Co-doped SnO2 Thin Films Research Articles

Structural, optical and mechanical investigations on pure and Co-doped SnO2 thin films samples

Structural, optical and mechanical investigations on pure and Co-doped SnO2 thin films samples

Elaboration and characterization of Ni and Al co-doped SnO2 thin films prepared by spray pyrolysis technique for photovoltaic applications

In the present study, aluminum and nickel co-doped SnO2 thin films on glass substrates were successfully synthesized using the spray pyrolysis method. This study aims to discover the effect of aluminum (Al) dopant on the structural, optical, and electrical properties of the prepared thin layers. All films deposited (pure, Ni-doped, and Al-Ni-codoped SnO2) were polycrystalline with a tetragonal structure and had a preferential orientation [110], according to XRD analyzes. The optical measurements revealed that all of the synthesized films have good transparency. Depending on the dopant concentration, Ni-Al-codoped SnO2 thin films had a transmittance that ranged between 75% and 85% in the visible and near-infrared spectrum. The electrical measurement confirmed that the electrical resistivity of the elaborated thin films decreases as the Al concentration increases. Therefore, these thin layers are promising for use as a transparent conductive layer in photovoltaic solar cells.

Elaboration and Characterization of Ni and Al Co-Doped Sno2 Thin Films Prepared by Spray Pyrolysis Technique for Photovoltaic Applications

Elaboration and Characterization of Ni and Al Co-Doped Sno2 Thin Films Prepared by Spray Pyrolysis Technique for Photovoltaic Applications

Study of Mn doping on the Structural, Optoelectronic and Photoluminescence Properties of F-Doped SnO<sub>2</sub> Sprayed Thin Films for Optoelectronic Applications

The aim of this work is the production and the characterisation of (SnO2: (Mn, F)) thin films with appropriate optoelectronic properties required for application as ohmic contacts in photovoltaic application devices. Transparent conducting Manganese-fluorine co-doped tin oxide (SnO2: (Mn, F)) thin films have been deposited onto preheated glass substrates using the chemical spray pyrolysis (CSP) method. The ([Mn2+]/[Sn4+]) atomic concentration ratio (y) in the spray solution is varied between 0 and 8 at. %. The structural, the opto-electrical and the photoluminescence properties of these thin films have been studied. It is found that the deposited thin films are polycrystalline with a tetragonal crystal structure corresponding to SnO2 phase having a preferred orientation along the (200) plane. Transmission and reflection spectra reveal the presence of interference fringes indicating the thickness uniformity and the surface homogeneity of the deposited samples. Photoluminescence behaviour of Mn-F co-doped SnO2 thin films was also studied. Photoluminescence spectra reveal the presence of the defects like oxygen vacancies in the materials. In addition, The electrical resistivity, volume carrier concentration, surface carrier concentration and electrical mobility were determined from Hall Effect measurements and the following results were obtained: n-type conductivity in all the deposited thin films, a low resistivity of 1.50×10-4 Ω cm, and a high electrical mobility of 45.40 cm2 V-1 s-1 with Mn co-doping concentration equals to 7 at. %. These experimental results show that the electrical properties of these thin films where greatly improved making them suitable as ohmic contacts in photovoltaic applications devices.

Effect of Co doping on optical parameters of SnO2 thin films

Abstract SnO2 thin films are deposited using spray pyrolysis technique on p-type silicon (Si) substrate by varying the Cobalt (Co) doping ratio from 3 to 5 at % in order to investigate the effect of the doping on the optical parameters of these films. Optical reflectance measurements are performed both for films and substrate. A simple analysis which is created as a combination of three different methods proposed earlier including the effect of the substrate is applied for the optical characterization of Co-doped SnO2 thin films. In addition to thickness, optical parameters such as refraction index and extinction coefficients are also obtained accurately, by applying this created procedure. The optical band gap and Urbach energy of the films are determined from the spectral dependence of the absorption coefficient. The refraction index and band gap energy of SnO2 films are found to be decreasing whereas Urbach energy is found to be increasing with increasing Co doping ratio. The roughness value of Co-doped SnO2 thin films on p-type Si is obtained with such a high precise only from reflectance spectrum.

