Room temperature sintering of polar ZnO nanosheets: I-evidence

Abstract

During storage the ZnO crystals grew mainly by the partial merging of their polar surfaces in a process triggered by the action of moisture, oxygen and, in the absence of these two agents, light.The mechanism of this intriguing phenomenon will be analyzed in detail in the second part of this work.

Barium‐Doped Zinc Oxide Thin Films as Highly Efficient and Reusable Photocatalysts

“…Since the surface energy is minimum along the (002) direction, its growth rate will be comparatively lower than the high surface energy (100) and (101) orientations. Furthermore, the (002) orientation exhibits a more polar nature than the (100) and (101) which facilitates the charge carrier separation and surface reactivity . The polarity of ZBO structures can be evaluated using the intensity ratio (I 002 /I 100 ) of the XRD data and has been found to be increased with the increase of Ba content due to more polarity on Ba−O bond .…”

“…Furthermore, the (002) orientation exhibits a more polar nature than the (100) and (101) which facilitates the charge carrier separation and surface reactivity . The polarity of ZBO structures can be evaluated using the intensity ratio (I 002 /I 100 ) of the XRD data and has been found to be increased with the increase of Ba content due to more polarity on Ba−O bond . Thus this preferential orientation along the c – direction is useful in piezoelectric applications and other optoelectronic applications such as photovoltaic devices, photodetectors and sensors …”

“…[28] The polarity of ZBO structures can be evaluated using the intensity ratio (I 002 /I 100 ) of the XRD data and has been found to be increased with the increase of Ba content due to more polarity on BaÀ O bond. [28] Thus this preferential orientation along the c -direction is useful in piezoelectric applications and other optoelectronic applications such as photovoltaic devices, photodetectors and sensors. [28] The SEM images of the ZBO films with different doping concentrations are shown in Figure 2.…”

“…[28] Thus this preferential orientation along the c -direction is useful in piezoelectric applications and other optoelectronic applications such as photovoltaic devices, photodetectors and sensors. [28] The SEM images of the ZBO films with different doping concentrations are shown in Figure 2. Figure 2(a-d) represents the hexagonal plate-like structure as the doping concentration (x) varied from 0 to 0.2 and the orientation of the plates is in accordance with the texture coefficient.…”

Room temperature sintering of polar ZnO nanosheets: II-mechanism

“…In the first part of this work [1] it was concluded that polar ZnO nanosheets of high specific surface area (~120 m 2 /g) lost up to 75% of their specific surface area in about two months during their storage in closed transparent polypropylene vials kept under the light of the laboratory on worktop tables. Loss of surface area occurred in parallel with the growth of nanocrystals, mainly by the partial merging of their polar surfaces at the expense of the small mesopores (~5 nm pore size) initially present in the nanosheets.…”