Low-Temperature Solvothermal Route to GaN Nanoparticles
- PDF / 579,701 Bytes
- 6 Pages / 612 x 792 pts (letter) Page_size
- 105 Downloads / 224 Views
Low-Temperature Solvothermal Route to GaN Nanoparticles Jianjun Wang, Luke Grocholl, and Edward G. Gillan* Department of Chemistry University of Iowa Iowa City, Iowa 52242-1294 ABSTRACT We report a straightforward, non-aqueous solvothermal method for the production of nanoscale gallium nitride structures. Nanoparticles with spherical and rod-like morphologies are produced via in situ gallium azide precursor synthesis and decomposition in superheated toluene or THF. The solution reaction between gallium chloride and sodium azide produces an insoluble azide precursor that is then solvothermally decomposed to GaN at temperatures below 260 ºC. The resulting products are poorly crystalline but thermally stable and crystallize to hexagonal GaN upon annealing at 750 ºC. Product morphologies include spherical particles (ca. 50 nm) and nanorods. Upon annealing, the nanoparticles coalesce into larger organized crystalline structures with hexagonal facets. INTRODUCTION Group 13 nitrides are central to a class of light emitting semiconductors that are finding increasingly utility in device applications such as high intensity blue lasers and full color displays.[1] The heavier nitrides, GaN (Eg = 3.4 eV) and InN (Eg = 1.9 eV), have useful band gaps in the visible region and form a wide range of solid solutions. Dual-source vapor phase processes, such as deposition using Me3Ga and NH3 at 800 – 1200 ºC, are most commonly used to grow gallium nitride films.[2] Gallium nitride is thermally unstable and decomposes to the elements before melting (≥ 1700 ºC), which makes it difficult to produce single crystals by hightemperature melt-based synthetic methods.[3] There are reports of the synthesis of GaN crystals from molten gallium and N2 at 700 ºC in a sodium flux generated from NaN3 decomposition[4] and long nanorod architectures have been observed from catalyzed reactions between gallium and NH3 above 900 ºC.[5] Solid-state metathesis reaction between GaCl3 and Li3N/NH4Cl also rapidly produce crystalline GaN powders.[6] The solid-state pyrolysis of polymeric gallium amides, such as [Ga(NH)3/2]n[7] and (H2GaNH2)n,[8] produce GaN powders at low temperatures. Of most relevance to the present work, a thermally unstable triethylamine adduct of gallium azide [Et3N•Ga(N3)3] was isolated, which upon amine removal rapidly decomposes to GaN nanoparticles.[9] While high-temperature solution reactions are well developed for water-based (hydrothermal) syntheses, there is much less work on non-aqueous systems. Recently nonaqueous solvents have been utilized in the solvothermal synthesis of technologically useful optical and semiconductor nanomaterials[10] and the 13-15 nanorods.[11] Solution routes to metal nitrides are much less prevalent than those for chalcogenides or pnictides. Some promising routes include GaN nanoparticles from GaCl3 and Li3N in superheated benzene,[12] GaN crystals and nanocrystallites from the reaction of gallium or gallium amides with supercritical NH3,[13] and GaN nanoparticles from the rapid decomposition of gallium azi
Data Loading...
