High emissivity, high temperature resistant coating for surface temperature measurement using IR-pyrometer

I want to measure the surface temperature of silicon chips with IR-pyrometer. As the emissivity of silicon varies strongly in dependance of temperature, I need to coat the chip surface with a material with following specification:

- high and constant emissivity (>0.9) for wavelength of 1.6um in temperature range of 400-1000 °C in nitrogen atmosphere (i.e., no oxidation will take place).

- easy to apply on polished silicon surface forming thin (<1um) and homogeneous films.

- electrically insulating

- easy to remove after use (e.g., soluble in some chemicals or in oxygen-plasma)

- no mechanical strength is required

Do you know any material which can fill the demands above, even if partially? Can e.g. carbon black be used in this case? I'd appreciate any suggestions!