Collaborative research at the University of Notre Dame has demonstrated that electronic interactions play a significant role in the dimensional crossover of semiconductor nanomaterials. The laboratory of Masaru Kuno, professor of chemistry and biochemistry, and the condensed matter theory group of Boldizsár Jankó, professor of physics, have now shown that a critical length scale marks the transition between a zero-dimensional quantum dot and a one-dimensional nanowire.
The findings are published in a paper in Nature Communications; Kuno's group performed the experiments that led to the discovery while Jankó's group provided theoretical support. Matthew McDonald and Rusha Chatterjee of Kuno's laboratory and Jixin Si of Jankó's group are also authors of the paper.
A quantum dot possesses the same physical dimensions in every direction, while a nanowire exhibits one dimension longer than the others. This means that quantum dots and nanowires made of the same material possess different optical and electrical properties at the nanoscale, as these properties are exquisitely size- and shape-dependent.
"All of the introductory-level solid state or semiconductor textbooks need to revise what they say about dimensional crossover. This is another example where interactions make things completely different."Boldizsár Jankó, University of Notre Dame
Understanding the size- and shape-dependent evolution of nanomaterial properties has been a central focus of nanoscience over the past two decades. Nevertheless, scientists have never definitively established how a quantum dot evolves into a nanowire as its aspect ratio is made progressively larger. Do quantum properties evolve gradually or do they suddenly transition?
Kuno's laboratory has now discovered that a critical length exists where a quantum dot becomes nanowire-like. The researchers achieved this breakthrough by conducting the first direct, single-particle absorption measurements on individual semiconductor nanorods, an intermediate species between quantum dots and nanowires. They used single particle measurements rather than ensemble measurements to avoid the effects of sample inhomogeneities. Furthermore, they employed an absorption approach, rather than the oft-used emission approach, to circumvent existing limitations of modern emission-based single particle microscopy, namely its restriction to highly-fluorescent specimens.
This discovery marks a significant advance in our understanding of the size- and shape-dependent quantum mechanical response of semiconductor nanostructures. "All of the introductory-level solid state or semiconductor textbooks need to revise what they say about dimensional crossover," Jankó said. "This is another example where interactions make things completely different."
Beyond this, Kuno suggests that the single-particle absorption approach advanced in the study "has practical, real-world applications, maybe 40 years down the road." Examples include the generic and label-free ultrasensitive detection of chemical and biomolecular species of paramount interest for homeland security and public health.
This story is adapted from material from the University of Notre Dame, with editorial changes made by Materials Today. The views expressed in this article do not necessarily represent those of Elsevier. Link to original source.