What are the main challenges of fabricating self-assembled quantum dots on different substrates?

2 Size and shape control

Another challenge of fabricating self-assembled quantum dots on different substrates is controlling the size and shape of the quantum dots, which determine their optical and electronic properties. The size and shape of the quantum dots depend on various factors, such as the growth temperature, the deposition rate, the surface diffusion, the nucleation density, and the interaction with the substrate. These factors can vary depending on the type of substrate and the quantum dot material, making it difficult to achieve uniform and reproducible quantum dots. Moreover, some quantum dot materials, such as lead sulfide or lead selenide, tend to form elongated or branched structures rather than spherical or pyramidal ones, which can affect their performance and integration. Therefore, researchers have to optimize the growth conditions, use surfactants or additives, or employ post-growth treatments to control the size and shape of the quantum dots.

3 Surface passivation

A third challenge of fabricating self-assembled quantum dots on different substrates is passivating the surface of the quantum dots, which can have a significant impact on their stability and functionality. The surface of the quantum dots can have dangling bonds, defects, or impurities that can trap electrons or holes, reduce the quantum yield, or cause non-radiative recombination. Moreover, the surface of the quantum dots can react with oxygen, water, or other molecules in the environment, leading to degradation or oxidation. Therefore, researchers have to coat the surface of the quantum dots with organic or inorganic ligands, such as thiols, amines, silanes, or oxides, that can bind to the surface atoms and form a protective layer. However, the choice of the ligand and the coating method can also affect the properties and the compatibility of the quantum dots with the substrate and the device.

4 Integration and alignment

A fourth challenge of fabricating self-assembled quantum dots on different substrates is integrating and aligning them with other components or devices. Quantum dots can have different electrical, optical, or mechanical properties than the substrate or the device, which can cause interface or compatibility issues. For example, quantum dots can have different band gaps, work functions, or carrier mobilities than the substrate or the device, which can affect the charge transfer, the current flow, or the voltage output. Moreover, quantum dots can have different orientations, positions, or densities on the substrate, which can affect the coupling, the emission, or the detection of light. Therefore, researchers have to use techniques such as selective area growth, lithography, patterning, or self-assembly to integrate and align the quantum dots with the substrate and the device.

6 Future prospects

A sixth challenge of fabricating self-assembled quantum dots on different substrates is exploring their future prospects and applications. Quantum dots have a lot of potential in various fields, such as nanomedicine, solar cells, quantum computing, and sensors. However, there are still many challenges and limitations that need to be overcome before they can be widely used and commercialized. For example, quantum dots need to be more stable, efficient, scalable, biocompatible, and environmentally friendly. Moreover, quantum dots need to be integrated and aligned with other materials and devices that can enhance their functionality and performance. Therefore, researchers have to develop new strategies and methods to fabricate self-assembled quantum dots on different substrates and to exploit their unique properties and advantages.