Disorder increasingly affects performance as electronic devices are reduced in size. The ionized dopants used to populate a device with electrons are particularly problematic, leading to unpredictable changes in the behavior of devices such as quantum dots each time they are cooled for use. We show that a quantum dot can be used as a highly sensitive probe of changes in disorder potential and that, by removing the ionized dopants and populating the dot electrostatically, its electronic properties become reproducible with high fidelity after thermal cycling to room temperature. Our work demonstrates that the disorder potential has a significant, perhaps even dominant, influence on the electron dynamics, with important implications for "ballistic" transport in quantum dots.
The study of electron motion in semiconductor billiards has elucidated our understanding of quantum interference and quantum chaos. The central assumption is that ionized donors generate only minor perturbations to the electron trajectories, which are determined by scattering from billiard walls. We use magnetoconductance fluctuations as a probe of the quantum interference and show that these fluctuations change radically when the scattering landscape is modified by thermally-induced charge displacement between donor sites. Our results challenge the accepted understanding of quantum interference effects in nanostructures.
Scanning tunneling microscopy (STM) and orbital mediated tunneling spectroscopy (OMTS) are reported for
1,5-di(octyloxy)anthracene (15DA) adsorbed on highly ordered pyrolytic graphite (HOPG). 15DA forms well-ordered monolayers either at the interface between HOPG and 1-phenyloctane or at the HOPG−air or HOPG−vacuum interface when spin doped from octane or dichloromethane. Octyl chain interdigitation and planar
adsorption of the anthracene ring combine to produce structures which are stable independent of the adsorption
method. The observed unit cell has a = 1.76 ± 0.06 nm, b = 1.07 ± 0.06 nm, and α = 77 ± 3°. Molecular
orbital calculations are combined with bias-dependent imaging and OMTS results to show that the highest-occupied molecular orbital (HOMO) dominates the tunneling process over the voltage range from −2.5 to
+1.0 V. The HOMO of 15DA on HOPG is found to occur at −7.0 eV below the vacuum level, in good
agreement with previous UPS studies and with our calculations for the free molecule. We also report the first
synthesis of 15DA.
Many methods exist for quantifying the fractal characteristics of a structure via a fractal dimension. As a traditional example, a fractal dimension of a spatial fractal structure may be quantified via a box-counting fractal analysis that probes a manner in which the structure fills space. However, such spatial analyses generally are not well-suited for the analysis of so-called "time-series" fractals, which may exhibit exact or statistical self-affinity but which inherently lack well-defined spatial characteristics. In this chapter, we introduce and investigate a variety of fractal analysis techniques directed to time-series structures. We investigate the fidelity of such techniques by applying each technique to sets of computer-generated timeseries data sets with well-defined fractal characteristics. Additionally, we investigate the inherent challenges in quantifying fractal characteristics (and indeed of verifying the presence of such fractal characteristics) in time-series traces modeled to resemble physical data sets.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.