Preparation and characterization of ZnS thin films by the chemical bath deposition method (Conference Presentation)

Preparation and characterization of ZnS thin films by the chemical bath deposition method

In this study, Al/PbO/p-Si thin films were produced using two highly economical and practical methods: chemical bath deposition (CBD) and successive ionic layer adsorption and reaction (SILAR). The structural and optical properties of the produced thin films were examined in detail and the results were compared according to the production methods. XRD analysis revealed the prominent presence of the tetragonal (α-PbO) and orthorhombic (β-PbO) phases of PbO. The crystallite sizes of PbO thin films were calculated using Debye–Scherrer and Williamson–Hall methods. It was determined that the PbO thin film produced by the CBD method had larger average crystallite sizes compared to those produced by the SILAR method (CBD D = 42.93 nm, SILAR D = 35.67 nm from Scherrer’s formula). The formation of the PbO2 crystal phase in the PbO thin film produced by the SILAR method caused the lattice strain to increase from 2.93 × 10–4 to 4.03 × 10–4. It was also observed that the thin film produced by the SILAR method was better crystallized and exhibited less amorphization than the CBD method. The PbO thin film produced by the CBD method exhibited a tightly bound, porous structure composed of rod-shaped or irregularly layered grains. SEM results showed that the surface of the PbO thin film produced by the SILAR method was found to consist of dense micro-spherical aggregates, and had smaller porosities and particle formations than that produced by the CBD method. From the UV–visible light transmittance spectra, the band gap energy was determined for CBD and SILAR and found to be 3.61 eV and 3.75 eV, respectively. Moreover, the electrical and interface properties of the Al/PbO/p-Si MOS Schottky diode, formed using CBD and SILAR methods on p-type silicon (p-Si) substrate, were analyzed in detail. Important parameters such as current–voltage (I–V), differential resistance (Rj), and interface state density (Nss) were examined under dark and illuminated conditions. As a novel result, the electronic performance of the Al/PbO/p-Si MOS Schottky diode produced by the SILAR method is higher than that produced by the CBD method.Graphical abstract

Zinc Sulphide is one of most studied semiconductor with wide band gap (3.5–3.9 eV) versatile material due to its physical and chemical properties. ZnS is a non-toxic material and a suitable candidate to be a buffer layer for heterojunction solar cells. In this study, Zinc Sulphide (ZnS) thin films were deposited by chemical bath deposition technique using Zinc Acetate Dihydrate [Zn (CH3COO)2. 2H2O] and Thiourea [CH4N2S]. The ZnS thin films samples were characterized by UV-Vis NIR Spectroscopy, X-ray diffraction (XRD), Scanning Electron Microscopy (SEM), Energy Dispersive Spectroscopy (EDX), Fourier-Transform Infrared Spectroscopy (FTIR) and Thin-Film Measurement Instrument. FTIR spectra confirmed the presence of ZnS bond in the crystalline thin film. XRD data confirmed the cubic structure of the deposited thin film only when the amount of Thiourea was increased and the complexing agent Hydrazine Hydrate was replaced with Tri-Sodium Citrate. Crystallite size and strain were estimated using Debye-Scherrer model and Williamson-Hall model and lattice constant was estimated using Nelson-Riley plot. Otherwise, XRD showed the amorphous phase. UV-Vis data confirmed ZnS thin films as enough transmittive and it showed higher bandgap. Thin-Film Measurement Instrument was used to measure the thickness of the ZnS thin films. Synthesized ZnS thin films exhibited promising characteristics for using as the buffer layer of the heterojunction solar cells. Highlights • ZnS thin films were prepared successfully by simple, low cost and environment friendly chemical bath deposition method. • XRD measurement confirmed both Amorphous and Crystalline phase of ZnS thin films. • By changing the precursor only can be achieved crystalline phase from amorphous phase of ZnS thin film. • The amount of precursor and deposition conditions can be optimized to produce crystalline ZnS thin film.

