•CBD-CdSe thin films were successfully prepared for temperatures in the range 0–80 °C.•Phase transformation of CBD CdSe NPs was obtained by varying the growth temperature.•Depending on Temperature ...the particle size can take values in the 7–12 nm range.•CdSe NPs bandgap as function of T show evidence of the effect of the phase transition.•The Raman spectrum for Tbc shows modes related with the disorder of the CdSe lattice.
Structural and electronic properties characterization results show that the crystallographic structure of CdSe films, deposited by chemical bath synthesis, is controlled by the bath growth temperature. The synthesis parameters employed produced a set of nanostructured CdSe films on glass substrates with controlled crystal structure. The effect of bath temperature (Tb) on CdSe films was studied in the 0 ≤ Tb ≤ 80 °C range. The average crystal diameter (AD) of the films lies within the 7 ≤ AD ≤ 12 nm interval, where AD depends on the selected Tb. X-ray diffractograms (XRD) shown that at low Tb values the formation of the hexagonal wurtzite (WZ) is promoted while at the other extreme the cubic zinc-blende (ZB) crystalline structure dominates. It is observed that the WZ → ZB transition occurs at the critical temperature Tbc ~ 40 °C. The AD in each films for CdSe-NP’s was obtained from XRD analysis employing the Scherrer-Debye formula. The values of the lattice interplanar spacing (IS), determined from XRD analysis, as function of Tb increases continuously except at temperatures around Tbc where a local minimum is observed. The presence of stress acting on CdSe NP’s is identified by correlating the IS values with the crystalline structure: compression occurs for 0 ≤ Tb ≤ 40 °C, and tension for 50 ≤ Tb ≤ 80 °C. The band gap energy, obtained from optical absorption spectra, decreases monotonically but a local minimum is observed at Tbc = 40 °C. Results from Raman spectroscopy show that the CdSe Raman LO-mode hardens for Tbc as consequence of the WZ ↔ ZB structural transition.
•CdS was successfully doped with gold synthesized by Chemical Bath Deposition.•The incorporation of gold into the CdS lattice reduces the nanoparticle size.•Photoluminescence shows excitonic ...radiative emissions due to nanoparticles.•High resolution XPS spectra of CdS and CdS-Au films confirm their formation.•HRTEM micrographs of CdS and CdS-Au films confirm their nanocrystallinity.
In this work highlights the modifications of the crystalline structure and properties of the nanostructured cadmium sulphide (CdS) thin films, including gold quantum dots grown to form a hybrid metal-semiconductor system. By means of chemical bath deposition (CBD) good quality thin films are obtained, with the advantage of doping in-synthesis with no required additional steps. Film thicknesses around 100 nm were determined by ellipsometry. The binding energies of elements in the CdS and CdS-Au samples were measured by X-ray photoelectronic spectroscopy (XPS). The materials crystalline structure was studied by X-ray diffraction (XRD). A change from disperse like-single-crystalline (highly oriented) CdS NP’s films to monodisperse CdS NP’s–Au QD’s like-single-crystalline samples was observed. This behaviour was confirmed by TEM micrographs. The samples properties pass from an intermediate quantum confinement regime (IQCR) in CdS to a strong one (SQCR) in CdS-Au. The Raman vibrational spectra allowed the analysis of the phonon emissions in CdS, where the Raman shift gives structural information and confirms the effects of IQCR in CdS and the SQCR in CdS-Au. The optical UV–Vis characterization describes the effect of the structural modifications, with an optical band gap shift at higher energy in the CdS-Au sample related to the SQCR. Photoluminescence (PL) measured at room-temperature shows a decrease of PL intensity in CdS-Au film due to via defects-recombination, with respect to that in CdS. This fact is interpreted as an effect of a decreasing of surface defects due to passivation by the Au presence.
•Thin films of high crystalline quality were obtained by chemical bath deposition.•Polycrystalline thin films obtained using ammonia nitrate as complexing agent.•Galena and Lanarkite phases were ...obtained using polyethyleneimine complexing agent.•The thin films of chemical-bath-deposition lead sulphide present quantum confinement.
