The IBM high resolution STEM project has now reached the point where integration of new subsystems into the instrument is the main activity. During the past three years, we have demonstrated a 50meV EELS resolution using a high brightness electron monochromator incorporated into the electron gun [1, 2, 3], and better than 0.14mn spatial resolution using spherical aberration correction at 120KeV. [4] Recent effort has been to identify and remove many sources of instabilities in the original instrument; to rebuild several existing subsidiary pieces of equipment such as the ADF detector, the EELS spectrometer electron optical coupling, and the EELS CCD detection system; and to set up software and hardware control of each system to allow routine operation.
The new STEM column is summarized in Fig. 1. Briefly, the original VG gun flange has been lowered about 4cm, using a spacer, to allow insertion of the Fringe Field monochromator.