The emmisivity valus of silicon can be found in
Mat. res. soc. syposium vol 52 1986
The title of the book is
"temperature measurement and control in a Rapid thermal processor:
Ronald E. Sheets.

and
Japan Journal of appl. phys. v.6, no3 (march 1967) pp 339-347
by
T. Sato

sato deals with the emmisivity for the entire range of temperature.

good luck
padmaja