Doctoral position in experimental characterization of semiconductor nanocrystals

100%, Zurich, fixed-term

The Optical Materials Engineering Laboratory (Prof. David J. Norris) in the Department of Mechanical and Process Engineering (D-MAVT) at ETH Zurich investigates the synthesis, growth, structure, and optical properties of nanomaterials. Our interdisciplinary and international team combines materials chemistry, optical spectroscopy, electron microscopy, theoretical modeling, and numerical simulation to understand and control materials at the nanoscale.

Nanometer-scale semiconductor crystallites exhibit optical properties (e.g., absorption and emission spectra) that are strongly dependent on their size. Because this property is useful for creating tunable optical materials for optoelectronic applications ranging from displays and infrared cameras to nanophotonics and quantum technologies, chemical syntheses have been developed that produce nanocrystals from various semiconductors. The most advanced protocols are those that lead to quasi-spherical particles (known as colloidal quantum dots).

However, even state-of-the-art nanocrystal samples contain distributions in particle size and morphology that limit their optical performance.

Two classes of semiconductor nanocrystals have been discovered as exceptions to this rule. They display an unusual form of "discrete" growth, jumping between a series of specific sizes. In particular, "magic-sized" nanocrystals grow through a sequence of well-defined sizes. This observation suggests that nanocrystals with exceptionally precise dimensions may be possible.

The central aim of this project is to determine how closely individual magic-sized nanocrystals approach atomic-scale perfection and how their size, shape, composition, surface chemistry, and structure influence their optical properties. Advanced single-particle microscopy and spectroscopy will be used to uncover variations that are hidden in conventional measurements. The resulting understanding will guide the synthesis and optimization of semiconductor nanocrystals for applications requiring highly uniform optical properties.

The doctoral student will characterize semiconductor nanocrystals using complementary optical and structural experimental techniques. The initial focus will be on CdSe magic-sized nanocrystals, with the work subsequently expanding to nanocrystals of different sizes, compositions, surface treatments, and heterostructures, including core/shell and InP nanocrystals.

The project will investigate how variations in nanocrystal size, shape, composition, surface chemistry, and structure influence optical properties. Ensemble and single-particle spectroscopy will be used to quantify optical heterogeneity and determine how closely magic-sized nanocrystals approach atomic-scale perfection. Measurements will examine properties such as emission line widths, excited-state dynamics, spectral fluctuations, and the suitability of selected nanocrystals as single-photon emitters.

These optical studies will be complemented by advanced structural characterization. In particular, the student will use cryogenic electron microscopy and single-particle analysis to determine the three-dimensional structures of semiconductor nanocrystals with near-atomic or atomic-scale resolution. The experiments will examine nanocrystal shape, including the possible truncation of tetrahedral magic-sized nanocrystals, and how it varies with particle size, material composition, surface treatment, and isolation procedure.

The doctoral student will work closely with researchers responsible for nanocrystal synthesis and theoretical modeling. This interaction is central to the project: advanced samples will be supplied for optical and structural measurements, while the characterization results will guide improvements in nanocrystal synthesis, surface treatment, and structural control. The experiments will use the laboratory's optical microscopy and spectroscopy infrastructure as well as the state-of-the-art electron microscopy facilities available at ETH Zurich.

In addition to research, the doctoral candidate will contribute to general laboratory activities and will have…