Page 31 - report P Lemoine feb 2013c

31

are;

· Determination of the contact depth h c (h c=h-eL/S) from h and L and S; the
stiffness measured as the slope of the unloading curve at depth h.

2
1/2
· Determination of the projected contact area A (A= 24.5h c + a 1h c+a 2h c +..),

where the coefficient a i are determination form a calibration experiment on
fused silica.

· Determination of the hardness H=L/A

1/2
· Determination of the reduced modulus E*=S/(2A )

2
2

· Determination of the E value from (1/E*)=(1-n t )/E t+(1-n)/E, where n t and E t
are the Poisson ratio and Young modulus of the tip and n and E are the
Poisson ratio and Young modulus of the sample.

Finally, by using continuous stiffness measurement (CSM), one can calculate the E
and H values for every point of the loading segment and produce curves as shown in

figure B4

25

20
Hardness (GPa) 15

10

5
silicon
50nmDLC/si
0
0 20 40 60 80 100
Displacement (nm)

-
Figure B4: H(d) curve for a coated and uncoated Si substrate. Loading at 0.05 s 1
constant strain rate up to 100nm depth.

31

PDF Created with deskPDF PDF Writer - Trial :: http://www.docudesk.com