188
GLOSSARY
the
characteristic X-rays.
The
bremsstrahlung-excited Auger electron
features
can be
helpful
for
determining
the
various
Auger
parameters
needed
to
identify
chemical states.
Chemical
Shift
Change
in
peak energy arising
from
a
change
in the
chemical environ-
ment
of the
atom.
Compositional Depth
Profile
Chemical
or
atomic composition measured
as a
function
of
distance
normal
to the
surface.
Constant
AE
Mode
(constant analyser energy mode,
CAE
mode
or
fixed
analyser transmission mode,
FAT
mode)
Mode
of
electron energy analyser operation which varies
the
electron
retardation
but
keeps
the
pass energy constant
in the
energy dispersive
portion
of the
analyser. This mode
is
often
used
in XPS to
maintain
a
high-
and
constant-energy resolution throughout
the
spectrum.
Constant
AE/E
Mode
(constant retardation ratio mode,
CRR
mode
or
fixed
retardation ratio mode,
FRR
mode)
Mode
of
electron energy analyser operation which varies
the
retarding
potential
so
that
the
pass energy
in the
energy dispersive portion
of the
analyser
is a
constant fraction
of the
original vacuum level referenced
kinetic energy.
This
mode
is
often used
in AES to
improve
the
signal-to-
noise
ratio
for
high-energy emitted electrons
at the
expense
of
spectral
resolution.
Depth Profiling
Monitoring
of
signal intensity
as a
function
of a
variable
which
can be
related
to
distance normal
to the
surface
usually,
sputtering
time.
Depth
Resolution
Depth range over which
a
signal changes
by a
specified quantity when
reconstructing
the
profile
of an
ideally sharp interface between
two
media
or a
delta layer
in one
medium.
The
precise quantity
to be
used
depends
on the
signal
function
with depth. However,
for
routine analyti-
cal
use,
a
convention
of the
depth
at an
interface
over which
the
signal