This work presents the structural characterisation of PbS nanofilms deposited by the chemical bath deposition technique at 70±2 °C using Polyethyleneimine, Triethanolamine and Ammonium nitrate as complexing agents, which allow a controlled and constant ion by ion reaction in aqueous medium whose chemical bath reactions take place in basic solutions with typical pH values 9–12, distinguishing the complexes obtained by their thermodynamic stability and kinetic stability. The PbS fundamental stretching frequencies were determined by Fourier transform infrared spectroscopy. X-ray photoelectron spectroscopy gives the relative atomic composition and identification of the most intense photoelectron transitions S2p (164 eV) and Pb4f 7/2 (137.34 eV) for the PbS-Nitrate film, which are associated with the Pb (II) oxidation state. The shift to higher binding energies, Pb4f7/2 (139.01 eV) for PbS-Polyethyleneimine and PbS-Triethanolamine show the presence of PbO2 with oxidation state Pb (IV). X-ray diffraction analysis and Raman spectroscopy reveal that PbS deposited nanofilms had pure cubic galena crystalline phase when ammonium nitrate was used as complexing agent, with the Polyethyleneimine complexing agent, the formation of cubic PbS in cubic phase with monoclinic Lanarkite Pb2(SO4)2 traces were observed. Finally, using Triethanolamine as complexing agent, cubic phase PbS with orthorhombic Anglesite and lead oxide (x∼1.57) traces were found. The surface morphology of the samples was obtained by High Resolution Transmission Electron Microscopy. The thin films show three direct band gaps, around 0.77–0.78 and 0.84–0.88 eV belonged to the mid-trap state caused by –Pb dangling bond and S+2 levels and the band gap energy at 0.91–1.10 eV was attributed to the quantum confinement associated to grain size, which were obtained by transmittance.
In this work, the characterization of the enhanced structural and optical properties of the cadmium sulphide (CdS) nanostructured semiconductor associated with doping with metallic gold ions is ...presented. Thin films of good structural quality were obtained by chemical bath deposition and doped in-synthesis without the need for additional steps required. A controlled thickness of the thin films around 100 nm was confirmed by ellipsometry measurements. The binding energies of the CdS matrix and its interactions with the metallic gold ion were determined by X-ray photoelectron spectroscopy. The crystallinity and crystalline phase of the CdS matrix were studied by X-ray diffraction, obtaining that the predominant crystalline phase was Zinc blende. Furthermore, a change from monocrystalline to polycrystalline structure was observed in the gold-doped films, this behaviour was confirmed by TEM micrographs. In addition to the different levels of quantum confinement promoted by the transition metal. By Raman spectroscopy was confirmed that the predominant crystalline phase is zinc blende, additionally the vibrational Raman spectra allowed the analysis of the phononic interactions of the CdS binary where the Raman shift gives structural information and confirms the effects of quantum confinement. Optical properties were characterized by UV–Vis spectroscopy, which describes the effect of crystalline structural changes with shifts in the optical band gap energy of the evaluated samples with respect to the bulk CdS, related to the different levels of quantum confinement given by dopant metallic gold.
The present study details the changes in photoluminescence properties stimulated by the structural changes in consequence of doping the II–VI nanocomposite thin‐film semiconductor cadmium sulfide ...(CdS) with the IB metallic ion Ag+. The synthesis of the matrix and doped semiconductors was performed using low‐temperature chemical bath deposition (CBD). The doping percentage of the CdS matrix was determined by energy‐dispersive X‐ray spectroscopy (EDS) with a value around 3%. The crystallographic study shows a cubic (1 1 1) preferential growth plane for the undoped material. Both X‐ray and HRTEM characterizations show the presence of a polycrystalline structure for the Ag+‐doped sample. Measurements of particle size from HRTEM micrographs confirm quantum confinement with a reduction of the average particle size from 5.46 to 4.12 nm in the doped sample. The photoluminescence study shows intense downshifted emissions in the green range of the visible spectrum. This could be due to the shallow electron traps formed by crystalline defects in the lattice, which are induced by the metallic ion. This study also shows higher‐energy emissions due to the decrease of the particle size below the effective CdS exciton Bohr radius.
Ag+ doping induces novel optical effects on the nanostructured semiconductor cadmium sulfide (CdS). The nanocomposite was obtained by chemical bath deposition (CBD). This technique allows in‐synthesis doping which promotes structural modifications stimulating luminescent emissions not possible in the undoped material.
We present the structural and optical characterization of cadmium selenide sulphur (CdSe1-ySy) deposited by chemical bath deposition (CBD) technique at low-temperature (20 ± 2 °C). The sulphur molar ...fraction is varied from 0 to 42.13%. The chemical stoichiometry is estimated by energy-dispersive X-ray spectroscopy (EDS). The CdSe1-ySy shows hexagonal wurtzite crystalline phase, which was found by X-ray diffraction (XRD) analysis and it was confirmed by Raman spectroscopy. The average grain size of the CdSe1-ySy films was ranged from 1.20 to 1.68 nm that was determined by Debye-Scherrer equation from W(002) direction and it was confirmed by high resolution transmission electron microscopy (HRTEM). This average grain size indicates a high quantum confinement because of it is smaller than the Bohr radii of CdS (2.8 nm) and CdSe (4.9 nm). Raman spectra show two dominant vibrational bands about 208 and 415 cm−1 associated at CdSe-1LO-like and CdSe-2LO-like. By transmittance measurements at room temperature are found that the optical band gap energies vary from 1.86 to 2.16 eV in the range of investigated sulphur molar fraction. Room temperature photoluminescence shows radiative bands in the visible range and a dominant band in the UV range, approximately 3.0 eV, which can be associated with a radiative transition, bound exciton to donor impurity.
