Abstract
The bandgap of a semiconductor is one of its most important electronic properties. It is often considered to be a fixed property of the semiconductor. As the dimensions of semiconductors reduce, however, many-body effects become dominant. Here, we show that doping and dielectric, two critical features of semiconductor device manufacturing, can dramatically shrink (renormalize) the bandgap. We demonstrate this in quasi-one-dimensional semiconducting carbon nanotubes. Specifically, we use a four-gated device, configured as a p-n diode, to investigate the fundamental electronic structure of individual, partially supported nanotubes of varying diameter. The four-gated construction allows us to combine both electrical and optical spectroscopic techniques to measure the bandgap over a wide doping range.
Highlights
The bandgap is one of the most important electronic properties of a semiconductor
In the early studies of STS14,15, a diameter dependence that coincided with the one from a single-particle picture was observed. We examine this value in the context of both the photophysics and electronic properties of single-walled carbon nanotubes (SWNTs) for different diameter nanotubes and challenge its ubiquitous use to characterize SWNTs
The doping induced bandgap renormalization is a many-body effect that is enhanced in 1-D systems[10,21]
Summary
The bandgap is one of the most important electronic properties of a semiconductor. For example, the bandgap determines the emission wavelength of LEDs and Lasers. Semiconducting single-walled carbon nanotubes (SWNTs) are promising materials for optoelectronic and electronic applications[2,3,4] They are quasi-one-dimensional (1-D) materials that are characterized by (n,m) chiral indices, which define their structure and diameter. With doping using gating techniques, the bandgap shrinks further due to enhanced electron-electron interaction from the 1-D confinement We show that both effects are large and demonstrate their diameter dependence for the first time. In the early studies of STS14,15, a diameter dependence that coincided with the one from a single-particle picture was observed We examine this value in the context of both the photophysics and electronic properties of SWNTs for different diameter nanotubes and challenge its ubiquitous use to characterize SWNTs. We focus on the low-doping characteristics, which is permitted by our special device construction
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