Znx Cd1-x S single-crystal nanoribbons of controlled composition (where 0 ≤ x ≤ 1) can be synthesized by combining laser ablation with thermal evaporation. The nanoribbons exhibit lasing emission that can be continuously tuned within the ranges of 340-390 nm and 485-515 nm. These results suggest that Znx Cd1-x S nanoribbon lasers of pre-selected "tunable" wavelengths between 340 and 515 nm may be achievable by tailoring the value of x.

Wavelength-Controlled Lasing in ZnxCd1–xS Single-Crystal Nanoribbons†

A comprehensive study is reported of the photoluminescence properties of ZnS thin films between 1.6 and 320 K grown by metalorganic molecular beam epitaxy and chemical beam epitaxy on GaAs substrates. Both heavy- and light-hole free excitons were observed at low temperatures with linewidths of 7.0 and 5.3 meV, respectively, as well as donor- and acceptor-bound excitons and free-to-bound recombination along with their longitudinal optical (LO) phonon replicas. The free exciton emission was observed up to 320 K, and enabled the room temperature band gap of ZnS to be unambiguously determined as 3.723 eV. The temperature dependence of the peak position, intensity, and linewidth was well described by the conventional empirical relations and by Toyozawa’s exciton line shape theory. The bound exciton peak positions were found to follow the temperature dependence of the band gap whereas the free-to-bound recombination feature was displaced by (1/2)kT above the band gap energy. Thermal quenching of the donor-bound...

Photoluminescence properties of ZnS epilayers

Structure, composition and optical properties of ZnS thin films prepared by spray pyrolysis

Crystalline zinc sulfide (ZnS) thin films were prepared by chemical bath deposition (CBD) using the mixed aqueous solutions of zinc acetate, thiourea and tri-sodium citrate, where tri-sodium citrate was used as the complexing agent. The thin films were characterized by x-ray diffraction (XRD), scanning electron microscopy (SEM) and optical absorption. The as-deposited thin films were surface homogeneous with pure wurtzite structure and the optical band gap of the film was estimated to be 3.53 eV.

https://iopscience.iop.org/article/10.1088/0268-1242/18/7/313/pdf

Chemical bath deposition of crystalline ZnS thin films

http://www.fst.rnu.tn/lpmc/documents/publications/pub2006/29-06.pdf

Effect of pH on the properties of ZnS thin films grown by chemical bath deposition

Thin films of high-quality ZnS were grown on (001) GaAs and (111) Si substrates by metal-organic chemical-vapor deposition. 2-K reflectivity was used to analyze various samples grown at different temperatures. The spectra show two structures at 3.801 eV corresponding to the free exciton and at 3.871 eV corresponding to the ${\mathit{E}}_{0}$+${\mathrm{\ensuremath{\Delta}}}_{0}$ transition. Theoretical reflectivity spectra were calculated using the spatial dispersion model with two oscillators. Thus, the transverse energies, the longitudinal transversal splitting, the oscillator strengths, and the damping parameters were determined for both the free exciton and the split-off exciton of ZnS. Photoluminescence measurements were also carried out using an excimer laser (308 nm). Both light-hole and heavy-hole excitons were observed, which allow for the determination of the strain that exists in the layer. This strain is due only to the difference between the thermal-expansion coefficients of the GaAs substrate and the ZnS epilayer, and was demonstrated to be a tensile strain. This paper also presents results on the band-gap energy variation as a function of the temperature and photoluminescence spectra when the excitation was varied from weak to very high densities (15 MW/${\mathrm{cm}}^{2}$).

Reflectivity and photoluminescence measurements in ZnS epilayers grown by metal-organic chemical-vapor deposition

We have grown high-purity ZnS layers by metal organic vapour-phase epitaxy onto (100) GaAs and (111) Si substrates using triethylamine dimethylzinc. As is usually reported, the morphology and the crystalline quality assessed by the optical Nomarski microscopy and by double X-ray diffraction are similar on both substrates. However, we demonstrate for the first time, using reflectivity experiments along with a theoretical fit, that the crystalline quality of the sample deposited onto Si substrates is much poorer. This observation is interpreted in terms of antiphase defects related to the lack of polarity of the Si substrate.

Reflectivity analysis of ZnS layers grown on GaAs and Si substrates by metal organic vapour-phase epitaxy

An investigotion of the photoreflectance and photoluminescence spectra of 45 period ZnS-ZnSe strained layer superlattice having well and barrier widths of 3.3 and 3.7 nm, respectively, is reported. Heavy hole (e 1 hh 1 ) and light hole (e 1 lh 1 ) excitons are well resolved in the 2 K photoreflectonce spectrum. The energies of these transitions are calculated within the envelope function framework, generalized to strained layers. The valence and conduction band offsets are the principal parameters in this calculation. Thus, two different approaches are set in competition to determine these quantities. The first is based on theoretical models while the second uses a «semi-experimental» method. The latter method gives a free-standing type-I superlattice with optimal agreement between photoreflectance measurements and theory. Also the importance of a precise knowledge of the exciton binding energy (enhanced because of the reduced dimensionality) for an accurate bond offset determination is shown. This binding energy is estimated for the heavy hole exciton from a variational calculation

Excitonic transitions and band offset calculations in a short period ZnS-ZnSe superlattice

The X-ray diffraction pattern of MOVPE-grown ZnSe/InP epilayers in the thickness range between 0.15 and 2.2 μm shows that the relaxation is obtained for a few monolayers. The splitting between light hole E 1h and heavy hole E hh excitonic transitions is observed at 4.2 K by reflectivity and is explained in terms of thermoelastic strain due to the difference in the thermal expansion coefficients of layer and substrate. In addition photoluminescence is studied and shows neutral-donor-bound-exciton lines I 2 and I' 2 as well as the neutral-acceptor-bound-exciton line I 1

Optical Measurements in MOVPE-Grown ZnSe/InP Epilayers

The optical properties of ZnTe epilayers grown by low-pressure metal organic vapour phase epitaxy on GaAs and GaSb substrates are studied. The layers are grown by using the halide-free triethylamine dimethylzinc adduct and di-isopropyl telluride as zinc and tellurium precursors, respectively. A detailed analysis of the residual strain is offered as a function of layer thickness and substrate nature via reflectivity measurements performed at pumped liquid helium temperature. This is completed by an extensive analysis of near-band-edge photoluminescence spectra in order to discriminate the contribution of residual impurities. Using these precursors ZnTe layers with extremely low contamination rates are obtained.

A. Abounadi

Papers

Reflectivity and photoluminescence measurements in ZnS epilayers grown by metal-organic chemical-vapor deposition

Reflectivity analysis of ZnS layers grown on GaAs and Si substrates by metal organic vapour-phase epitaxy

Excitonic transitions and band offset calculations in a short period ZnS-ZnSe superlattice

Optical Measurements in MOVPE-Grown ZnSe/InP Epilayers

Optical Properties of Wide‐Gap II‐VI ZnTe Epilayers