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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.

No MeSH data available.


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SEM images of (a) 6-nm and (b) 12-nm ‘seed layer’ Au thin film annealed at 800°C on SiC substrate.
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Figure 1: SEM images of (a) 6-nm and (b) 12-nm ‘seed layer’ Au thin film annealed at 800°C on SiC substrate.

Mentions: It has been shown, in the literature, that the starting Au seed layer thickness can significantly influence the final outcome of the nanostructures [10,12,15]. The nanostructures, in this work, have been grown on Au-coated hexagonal SiC surfaces. During the temperature ramp, from approximately 400°C, the Au film is found to efficiently transform into islands of Au droplets. In addition to this, the clusterization of the Au layer is expected to follow the ripening process during the early stages of synthesis. As discussed by Ruffino et al.[28], the ripening process results in the formation of 3D nanostructures, due to the thermally activated surface diffusion of Au atoms. To gain detailed understanding of both the seed layer clustering and subsequent ZnO nanostructure formation, it was important to understand the clusterization processes exhibited by different Au layer thicknesses: in our experiment, 6 and 12 nm. To follow the change in Au layer morphology and to evaluate the size distribution of Au nanoparticles, SEM images were assessed. Figure 1 shows typical SEM images of the nanoparticles obtained for the different Au layer thicknesses followed by thermal annealing at 800°C in Ar ambient without ZnO growth precursors. For both thicknesses, the Au films were effectively converted into uniformly distributed spherical and/or hexagonal-like nanoparticles. This behavior can be explained by the non-wetting characteristics between Au and SiC substrate interface. Notably, with increasing Au film thickness from 6 to 12 nm, the coverage density of Au nanoparticles were found to decrease from around 130 μm-2 (Figure 1a) to 5 μm-2 (Figure 1b), respectively. As expected, the thickness of the initial Au layer strongly affects the density of the Au nanoparticles and, hence, as shown later in this work, the density of the resulting ZnO nanostructures produced. The insets in Figure 1a, b show the Au cluster size distribution for the Au layer thickness of 6 and 12 nm, respectively annealed at 800°C for 30 min in Ar ambient.Based on these observations, we first carried out the growth on the 6-nm Au seed layer samples. In Figure 2a, b, typical SEM and STEM images of ZnO NWs grown at 850°C for 90 min are presented. From Figure 2a, b, it can be seen that a high-density NW with an exceptional degree of material orientation perpendicular to the SiC substrate is achieved. From the SEM and STEM images, typical NW length and diameter were determined to be around 1 to 2 μm and 30 to 140 nm, respectively (longer nanowires can be obtained simply by increasing the growth time). Based on the nanowire length and growth time, the growth rate for the present NWs was determined to be approximately 15 to 20 nm/min. Figure 2c,d shows typical SEM and STEM images of vertically oriented ZnO NWLs grown at 900°C for 180 min. From Figure 2c, d, it is noticeable that the measured height and widths of the NWLs were also found to be consistent with those measured for the NWs, thus suggesting a similar growth process for both types of nanostructures.


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 (a) 6-nm and (b) 12-nm ‘seed layer’ Au thin film annealed at 800°C on SiC substrate.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4127525&req=5

Figure 1: SEM images of (a) 6-nm and (b) 12-nm ‘seed layer’ Au thin film annealed at 800°C on SiC substrate.
Mentions: It has been shown, in the literature, that the starting Au seed layer thickness can significantly influence the final outcome of the nanostructures [10,12,15]. The nanostructures, in this work, have been grown on Au-coated hexagonal SiC surfaces. During the temperature ramp, from approximately 400°C, the Au film is found to efficiently transform into islands of Au droplets. In addition to this, the clusterization of the Au layer is expected to follow the ripening process during the early stages of synthesis. As discussed by Ruffino et al.[28], the ripening process results in the formation of 3D nanostructures, due to the thermally activated surface diffusion of Au atoms. To gain detailed understanding of both the seed layer clustering and subsequent ZnO nanostructure formation, it was important to understand the clusterization processes exhibited by different Au layer thicknesses: in our experiment, 6 and 12 nm. To follow the change in Au layer morphology and to evaluate the size distribution of Au nanoparticles, SEM images were assessed. Figure 1 shows typical SEM images of the nanoparticles obtained for the different Au layer thicknesses followed by thermal annealing at 800°C in Ar ambient without ZnO growth precursors. For both thicknesses, the Au films were effectively converted into uniformly distributed spherical and/or hexagonal-like nanoparticles. This behavior can be explained by the non-wetting characteristics between Au and SiC substrate interface. Notably, with increasing Au film thickness from 6 to 12 nm, the coverage density of Au nanoparticles were found to decrease from around 130 μm-2 (Figure 1a) to 5 μm-2 (Figure 1b), respectively. As expected, the thickness of the initial Au layer strongly affects the density of the Au nanoparticles and, hence, as shown later in this work, the density of the resulting ZnO nanostructures produced. The insets in Figure 1a, b show the Au cluster size distribution for the Au layer thickness of 6 and 12 nm, respectively annealed at 800°C for 30 min in Ar ambient.Based on these observations, we first carried out the growth on the 6-nm Au seed layer samples. In Figure 2a, b, typical SEM and STEM images of ZnO NWs grown at 850°C for 90 min are presented. From Figure 2a, b, it can be seen that a high-density NW with an exceptional degree of material orientation perpendicular to the SiC substrate is achieved. From the SEM and STEM images, typical NW length and diameter were determined to be around 1 to 2 μm and 30 to 140 nm, respectively (longer nanowires can be obtained simply by increasing the growth time). Based on the nanowire length and growth time, the growth rate for the present NWs was determined to be approximately 15 to 20 nm/min. Figure 2c,d shows typical SEM and STEM images of vertically oriented ZnO NWLs grown at 900°C for 180 min. From Figure 2c, d, it is noticeable that the measured height and widths of the NWLs were also found to be consistent with those measured for the NWs, thus suggesting a similar growth process for both types of nanostructures.

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