Electronic structure of CdTe nanocrystals: a tight-binding study

Pérez-Conde, J.; Bhattacharjee, A. K.

doi:10.1016/s0038-1098(99)00064-2

Cited by 28 publications

(27 citation statements)

References 26 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…The calculated E g values are 1.85 and 1.74 eV for relaxed 4.5 nm and 6.5 nm samples, respectively. These results agree well with available experimental data [38].…”

Section: Computational Frameworksupporting

confidence: 92%

“…[37]. With the same model and parameters, P erez-Conde et al [38] reported that the calculated size dependence of CdTe QD's energy gap shows reasonable agreement with available experimental data. The open source NEMO 3-D tool [27] which includes atomic strain effect due to its fundamental atomistic representations is employed to perform the ETB calculations.…”

Section: Computational Frameworkmentioning

confidence: 56%

See 1 more Smart Citation

Deformation-induced blueshift in emission spectrum of CdTe quantum dot composites

Xiao

Fang

Bai

et al. 2017

Composites Part B: Engineering

View full text Add to dashboard Cite

a b s t r a c tPolymer or glass films impregnated with quantum dots (QDs) have potential applications for mesoscale stress/strain sensing in the interior of materials under mechanical loading. One requirement in the development of such nanocomposite sensor materials is the establishment of calibrated relations between shifts in the emission spectrum of QD systems and the input stress/strain on the composites. Here, we use a multiscale computational framework to quantify the strain-dependent blueshift in the emission spectrum of CdTe QDs uniformly distributed in a matrix material under loading of a range of strain triaxiality. The framework, which combines the finite element method, molecular dynamics simulations and the empirical tight-binding method, captures the QD/matrix interactions, possible deformationinduced phase transformations and strain-dependent band structures of the QDs. Calculations reveal that the response of the QDs is strongly dependent on state of input strain. Under hydrostatic compression, the blueshift increases monotonically with strain. Under compression with lateral/axial strain ratios between 0.0 and 0.5, the blueshift initially increases, reaches a peak at an intermediate strain, and subsequently decreases with strain. This trend reflects a competition between increases in the energy levels associated with the conduction and valence bands of the QDs. The deformation-induced blueshift is also found to be dependent on QD orientations. The averaged blueshift over all orientations for the composite under uniaxial strain condition explains the blueshift variation trend observed in laser-driven shock compression experiments. Based on the simulation result, guidelines for developing QD composites as stress/strain sensing materials are discussed.

show abstract

“…The calculated E g values are 1.85 and 1.74 eV for relaxed 4.5 nm and 6.5 nm samples, respectively. These results agree well with available experimental data [38].…”

Section: Computational Frameworksupporting

confidence: 92%

Section: Computational Frameworkmentioning

confidence: 56%

Deformation-induced blueshift in emission spectrum of CdTe quantum dot composites

Xiao

Fang

Bai

et al. 2017

Composites Part B: Engineering

View full text Add to dashboard Cite

show abstract

“…We have developed a symmetry-based TB approach which has been applied to CdTe (Refs. [10,11]) and CdSe (Ref.[12]) NC's as well as CdS/HgS/CdS and ZnS/CdS QDQW's (Refs. [13] and [14]).…”

mentioning

confidence: 99%

Exciton fine structure in semiconductor nanocrystals in the tight‐binding method

Pérez-Conde

Bhattacharjee

Pons

2003

phys. stat. sol. (c)

View full text Add to dashboard Cite

We present a symmetry-based tight-binding (TB) method for calculating the exciton states and optical spectra in spherical semiconductor quantum dots (QD's). Here we focus on the resonant photoluminescence (PL) Stokes shift between the first optically active level and the ''dark" exciton ground state for nanocrystals (NC's). The method has so far been applied to CdSe and CdTe NC of diameter up to 6 nm. The experimental gaps and Stokes shifts show satisfactory agreement with the theoretical results. We have also investigated two series of quantum dot quantum wells (QDQW's). One of them is based on CdS cores which act as energy barrier; HgS well layers are intercalated between the core an additional CdS clad. The second serie of QDQW's is based on ZnS cores and CdS layers as wells. The experimental absorbance edges in the latter are quantitatively reproduced by our model which allows us to confidently predict the corresponding Stokes shifts.The confinement-induced blueshift of the fundamental gap and the discretization of the energy spectrum were early studied in the effective mass approximation (EMA) [1], progressively refined by taking into account the degeneracy of the valence band [2]. Atomistic approaches based on TB [3] or pseudopotential [4] methods provide a better description in the strong-confinement regime, where the QD radius R is smaller than the bulk exciton Bohr radius a B . It was early recognized that the quantum confinement also increases the overlap between the electron (e) and hole (h) charge distributions leading to an enhanced Coulomb interaction. But this energy scales as 1=R, while the confinement energy increases much faster ($ 1=R 2 in the EMA) with decreasing R. Thus, it seemed adequate to treat the e-h Coulomb interaction perturbatively, yielding a small decrease of the optical gap. More recently, the discovery of resonant PL Stokes shifts [5][6][7], attributed to the e-h exchange interaction, stimulated a strong interest in the theoretical investigation of the excitonic fine structure [7][8][9]. We have developed a symmetry-based TB approach which has been applied to CdTe (Refs. [10,11]) and CdSe (Ref.[12]) NC's as well as CdS/HgS/CdS and ZnS/CdS QDQW's (Refs. [13] and [14]). Here we present a short review.

show abstract

“…[87] In a recent study, [88] we presented theoretical results for the structural and electronic properties of CdSe/CdS and CdS/CdSe core/shell nanoparticles that have also been the focus of significant experimental interest, [89][90][91][92] although theoretical studies of these, or related, systems are extremely scarce. [76,93,94] In particular, only one of these studies [94] included any estimate of the energetics and structural properties of these materials and, to the best of our knowledge, no studies have addressed stability and diffusion processes. These processes, which are of importance for degradation, were also addressed briefly in our work.…”

Section: Embedded Structures (Core/shell Systems)mentioning

confidence: 99%

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

et al. 2005

View full text Add to dashboard Cite

An overview of recent density‐functional‐based studies on the structure, surface structure and electronic and optical properties of CdS, CdSe and CdS/CdSe semiconductor nanoparticles is given. In particular, the effects of organisation, embedding and surfactants on the properties of these particles are discussed and illustrated by our own results and literature examples. The surface stabilisation by ligands, core/shell embedding or superstructure organisation combined with electronic structure stabilisation of these nanoparticles directly influences their properties: for stabilised nanoparticles a size‐dependent decay of the lowest optical excitation energy towards the value of the bulk is found, as observed experimentally. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2005)

show abstract

Electronic structure of CdTe nanocrystals: a tight-binding study

Cited by 28 publications

References 26 publications

Deformation-induced blueshift in emission spectrum of CdTe quantum dot composites

Deformation-induced blueshift in emission spectrum of CdTe quantum dot composites

Exciton fine structure in semiconductor nanocrystals in the tight‐binding method

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

Contact Info

Product

Resources

About