Enhanced optical transparency and electrical conductivity of Ba and Sb co-doped SnO2 thin films

The highly conducting Ba and Sb co-doped SnO2 (BATO) thin films have been deposited on the glass substrates by cost-effective spray pyrolysis method. The structural, surface, optical properties of the films are investigated as a function of fixed Sb and varying Ba doping concentrations. X-ray diffraction data indicated the films to be polycrystalline with a tetragonal crystal structure. The 2 wt % Ba and 5 wt % Sb co-doped (BATO2) film showed higher average transmittance of about 85% in the visible region and the estimated direct bandgap value was 3.71 eV. The BATO2 film also showed relatively low resistivity of 4.415 × 10−4 Ω cm and sheet resistance of 23.14 Ω/□ than films of other concentration. A temperature-dependent electrical conductivity measurement was carried out to investigate the conduction mechanism of the films by estimating the activation energies using Arrhenius plots. Temperature-dependent electrical properties of the films are also theoretically verified using Kröger–Vink notation. At the higher temperature region, the electrical properties were analyzed in terms of ionic carrier concentration and oxygen partial pressure. These experimental results indicate that the Ba and Sb co-doped SnO2 thin film is a potential candidate for alternative transparent conducting electrode application.

First investigation of structural and optoelectronic properties of F and Ni co-doped SnO2 sprayed thin films

Transparent conducting Nickel-fluorine co-doped tin oxide (SnO2: (Ni, F)) thin films were synthesized chemically by spray pyrolysis technique (CSP) using various Ni concentrations onto hot glass substrates. The [Ni2+]/[Sn4+] atomic concentration ratio (y) in the spray solution was varying from 0 to 3 at. % by a step of 1 at. %. The y variation effect on the structural, optical and electrical properties was studied. It was found from the X-ray diffraction analysis that the films were polycrystalline with tetragonal structure corresponding to pure SnO2 phase having the (200) as preferred growth direction. The optical band gap energy increased from 3.71 to 3.88 eV with increasing the nickel doping concentration in the spray solution. Photoluminescence behaviour of Ni-F co-doped SnO2 thin films was also studied. In addition, electrical resistivity (ρ), volume carrier concentration (Nv), and Hall mobility (μ) were determined from Hall Effect measurements and it was found that all the elaborated thin films had n-type conductivity. The lowest resistivity of 3.16 × 10−5 Ω.cm, and highest Hall mobility of 10.07 × 105 cm2.V-1.s-1 were obtained at a Ni concentration of 3 at. %.

Visible and IR transparent Co-doped SnO2 thin films with efficient electromagnetic shielding performance

Transparent and electromagnetic (EM) shielding Co-doped SnO2 (CTO) thin films were fabricated using ultrasonic-assisted spray pyrolysis deposition. Structural and chemical investigations showed that the Co2+ ions were substitutionally incorporated into the Sn4+ lattice sites of the SnO2 crystal and that the Co concentration increased with increasing the Co source content. The incorporated Co ions acted as a magnetic dopant and as an electrical acceptor to compensate for the free charge carriers in SnO2. Co-doping could modulate the two conflicting efficiencies of the EM shielding performance in the frequency range of 1.5–18 GHz and the infrared transmittance of the SnO2 thin films.

Effect of annealing on the structural, morphological, optical and electrical properties of Al-Zn co-doped SnO2 thin films

ABSTRACTAluminum–Zinc co-doped SnO2 thin films were successfully synthesised onto glass substrates by spray-pyrolysis processing. The structural, morphological, optical and electrical properties of co-doped thin films as deposited at 400˚C, 500˚C, and 600˚C and were studied using various techniques. The XRD results show the films possessed polycrystalline SnO2 with tetragonal rutile structure. The average crystallite size found to be 39 (pure) and 31 nm (co-doped). AFM images showed the annealing temperature effects surface morphology of the films. The transmittance of thin films is up to 80 to 85% in the visible region. The bandgap of the films has been calculated for different annealing temperature and they lie within the range of 3.87 – 4.21 eV. Electrical properties of co-doped thin films were studied through Hall measurement. Furthermore, the prepared co-doped thin films will be useful in optoelectronics and gas sensing applications.

GaN codoping and annealing on the optoelectronic properties of SnO2 thin films

Transparent GaN doped SnO2 thin films were deposited on glass substrates by e-beam evaporation with GaN:SnO2 targets of various GaN weight ratios. The effects of doping level and annealing temperature on the optoelectronic properties of GaN codoped SnO2 thin films were investigated. A conversion from n-type conduction to p-type was observed for GaN doped thin films upon annealing at 440 °C regardless doping level. However, it converted back to n-type conduction at various higher temperatures depending on GaN doping levels. Hole concentration for p-type GaN:SnO2 thin films could be achieved as high as 1.797 × 1019 cm−3 because of the codoping of Ga and N. Hall measurements showed that upon proper thermal treatments, Ga3+-Sn4+ and N3−-O2− substitution reactions occurred in the thin films, which regulated the polarity of conduction and carrier concentration. The formation of No substitutions in the GaN:SnO2 thin films and decomposition of them at certain higher temperature were mainly responsible for the n-p-n conduction transition.

