Epitaxial metal nitride films are prepared using a general chemical solution approach. A polymer‐assisted deposition to prepare epitaxial cubic TiN, metastable AlN, and ternary nitride Ti1−xAlxN films is demonstrated. The structural, optical and electrical properties of the films are investigated, and may be of interest for many technological applications.
We have demonstrated the ability to apply thin conformal films onto complex nanostructures using a polymer assisted deposition technique. Sequestering the metal by binding it to a polymer results in a bottom‐up growth process that leads to conformal film deposition. We have deposited a thin film of the phosphor Eu:YVO4 on 60 μm thick anodiscs® with 200 nm pores resulting in highly luminescent nanostructures.
Exploding bridgewire (EBW) detonators were invented during the Manhattan Project over 75 years ago. Initially developed for precise timing and reproducibility, they continue to be used in many applications. Despite widespread use and reliability, their mechanism for function remains controversial. They provide precision timing, yet their function is described in terms of a “lost time” accounting for nearly half of the function time. Buried in understanding the EBW function is the mystery of how an incoherent impulse such as powering a bridgewire yields the coherent energy output of a detonation. Even the general phenomena by which release of chemical energy in a crystalline organic explosive becomes associated with the sonic plane of a steady detonation wave remain uncertain. Here, we investigate the EBW function with a suite of diagnostics and show that stationary heating occurs during the “lost-time.” We use x-ray radiography to observe the propagation of a shock wave from bridgewire vaporization and establish that the origin of the radially emanating detonation wave is spatially separated from the initial shock. Utilizing the observed temperature as a boundary condition in our explosive response models yields a thermal ignition consistent with the “lost-time” and detonation location consistent with previous work. With these results, we define a direct thermal initiation mechanism for the EBW function consistent with previous integral observations and explain the displacement of initiation from the bridgewire burst in time and space.
Epitaxial GaN thin films have been deposited on (0001) sapphire substrates by a chemical solution approach of polymer-assisted deposition. The films are smooth with no detectable cracks or pores, as observed by scanning electron microscopy and atomic force microscopy. Microstructural studies by X-ray diffraction and transmission electron microscopy show that the GaN films have a hexagonal structure with an epitaxial relationship between the film and the substrate of (0001)GaN||(0001)Al2O3
and [112̅0]GaN||[101̅0]Al2O3
. The films with a room temperature resistivity of around 0.13 Ω·cm exhibit photoluminescence characteristic of wurtzite hexagonal GaN.
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