•CdSeS nanofilms were deposited by CBD at low-temperature on corning glass.•It has investigated the S molar fraction effect on structure properties of CdSe1−ySy.•The CdSeS grain size varied from 1.199 to 1.683 nm as function of the S molar fraction.•CdSeS had good optical properties as was obtained by 300 K photoluminescence.
Undoped cadmium selenide nanoparticles (CdSe-NP's) were grown on glass substrates by chemical bath synthesis (CBS). The particle size was controlled by means of the bath temperature (Tb), which was ...chosen within the interval 0–80 °C. X ray diffraction patterns indicate that CdSe-NP's grow in the hexagonal wurtzite (WZ) crystalline phase for low Tb values and in the cubic zinc-blende (ZB) structure for higher ones. The WZ → ZB transitions occurs at the critical temperature Tbc ≅ 40 °C. Considering the CdSe-NP's like spheres as an approximation, the average size, calculated by using the Scherrer formula, is in the range 7.0–12.2 nm. The Arrhenius plot of the natural logarithm of the diameter versus the inverse of the absolute temperature (Tb + 273.6 K) reveals two slopes which were identified as activation energies related with two thermally activated processes of the growing NP's phases. The photoluminescence spectra show, in general, three type of emissions, which were associated with the more probable electronic transitions: a) near band edge emission, b) donor or acceptor level-band, c) donor-acceptor (DAP). The spectrum when Tb = 40 °C shows more PL bands, that is because the DAP band splits in two bands. This splitting has been associated to the presence of tetrahedral and octahedral Cd-interstitial donor levels in ZB and WZ CdS, respectively, when mixed phases are present in the material at the critical temperature of phase transition.
It presents the characterization of rare earths (Eu,Ce)-doped CdS nanofilms that were synthesised by the growth technique chemical bath deposition (CBD) at the reservoir temperature of 70±2°C. The ...doping of CdS with rare earths is performed by varying the synthesis time from 60 to 135 min. The rare earths molar concentration was range from 0.0≤x≤3.5, which was determined by energy dispersive X-ray spectroscopy. X-ray diffraction (XRD) analysis and Raman scattering reveal that CdS nanofilms showed the zinc blende (ZB) crystalline phase. The CdS average nanocrystal size was ranged from 1.84 to 2.67 nm that was determined by the Debye–Scherrer equation from ZB (111) direction, which was confirmed by transmission electron microscopy. Raman scattering shows that the lattice dynamics is characteristic of bimodal behaviour and the multipeaks adjust of the first optical longitudinal mode for the (Eu,Ce)-doped CdS, which denotes the Raman shift of the characteristic peak about 305 cm−1 of the CdS nanocrystals. The CdS nanofilms exhibit a direct bandgap that slightly decreases with increasing doping, from 2.50 to 2.42 eV, which was obtained by room temperature transmittance. The room-temperature photoluminescence of CdS shows the band-to-band transition at 2.88 eV, which is associated to quantum confinement and a dominant radiative band at 2.37 eV that is called the optical signature of interstitial oxygen. The Eu3+-doped CdS photoluminescence shows the dominant radiative band at 2.15 eV, which is associated to the intra-4f radiative transition of Eu3+ ions that corresponds to the magnetic dipole transition, (5D0→7F1). For the Ce3+-doped CdS the dominant radiative transition, at 2.06 eV, is clearly redshifted, although the passivation of the CdS nanofilms by Ce was approximately by a factor about 21 for the best results.
Pb
2
+
-doped CdS nanofilms are prepared using the growth technique chemical bath deposition (CBD) under optimum conditions lead acetate at the reservoir temperature of 20 ± 2 °C. The Pb
2+
molar ...concentration was in the range 0.0 ≤
x
≤ 0.19.67, which was determined by energy-dispersive X-ray spectroscopy (EDS). The X-ray diffraction results show that the films are of PbS–CdS composites with individual CdS and PbS planes. The X-ray diffraction (XRD) analysis and Raman scattering reveal that CdS-deposited films showed the zincblende (ZB) crystalline phase. The average grain size of the CdS films ranged from 1.21 to 6.67 nm that was determined by the Debye–Scherrer equation from ZB (111) direction, and it was confirmed by high-resolution transmission electron microscopy (HRTEM). Raman scattering shows that the lattice dynamics is characteristic of bimodal behaviour and the multipeaks adjust of the first optical longitudinal mode for the Pb
2+
-doped CdS denotes the Raman shift of the characteristic peak in the range of 305–298 cm
−1
of the CdS crystals, which is associated with the lead ion incorporation. The films exhibit three direct bandgaps, ~2.44 eV attributed to CdS; the other varies continuously from 1.67 to 1.99 eV and another disappears as Pb
2+
molar fraction increases.
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