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Controlled growth of 1D and 2D ZnO nanostructures on 4H-SiC using Au catalyst.

Dahiya AS, Opoku C, Alquier D, Poulin-Vittrant G, Cayrel F, Graton O, Hue LP, Camara N - Nanoscale Res Lett (2014)

Bottom Line: A perfect control of nanostructure growth is a prerequisite for the development of electronic and optoelectronic device/systems.From experimental observations, we have ascribed the growth mechanisms of the different ZnO nanostructures to be a combination of catalytic-assisted and non-catalytic-assisted vapor-liquid-solid (VLS) processes.We have also found that the different ZnO nanoarchitectures' material evolution is governed by a Zn cluster drift effects on the SiC surface mainly driven by growth temperature.

View Article: PubMed Central - HTML - PubMed

Affiliation: Université François Rabelais de Tours, CNRS, GREMAN UMR 7347, 16 rue Pierre et Marie Curie, Tours 37071, France.

ABSTRACT
A perfect control of nanostructure growth is a prerequisite for the development of electronic and optoelectronic device/systems. In this article, we demonstrate the growth of various ZnO-derived nanostructures, including well-ordered arrays of high aspect ratio single crystalline nanowires with preferred growth direction along the [0001] axis, nanowalls, and hybrid nanowire-nanowall structures. The growths of the various ZnO nanostructures have been carried out on SiC substrates in a horizontal furnace, using Au thin film as catalyst. From experimental observations, we have ascribed the growth mechanisms of the different ZnO nanostructures to be a combination of catalytic-assisted and non-catalytic-assisted vapor-liquid-solid (VLS) processes. We have also found that the different ZnO nanoarchitectures' material evolution is governed by a Zn cluster drift effects on the SiC surface mainly driven by growth temperature. Au thin film thickness, growth time, and temperature are the parameters to optimize in order to obtain the different ZnO nanoarchitectures.

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SEM images of ZnO NWs and Zn cluster drift phenomenon. SEM images of ZnO NWs grown for 10 min on high density of Au nanoparticles at (a) 850°C and (b) 900°C or on low density of Au nanoparticles at (c) 850°C and (d) 900°C. As pointed out by the arrows in (c), the ZnO NWs appear to protrude from the edges of the Au nanoparticles, while the arrows in (d) show the random motion of Zn cluster drift.
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Figure 6: SEM images of ZnO NWs and Zn cluster drift phenomenon. SEM images of ZnO NWs grown for 10 min on high density of Au nanoparticles at (a) 850°C and (b) 900°C or on low density of Au nanoparticles at (c) 850°C and (d) 900°C. As pointed out by the arrows in (c), the ZnO NWs appear to protrude from the edges of the Au nanoparticles, while the arrows in (d) show the random motion of Zn cluster drift.

Mentions: To gain a better understanding of the growth processes/mechanisms responsible for the formation of the various ZnO nanostructures, the early stages of material synthesis are crucial. Hence, as presented in Figure 6, we have examined nanostructure growth processes varying the main synthesis parameters, i.e., Au layer thicknesses and temperature, keeping all the other parameters, such as time (10 min), constant. Figure 6a, b shows, respectively, the SEM images of the resulting ZnO nanostructures grown at 850 and 900°C on the high-density Au nanoparticle sample (6 nm Au). From Figure 6a, at 850°C, the resulting ZnO nanostructures resemble NW formation (see also Figure 2a, b), while at 900°C, in Figure 6b, it can be seen that a complete nanostructured network formation has been started. However, the nanostructure density, in such samples, makes it difficult to elucidate the exact growth mechanism. Further, similar experiments were carried out on samples exhibiting low density of Au nanoparticles (12 nm Au). Figure 6c, d shows the SEM images of the resulting ZnO nanostructures grown at 850 and 900°C, respectively. At 850°C, the ZnO NWs appear to protrude from the edges of the Au nanoparticles, as pointed out by arrows in Figure 6c. For the sample grown at 900°C, one can note that Zn clusters appear to drift significantly, with no preferential direction, as indicated by the arrows in Figure 6d. It is important to mention that this behavior was absent at 850°C, leading only to NW growth. Using a similar synthesis approach, Shi et al. [19] have demonstrated the random motion of Zn cluster drift effects above 700°C during the synthesis of ZnO nanostructures (nanowires, nanofins, and hybrid nanowire-nanofins) on gallium nitride (GaN) substrate. The authors then used thermally activated Brownian motion of the Zn clusters to explain the evolution of their NWLs. The major difference between their work and the present investigations is the temperature of Zn drift. Such a disparity in temperature-activated Zn cluster drift may be related to the fact that their growth was performed at comparatively lower pressure (20 Torr), without any metal catalyst (Au in our case). As the Zn clusters were not attached to any seed particles, the probability of Zn cluster drift on the surface is expected to be higher at comparatively lower temperature. However, one can notice that the length of the drift appeared to be influenced by the synthesis temperature, similar to observations in [19]. Indeed, at 850°C (Figure 6a, b, c), we observed a negligible drift, while, at 900°C, the length of the drift was found to vary from 100 to 400 nm. In the case of the high-density Au nanoparticles on SiC substrate, the average distance between neighboring Au nanoparticles was measured to be less than 200 nm. Hence, at 900°C, the drift phenomenon is effectively halted when a Zn cluster encounters another Zn cluster trace or a Au nanoparticle, as mentioned in [19]. This in turn resulted in the formation of interconnected networks of ZnO, as shown in Figure 6b. This is the exact observation that can be made in Figure 7b, where NWLs are obtained on high Au particle densities and at comparatively higher growth temperatures (900°C), as a result of the Zn clusters coalescing.


