Cadmium selenide: Surface and nanoparticle energetics

Abstract

Cadmium selenide (CdSe) belongs to a class of important II-VI semiconductors widely used in optical, sensor, and laser materials and quantum-dot light-emitting diodes. Here we present the first direct calorimetric measurement of the surface energy of wurtzite CdSe. CdSe nanoparticles with particle size between 20 and 60 nm were prepared by a hydrothermal method without additives to control morphology, and the surface energy was derived from the drop solution enthalpies in molten sodium molybdate and from water adsorption calorimetry. The surface energy of the hydrated surface is 1.31 6 0.26 J/m 2 , whereas that of the anhydrous surface is 1.65 6 0.27 J/m 2 . These values are significantly lower than those for ZnO and many other oxides.

Effect of interaction of external surfaces on the symmetry and lattice distortion of CdSe nanocrystals by molecular dynamics simulations

“…Our simulations of small CdSe nanoparticles (not the subject of the present report) yielded the following values of surface energy for low-index atomic surfaces: 2.18 eV/atom for (100), 2.11 eV/atom for (110), 1.78 eV/atom for (111)A, and 2.40ev/atom for (111)B surfaces. This is in general agreement with the experimental values reported in the literature (Xu et al 2011 ). The differences between various surfaces naturally reflect the density of the broken atomic bonds at the surface.…”

Ligand-stabilized CdSe nanoplatelet hybrid structures with tailored geometric and electronic properties. New insights from theory

“…However, the experimental measurement of two dimensional energetic properties like the surface formation energy is difficult and it can give ambiguous results because extremely clean materials are needed, in which the uniformity of the exposed surface is insured, which is oen not the case. 20 The difficulties related to experimentally obtaining an accurate description of the electronic and geometric properties at an atomistic scale further valorize the use of theoretical methods. Computational approaches have proven to be useful tools to simulate both bulk and surface properties of semiconductors, 21,22 as well as adsorption of ligands or functional molecules on their surfaces.…”

Investigation of the bulk and surface properties of CdSe: insights from theory

“…It is one of the cleavage surfaces of the wurtzite structure, besides the (11À20) surface. It has been studied extensively both at the experimental 10,12 and theoretical levels. 66,67 The experimental measurement of two dimensional energetic properties like the surface formation energy is difficult and it can give ambiguous results because extremely clean materials are needed, in which the uniformity of the exposed surface is assured, which is often not the case.…”

“…8 Its wurtzite and zinc blende polymorphs are the two stable phases under ambient conditions. 9 Several experimental [10][11][12] and theoretical studies 9,[13][14][15][16][17] examined its bulk and surface properties. From a modeling point of view, Wang et al gave a detailed description of the relaxation and the electronic structure of CdSe bulk crystals in both wurtzite and zinc blende phases, as well as the (10À10) and (11À20) cleavage surfaces 13 using an sp 3 semiempirical tight-binding model, and validated their theoretical investigation by comparing their results to bulk optical and X-ray photoemission data.…”