Hi,
According to  by James D. Plummer, the young's
modulus for Si: Y100=1.3*10^12 dyne cm(-2), Y111=1.9*10^12 dyne cm(-2). I
guess different orientation has different atom density, thus different
modulus.

For small structure, for example, cross section of Si beam less than 200nm^2,
young's moduls maybe 37 times larger according to one paper. This may be
caused by size effects.

As to polysilicon, different deposition process, specimen fabrication methods,
mount, test and measurement will all lead to difference. But not so large
according to Sharpe (Experimental Mechanics, vol 43, no3, 2003),it should be
around 158 (10) Gpa.

Hope it is helpful.

Regards,
Yilei Zhang