Colloidal versus epitaxial quantum confined systems: the influence of a surface on optoelectronic properties of nanomaterials

在蓬勃发展的纳米技术领域，我们仍处于小规模工具开发的初级阶段。这些工具与周围环境的相互作用，包括比工具本身还大的复杂分子，还没有得到很好的理解。我们感兴趣的工具是晶体半导体粒子，它们非常小，可以在一张纸的边缘容纳上万个以上。这些纳米大小的粒子被称为量子点，以强调它们的行为受量子力学定律的支配。从这个意义上说，它们的行为就像人造原子，我们可以为其设计特性，最终制造出全新的材料。然而，与天然原子相比，我们没有相当于元素周期表的元素来指导我们量子点如何相互作用以及与其他分子的相互作用。为了探测这种相互作用，我们将使用量子点发出的光。光的颜色（波长）是我们可以通过改变量子点的大小来设计的属性之一。当量子点被合成并保存在液体中时，发出的光也会随机地闪烁，但有趣的是，当量子点在半导体固体中生长时，这些波动不会发生。随着光强和波长的增加，这种闪烁的统计量构成了研究量子点内外原子集体相互作用动力学的第三个参数。三种类型的量子点样本将通过其发射的光进行探测：一种是在半导体表面上的量子点，一种是在量子相互作用范围内的半导体表面下的量子点，还有一种是嵌入导电聚合物中的量子点。对于最后一个样品，我们将能够通过导电聚合物器件通过电流为量子点提供能量，而其他样品则通过激光激发获得能量。对这种有机聚合物器件中量子点的研究将有助于从太阳能电池到发光器件的新一代透明、柔韧、轻量化甚至可打印技术的发展。

In the blooming field of nanotechnology, we are still in the infancy of tool development at this small scale. The interaction of these tools with the environment surrounding them, including complex molecules which can be bigger than the tool itself (!), is not well understood. The tools we are interested in are crystalline semiconductor particles so small that one could fit more than ten thousands of them on the edge of a piece of paper. These nanometer-sized particles are called quantum dots to underline that their behaviour is governed by the laws of quantum mechanics. In this sense, they behave like artificial atoms for which we can engineer the properties eventually leading to entirely new materials. However compared to the natural atoms, we don't have the equivalent of a periodic table of elements to guide us on how the quantum dots interact together and with other molecules. To probe this interaction, we will use the light emitted by the quantum dots. The color (wavelength) of this light is one of the properties we can engineer simply by changing the quantum dot size. The emitted light also blink on and off randomly when the quantum dots are synthesized and kept in a liquid, but these fluctuations interestingly do not occur when the quantum dots are grown in a semiconductor solid. With the light intensity and wavelength, the statistics of this blinking constitute a third parameter to investigate the collective interaction dynamics of the atoms inside and outside the quantum dots. Three types of quantum dot samples will be probed through their emitted light: one where the quantum dots are on a semiconductor surface, one where the quantum dots will be buried just below the semiconductor surface within range of quantum interactions and one where the quantum dots are embedded in conductive polymers. With this last sample, we will be able to give energy to the quantum dots by passing current through the conductive polymer device whereas the other samples receive energy via excitation with a laser. Research on quantum dots in this organic polymer device will contribute to the development of a whole new generation of transparent, flexible, light-weight and even printable technologies from solar cells to light emitting devices.