Growth of Gallium Nitride Textured Films and Nanowires on Polycrystalline Substrates at sub-Atmospheric Pressures

Chandrasekaran, Hari; Sunkara, Mahendra

doi:10.1557/proc-693-i3.30.1

Cited by 16 publications

(29 citation statements)

References 11 publications

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“…The experiments using nitrogen and oxygen were performed at relatively high temperatures of 1000 o C. See the SEM in Figure 3(a) for a high density of the resulting GaN nanowires. 20 The GaN experiments were performed in both ECR plasma and hot filament reactor setups and yielded similar results. …”

Section: Gallium Oxide and Gallium Nitride Nanowiresmentioning

confidence: 91%

Chemical design of inorganic nanowires, nanotubes and nanowire networks

Sunkara

Vaddiraju

Bhimarasetti

et al. 2004

Nanosensing: Materials and Devices

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Inorganic nanowires are expected to play a central role in the re-engineering of products with applications in composites, thin films, nanodispersions, energy conversion devices, sensors, nanoelectronic devices and optics. The synthesis of materials at the nanoscale might also help in the discovery of new phases with interesting properties. However, the synthesis strategies for inorganic nanowires is quite limited and have not reached the level of maturity needed for either bulk manufacturing or for controlling nanowire characteristics such as sub 10 nm diameters and different growth directions. In this regard, we report several synthesis strategies that potentially offer in-situ control over the resulting nanowire characteristics such as size, growth direction and an ability to form two-dimensional networks. The techniques described here could be scaled up easily for bulk production of various nanostructures. Our preliminary results suggest that the nanowires form stable dispersions in both organic and aqueous solvents compared to nanoparticles of the same material. INTRODUCTIONIn the last few years, the synthesis of inorganic nanowires and nanotubes has gained tremendous importance for several reasons 1 (a) the availability of nanowires allows for rapid experimental understanding of the physics and chemistry of materials under reduced dimensions; 2 (b) the synthesis of materials at the nanometer scale could lead to the discovery of new phases through their structural variations, for example -nanotubes; 3 (c) the availability of nanowires and nanotubes in large quantities could allow for bottom-up assembly techniques for several engineering application areas such as composites, electronics, catalysts and optics; 4 and (d) the possibility of growing perfect crystals at the nanoscale. However, the nanowire quantities required for particular applications vary. These requirements range from bulk quantities for composites and thin films to single wires for sensors and electronic devices to large area arrays for field emission based applications. The growth of one-dimensional crystals in the form of micron-scale whiskers has been known for several decades starting in 1940s 5 and was formalized as the Vapor-Liquid-Solid method in 1964. 6 More recently in 1991, a similar strategy was employed to discover the growth of carbon nano-tubular structures. 7The vapor-liquid-solid (VLS) method employs catalyst clusters to template one-dimensional growth. In the VLS technique, a vapor phase solute is selectively dissolved into metal droplets, and it precipitates one-dimensionally due to the metal droplet size confinement. Recognizing the fact that one can reduce the resulting wire size by reducing the metal droplet size, several researchers sought different ways of creating smaller clusters and providing solutes using different means. The notable techniques involved laser ablation of solid targets containing metal catalysts, 8 thermal chemical vapor deposition 9 over catalyst cluster dispersions on supports and gold clusters dis...

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Section: Gallium Oxide and Gallium Nitride Nanowiresmentioning

confidence: 91%

Chemical design of inorganic nanowires, nanotubes and nanowire networks

Sunkara

Vaddiraju

Bhimarasetti

et al. 2004

Nanosensing: Materials and Devices

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“…The spontaneous nucleation and basal growth of 1-D crystals from low-melting metal melts also applies directly to GaN precipitation from Ga melts, as the solubility of nitrogen in Ga is quite small [11]. In fact, the direct reactions of Ga with nitrogen plasma [12] and dissociated ammonia [13] have already been shown to result in GaN nanowires. The growth directions of the resulting nanowires from these studies were different, i.e., GaN nanowires grew in <10-10> direction with nitrogen plasma at higher temperatures [12] and in <11-20> direction by reacting Ga directly with ammonia [13].…”

