Table 2. Parameter values obtained from fitting the FS–load plots under different external applied voltage with equation (2).

Tip Bias (V)	E (kV/cm)	Slope	Intercept	Adj R–square
0	0	0.390	9.89	0.996
3	54.5	0.339	27.18	0.991
6	109	0.324	38.33	0.995
9	164	0.307	39.93	0.984
12	218	0.297	40.59	0.992