  The behavior of the aromatic features as a function of metallicity/radiation
field hardness in M101 HII regions and starburst galaxies is investigated using
Spitzer/IRS spectra. These spectra reveal that the 6.2, 7.8+8.6, and 11.3
micron aromatics have different dependencies on metallicity/radiation field
hardness. Specifically, the 6.2 and 7.8+8.6 micron aromatics are weak or absent
at a metallicity, 12+log(O/H), of approx. 8.0 while the 11.3 micron feature
remains relatively strong. These results apply to both the M101 HII regions and
starbursts showing that HII regions can indeed be thought of as
``mini-starbursts.'' Comparison of this work with various candidate materials
results in a good match with the annealing behavior in Quenched Carbonaceous
Composite (QCC) which is an amorphous, hydrogenated, carbonaceous solid.
