Low-temperature fabrication and random laser action of doped zinc oxide nanoneedles

Zinc oxide (ZnO) thin films grown on SiO₂-coated Si substrates by filtered cathodic vacuum arc (FCVA) at 200 °C was irradiated with Ar⁺ ions with a simultaneous supply of Fe atoms or with N₂⁺ ions (without Fe) at room temperature to fabricate Fe- or N-doped ZnO nanoneedles, respectively. The morphological structure of the doped nanoneedles was almost identical with that of non-doped nanoneedles. The detailed analyses by energy dispersive X-ray spectroscopy combined with transmission electron microscope revealed that Fe was doped at and beneath the surface of the nanoneedles as well as at the needle tip. Random lasing was observed for both Fe- and N-doped ZnO nanoneedles thus fabricated, and the lasing peaks detected were redshifted compared with those attained for non-doped ZnO nanoneedles. Since the lasing wavelength, and hence the bandgap, was readily tunable, the combination of FCVA and ion-irradiation methods was concluded to be quite promising to fabricate 1D nanostructures for optoelectronics applications at low temperatures.