Verlag des Forschungszentrums Jülich
JUEL-2571
Frohn, Josef
Aufbau eines Rastertunnelmikroskopes mit integriertem Zylinderspiegelanalysator
78 S., 1992
Abstract
A cylindrical mirror analyser has been integrated in a scanning tunneling microscope
(STM). With this analyser the energy distribution of backscattered electrons has been
measured. The electrons originate from a field emission tip positioned close to the investigated
samples.
The influence of the field emission tip on the electron trajectories has been calculated
numerically. As a consequence of these calculations a further electrode has been introduced
near the tip to optimize the elccron optical properties of the analyser.
To enable a special tip preparation, which is necessary for the operation of the STM in
the field emission mode, the setup is equiped with facilities for field ion and field emission
nucroscopy.
Using the instrument in the STM-mode, atomic resolution of the (l00) surface of copper
has been achieved. Beyond these test measurements a detailed investigation of the step
structure on Cu(100) and various Cu(lIn) surfaces has been performed (n = 7, 11, 13
and 19). The step structure is very sensitive to remanent trace contamination, which
decorate the steps and prohibit kink diffusion. Therefore great care was taken in the
sample preparation.
Because of the high mobility of the kink atoms at metal surfaces the step edges appear
frizzy in the STM topographs. It became possible to measure the activation energy for
kinks although individual kinks can not be resolved by STM. These measurements give
also some strong hints for an attractive interaction between steps at intermediate distances
of 4 to 5 atomic diameter and a repulsive interaction at shorter separation.
The step-step interaction plays an important rule for the stability of crystal faces. In the
case of Cu(117) the short range repulsion between the steps dominates and stabilizes this
surface. The attractive interaction at greater distances leads to a facetting of the investigated
vicinal surfaces. This result is discussed in the context of former experiments
studying the thermal roughening transition.
Neuerscheinungen
Schriften des Forschungszentrums Jülich
Ihre Ansprechperson
Heike Lexis
+49 2461 61-5367
zb-publikation@fz-juelich.de