In recent years, physicists and electronic engineers have been trying to identify materials that could be used to fabricate new types of electronic devices. One-dimensional (1-D) and two-dimensional (2-D) materials have been found to have particularly advantageous characteristics, particularly for the development of new generations of nanoelectronics (electronic components at the nano scale).
Such 1-D and 2-D materials, such as graphene, monolayer molybdenum disulfide, silicon nanowires and silicon nanosheets, could also play a crucial role within the semiconductor industry, as they could help to develop increasingly small transistors. Transistors are the basic building blocks of many modern electronic devices, which can store and control bits of binary information (i.e., zeroes and ones).
Despite their well-documented advantages, emerging low-dimensional materials can have a relatively small amount of so-called free charges compared to 3-D materials. In the context of electronic components, a free charge is an electron or hole (i.e., lack of an electron in an atomic lattice that acts as a positively charged electron) that is not tightly bound to the atomic lattice and is therefore able to move around freely throughout a material in response to external fields and applied voltages. Free charges have a number of important functions, one of which is their contribution to what is known as the screening effect.
In fact, free charges can redistribute themselves to create sharp electric potential profiles in both materials and devices, including in transistors. Therefore, the greater the number of free charges that material possesses, the sharper the resulting electric potential. This particular function is especially crucial for the development of tunnel field-effect transistors, which heavily rely on the quantum tunneling of electrons across junctions.
Researchers at McGill University and NanoAcademic Technologies have recently identified a strategy that could compensate for the lack of free charges observed in both 1-D and 2-D materials. In their paper, published in Physical Review Letters, they proposed the use of this strategy, which is based on the engineering of bound charges, to develop silicon nanowire transistors.
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