上海交通大学：《Structural and Chemical Characterization of Materi》教学资源_HW

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=Cs3 , 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 Cs2, 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