Instant Message with Mark on the Microprobe
This blog is only for understanding more about the Microprobe and stuff...
MidnightYell2003: howdy
MidnightYell2003: does carly work at the
microprobe thing?
IrNobleMetal: yeah
IrNobleMetal: why?
MidnightYell2003: ok maybe you can tell me,
what exactly is the microprobe?
IrNobleMetal: A microprobe is sort of a souped up
electron microscope....
IrNobleMetal: do you know what an electron
microscope is?
IrNobleMetal: and how it works
MidnightYell2003: is it like an SEM or scanning
electron microscope?
IrNobleMetal: yeah
MidnightYell2003: ok then no
MidnightYell2003: i just heard of it
IrNobleMetal: exactly, do you know how they work?
(cause I gotta give you some background first)
MidnightYell2003: not exactly
MidnightYell2003: maybe you can explain it
better
IrNobleMetal: ok, for these types of instruments you
basically generate a beam of electrons that you spray
across the surface of a sample...
MidnightYell2003: ok
IrNobleMetal: you spray the electron beam in a rhastor
pattern--just like a TV screen, you know how that
works?
IrNobleMetal: start at the top, scan across, go down
one line, scan across, and repeat til you get to the
bottom of the screen
IrNobleMetal: you dig?
MidnightYell2003: for the most part...
MidnightYell2003: and stuff
IrNobleMetal: ok, well you scan across the surface of
the sample but you do this over a VERY small area...
IrNobleMetal: this is roughly a square pattern and it
could be a millimeter square or it could be less than a
micrometer square
MidnightYell2003: like how small?
MidnightYell2003: ok
IrNobleMetal: as you scan this electron beam across
the surface, electrons are reflected in SEVERAL
different and distinct ways. You pick up these reflected
electrons through different types of detectors....
IrNobleMetal: at the same time that this is going on, the
signal from one of these detectors is being displayed on a
TV monitor....
MidnightYell2003: i see...
IrNobleMetal: as the beam sweeps across the sample,
the beam in the CRT (the TV monitor) is also sweeping
across the screen, creating an image
IrNobleMetal: ....
IrNobleMetal: electrons are reflected in different ways
by different materials....
IrNobleMetal: heavy elements (gold, lead, uranium)
reflect electrons strongly....
MidnightYell2003: yeah...
IrNobleMetal: light elements (oxygen, carbon, lithium)
don't reflect much
MidnightYell2003: ok
IrNobleMetal: so if you have a detector detecting the
quantity of electrons reflected gold would appear really
bright, lithium would appear really dark....
IrNobleMetal: this is an oversimplification, in reality it's
the average weight of a compound (eg: SiO2 or PbPO4)
IrNobleMetal: the compound with lead has a much
higher average weight (z-value) so it would show up
brighter
IrNobleMetal: for a SEM (non-microprobe) you often
have samples with raised features and you're often
looking at shapes like those great black and white
pictures of ants magnified nine zillion times etc....
IrNobleMetal: this is possible because the surface of an
ant isn't flat and so the electrons reflect differently from
the different angles of incidence.....
IrNobleMetal: you gettin' this?
MidnightYell2003: yeah, hang on, phone...
IrNobleMetal: ahh
MidnightYell2003: ok sorry, reading...
IrNobleMetal: that makin' sense to you?
MidnightYell2003: kinda, so what exactly is
different between microprobe and SEM?
IrNobleMetal: well, all those electrons bouncing
around that I was telling you about??
MidnightYell2003: yeah..
IrNobleMetal: the microprobe has a lot more
capabilities as far as detecting the different types of
reflection/flouresence etc..
IrNobleMetal: SEMs are MUCH better at very very
VERY high resolution, high magnification of shapes
IrNobleMetal: microprobes are much much better at
determining the exact chemistry of a vanishingly small
quantity of material
IrNobleMetal: that's the short answer
MidnightYell2003: wow cool
IrNobleMetal: you want chemistry, get a microprobe
you want high resolution images get an SEM
MidnightYell2003: how many microprobes are
there in the world or whatever?
IrNobleMetal: no idea, but not too many I'll bet less
than a thousand. really only two companies that make
them: Cameca (made TX A&M's) and PGT (Precission
Gamma Tech)
MidnightYell2003: is there anymore in Texas?
like does t.u. have one?
IrNobleMetal: Probably, I'll bet the t-sips, and rice
both have them, maybe a few others
MidnightYell2003: interesting
MidnightYell2003: how many different
departments use it?
