Hexagonal
boron nitride nanowall thin films were deposited on Si(100)
substrates using a Ar(51%)/N2(44%)/H2(5%) gas
mixture by unbalanced radio frequency sputtering. The effects of various
target-to-substrate distances, substrate temperatures, and substrate
tilting angles were investigated. When the substrate is close to the
target, hydrogen etching plays a significant role in the film growth,
while the effect is negligible for films deposited at a farther distance.
The relative quantity of defects was measured by a non-destructive
infrared spectroscopy technique that characterized the hydrogen incorporation
at dangling nitrogen bonds at defect sites in the deposited films.
Despite the films deposited at different substrate tilting angles,
the nanowalls of those films were found to consistently grow vertical
to the substrate surface, independent of the tilting angle. This implies
that chemical processes, rather than physical ones, govern the growth
of the nanowalls. The results also reveal that the degree of nanowall
crystallization is tunable by varying the growth parameters. Finally,
evidence of hydrogen desorption during vacuum annealing is given based
on measurements of infrared stretching (E
1u) and bending (A
2u) modes of the optical
phonons, and the H–N vibration mode.
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