X-ray irradiation damage in ultra-thin SiO2 films has been investigated on
an atomic scale using scanning tunneling microscopy (STM). From the X-ray p
hotoelectron spectroscopy time-dependent measurement, the creation of hole
traps and the successive electron trapping are observed with increasing irr
adiation time. In both cases, bright spot, are observed in the STM images.
We conclude that the bright spots which appeared in the hole trapping durat
ion correspond to the hole traps in the SiO2 film, The bright spots which a
ppeared in the electron trapping duration are larger in height and diameter
in the STM images than those that appeared in the hole trapping duration.
Although most of the bright spots in the hole trapping duration vanish with
annealing at 600 degreesC, the larger bright spots remain after the anneal
ing. It is considered that the larger bright spots in the electron trapping
duration correspond to leakage sites in the ultra-thin SiO2 films. Moreove
r, these trap sites are considered to originate from surface defects prc-ex
isting on a clean Si(100) surface.