Chatrin Svensson

Size-selected nanocrystals of III–V semiconductor materials by the aerotaxy method

In this paper we present a fabrication route to produce size-selected III-V semiconductor nanocrystals via a simple, reliable, and efficient aerosol route. Since this approach includes the reaction of aerosol particles and a self-organized growth of a new compound, all in the aerosol phase, we call this process aerotaxy. Size-selected nanocrystals of different III-V compounds in a diameter range below 20 nm were fabricated using this method. Through the reaction of arsine with gallium droplets or of phosphine with indium droplets, GaAs and InP clusters were formed. Our approach opens the possibility to produce contamination-free and size-selected nanocrystals of compound semiconductor materials with considerable freedom in composition and size.

Aerosol Fabrication of Nanocrystals of InP

Nanocrystals of indium phosphide, with diameters of around 10 nm, have been produced via an aerosol route. The method is based on the formation of monodisperse indium droplets and the subsequent reaction with phosphine at elevated temperature. The size of the final InP nanocrystal is self-limited by the size of the introduced size-selected In droplet. This size can be tuned carefully, thus this method allows a narrow size distribution of the nanocrystals. The kinetics of the reaction of In to produce InP depends on the temperature and the phosphine flow. Extensive high resolution transmission electron microscopy studies lead to a consistent picture of the process. Our approach opens the possibility for efficient production of size-selected semiconductor nanocrystals and it will allow new types of self-assembly and control of quantum dots.

Indium enrichment in Ga1−xInxP self-assembled quantum dots

Quantum dots of Ga1−xInxP on GaP (001) have been grown by low-pressure metalorganic vapor phase epitaxy at 650 °C with varying (Ga,In)P coverages. The quantum dots were extensively characterized by transmission electron microscopy (TEM), atomic force microscopy, energy dispersive x-ray spectroscopy, and temperature-dependent photoluminescence spectroscopy (PL). With increasing coverage the dots develop first as flat, extended hills with more or less pronounced {113} facets. Subsequently, on top of these hills, smaller, well-faceted, In-rich dots are formed. The PL intensity emitted from these dots is first constant and then increases with increasing temperature towards a maximum at about 200 K before it decreases. We present a model which explains the experiments, assuming In-rich dots surrounded by Ga-rich barriers. No evidence of alloy ordering was found in the TEM measurements.

InP nanocrystals via aerosol route

Indium phosphide nanocrystals, with diameters of around 10 nm, have been produced via an aerosol route. The production method allows a narrow size distribution of the nanocrystals. The method is based on the formation of monodisperse indium droplets and the subsequent reaction with phosphine at elevated temperature. The kinetics of the reaction of In to produce InP depends on the temperature and the phosphine flow. The size of the final InP nanocrystal is self-limited by the size of the introduced size-selected In droplet. This size can be tuned carefully. Since the new material grows in a self-organized fashion within the aerosol phase we call this process aerotaxy. Our approach opens the possibility for efficient production of size-selected semiconductor nanocrystals and it will allow new types of self-assembly and control of quantum dots.

Structural Characterisation of GaP B Nanowires by HRTEM

GaP B nanowires are dominated by (111) twins orthogonal to the growth direction and show well-developed {111} side-facets. Based on this, a 3D-model has been constructed with a cross-section of an octahedron used as a building block. The twins can be of ortho- or para type i.e. by 60° about the growth axis or 180° in the twin plane. The segment thickness variation follows an exponential distribution with a clear dependence on growth temperature. Multislice simulations show different features of the twin types that are useful for further characterisation.

Aerosol fabrication of nanocrystals of InP and related materials

Indium phosphide nanocrystals, with diameters of around 10 nm, have been produced via an aerosol route. The method is based on the formation of monodisperse indium droplets and the subsequent reaction with phosphine at elevated temperature. The size of the final InP nanocrystal is self-limited by the size of the introduced size-selected In droplet. This size can be tuned carefully, thus this method allows a narrow size distribution of the nanocrystals. The kinetics of the reaction of In to produce InP depends on the temperature and the phosphine flow. Extensive high resolution transmission electron microscopy studies lead to a consistent picture of the process. This process has been demonstrated for the fabrication of InP as well as GaAs nanocrystals. Our approach opens the possibility for efficient production of size-selected semiconductor nanocrystals and it will allow new types of self-assembly and control of quantum dots.