DESIGN CONSIDERATIONS AND PERFORMANCE OF A COMBINED SCANNING TUNNELING AND SCANNING ELECTRON-MICROSCOPE

We designed and built a combination of a scanning tunneling microscope (STM) and a scanning electron microscope (SEM) which is working under ultrahigh vacuum conditions (base pressure typically 7.10(-11) mbar). The SEM is ideally used ibr surveying the sample and to control the S TM tip positioning, while the STM extends the resolution range into th e atomic scale. The design concept allows moving the STM tip freely ov er the sample under SEM control and using both imaging techniques simu ltaneously. The system is equipped with an electron energy analyzer (c ylindrical sector analyzer) providing Auger electron spectroscopy, sca nning Auger microscopy (SAM) and x-ray photoelectron spectroscopy capa bilities, In addition, low energy electron diffraction and reflection high energy electron diffraction facilities are installed. In order to use these very different imaging techniques in situ, several special solutions had to be incorporated in the design af the system; they are described in detail. Some results are presented which demonstrate the performance of the STM/SEM system. Atomic resolution of the STM, a SE M resolution of up to 20 nm, and a SAM resolution of better than 100 n m were achieved. (C) 1997 American Institute of Physics.