5 research outputs found
Taming Atomic Defects for Quantum Functions
Single atoms provide an ideal system for utilizing fundamental quantum
functions. Their electrons have well-defined energy levels and spin properties.
Even more importantly, for a given isotope -- say, C -- all the atoms
are identical. This creates a perfect uniformity that is impossible to achieve
in macroscopic-size quantum systems. However, herding individual atoms is a
very difficult task that requires trapping them with magnetic or optical means
and cooling them down to temperatures in the nanokelvin range. On the other
hand, the counterpart of single atoms -- the single defects -- may be as good
as atom-based quantum systems if not better. These defects, also referred as
quantum defects, possess the favorable energy, spin, and uniformity properties
of single atoms and remain in their place without the help of precisely tuned
lasers. While the number of usable isotopes is set, the combinations of defects
and their host material are practically limitless, giving us the flexibility to
create precisely designed and controlled quantum systems. Furthermore, as we
tame these defects for the quantum world, we bring about transformative
opportunities to the classical world in forms such as ultradense electronic
devices and precise manufacturing. In this research insight, we introduce some
of our recent work on precisely controlled creation and manipulation of
individual defects with a scanning tunneling microscope (STM). We also discuss
possible pathways for utilizing these capabilities for the development of novel
systems for Quantum Information Science (QIS) applications such as quantum
information processing and ultrasensitive sensors
Contactless Determination of Electrical Conductivity of One-Dimensional Nanomaterials by Solution-Based Electro-orientation Spectroscopy
Nanowires of the same composition, and even fabricated within the same batch, often exhibit electrical conductivities that can vary by orders of magnitude. Unfortunately, existing electrical characterization methods are time-consuming, making the statistical survey of highly variable samples essentially impractical. Here, we demonstrate a contactless, solution-based method to efficiently measure the electrical conductivity of 1D nanomaterials based on their transient alignment behavior in ac electric fields of different frequencies. Comparison with direct transport measurements by probe-based scanning tunneling microscopy shows that electro-orientation spectroscopy can quantitatively measure nanowire conductivity over a 5-order-of-magnitude range, 10<sup>–5</sup>–1 Ω<sup>–1</sup> m<sup>–1</sup> (corresponding to resistivities in the range 10<sup>2</sup>–10<sup>7</sup> Ω·cm). With this method, we statistically characterize the conductivity of a variety of nanowires and find significant variability in silicon nanowires grown by metal-assisted chemical etching from the same wafer. We also find that the active carrier concentration of n-type silicon nanowires is greatly reduced by surface traps and that surface passivation increases the effective conductivity by an order of magnitude. This simple method makes electrical characterization of insulating and semiconducting 1D nanomaterials far more efficient and accessible to more researchers than current approaches. Electro-orientation spectroscopy also has the potential to be integrated with other solution-based methods for the high-throughput sorting and manipulation of 1D nanomaterials for postgrowth device assembly