Solid-state metathesis reactions under pressure: A rapid route to crystalline gallium nitride

Abstract

High pressure chemistry has traditionally involved applying pressure and increasing temperature until conditions become thermodynamically favorable for phase transitions or reactions to occur. Here, high pressure alone is used as a starting point for carrying out rapid, self-propagating metathesis reactions. By initiating chemical reactions under pressure, crystalline phases, such as gallium nitride, can be synthesized which are inaccessible when initiated from ambient conditions. The single-phase gallium nitride made by metathesis reactions under pressure displays significant photoluminescence intensity in the blue/ultraviolet region. The absence of size or surface-state effects in the photoluminescence spectra show that the crystallites are of micron dimensions. The narrow lines of the x-ray diffraction patterns and scanning electron microscopy confirm this conclusion. Brightly luminescent thin films can be readily grown using pulsed laser deposition.

Bright Blue Photo‐ and Electroluminescence from Eu2+‐Doped GaN/SiO2 Nanocomposites

“…The lattice parameters for the hexagonal GaN [a = 3.187(1) and c = 5.183 (3)] are in agreement with those reported in the literature for the bulk GaN. [25,42] The broad hump observed around 25°(2h) is from the amorphous silica. The exact nature of the silica material (nitride or oxynitride) is not clear due to the broadening of the peak but it is likely there might be some oxynitride formation (vide infra).…”

Preparation of Mn3O4 nanocrystallites by low-temperature solvothermal treatment of γ-MnOOH nanowires

“…Especially, when EDA and EG coordinated with Mn 3+ , the short distance between manganese and nitrogen or oxygen atom in the coordination compound is favorable for electron to transfer from N or O to Mn 3+ [29,30], resulting in the reduction of g-MnOOH to Mn 3 O 4 . Meanwhile, the elevated pressure autogenerated in the solvothermal system affords a greater driving force for the reaction process [32,33]. To improve our understanding of the solvothermal reduction mechanism, experiments were performed under similar conditions when EDA and EG were replaced by several nonreducibility (or less reducibility) solvents such as tetrachloride, n-hexane, benzene, pyridine, acetone, and dimethylsulfoxide.…”

Ga2O3 and GaN Semiconductor Hollow Spheres

“…[10,11] The future of full-colored, flat panel displays, blue lasers, and optical communication is likely to be based on GaN. [5,12] Nanostructured Ga 2 O 3 and GaN with varied morphology, for instance, nanoparticles, [13] nanorods, [14] nanowires, [3,15] nanobelts, [4,16] and nanotubes [5][6][17][18] have been prepared. However, monodispersed spherical structures of the two semiconductor compounds have not been prepared up to now.…”