http://en.cnki.com.cn/article_en/cjfdtotal-qjgy200306005.htm

http://www.sciencedirect.com/science/article/pii/S1350449508000558

With a dielectric constant close to one, high reflection cannot be achieved. Assuming normal incidence and [(n-1)/(n+1)]^2 = 0.8, n needs to be nearly 18 and the corresponding dielectric constant would be about 4.23...

Thanks @ Prof. Thomas Mayerhöfer for your valuable suggestion.

Ok ... The value of dielectric constant can be compromised. Need your more help.

Please suggest any highly reflecting material  with good thermal stability.

Thanks

Metal nitrides might be what you are looking for...

http://www.nature.com/articles/srep38647

Thanks Prof. Thomas Mayerhöfer for your help.

I shall read this article, I hope this will help.

Thanks a lot

TiAlN

TiN is much stable at higher temperature!

Only Aluminium Metal will give you a reflectance of 80% in the UV, VIS and NIR.  The dielectric constant is however around 10.  Nickel will give you about 60% reflectance with a dielectric constant around 5.

Thanks a lot @Prof. Kobus Venter

@Prof. David Mulati

and

Dear Dr. Muhammad Farooq Khan Niazi

Good response Prof. Kobus.

You need an alloy of aluminium. 

Thanks Prof. David for your valuable suggestion

Regards

Abdul Ghafar Wattoo

I would like to recommend you three type of electrode or option, if you have no problem with the surface smoothness, as given below:

1. You can try with pure Al about 200nm with deposition rate 3 A/sec in 8x10-4 pa.

2. Stack of Ni (1 nm) /Al (200nm), by using low deposition rate around 0.5-0.3/A/Sec for very thin Ni (1nm) layer and then subsequently using 3 A/Sec for thicker Al (200nm). Your sample surface roughness should be very low before the Ni/Al evaporation. Physical evaporation method

3. You can try Rh, which has high reflectivity but little difficult to grow it. You can challenge Rh in the spattering machine. Good luck

Dear Prof. Dr. M. Ajmal Khan

Thank you very much for your good suggestions.

I appreciate

Regards

Abdul Ghafar Wattoo