The plot in Figure 5 displays the histogram of the NW base diameter for both cases. It highlights the loss of thinner NW families (with diameters lower than 200 nm) as a consequence of Ar+ irradiation, and revealed a better resistance of wider ZnO NWs to the irradiation as a consequence of their lower surface/volume ratio. As a consequence, we noticed an increase of the thicker irradiated NW frequency (d > 200 nm) compared to the unirradiated ones, which was in agreement with HR-SEM observations. Similar behavior occurs with regard to the NW length. All the morphological changes can be explained considering the effect of the Ar+ ion impinging on the NWs and the progressive annihilation of thinner

ZnO NWs, an effect that is reinforced PLX-4720 molecular weight as the irradiation fluence is increased. During the irradiation, the upper parts of the NWs suffer more morphological changes than

the lower shadowed parts and in some cases even disappear. The additional formation of ‘pencil-like’ (inset of Figure 4b) tip shapes, only observed in irradiated wires, confirms these later ideas. Figure 4 CTEM images check details showing two representative ZnO NWs (a, b). Extracted from unirradiated and irradiated (fluence = 1017 cm−2) areas, respectively. The insets of both figures show the nanowire tip details; note that the irradiated NW tip is faceted as a consequence of the strike by Ar+ energetic particles. Figure 5 Diameter distribution in the lower part of nanowires. Scraped from both the unirradiated and irradiated (fluence = 1017 cm−2) areas. The NW diameter NW frequency increases for the latter case. It is well known that the damage level expected for an irradiation process in nanometric materials is much higher than in the bulk due to a larger surface-to-volume ratio, which can induce surface modifications and defect Methocarbamol cluster formation. However, despite the irradiation process, TEM micrographs

of our NWs indicate that the amorphization degree for most irradiated areas is minimal, and the ZnO NWs generally preserve their good crystalline quality. Figure 6a is an example of HR-TEM image corresponding to one scraped NW from the area irradiated with the Selleckchem NVP-BSK805 highest fluence (1017 cm−2), which reveals the single-crystalline nature of the NW grown along the [11–20] direction that is one of the three types of fast growth directions in the ZnO NW generation [44]. The inset shows its corresponding fast Fourier transform (FFT), which is consistent with the wurtzite structure of ZnO observed along the [0001] zone axis. Although the high crystalline quality is obvious here and well-defined atomic columns are clearly visible, some ZnO NWs however display stacking faults and dislocations, as well as no well-defined boundaries when observing the wire surface. Such structural modifications are results of preferential bombardment in determined areas of the wires, as can be observed in the NW tip presented in Figure 6b.