Seppo Lindroos

Growth of CuS thin films by the successive ionic layer adsorption and reaction method

Abstract The growth of copper sulfide thin films by the successive ionic layer adsorption and reaction (SILAR) method at room temperature and normal pressure was studied. The CuS films were characterized by chemical analysis, XRD, SEM and UV spectroscopy. The growth rate of CuS was proportional to copper precursor concentration. The films were polycrystalline and showed no preferred orientation. The surface of the CuS thin films was rough compared with CdS films, which were used as buffer layer on ITO and glass substrates to enhance the weak adhesion of CuS to oxide surfaces.

SILAR deposition of CdxZn1-xS thin films

Abstract Cd x Zn 1− x S thin films were grown on (100)GaAs by the successive ionic layer adsorption and reaction (SILAR) technique from dilute aqueous precursor solutions. Crystallinity, refractive index and morphology of the thin films were studied as a function of composition and thickness of the films. The Cd x Zn 1− x S films were polycrystalline and cubic. The crystallite size and refractive index of the films increased when the film thickness and Cd concentration in the Cd x Zn 1− x S thin films increased. It was found that tensile stress dominates in thin films when Cd concentration is lower than x ≤0.54 and the change of the residual stress to the compressive one takes place after that. Correlation between the growth mode and residual stress is demonstrated.

Growth of ZnS, CdS and multilayer ZnS/CdS thin films by SILAR technique

Abstract Successive ionic layer adsorption and reaction (SILAR) technique was used to deposit cadmium sulfide (CdS) and zinc sulfide (ZnS) thin films on (100)GaAs. CdS thin films were also grown on ITO-covered glass substrates. Multilayer CdS/ZnS thin films were deposited on glass substrates. The crystallinity of the thin films was characterized by means of X-ray diffraction and they all turned out to be polycrystalline. The thin films looked relatively smooth and homogeneous in scanning electron microscopy (SEM) images. Energy dispersive X-ray analysis (EDX) and Rutherford backscattering spectroscopy (RBS) proved nearly 1 : 1 stoichiometry for the multilayer samples. Thickness of the thin films was measured by RBS and chemical analysis.

Growth of strongly orientated lead sulfide thin films by successive ionic layer adsorption and reaction (SILAR) technique

Lead sulfide thin films were grown at room temperature by the successive ionic layer adsorption and reaction (SILAR) technique on soda lime glass, ITO and Al2O3 covered glass, SiO2, (100)Si and (111)Si substrates. SILAR utilises sequential treatment of the substrate with aqueous precursor solutions. Dilute solutions of lead acetate and thioacetamide were used as precursors for Pb2+ and S2–, respectively. The lead precursor solution also contained triethanolamine (tea) as a complexing agent, with a Pb: tea mole ratio of 1 : 2. On glass the growth rate was 0.12 nm per cycle with 0.2 mol dm–3 lead and 0.4 mol dm–3 thioacetamide solution. The appearance of the films was metallic. X-Ray diffraction studies revealed a strong [200] orientation of the films. According to the Rutherford back-scattering (RBS) and nuclear reaction analysis (NRA) results the films were stoichiometric PbS and contained small amounts of some lighter impurities, possibly O and H. Scanning electron microscope (SEM) images revealed that the films were rather rough and consisted of grains with a diameter approximately corresponding to the thickness of the film.

Growth of ZnS thin films by liquid-phase atomic layer epitaxy (LPALE)

Abstract ZnS thin films were grown by the LPALE method on soda lime glass, ITO- and Al2O3-covered glass and Si substrates. 0.05–0.2M ZnCl2 and Na2S solutions were used as immersion solutions. Immersion time was 20 s. Depending on the concentrations the rinsing time was 100–200 s and the flow rate of water 600–800 ml/min. The growth rate was 0.7–0.8 A/ cycle with concentrations ZnCl2 0.1M and Na2S 0.05M, and 1.7–2.0 A/ cycle with doubled concentrations. The appearance of the films was smooth and no cracks could be detected. The films were polycrystalline with presumably cubic structure and showed slight (111) preferential orientation. The S/Zn ratio was approximately 0.8 and the films contain uniformly distributed oxygen.