Influence of deposition temperature on ZnS thin film performance with chemical bath deposition

Tin oxide (SnO2) thin films were deposited on glass substrate by Chemical Bath Deposition (CBD), Drop-Cast and Dip-Coating method. The thin films were post-annealed at 500°C for 2 hours. The structural, optical, and electrical properties of the SnO2 thin films were investigated by using XRD, FTIR, SEM, EDX, UV-Vis spectroscopy, and Electrometer experiment. The XRD patterns of SnO2 thin films deposited on glass substrate by CBD method, Drop-Cast method and Dip-Coating method showed cubic, tetragonal and amorphous structures respectively. The FTIR spectrum exhibited the strong presence of SnO2 with the characteristic vibrational mode of Sn-O-Sn. The SEM analysis was observed that the surface morphology of the thin films toughly depends on the deposition methods of the SnO2 thin films. EDX measurement confirmed that the thin films are the composition of Tin (Sn) and Oxygen (O2). The optical band gap of SnO2 thin films deposited by CBD method, Drop-Cast method and Dip-Coating method is found to be 3.12 eV, 3.14 eV and 3.16 eV respectively. Thin films deposited by Dip-Coating method showed the highest band gap. The electrical results confirmed that the SnO2 thin films are good conductors and pursued Ohm’s Law. These properties of the SnO2 thin films brand are appropriate for application in solar cell assembly, gas sensor devices and transparent electrodes of panel displays.

ZnS thin films were deposited on indium tin oxide glass substrate using the chemical bath deposition method. The deposited films were characterized by X-ray diffraction and atomic force microscopy. The influence of bath temperature on the structure and morphology of the thin films was investigated at three different bath temperatures of 60, 70 and 80 C in the presence of sodium tartrate as a complexing agent. The XRD results indicated that the deposited ZnS thin films exhibited a polycrystalline cubic structure. The number of ZnS peaks increased from three to four peaks as the bath temperature was increased from 60 to 80 C based on the XRD patterns. From the AFM measurements, the film thickness and surface roughness were found to be dependent on the bath temperature. The grain size increased as the bath temperature was increased from 60 to 80 C.

ABSTRACTPolycrystalline <100 nm thin CdS films deposited by the chemical bath deposition (CBD) method are used as n-type window layer in high efficiency heterojunction CuInSe2, Cu2ZnSnS4, and CdTe solar cells. The major shortcoming of the CdS films is its stability and high sub-bandgap absorption. In the present work, an alternative window layer for the heterojunction solar cells based on cadmium oxysulfide Cd(S,O) thin films formed by the CBD method is described. The ∼100 nm thin Cd(S,O) films formed by co-deposition of CdS with CdO show high >85% optical transmittance over 550-1000 nm region compared to 70% transmission in CdS films. Cd(S,O) film formed with highly conformal coverage showed as direct optical band gap of 2.19-2.09 eV depending on the CdO fraction in the film. The CBD growth of CdS is via controlled release of S2- and Cd2+ ions in an alkaline medium through complexing to prevent CdS or Cd(OH)2 as colloids in the solution phase. In the present method, by altering the substrate conditions we carried out controlled Cd(OH)2 deprotonation reaction to form CdO over the substrate concurrently with CdS to deposit Cd(S,O) films. These films are polycrystalline having wurtzite structure identified by (002), (110) and (112) x-ray diffractions. Formation of Cd(S,O) phase is confirmed by Raman spectra which besides the characteristic CdS 1LO and 2LO modes at 300 and 600 cm-1, also showed Raman lines from CdO at 1094 cm-1 and 943 cm-1 assigned as overtone of 2LO phonon modes at the L or Γ points of the Brillouin zone of CdO.

Effect of substrate and Zn doping on the structural, optical and electrical properties of CdS thin films prepared by CBD method

Chemically grown highly crystalline PbS thin films with ethylenediamine tetraacetic acid complexing agent

The present study employed the spin-coating method for the preparation of nanostructured crystalline zinc oxide (ZnO) thin films on FTO glass substrates. Subsequently, cadmium selenide (CdSe) layers were deposited on the surfaces using two distinct chemical methods: successive ionic layer adsorption and reaction (SILAR) and chemical bath deposition (CBD). The obtained films were then characterized by a variety of analytical methods, including XRD, SEM, AFM, EDX spectroscopy, UV–vis spectrophotometry, and linear sweep voltammetry. The XRD and SEM studies demonstrated that all of the films exhibited a polycrystalline nature, with the crystallinity of the cadmium selenide thin films prepared using the SILAR method exceeding that obtained by the CBD method. The SEM and AFM images revealed the uniformity of the cadmium selenide films on the FTO substrates, with no visible cracks or pores. The EDX spectra confirmed the presence of the expected elements in the thin films. The optical band gaps (Eg) for CdSe prepared with the SILAR or CBD method were determined to be 1.85 and 1.97 eV, respectively.

