Three-fold symmetrically distributed GaN nanowire (NW) arrays have been epitaxially grown on GaN/sapphire substrates. The GaN NW possesses a triangular cross section enclosed by (0001), (2112), and (2112) planes, and the angle between the GaN NW and the substrate surface is approximately 62 degrees . The GaN NW arrays produce negative output voltage pulses when scanned by a conductive atomic force microscope in contact mode. The average of piezoelectric output voltage was about -20 mV, while 5-10% of the NWs had piezoelectric output voltages exceeding -(0.15-0.35) V. The GaN NW arrays are highly stable and highly tolerate to moisture in the atmosphere. The GaN NW arrays demonstrate an outstanding potential to be utilized for piezoelectric energy generation with a performance probably better than that of ZnO NWs.
Free-standing single-crystal NiSi 2 nanowires (NWs) were synthesized on Ni foil with a simple vapor transport method. The growth of previously elusive Si-rich silicide NWs was achieved with the addition of NiCl 2 powders in front of the Ni substrate upstream. The presence of NiCl 2 gas enhanced the condensation of Si and suppressed the supply of Ni atoms in the subsequent reactions. As the NWs maintain low resistivity, can carry very high currents, and possess excellent field emission properties, the growth of NiSi 2 NWs shall lead to significant advantages in the fabrication of Si nanodevices.
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