原子层沉积法制备纳米晶/ Al $_2$ O $_3$复合薄膜的发光
Robust and Bright Photoluminescence from Colloidal Nanocrystal / Al$_2$O$_3$ Composite Films fabricated by Atomic Layer Deposition
摘要：
胶体纳米晶体是一类很有前途的荧光材料，其自发发射特征可以通过其组成、几何形状和尺寸在宽光谱范围内进行调节。然而，对嵌入纳米晶体薄膜在精心制作的设备的几何形状，一个显着的缺点是它们的发射性能的敏感性，如光刻，金属或氧化物沉积等进一步的制造工艺在这项工作中，我们展示了如何明亮的发射和强大的薄膜可以通过结合从解决方案通过spin 2涂层与随后的原子层沉积氧化铝的沉积。对于所得的复合膜，层厚度可以在纳米级上控制，并且它们的折射率可以通过沉积的氧化铝的量进行微调。椭圆偏振法用于测量介电常数的实部和虚部，其给出了直接访问膜的波长依赖的折射率吸收。详细分析的薄膜的核-壳结构的不同形状和不同的壳厚度的光致发光的行为和衰减寿命的氧化铝沉积所引起的非辐射率的变化，允许相关的物理。我们表明，这种复合薄膜的光发射性能是稳定的波长和强度超过几个月，从加热过程中完全恢复到240 $^\circ$ C的光致发光。后者特别令人感兴趣，因为它证明了对典型热处理的鲁棒性，所述典型热处理在几个工艺步骤中是需要的，如基于抗蚀剂的光刻和通过金属或氧化物的热或电子束蒸发的沉积。
英文摘要：
Colloidal nanocrystals are a promising fluorescent class of materials, whose spontaneous emission features can be tuned over a broad spectral range via their composition, geometry and size. However, towards embedding nanocrystals films in elaborated device geometries, one significant drawback is the sensitivity of their emission properties on further fabrication processes like lithography, metal or oxide deposition, etc. In this work, we demonstrate how bright emitting and robust thin films can be obtained by combining nanocrystal deposition from solutions via spin2 coating with subsequent atomic layer deposition of alumina. For the resulting composite films, the layer thickness can be controlled on the nanoscale, and their refractive index can be finely tuned by the amount of deposited alumina. Ellipsometry is used to measure the real and imaginary part of the dielectric permittivity, which gives direct access to the wavelength dependent refractive index absorbance of the film. Detailed analysis of the photophysics of thin films of core-shell nanocrystal with different shape and different shell thickness allow to correlate the behavior of the photoluminescence and of the decay life time to the changes in the non-radiative rate that are induced by the alumina deposition. We show that the photoemission properties of such composite films are stable in wavelength and intensity over several months, and that the photoluminescence completely recovers from heating processes up to 240$^\circ$C. The latter is particularly interesting, since it demonstrates robustness to the typical heat treatment that is needed in several process steps like resist-based lithography and deposition by thermal or electron beam evaporation of metals or oxides.
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