  High resolution angle-resolved photoemission measurements are carried out to
systematically investigate the effect of cleaving temperature on the electronic
structure and Fermi surface of Sr$_2$RuO$_4$. Different from previous reports
that high cleaving temperature can suppress surface Fermi surface, we find that
the surface Fermi surface remains obvious and strong in Sr$_2$RuO$_4$ cleaved
at high temperature, even at room temperature. This indicates that cleaving
temperature is not a key effective factor in suppressing the surface bands. On
the other hand, in the aged surface of Sr$_2$RuO$_4$ that is cleaved and held
for a long time, the bulk bands can be enhanced. We have also carried out laser
ARPES measurements on Sr$_2$RuO$_4$ by using vacuum ultra-violet laser (photon
energy at 6.994 eV) and found an obvious enhancement of bulk bands even for
samples cleaved at low temperature. These information are important in
realizing an effective approach in manipulating and detecting the surface and
bulk electronic structure of Sr$_2$RuO$_4$. In particular, the enhancement of
bulk sensitivity, together with its super-high instrumental resolution of VUV
laser ARPES, will be advantageous in investigating fine electronic structure
and superconducting properties of Sr$_2$RuO$_4$ in the future.
