Semiconductor Nanoparticles for Novel Transistors

Smartphones, computers, televisions, radios, power chargers - transistors can be found in almost every electrical device. Therefore, these small, electronic semiconductor components are among the most important active components of electronic circuits. Nowadays, such electronic components are expected to become smaller, more flexible, and more powerful than the examples in the image. However, a high-performance, flexible, thin-film transistor technology is still missing.

Especially field-effect transistors (FETs), a type of transistors, are attractive because they can be switched almost without power loss, are relatively insensitive to overvoltages and are also relatively inexpensive. They consist of three connectors: source, gate and drain. A voltage between the control electrode (gate) and the source electrode regulates the charge carrier density and consequently the current flow between source and drain. The individual components can be arranged vertically, meaning stacked on top of each other. This design can further reduce the footprint of already nm-sized transistors, enabling more of those components to be placed in the same area. The increased transistor count allows for more complex circuits and also reduces device power consumption, making low-energy devices possible.

For these nano-sized transistors, nano-sized materials and arrangement control are necessary. In the last decades different functional nanoparticles have been successfully fabricated and studied in detail. It is possible to precisely control the physical and electronic properties of nanocrystals (NCs) via parameters such as size, shape and composition. Especially semiconductor nanocrystals have the potential to achieve a breakthrough in transistor performance, as they overcome the intrinsic low carrier mobility of organic semiconductors.

In this work, we strive to use different NCs for vertical transistors, which allow to easily realize high-performance devices without nanostructuring. Therefore, NCs like AgInS₂ or ZnTe are synthesized to replace the widely studied but more toxic Cd-containing materials. Commonly, the as-synthesized NCs are capped with bulky, insulating hydrocarbon-containing ligands which have to be removed in an additional thermal or chemical step. However, this postsynthetic treatment often results in the formation of defects or the removal doesn’t work completely. To avoid the necessity of such a step and to improve the electronic communication, the modification with inorganic ligands is the second focus of this work. The materials are then characterized in terms of their film-forming properties and electronic parameters to finally fabricate some vertical FETs.

Literature recommendations:

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