IrNobleMetal: the one that we have set the department
back about 750 GRAND
MidnightYell2003: wow nice
IrNobleMetal: a typical SEM doesn't run more than a
quarter mil
IrNobleMetal: a LOT of departments use it
IrNobleMetal: especially engineering
MidnightYell2003: which engineering? civil?
IrNobleMetal: nuclear engineering, some civil too
MidnightYell2003: oh i see
IrNobleMetal: lots of materials science....
MidnightYell2003: those people...
IrNobleMetal: they use it to see how metals form and
things of that nature
MidnightYell2003: because it seems to me that
not a lot of people even know it exists
IrNobleMetal: that's probably true, not well publicized
IrNobleMetal: I have helped a lot of grad students
from the chemistry department prepare samples for it
though
IrNobleMetal: oh, and archeology uses it a lot
MidnightYell2003: but it's like some people who i
think should know about it, dont... like a lot of
people in the chem department and even in the
civil department, its weird
IrNobleMetal: yeah, well, all the cool people know
about it: Me, DrGuillemette...
MidnightYell2003: hehe yeah
MidnightYell2003: so what does carly do?
IrNobleMetal: she prepares samples by mounting them
(either in epoxy or on SEM stubs) then she polishes the
ones she mounts in epoxy and carbon coats them all
IrNobleMetal: remember all those electrons?
MidnightYell2003: uh huh
IrNobleMetal: well, you have to conduct them away
(typically with gold or carbon) otherwise the sample will
build up a static charge and deflect the beam (no good)
IrNobleMetal: dude, sorry but it's late and I gotta get
up early tomorrow
IrNobleMetal: if I don't hit the sack I'll turn into a
pumpkin
MidnightYell2003: hehe yikes
MidnightYell2003: well cool, thanks for the info
and what not
IrNobleMetal: no prob, there's LOTS more to know
IrNobleMetal: sorry it would take me a week to type it
all
MidnightYell2003: hehe, well get started...
IrNobleMetal: LOL
IrNobleMetal: I'll get started sleeping, how bout that
IrNobleMetal: good night dude
MidnightYell2003: done and done
MidnightYell2003: 'night
IrNobleMetal: bye
IrNobleMetal signed off at 12:26:01 AM.
MidnightYell2003: howdy
MidnightYell2003: does carly work at the
microprobe thing?
IrNobleMetal: yeah
IrNobleMetal: why?
MidnightYell2003: ok maybe you can tell me,
what exactly is the microprobe?
IrNobleMetal: A microprobe is sort of a souped up
electron microscope....
IrNobleMetal: do you know what an electron
microscope is?
IrNobleMetal: and how it works
MidnightYell2003: is it like an SEM or scanning
electron microscope?
IrNobleMetal: yeah
MidnightYell2003: ok then no
MidnightYell2003: i just heard of it
IrNobleMetal: exactly, do you know how they work?
(cause I gotta give you some background first)
MidnightYell2003: not exactly
MidnightYell2003: maybe you can explain it
better
IrNobleMetal: ok, for these types of instruments you
basically generate a beam of electrons that you spray
across the surface of a sample...
MidnightYell2003: ok
IrNobleMetal: you spray the electron beam in a rhastor
pattern--just like a TV screen, you know how that
works?
IrNobleMetal: start at the top, scan across, go down
one line, scan across, and repeat til you get to the
bottom of the screen
IrNobleMetal: you dig?
MidnightYell2003: for the most part...
MidnightYell2003: and stuff
IrNobleMetal: ok, well you scan across the surface of
the sample but you do this over a VERY small area...
IrNobleMetal: this is roughly a square pattern and it
could be a millimeter square or it could be less than a
micrometer square
MidnightYell2003: like how small?
MidnightYell2003: ok
IrNobleMetal: as you scan this electron beam across
the surface, electrons are reflected in SEVERAL
different and distinct ways. You pick up these reflected
electrons through different types of detectors....
IrNobleMetal: at the same time that this is going on, the
signal from one of these detectors is being displayed on a
TV monitor....
MidnightYell2003: i see...
IrNobleMetal: as the beam sweeps across the sample,
the beam in the CRT (the TV monitor) is also sweeping
across the screen, creating an image
IrNobleMetal: ....
IrNobleMetal: electrons are reflected in different ways
by different materials....
IrNobleMetal: heavy elements (gold, lead, uranium)
reflect electrons strongly....
MidnightYell2003: yeah...
