent transparency. With XPS I found only titanium oxide.
You should vary Ar presure and RF power to get a acceptable deposition rate.
try to use metallic target like (Titanium ) with reactive gas ( oxygen ) and use DC sputtering or DC magnetron sputtering instead of using RF to get (TiO2) in order to enhance sputtering yield
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