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jUNE |
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jULY |
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M |
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13 |
14 |
15 |
16 |
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31 |
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First
began working with the ellipsometer. Alignment of the ellipsometer as well as
cleanliness of my glassware is a critical part of
collecting accurate and reproducible data. My cleaning
technique involves glass etch which consists of hydrofluoric and nitric acids.
This
process actually “eats” away about an angstrom of glass inside the bottles
removing any filth inside the glass.
June
03, 2009:
I
spent today looking for some more of the bottles we use in ellipsometry. Once
found, I spent the rest of the day using the glass etch
on each of these bottles.
June
04, 2009:
It
is important to only fill each bottle exactly half-way to get accurate readings
on the ellipsometer. In order to find the half-volume
inside each
of my bottles, I have filled each bottle with water and weighed the amount of
water used to fill bottle. Using the density of
water, I
am able to determine the half-volume of each bottle.
June
05, 2009:
I
spent today taking data samples of pure water in order to have a value to
compare our solutions to.
Upon
the suggestion of Dr. Law, I made a stock solution of 1.4M stock solution in
hopes that it will be easier to have on solution already
made rather than making a fresh solution every day. I began
collecting samples of various concentrations of NaI
solutions.
June
10, 2009:
My data collected yesterday is not
reproducible today and I am getting a value of 0 for the imaginary coefficient
of ellipticity, Im(Rho), at
the Brewster angle, which is impossible and leads us to believe something is
wrong in either my alignment or something else.
June
11, 2009:
I
am checking the water values in every bottle again to determine if we get
consistent results. We do not get consistent results so it is
assumed that my bottles are unclean.
June
12, 2009:
I
first cleaned my bottles with soap and water, and then checked for consistent
results with pure water. This yields inconsistent results
once again. Next we try to sonicate the bottles with soap
and water and being sure to rinse the bottles very well. Again, we see
inconsistent
results. As a last resort the bottles are glass etched, and fairly consistent
values are seen.
Data
is collected again for the NaI solutions first of a
1.1M concentration then with a .11M concentration. Both of these data
collections
contain some results with zero at the Brewster angle, so
again it is assumed something is wrong.
June
16, 2009
The
bottles are cleaned, and new solutions are made in order to be sure the zero
values are not due to filth in the bottles. Again values of
zero at the Brewster angle are found.
June
17, 2009:
Tests
are done on the ellipsometer in order to make sure the ellipsometer is working
correctly. The tests prove the ellipsometer is working
fine.
June
18, 2009:
A
brand new stock solution is made and still the results are inconsistent.
June
19, 2009:
It
is realized by Dr. Law that our glass bottles act as a lens thus causing our
laser beam to diverge. A lens is put in between the birefringence
modulator and the solution.
With
the lens in place, data is collected once more for pure water samples.
June
23, 2009:
Water
values are again inconsistent and do not match the accepted value. Tests are
done with our sample of carbon tetrachloride which
is sealed (thus completely clean) and has a known value. These results are
consistent and closely match the accepted value, thus determining
that the lens does not have an effect on our values and should not skew the
water values nor give such a broad range.
June
24, 2009:
As
suggested by Haeng Sub, measurements are taken at
various spots on the bottle, and noted whether the reflected beam from the
bottle
is bright or dim. This is done in order to see if there is a
correlation between bright and dim reflectance and the measured coefficient of
ellipticity value measured. No correlation was determined
June
25, 2009:
Glass
etched the bottles in the morning.
Upon
the suggestion of Dr. Law, the sensitivity on the ellipsometer is changed to
10mV rather than 100mV. This gives the most accurate
Rho(Im) value so far with the
smallest deviation. We now have an accepted water value.
June
30, 2009:
Measurements
are taken for 1.1M NaI and .11MNaI solutions. Again,
the data has a broad range and even exceeds the water value.
July
1, 2009:
Since
the label on the NaI salt says to keep the salt out
of the light. It is hypothesized that the salt solutions also need to be made
in the
dark. This seems to prove true for the first sample 1.15M NaI solution, however the results
are not reproducible. The following week
is dedicated to obtaining reproducibility. No reproducible
results are reached.
Since
there is limited NaI salt left, and it is difficult
to keep the salt in complete darkness, I switch to working with NaBr, the next largest
and polarizable salt. The first solution made is 1.0M NaBr. When tested, the water value is obtained. So a 2.0M NaBr solution is made and
yields the same result. Finally, a 3.0M solution is made
however, the same scenario occurs. The solution is left untouched for 2 hours,
and
when the Rho(Im) value is measured
again, the result is negative. After two more hours the results appear more
negative. It is hypothesized
that the solution cannot be shaken just prior to measurements as it requires
time to come to equilibrium.
July
10-12, 2009:
Our equilibrium hypothesis is
reinforced by data collected throughout the past three days, and measurements
will be taken in order to determine whether or not there is a dependence on
concentration.
July 13, 2009:
I begin
collecting data on the 2.25M NaBr solution to
determine concentration dependence of the equilibrium time.