Films 2000A, Thicknesses Measured with Profilometer
d030313-2 oxygen doping
undoped
on mocvd gan
films 2000A, thicknesses measured with profilometer
buffer anywhere from 2-3 microns
on sapphire is 4000A
magnetism
measured in SQUID magnetometer
signal better on mocvd gan
emu/cm2: 3% with and without O better than 5%
1. d030313, d030408-1, identical magnetization
2. d030408-2
3. d030404-1
difference between 1st and 4th is ~an order of magnitude
10-4 or 10-5 emu/cm2
d030408-2 closer to d030404-1 than to the other magnetizations
this trend is always there, has been consistent over the course of a couple years
pretty consistent values sample-to-sample
hysteresis loops
coercive fields 80-120 oersteds
fc/zfc magnetization vs. temperature
cool down to 10K under field, let it warm back up under no field
look at difference between two curves
curie temperature above RT, curie temps above 350K
O may help Mn sit on Ga site rather than interstitial (speculation)
trying to do EXAFS to get more out of that, but the data is really messy and the modeling is hard
EXAFS – did all of the mocvd gan samples that we have
when there’s a clear second phase, can see the difference in EXAFS – peak is clearly shifted
didn’t really get anywhere trying to model it to say what the difference is
clean samples
probably OK to rinse in methanol or acetone
they dip them in DI water
Mn concentration
auger spectroscopy, do a ratio of peaks
we know 3% has less than 5%, but better than that is a little iffy
also have compared implanted samples to make sure auger spectra results are reasonable
had SIMS done but couldn’t get exact number because of lack of standards
XRD
looking for presence or absence of additional peaks
do this in powder XRD
if try to do high res to get lattice constant, get a lot of buffer signal in there
lattice constant vs. Mn conc was from sapphire substrate samples (d0109)
don’t know about crystallite size
TEM
on sample similar to d030313
need extra nitrogen
if not enough nitrogen, you get a lot of GaMn
position of XRD peaks consistent with GaxMny, but we don’t really know what x and y are
have parms pretty well figured out by now, aren’t growing many second phase samples
carrier concentration
MOCVD
3% no O – insulating, can’t get a measurement
can’t get a good Hall measurement
O-doped: n-type, 1018 is concentration
grow undoped (no Mn) can get 1016, probably lowering carrier concentration below that with Mn
tried to do magnetic transport data
anomalous hall effect – can see it, but the data need to be re-run