SiC nanowires were grown on monocrystalline 4H-SiC wafers by chemical vapor deposition using the vapor-liquid-solid growth mode. The growth direction of the nanowires was dictated by the crystallographic orientation of the 4H-SiC substrates. Two distinct types of nanowires were obtained. The first type crystallized in the 3C polytype with the AE111ae nanowire axes. These nanowires grew at 20°with respect to the substrate c-planes and exhibited high densities of stacking faults on those {111} planes that are parallel to the substrate c-planes. The second type featured the 4H structure albeit with a strong stacking disorder. The stacking faults in these nanowires were perpendicular to the [0001] nanowire axes. Possible growth mechanisms that led to the formation of 3C and 4H polytypes are discussed.
Several different growth directions of SiC nanowires
(NWs) determined
by the substrate surface crystallographic orientation were achieved
by conducting vapor–liquid–solid growth on the top surfaces
and the sidewalls of the 4H-SiC mesas. When substrate-dependent (i.e.,
epitaxial) growth was ensured, six possible crystallographic orientations
of 3C-SiC NW axis with respect to the 4H-SiC substrate were realized.
They all were at 20° with respect to the substrate c plane, and their projections on the c plane corresponded
to one of the six equivalent ⟨101̅0⟩ crystallographic
directions. All six orientations were obtained simultaneously when
growing on the (0001) top surface of the 4H-SiC wafer or on the mesa
tops. In contrast, no more than two NW orientations coexisted when
grown on any particular crystallographic plane of a mesa sidewall.
In particular, the {101̅0} mesa sidewall plane resulted in only
one NW orientation, thereby producing well-aligned NW arrays desirable
for device applications.
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