Section: Introductionmentioning

confidence: 99%

“…In fact, the direct reactions of Ga with nitrogen plasma [12] and dissociated ammonia [13] have already been shown to result in GaN nanowires. The growth directions of the resulting nanowires from these studies were different, i.e., GaN nanowires grew in <10-10> direction with nitrogen plasma at higher temperatures [12] and in <11-20> direction by reacting Ga directly with ammonia [13]. Both directions are perpendicular to the non-polar surfaces of wurtzitic GaN and the synthesis of GaN wires with <0001> direction, i.e., normal to the polar surface is still elusive.…”

Section: Introductionmentioning

confidence: 99%

Direction dependent homoepitaxial growth and bandgap of GaN nanowires

Sunkara

Chin

2006

SPIE Proceedings

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Here, we report a direct synthesis approach for obtaining GaN nanowires with control on growth directions: <0001> or c-direction, and <10-10> or a-direction, on amorphous substrates. The direct nitridation of Ga droplets using either dissociated ammonia or N 2 /H 2 plasma resulted in GaN nanowires with <0001> growth direction; and the vapor transport of controlled (low) amounts of Ga flux in the presence of dissociated ammonia resulted in GaN nanowires with <10-10> growth direction. In both cases, the resulting GaN nanowires have diameters as small as 20 nm and lengths exceeding one hundred microns. Photoluminescence measurements showed that the bandgap of <10-10> wires blue-shifted by 50 meV from the wires with <0001> direction. Homo-epitaxial growth studies onto the pre-synthesized a-direction GaN nanowires led to belt or ribbon shaped morphologies. Homo-epitaxial growth onto c-direction wires developed micro hexagonal prism morphologies. The island growth morphologies observed on the hundred micron long, sub 30 nm size nanowires suggest that the surface transport of adatoms on c-direction wires exhibit ballistic transport or "onedimensional" transport with mean distances over several tens of microns.

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“…al on self-oriented growth of GaN films. [14][15][16] In this process, upon exposure of metallic Ga to plasma-activated nitrogen atoms, GaN platelets nucleate and coalesce on the surface of the molten Ga. During the process, these platelets self-orient and form an epitaxial layer. In a following step, hydride vapor phase epitaxy (HVPE), which is characterized by high growth rate and excellent crystal quality, is used for epitaxial thickening of these layers to obtain millimeter thick GaN wafers.…”

Section: Ganmentioning

confidence: 99%

“…141 when grown directly out of Ga films supported on amorphous substrates in the presence of N2 plasma at sub-atmospheric pressures. [14][15][16] The proposed concept, Figure 2.8a, states that different platelets tend to move toward each other and form chemically bonded junctions at the edges where the growth is faster. The movement of the platelets, produced by the force of these bonds, causes the platelets to align themselves with respect to each other, which facilitates in their conjoining, see Figure 2.8b.…”

Section: Nitride Fluxmentioning

confidence: 99%

Plasma-assisted liquid phase epitaxy of gallium nitride using molten gallium.

Jaramillo-Cabanzo¹

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I would like to acknowledge the staff at the Conn Center for Renewable Energy Research and the Chemical Engineering department. A special acknowledgment is made to Dr. William Paxton who always was willing to help me. I would also like to thank all my lab mates from whom I never stopped learning. My experience at the University of Louisville would not have been the same without them. I am very grateful to my friends for always letting me know that they are there for me. Specially, I would like to thank Alejandro Martinez for looking out for me, and Lisa Michelson for making my life easier. Lastly, I would like to express my deepest gratitude to my family for their unconditional love and for supporting me in whatever I do.

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Growth of Gallium Nitride Textured Films and Nanowires on Polycrystalline Substrates at sub-Atmospheric Pressures

Cited by 16 publications

References 11 publications

Chemical design of inorganic nanowires, nanotubes and nanowire networks

Chemical design of inorganic nanowires, nanotubes and nanowire networks

Direction dependent homoepitaxial growth and bandgap of GaN nanowires

Plasma-assisted liquid phase epitaxy of gallium nitride using molten gallium.

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