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Theses

Density of states, band offset and charge injection in one-dimensional semiconductor nanostructures studied with multiple probes scanning tunneling microscopy

Nemanja Peric 1, 2
2 PHYSIQUE - IEMN - Physique - IEMN
IEMN - Institut d’Électronique, de Microélectronique et de Nanotechnologie - UMR 8520
Abstract : The traditional transistor miniaturization is resulting in devices experiencing quantum effects. Rather than fighting these effect by developing new architectures of conventional silicon-based devices, the long-term solution might be in revisiting existing knowledge of these fundamental concepts and studying them in a well-controlled and methodological manner. Consequently, the newly emergent insights could be applied to the keystones of modern-day electronic devices, such as one-dimensional shape and the presence of heterointerface, but on different materials. This, in fact, has a potential to yield an alternative approach to information processing and computation.Nowadays, it is possible to obtain nanostructures of any shape and size due to recent breakthroughs in nanofabrication. This thesis aims to exploit such possibilities to simulate an experimental environment in which quantum confinement effect can be studied in a controlled manner on different one-dimensional semiconductor nano-heterostructures. At first, a reliable methodology will be developed to accurately determine the band alignment between two dissimilar semiconductors comprising a heterointerface. This will be achieved on planar one-dimensional InGaAs nanostructures grown on InP by selective area molecular beam epitaxy, a nanofabrication method which, to date, offers the best control of nanostructure shape, size, position, and orientation in ultrahigh vacuum. The surface reconstruction, as well as the entire structure morphology will be investigated in great detail by means of atomic force microscopy and scanning tunneling microscopy, while the aforementioned growth will be described by modeling the diffusion dynamics. A combination of low-temperature two-probe scanning tunneling spectroscopy and room-temperature four-probe contact measurements will be utilized to obtain accurate information about the band alignment and charge transport of the heterosystem.Once proven successful, the approach will be employed to study nanostructures of much smaller dimensions, where quantum size effect is ever-present: colloidal CdSe nanoplatelets, which imitate the typical optical characteristics of epitaxial quantum wells, but, due to anisotropic lateral dimensions, make the understanding of the impact of finite lateral confinement on the behavior of the free charge carriers more complex. In addition to the study of the morphology of the nanoplatelets and of their optical transitions, low-temperature scanning tunneling microscopy and spectroscopy investigations will be performed. Once drop-casted onto a gold substrate, the density of states of the nanoplatelets will be directly probed in order to accurately determine the extent of quantum confinement experienced by the carriers as a function of the nanoplatelets thickness, temperature and spatial configuration. The results which are, on one hand, inconsistent with foregoing quantum well-like perception found in literature, while on the other, perfectly in line with our tight binding calculations, will establish a solid baseline for the follow-up study of CdSe/CdS core-crown nanoplatelets.
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Submitted on : Tuesday, November 16, 2021 - 1:05:11 PM
Last modification on : Monday, May 2, 2022 - 2:57:30 PM
Long-term archiving on: : Thursday, February 17, 2022 - 7:33:18 PM

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  • HAL Id : tel-03430762, version 1

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Nemanja Peric. Density of states, band offset and charge injection in one-dimensional semiconductor nanostructures studied with multiple probes scanning tunneling microscopy. Micro and nanotechnologies/Microelectronics. Université de Lille, 2021. English. ⟨NNT : 2021LILUI025⟩. ⟨tel-03430762⟩

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