I am trying to measeure spin seebeck effect for which I am growing a Pt bar(DC sputter) with thickness 10nm on top of a magnetic thin film. The resistance between two points of Pt bar comes out to be 0.7 kiloohms which is quite high for Pt. To sort out, I increased the thickness of Pt up to microns but resistance remained same. Any suggestion if someone has faced the same problem?
Can you check the structure of the Platinum bar under say, an electron microscope? Even in an SEM you can check the surface topography of the film to have an idea of how uniform the sputtering has been. You can use EDX to check it the Platinum is there at all. If the sputtering conditions are not optimum, the grain sizes may become too large or non-uniform and that may lead to a high resistance value. Also, I assume you are obviously doing a four-probe measurement to measure the resistance, even though you write 'resistance between two points of Pt bar'.
The thickness of the layer you use is very thin and might not be homogeneous as Indrani pointed out, the reason why I asked for details on the sputter conditions. Be aware that specific resistance of thin film layers is always higher than bulk value numbers of Pt in literature. It is not uncommon that specific reistance of metals is 2-5 times higher than bulk values, especially in the case of thin layers like yours.
@peter knapen
Sputter conditions are as follows: base pressure 10^-6, Working pressure Ar- 0.05 Torr, Ar flow rate-80sccm, substrate temperature-25k
@Indrani Chakraborty
Thank you Indrani. Checked through EDX, Pt is there.
Actually, I am not doing four probe method. I simply attached the knobs of DMM across the ends of Pt bar to measure resistance. I am not sure if it is the right method to do so.
Was your pressure really 50 mT? This is rather high for sputter processes. This has a big impact on your morphology and at this pressure you will create columnar growth of the Pt, which will raise the resistance. I would advise to go back to 5- 7.5 mT. You will get more microcrystalline material with better resistance.
All good suggestion. In addition to all the above suggestions, I would be worried about the base pressure. When you sputter Ti at low rate in a not so good base pressure leads to oxidation of Ti and leads to resistive films.
Paulson
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