Si (Silicon)

Silicon is used as an optical window primarily in the 3 to 5 micron band and as a substrate for production of optical filters. Large blocks of Silicon with polished faces are also employed as neutron targets in Physics experiments.

 

Physical and optical properties  

Transmission Range :	1.2 to 15 μm (1)
Refractive Index :	3.4223 @ 5 μm (1) (2)
Reflection Loss :	46.2% at 5 μm (2 surfaces)
Absorption Coefficient :	0.01 cm-1 at 3 μm
Reststrahlen Peak :	n/a
dn/dT :	160 x 10-6 /°C (3)
dn/dμ = 0 :	10.4 μm
Density :	2.33 g/cc
Melting Point :	1420 °C
Thermal Conductivity :	163.3 W m-1 K-1 at 273 K
Thermal Expansion :	2.6 x 10-6 / at 20°C
Hardness :	Knoop 1150
Specific Heat Capacity :	703 J Kg-1 K-1
Dielectric Constant :	13 at 10 GHz
Youngs Modulus (E) :	131 GPa (4)
Shear Modulus (G) :	79.9 GPa (4)
Bulk Modulus (K) :	102 GPa
Elastic Coefficients :	C11=167; C12=65; C44=80 (4)
Apparent Elastic Limit :	124.1MPa (18000 psi)
Poisson Ratio :	0.266 (4)
Solubility :	Insoluble in Water
Molecular Weight :	28.09
Class/Structure :	Cubic diamond, Fd3m

 

Refractive Index  

No = Ordinary Ray

µm	No	µm	No	µm	No
1.357	3.4975	1.367	3.4962	1.395	3.4929
1.5295	3.4795	1.660	3.4696	1.709	3.4664
1.813	3.4608	1.970	3.4537	2.153	3.4476
2.325	3.4430	2.714	3.4358	3.000	3.4320
3.303	3.430	3.500	3.4284	4.000	3.4257
4.258	3.4245	4.500	3.4236	5.000	3.4223
5.500	3.4213	6.000	3.4202	6.500	3.4195
7.000	3.4189	7.500	3.4186	8.000	3.4184
8.500	3.4182	10.00	3.4179	10.50	3.4178
11.04	3.4176

Product Notes

Silicon is grown by Czochralski pulling techniques (CZ) and contains some oxygen which causes an absorption band at 9 microns. To avoid this, Silicon can be prepared by a Float-Zone (FZ) process. Optical Silicon is generally lightly doped ( 5 to 40 ohm cm) for best transmission above 10 microns. Silicon has a further pass band 30 to 100 microns which is effective only in very high resistivity uncompensated material. Doping is usually Boron (p-type) and Phosphorus (n-type).

Tags: Si (Silicon)

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