IrNobleMetal: light elements (oxygen, carbon, lithium)
don't reflect much
MidnightYell2003: ok
IrNobleMetal: so if you have a detector detecting the
quantity of electrons reflected gold would appear really
bright, lithium would appear really dark....
IrNobleMetal: this is an oversimplification, in reality it's
the average weight of a compound (eg: SiO2 or PbPO4)
IrNobleMetal: the compound with lead has a much
higher average weight (z-value) so it would show up
brighter
IrNobleMetal: for a SEM (non-microprobe) you often
have samples with raised features and you're often
looking at shapes like those great black and white
pictures of ants magnified nine zillion times etc....
IrNobleMetal: this is possible because the surface of an
ant isn't flat and so the electrons reflect differently from
the different angles of incidence.....
IrNobleMetal: you gettin' this?
MidnightYell2003: yeah, hang on, phone...
IrNobleMetal: ahh
MidnightYell2003: ok sorry, reading...
IrNobleMetal: that makin' sense to you?
MidnightYell2003: kinda, so what exactly is
different between microprobe and SEM?
IrNobleMetal: well, all those electrons bouncing
around that I was telling you about??
MidnightYell2003: yeah..
IrNobleMetal: the microprobe has a lot more
capabilities as far as detecting the different types of
reflection/flouresence etc..
IrNobleMetal: SEMs are MUCH better at very very
VERY high resolution, high magnification of shapes
IrNobleMetal: microprobes are much much better at
determining the exact chemistry of a vanishingly small
quantity of material
IrNobleMetal: that's the short answer
MidnightYell2003: wow cool
IrNobleMetal: you want chemistry, get a microprobe
you want high resolution images get an SEM
MidnightYell2003: how many microprobes are
there in the world or whatever?
IrNobleMetal: no idea, but not too many I'll bet less
than a thousand. really only two companies that make
them: Cameca (made TX A&M's) and PGT (Precission
Gamma Tech)
MidnightYell2003: is there anymore in Texas?
like does t.u. have one?
IrNobleMetal: Probably, I'll bet the t-sips, and rice
both have them, maybe a few others
MidnightYell2003: interesting
MidnightYell2003: how many different
departments use it?
IrNobleMetal: the one that we have set the department
back about 750 GRAND
MidnightYell2003: wow nice
IrNobleMetal: a typical SEM doesn't run more than a
quarter mil
IrNobleMetal: a LOT of departments use it
IrNobleMetal: especially engineering
MidnightYell2003: which engineering? civil?
IrNobleMetal: nuclear engineering, some civil too
MidnightYell2003: oh i see
IrNobleMetal: lots of materials science....
MidnightYell2003: those people...
IrNobleMetal: they use it to see how metals form and
things of that nature
MidnightYell2003: because it seems to me that
not a lot of people even know it exists
IrNobleMetal: that's probably true, not well publicized
IrNobleMetal: I have helped a lot of grad students
from the chemistry department prepare samples for it
though
IrNobleMetal: oh, and archeology uses it a lot
MidnightYell2003: but it's like some people who i
think should know about it, dont... like a lot of
people in the chem department and even in the
civil department, its weird
IrNobleMetal: yeah, well, all the cool people know
about it: Me, DrGuillemette...
MidnightYell2003: hehe yeah
MidnightYell2003: so what does carly do?
IrNobleMetal: she prepares samples by mounting them
(either in epoxy or on SEM stubs) then she polishes the
ones she mounts in epoxy and carbon coats them all
IrNobleMetal: remember all those electrons?
MidnightYell2003: uh huh
IrNobleMetal: well, you have to conduct them away
(typically with gold or carbon) otherwise the sample will
build up a static charge and deflect the beam (no good)
IrNobleMetal: dude, sorry but it's late and I gotta get
up early tomorrow
IrNobleMetal: if I don't hit the sack I'll turn into a
pumpkin
MidnightYell2003: hehe yikes
MidnightYell2003: well cool, thanks for the info
and what not
IrNobleMetal: no prob, there's LOTS more to know
IrNobleMetal: sorry it would take me a week to type it
all
MidnightYell2003: hehe, well get started...
IrNobleMetal: LOL
IrNobleMetal: I'll get started sleeping, how bout that
IrNobleMetal: good night dude
MidnightYell2003: done and done
MidnightYell2003: 'night
IrNobleMetal: bye
IrNobleMetal signed off at 12:26:01 AM.
posted by Adrian @ 11:27 PM
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