Assemblies of CdS Quantum Particles Studied by the Attenuated Low Energy Photoelectron Spectroscopy

Abstract

We report on the direct observation of collective electronic properties in assembled CdS quantum particles (QPs) arranged in periodic layers. Within each layer the QPs are of the same average size, either 2.5 or 5 nm, and the layers are arranged in a cascade-like pattern. The electronic properties of the QPs were studied using a new method, the attenuated low energy photoelectron spectroscopy (A-LEPS), in which a "pump" laser excites the QPs and a "probe" laser ejects photoelectrons from the QPs and from the metal substrate. The A-LEPS method provides information about the populated electronic states of the QPs (including the splitting between the light/heavy hole and split-off bands) and how these states depend on the interparticle interactions.

Tight-Binding Method and Multiband Effective Mass Theory Applied to CdS Nanocrystals: Single-Particle Effects and Optical Spectra Fine Structure

“…4,12 To see how the optical spectrum is changed when oblate nanocrystals elongated in the z direction are considered, we carried out calculations for nanoparticles with a varying degree of ellipticity (µ 0 ). µ 0 is defined as µ 0 ) c 0 /b 0 -1, where c 0 is the length of the long z axis and b 0 is the length of the two short axes.…”

“…10 The consequences of shape uncertainty may be important because ellipticity has been predicted to affect strongly the oscillator strengths of CdSe nanocrystals 13 and has been suggested as a factor that might affect the hole level splitting in CdS samples. 4 Therefore, we carried out calculations for several nanocrystal sizes and shapes within the experimental uncertainty. The CdS sizes and shapes employed in our calculations correspond to those used in ref 10 and are the same as the ones assumed in the low-temperature fluorescence 11 and A-LEP.…”

“…The CdS sizes and shapes employed in our calculations correspond to those used in ref 10 and are the same as the ones assumed in the low-temperature fluorescence 11 and A-LEP. 4 We also assessed other possible uncertainties to check the robustness of our results. We evaluated the dependence of the low-lying hole levels on the spin-orbit parameter, λ a , to see whether the surprisingly large 1S 3/2 -1S 1/2 splitting recently inferred from photoelectron spectroscopy 4 can be explained.…”

The Effects of Organisation, Embedding and Surfactants on the Properties of Cadmium Chalcogenide (CdS, CdSe and CdS/CdSe) Semiconductor Nanoparticles

“…Because of their potential application as building blocks for electronic and optical devices, solvent-free particles (i.e., a non-liquid phase), either deposited on a substrate or incorporated into a solid phase, are advantageous to obtain adequate material handling. Some effort has been made to organise semiconductor nanoparticles, for example by Samokhvalov et al [99] and Lahav et al, [100,101] who have studied the collective electronic properties of self-organised CdS particles in hybrid LangmuirBlodgett films. Similarly, Hilbron et al [102] have obtained an arrangement by polymerisation of the surfactants.…”

Physical and Chemical Properties of Nano‐Sized Metal Particles

“…Three-dimensional superlattices involving nanocrystals of different metals (e.g., Pt and Au) and of metals and semiconductors (e.g., Au and CdS) have also been prepared and characterized [108]. Such assemblies can be made with polyelectrolytes such as poly(diallyldimethylammonium chloride) (PDDA), polyethyleneimine (PEI) [110,111], and poly(allylamine hydrochloride) (PAH), as well as with polymers such as poly-phenylenevinylene (PPV) [112,113].…”