Growth of PbS thin films on silicon substrate by SILAR technique

Lead sulfide thin films were grown on (100)Si and (111)Si crystalline substrates by successive ionic layer adsorption and reaction, (SILAR), technique from solution phase at room temperature and normal pressure. The stress development, crystallinity and crystallite size, morphology and roughness and composition of the films were characterized as a function of the film thickness. The PbS thin films were polycrystalline and cubic. The residual stress in PbS was tensile and changed depending on the growth mode and thickness of the PbS films.

Thin multilayer CdS/ZnS films grown by SILAR technique

Abstract Multilayer ZnS/CdS thin films were grown on glass, ITO-covered glass and (100)GaAs substrates by successive ionic layer adsorption and reaction (SILAR) technique at room temperature and ambient pressure. The layers in multilayer thin film structures were nominally 1–6 nm thick and the amount of layers varied so that the total thickness of 100–120 nm was achieved. The films were polycrystalline according to X-ray diffraction analysis and scanning electron microscopy. The interfaces between the separate cadmium sulfide (CdS) and zinc sulfide (ZnS) layers were not sharp, but contained thin Cd x Zn 1− x S solid solution layers. Annealing enhanced the mixing of the different layers and after 50 h at 300°C no separate CdS and ZnS X-ray reflections could be detected. About 20 nm thick layers could be detected as separate fields by scanning electron microscopy.

Growth and Characterization of Zinc Sulfide Thin Films Deposited by the Successive Ionic Layer Adsorption and Reaction (Silar) Method Using Complexed Zinc Ions As the Cation Precursor

Abstract Zinc sulfide thin films were grown by the successive ionic layer adsorption and reaction method on soda lime glass and on indium tin oxide covered glass, using diluted solutions of ZnCl 2 complexed with triethanolamine (TEA) or ethylenediamine as the cation precursor and a diluted solution of Na 2 S as the anion precursor. The growth rate of the ZnS film varied between 0.13 and 0.27 nm/cycle. The refractive indices were from 1.95 to 2.23, and the packing densities were from 72 to 90%. The highest refractive indices and packing densities were found in films grown on indium tin oxide with TEA-complexed zinc chloride as the cation precursor. The Zn:S ratio in the films was from 0.89 to 1.08. According to the X-ray diffraction study, the films were polycrystalline and presumably cubic. The EXAFS studies revealed that the crystallinity of the thin film deposited with TEA-complexed ZnCl 2 was similar to that of the films deposited with ZnCl 2 as the precursor. Annealing slightly improved the quality of the successive ionic layer adsorption and reaction grown ZnS films.

Lateral force microscopy and force modulation microscopy on SILAR-grown lead sulfide samples

In this study lateral force microscopy (LFM) and force modulation (FM) microscopy have been used for investigations on PbS thin films deposited on glass substrates with the successive ionic layer adsorption and reaction method (SILAR). Information of friction and surface elasticity obtained by scanning force microscopy revealed local surface properties of the thin films, which have been used to distinguish thin film constituents from environmental contamination and/or contamination due to the preparation process. Furthermore, these scanning force microscopy (SFM) applications yielded information about the surface coverage which is particularly important in the early stages of film deposition.

Growth of lead selenide thin films by the successive ionic layer adsorption and reaction (SILAR) technique

This paper describes the growth of lead selenide (PbSe) thin films on glass and on ITO-covered glass substrates at room temperature under normal pressure utilising the successive ionic layer adsorption and reaction (SILAR) technique. Aqueous precursor solutions, lead acetate complexed with triethanolamine and sodium selenosulfate, were used for lead and selenide, respectively. The films were found to be metallic and adherent. The properties of the films were characterised by means of X-ray diffraction (XRD), Rutherford back-scattering spectrometry (RBS), nuclear reaction analysis (NRA) and scanning electron microscopy (SEM).