Usually Cu-wires are used to connect the specimen to the measuring device or to the circuit. The problem is how to get ohmic contact between the Cu-wire and your sample (dielectric). Usually Au-coating or Ag-coating is used to make the elctrode on both faces of the dielectric capacitor. If you do not have a caoating unit, you can use silver dag or silver paste with a btush to spread a thin layer on both faces of the sample. Heating at moderate temperature to dry  or leave it at room temperature for some hours to dry. Now you can solder the CU-WIRE BY THE SILVER DAG OR SILVER PASTE AND LEAVE TO DRY . Then you can use the sample for measurement. Avoid using low temperature sodering. Spot weldinthe Cu-wires may be ideal if you have the instrumentation.

Dear, Said

Now my question is that, why we need ohmic ohmic contact for simple MIM capacitor and will this kind of contact be stable at such elevated temperature.

Dear Satyendra

To form a capacitor there should be two conducting surfaces with the dielectric in between. To construct the surface coating is essential so that the Cu-wire will be soldered or welded on. 

Alright sir, I got your point. Further, I want to clarify my understanding to you that as per your words, we want ohmic contact between plates of capacitor and connecting Cu wire. As we don't want any conduction through dielectric, hence dielectric-electrode interface should be rectifying. Am I right?? 

You need measurement upto 900 deg C, sorry Cu-wire will not work.

You have to use Pt wire contacts