Influence of process parameters on energetic properties of sputter-deposited Al/CuO reactive multilayers.

In this study, we demonstrate the effect of change of the sputtering power and the deposition pressure on the ignition and the combustion properties of Al/CuO reactive thin films. A reduced sputtering power of Al along with the deposition carried out at a higher-pressure result in a high-quality thin film showing a 200% improvement in the burn rate and a 50% drop in the ignition energy. This highlights the direct implication of the change of the process parameters on the responsivity and the reactivity of the reactive film while maintaining the Al and CuO thin-film integrity both crystallographically and chemically. Atomically resolved structural and chemical analyzes enabled us to qualitatively determine how the microstructural differences at the interface (thickness, stress level, delamination at high temperatures and intermixing) facilitate the Al and O migrations and impact the overall nano-thermite reactivity. We found that the deposition of CuO under low pressure produces well-defined and similar Al-CuO and CuO-Al interfaces with the least expected intermixing. Our investigations also showed that the magnitude of residual stress induced during the deposition plays a decisive role in influencing the overall nano-thermite reactivity. Higher is the magnitude of the tensile residual stress induced, stronger is the presence of gaseous oxygen at the interface. By contrast, high compressive interfacial stress aids in preserving the Al atoms for the main reaction while not getting expended in the interface thickening. Overall, this analysis helped in understanding the effect of change of deposition conditions on the reactivity of Al/CuO nanolaminates and several handles that may be pulled to optimize the process better by means of physical engineering of the interfaces.

Solid-State Neutron Detection Based on Methylammonium Lead Bromide Perovskite Single Crystals.

Perovskite-based semiconductors, such as methylammonium and cesium lead halides (MPbX3: M = CH3NH3+ or Cs+; X = I-, Br-, or Cl-), have attracted immense attention for several applications, including radiation detection, due to their excellent electronic and optical properties.1,2,3,4,5,6 In addition, the combination of perovskites with other materials enables unique device structures. For example, robust and reliable diodes result when combined with metal oxide semiconductors. This device can be used for detection of nonionizing and ionizing radiation. In this paper, we report a unique perovskite single-crystal-based neutron detector using a heterojunction diode based on single-crystal MAPbBr3 and gallium oxide (Ga2O3) thin film. The MAPbBr3/Ga2O3 diodes demonstrate a leakage current of ∼7 × 10-10 A/mm2, an on/off ratio of ∼102, an ideality factor of 1.41, and minimal hysteresis that enables alpha particle, gamma-ray, and neutron detection at a bias as low as (-5 V). Gamma discrimination is further improved by 85% by optimizing the thickness of the perovskite single crystal. The MAPbBr3/Ga2O3 diodes also demonstrate a neutron detection efficiency of ∼3.92% when combined with a 10B neutron conversion layer.