6.777J/2.751J Material Property Database

Material: Amorphous Silicon (a-Si)

Please note the most texts switch between a-Si and a-Si:H (10% hydrogenated amorphous silicon) at random. According to Madou (2001), page 298, “Unfortunately very little is known about the mechanical properties of amorphous Si.” This seems to be due to the optoelectronic application of the material. In most cases the mechanical properties were not available and where I deemed suitable, I included Si properties. I tried to indicate exactly which properties were included.

Property	Value	Reference	Image/URL (optional)
Mass density	For Silicon: 2.33 g/cm3	McGuire, G.E., “Semiconductor Materials and Process Technology Handbook” William Andrew Publishing/Noyes, 1988
Young's modulus	80±20 GPa	Freund, L.B. and Suresh, S., “Thin film materials”, Cambridge University Press, 2003, page 96
Poisson ratio	0.22	Freund, L.B. and Suresh, S., “Thin film materials”, Cambridge University Press, 2003, page 96
Stiffness Constants	(1) For Si [dynes/cm^2]: C11 = 1.67x10^12 C12 = 0.65x10^12 C44 = 0.79x10^12 (2) For Si [GPa]: E11 = 164.8 E12 = 63.5 E44 = 79.0	(1) McGuire, G.E., “Semiconductor Materials and Process Technology Handbook” William Andrew Publishing/Noyes, 1988 (2) Madou, M.J., “Fundamentals of Microfabrication”, CRC Press, 2001, page 198.
Tensile or fracture strength
Residual stress on silicon	For Poly-Si deposited with LPCVD (560-670 degrees C): -0.1 to -0.3 GPa	Ohring, M. “Material science of thin films”, Academic Press, 2002, page 743.
Specific heat
Thermal conductivity	For a-SI:H: 4x10^-6 [1/K]	Street, R.A., “Technology and application of amorphous silicon”, Springer, 2000, p242
Dielectric constant	For Si: 11.8	McGuire, G.E., “Semiconductor Materials and Process Technology Handbook” William Andrew Publishing/Noyes, 1988
Index of refraction	4.5 @ 600nm wavelength	Madou, M.J., “Fundamentals of Microfabrication”, CRC Press, 2001, page 298.
Electrical conductivity	σ = 3x10^-5 (ε=0.33 eV at T=310 K) σ = 270 (ε=0.77 eV at T=400 K)	Values [Ω^-1cm^-1] given for a-Si, prepared with glow discharge technique and has strong dependence on activation energy [eV] and temperature [K]. Le Comber, P.G. and Mort, J., “Electronic and structural properties of amorphous semiconductors”, Academic Press, New York, 1973, page 377.
Magnetic permeability
Piezoresistivity		Madou, M.J., “Fundamentals of Microfabrication”, CRC Press, 2001, page 200 gives an overview for Si, but does not mention anything for a-Si. He does state that the coefficient do depend on the crystal orientation of the material, so it is unclear whether or not a-Si will exhibit Piezoresistivity.
Piezoelectricity
Wet etching method	KOH (1) a-Si is etched by HF, but poly-Si is not (2)	(1) Perry, R.H. and Green, D.W., “Perry's Chemical Engineers' Handbook (7th Edition)”, McGraw-Hill, 1997 (2) O'Mara, W.C., Herring, R.B. and Hunt, L.P., “Handbook of Semiconductor Silicon Technology”, William Andrew Publishing, 1990
Plasma etching method	For Si: CF4 or SF6	Senturia, S.D., “Microsystem design”, Kluwer Academic Publishers, 2001, page 69.
Adhesion to silicon dioxide
Biocompatibility	For Si: yes, but cell- and protein adhesion remains problematic and there is considerable room for improvement.	Madou, M.J., “Fundamentals of Microfabrication”, CRC Press, 2001, page 511.
Hydrophobicity