Atomic Layer Deposition of Lead Sulfide Quantum Dots on Nanowire Surfaces

Abstract

Quantum dots provide unique advantages in the design of novel optoelectronic devices owing to the ability to tune their properties as a function of size. Here we demonstrate a new technique for fabrication of quantum dots during the nucleation stage of atomic layer deposition (ALD) of PbS. Islands with sub-10 nm diameters were observed during the initial ALD cycles by transmission electron microscopy, and in situ observations of the coalescence and sublimation behavior of these islands show the possibility of further modifying the size and density of dots by annealing. The ALD process can be used to cover high-aspect-ratio nanostructures, as demonstrated by the uniform coating of a Si nanowire array with a single layer of PbS quantum dots. Photoluminescence measurements on the quantum dot/nanowire composites show a blue shift when the number of ALD cycles is decreased, suggesting a route to fabricate unique three-dimensional nanostructured devices such as solar cells.

Entering the Era of Nanoscience: Time to Be So Small Vuk Uskokovíc

“…For example, during a recent ultrastructural characterization of graphene, it was impossible to tell whether the detected moving of a line of point defects was naturally occurring or it was due to the conversion of the electron beam energy to the thermal lattice movement. 144 Similarly, widely dispersed, irregular and flat PbS nanoparticles—relatively robust to start with—were seen transforming to uniform spherical particles after 11 min of residing under the TEM beam, 145 yielding a dramatic example of the fact well known from the basic tenet of the theory of measurements: both the observer and the observed are involved in defining the observed system’s qualities.…”

Thickness effects of yttria-doped ceria interlayers on solid oxide fuel cells

“…The YDC films discussed in this paper were all deposited by the ALD method. In the ALD growth mechanism, as the number of ALD cycles increases, the deposition process starts from island growth on the substrate to gradually form a complete film one submonolayer at a time [17,18]. Since the oxide ion incorporation is faster at the YDCePt interface than YSZePt interface, we want to guarantee that YDC films have fully covered the underlying YSZ electrolyte [13].…”

ALD for clean energy conversion, utilization, and storage

“…49 During the initial cycles, the nucleation of these ALD fi lms proceeded by island growth, enabling the direct fabrication of QDs without need for further processing. 50 This technique was used to coat the surface of Si nanowires (SiNWs) with a single layer of QDs shown in the transmission electron microscopy (TEM) image in Figure 3 a, allowing for incorporation into light-scattering architectures for enhanced absorption and charge extraction. These QD-SiNW hybrid structures exhibited a blueshift in photoluminescence with a decreasing number of ALD cycles ( Figure 3b ), illustrating that the optical properties can be tuned precisely.…”