Photoelectrochemical studies on polycrystalline CdS (chemical bath deposition) and CdSe (chemical bath and electro deposition) thin film electrodes

Since CdS material has a direct and wide band-gap, it is very potential for fabricating photovoltaic devices. Due to its wide band-gap, CdS film can be acted as a window material to combine with Cu(In, Ga)Se₂ film. To obtain a quite uniform, easily scaling-up, and inexpensive sample, the CdS thin film with a thickness of 50 nm was deposited by using chemical bath deposition (CBD) technique. Through varying annealing temperatures and holding times, the electrical and optical properties of CdS film could be obviously improved. By Hall measurements, the carrier concentration of CdS sample S8 annealed at 100°C with 20 min is the maximum and its surface resistivity is the minimum. Summarizing these measuring data, we find that the concentration and the mobility of sample S8 are 2.4×10²¹ cm^-3 and 20.5 cm²/v-s, respectively, and it is very suitable for applying to Cu(In, Ga)Se₂-based solar cell.

Effect of bath temperature on the efficiency and properties of Cu2O/ZnS/ZnO heterojunctions thin film prepared by electrodeposition and chemical bath deposition methods

Low-temperature wet chemical bath deposition (CBD) method is one of the most efficient and least hazardous solution-based techniques which is widely employed to grow ZnO NRs. In CBD method, a seed layer is usually deposited on the substrate. In this paper, high quality ZnO and aluminum doped ZnO (AZO) seed layers are sputtered on the indium tin oxide (ITO) coated glass. In continue, aligned ZnO NRs are grown on the AZO and ZnO seed layers via CBD technique. The effect of the growth time and seed layer on the physical properties of as-grown ZnO NRs are investigated. According to the results, the seed layer plays an essential role on the growth orientation and growth rate of the ZnO NRs. The ZnO NRs grown on AZO seed layer are more aligned rather than ZnO seed layer due to their higher texture coefficients. The relative photoluminescence (PL) intensity ratio of near band emission (NBE) to deep level emission (DLE) (INBE/IDLE) for the ZnO NRs grown on AZO and ZnO seed layers are calculated as 7.45 and 2.62, respectively. To investigate the performance of the as-grown ZnO NRs, near ultraviolet organic light-emitting diodes (UV-OLEDs) using ZnO NRs array as n-type material and poly [2-methoxy-5-(2-ethyl-hexyloxy)-1,4-phenylene-vinylene] (MEH-PPV) conjugated polymer as p-type material have been fabricated. The total concentration of traps (Nt), the characteristic energies (Et) and the turn-on voltages for the devices with the structures of ITO/AZO/ZnO NRs/MEH-PPV/Al (device A) and ITO/ZnO/ZnO NRs/MEH-PPV/Al (device B) are attained 7.65 × 1016 and 7.75 × 1016cm−3, 0.232 and 0.206eV, 23 and 21V, respectively. Moreover, based on the electroluminescence (EL) spectra, the NBE peaks for device A and B are obtained nearly in the wavelengths of 382 and 388nm, respectively. Finally, various charge carrier transportation processes of prepared UV-OLEDs have been studied, systematically.

Nowadays, different production methods of nanoparticles have been developed. Among novel wet-chemical processes, the Chemical Bath Deposition (CBD) method is used to synthesize nanoparticles more easily than the other method. In this investigation, titanium dioxide (TiO2) nanoparticles were synthesized by the Chemical Bath Deposition (CBD) method. Tetraisopropyl titanate (C12H28O4Ti), sodium hydroxide (NaOH) and ethanol were used as initial materials. Appropriate solvents were used for preparation of samples. CBD process was carried out at 50°C for 90 min and the obtained materials washed and then dried at room temperature for 48 hrs. For determining particle size and evaluation of morphological characteristics, X-ray diffraction (XRD) and transmission electron microscopy (TEM) were used. The TEM observation indicated that the average particles size of powder is about 10-30 nm and the shape of product is semi-spherical shape. The final results present that the CBD method is more suitable than the other process because of it showing a low processing cost and fine powders.