Controlled growth of 1D and 2D ZnO nanostructures on 4H-SiC using Au catalyst.

Dahiya AS, Opoku C, Alquier D, Poulin-Vittrant G, Cayrel F, Graton O, Hue LP, Camara N - Nanoscale Res Lett (2014)

SEM images of ZnO NWs and Zn cluster drift phenomenon. SEM images of ZnO NWs grown for 10 min on high density of Au nanoparticles at (a) 850°C and (b) 900°C or on low density of Au nanoparticles at (c) 850°C and (d) 900°C. As pointed out by the arrows in (c), the ZnO NWs appear to protrude from the edges of the Au nanoparticles, while the arrows in (d) show the random motion of Zn cluster drift.
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Related In: Results  -  Collection

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Figure 6: SEM images of ZnO NWs and Zn cluster drift phenomenon. SEM images of ZnO NWs grown for 10 min on high density of Au nanoparticles at (a) 850°C and (b) 900°C or on low density of Au nanoparticles at (c) 850°C and (d) 900°C. As pointed out by the arrows in (c), the ZnO NWs appear to protrude from the edges of the Au nanoparticles, while the arrows in (d) show the random motion of Zn cluster drift.
Mentions: To gain a better understanding of the growth processes/mechanisms responsible for the formation of the various ZnO nanostructures, the early stages of material synthesis are crucial. Hence, as presented in Figure 6, we have examined nanostructure growth processes varying the main synthesis parameters, i.e., Au layer thicknesses and temperature, keeping all the other parameters, such as time (10 min), constant. Figure 6a, b shows, respectively, the SEM images of the resulting ZnO nanostructures grown at 850 and 900°C on the high-density Au nanoparticle sample (6 nm Au). From Figure 6a, at 850°C, the resulting ZnO nanostructures resemble NW formation (see also Figure 2a, b), while at 900°C, in Figure 6b, it can be seen that a complete nanostructured network formation has been started. However, the nanostructure density, in such samples, makes it difficult to elucidate the exact growth mechanism. Further, similar experiments were carried out on samples exhibiting low density of Au nanoparticles (12 nm Au). Figure 6c, d shows the SEM images of the resulting ZnO nanostructures grown at 850 and 900°C, respectively. At 850°C, the ZnO NWs appear to protrude from the edges of the Au nanoparticles, as pointed out by arrows in Figure 6c. For the sample grown at 900°C, one can note that Zn clusters appear to drift significantly, with no preferential direction, as indicated by the arrows in Figure 6d. It is important to mention that this behavior was absent at 850°C, leading only to NW growth. Using a similar synthesis approach, Shi et al. [19] have demonstrated the random motion of Zn cluster drift effects above 700°C during the synthesis of ZnO nanostructures (nanowires, nanofins, and hybrid nanowire-nanofins) on gallium nitride (GaN) substrate. The authors then used thermally activated Brownian motion of the Zn clusters to explain the evolution of their NWLs. The major difference between their work and the present investigations is the temperature of Zn drift. Such a disparity in temperature-activated Zn cluster drift may be related to the fact that their growth was performed at comparatively lower pressure (20 Torr), without any metal catalyst (Au in our case). As the Zn clusters were not attached to any seed particles, the probability of Zn cluster drift on the surface is expected to be higher at comparatively lower temperature. However, one can notice that the length of the drift appeared to be influenced by the synthesis temperature, similar to observations in [19]. Indeed, at 850°C (Figure 6a, b, c), we observed a negligible drift, while, at 900°C, the length of the drift was found to vary from 100 to 400 nm. In the case of the high-density Au nanoparticles on SiC substrate, the average distance between neighboring Au nanoparticles was measured to be less than 200 nm. Hence, at 900°C, the drift phenomenon is effectively halted when a Zn cluster encounters another Zn cluster trace or a Au nanoparticle, as mentioned in [19]. This in turn resulted in the formation of interconnected networks of ZnO, as shown in Figure 6b. This is the exact observation that can be made in Figure 7b, where NWLs are obtained on high Au particle densities and at comparatively higher growth temperatures (900°C), as a result of the Zn clusters coalescing.

Bottom Line: A perfect control of nanostructure growth is a prerequisite for the development of electronic and optoelectronic device/systems.From experimental observations, we have ascribed the growth mechanisms of the different ZnO nanostructures to be a combination of catalytic-assisted and non-catalytic-assisted vapor-liquid-solid (VLS) processes.We have also found that the different ZnO nanoarchitectures' material evolution is governed by a Zn cluster drift effects on the SiC surface mainly driven by growth temperature.

View Article: PubMed Central - HTML - PubMed

Affiliation: Université François Rabelais de Tours, CNRS, GREMAN UMR 7347, 16 rue Pierre et Marie Curie, Tours 37071, France.

ABSTRACT
A perfect control of nanostructure growth is a prerequisite for the development of electronic and optoelectronic device/systems. In this article, we demonstrate the growth of various ZnO-derived nanostructures, including well-ordered arrays of high aspect ratio single crystalline nanowires with preferred growth direction along the [0001] axis, nanowalls, and hybrid nanowire-nanowall structures. The growths of the various ZnO nanostructures have been carried out on SiC substrates in a horizontal furnace, using Au thin film as catalyst. From experimental observations, we have ascribed the growth mechanisms of the different ZnO nanostructures to be a combination of catalytic-assisted and non-catalytic-assisted vapor-liquid-solid (VLS) processes. We have also found that the different ZnO nanoarchitectures' material evolution is governed by a Zn cluster drift effects on the SiC surface mainly driven by growth temperature. Au thin film thickness, growth time, and temperature are the parameters to optimize in order to obtain the different ZnO nanoarchitectures.

No MeSH data available.


Related in: MedlinePlus