theta=885/2/12000;	
	b=2     {nm}
	c=200  {nm}
	a=10   {nm}
	width=100{nm}
 	height=50{nm}
 
	electron=1.6e-19
	Avogardo=6.02e23
	epsilon0=8.85e-12
	epsilon=80
	boltzman=1.38e-23
	temperature=300
	sigma=-0.16
	n0=0.02    {mol/L}
	dp=1.96  {1e-9}
	dn=2.03  {1e-9}