HW assignment,due on April 23,2019 The resolution of a TEM is limited by diffraction(Ra)and by the spherical aberration which is expressed as:Rsph-Ca3,where Cs is the spherical aberration coefficient and a is the half-angle of the cone of light entering the objective lens. The TEM resolution is the quadratic sum of the diffraction resolution and spherical aberration resolution,given by the expressio:=R+R.The minimum R is obtained when R=Rph Estimate the optimum value of a and resolution limit of TEM at Cs~2,0.2 and 0.02 mm for an electromagnetic objective lens.And the accelerating voltage is 200 kV. Acc. Voltage λ(nm) (mm) Copt (mrad) mi (nm) (kV) 2 200 0.2 0.02
Acc. Voltage (kV) （mm） αopt （mrad） Rmin（nm） 200 2 0.2 0.02 The resolution of a TEM is limited by diffraction (Rd) and by the spherical aberration which is expressed as: Rsph=Cs3 , where Cs is the spherical aberration coefficient and is the half-angle of the cone of light entering the objective lens. The TEM resolution is the quadratic sum of the diffraction resolution and spherical aberration resolution, given by the expression: . The minimum R is obtained when Rd=Rsph . Estimate the optimum value of and resolution limit of TEM at Cs2, 0.2 and 0.02 mm for an electromagnetic objective lens. And the accelerating voltage is 200 kV. HW assignment, due on April 23, 2019