57Fe CEMS study on dilute metal ions codoped SnO2 thin films prepared by spray pyrolysis

Dilute Mn-Fe, Co-Fe and V-Fe codoped tin oxide films prepared by spray pyrolysis were characterized by 57Fe conversion electron Mossbauer spectrometry (CEMS) at room temperature (RT) and at 20 K. Two kinds of paramagnetic Fe3+ species were detected at RT; one doublet 1 (D1) with IS = 0.36–0.37 mm/s, QS = 0.69–0.75 mm/s and LW = 0.32–0.40 mm/s, and another doublet 2 (D2) with IS = 0.31–0.35 mm/s QS = 1.16–1.25 mm/s and LW = 0.46–0.52 mm/s. CEMS at 20 K provided more distinguished doublets than at RT. It is found that especially D2 with relatively small IS and large QS values are influenced by other metal ions codoped in SnO2 matrix, whereas D1 with relatively large IS and small QS has the parameters close to the models of Fe-VO1 and Fe-2VO1-Fe models (Nomura et al. Phys. Rev. B 75, 184411 2007; Mudarra Navarro et al. J. Phys. Chem. C 119, 5596–5603 2015).

Implantation of cobalt in SnO2 thin films studied by TDPAC

Here we report time differential perturbed angular correlation (TDPAC) results of Co-doped SnO2 thin films. Making use of stable Co and radioactive 111In implanted at the Bonn Radioisotope Separator with energies of 80 keV and 160 keV, respectively, it was possible to study the dopant incorporation and its lattice location during annealing. The hyperfine parameters have been probed as a function of temperature in vacuum. Two quadrupole interactions were observed. At high temperatures the dominant fraction for the probe nuclei can be assigned to the Cd-incorporation at the cation substitutional site in a highly disordered structure, obtained after implantation, to high crystallinity for the measurements at 873 K and 923 K. The similarity in TDPAC spectra obtained in undoped SnO gives indirect evidence that In and Co diffuse to different depths during the annealing process. Other interpretations will be discussed.

Achieving selectivity from the synergistic effect of Cr and Pt activated SnO2 thin film gas sensors

The enhanced selectivity due to the synergistic effect of Cr and Pt co-doping on gas sensing properties of SnO2 thin films, is reported. The undoped and Cr/Pt co-doped SnO2 thin films are deposited on the glass substrates by Ultrasonic Nebulized Spray Pyrolysis of Aqueous Combustion Mixture (UNSPACM). The as-deposited films are nanocrystalline in nature with crystallite size ∼3nm, as seen from x-ray diffraction and transmission electron microscopy (TEM). The chemical state of dopants is investigated using x-ray photoelectron spectroscopy. Further, the presence of separate Pt additives in SnO2 film is also confirmed using TEM studies. The gas sensing properties show that although Pt addition enhances the overall sensitivity, it does not improve the selectivity of the sensor. Nonetheless, Cr and Pt co-doped SnO2 films exhibit greater selectivity towards CO gas, while only Cr doped film exhibits selectivity towards NO2 gas at 275°C. The improved selectivity is attributed to the change in carrier concentration, oxygen stoichiometry and specific catalytic effect of the dopant ions.

Investigations on the crystalline, topographic, electrical and optical characteristics of doubly doped (Si + F) SnO2 films deposited using spray pyrolysis technique

Silicon and fluorine (Si+F) co-doped SnO2 thin films were deposited on soda lime glass substrate using the spray pyrolysis technique. The Si and F doping levels were varied from 0–10 and 2.5–10 in steps of 2.5at. %, respectively. Initially the optimum doping level of Si is found (7.5at. %) at which the film exhibits the minimum electrical resistivity value (4.23×10−3Ωcm) and then the doping level of F is varied and it is found to be better at 10at. % on which it offers lower resistivity of 1.96×10−4Ωcm. From the structural studies, it is observed that the preferential orientation of all the films is along (211) plane irrespective of dopant and level of doping, but the peak intensity decreases as the doping level increases. The average transmittance of the all the films is found to be around 75% in the visible region and the optical band gap of the films are found to be in the region of 3.79–3.99eV.

Modification of crystal anisotropy and enhancement of magnetic moment of Co-doped SnO2 thin films annealed under magnetic field.

Co-doped SnO2 thin films were grown by sputtering technique on SiO2/Si(001) substrates at room temperature, and then, thermal treatments with and without an applied magnetic field (HTT) were performed in vacuum at 600°C for 20 min. HTT was applied parallel and perpendicular to the substrate surface. Magnetic M(H) measurements reveal the coexistence of a strong antiferromagnetic (AFM) signal and a ferromagnetic (FM) component. The AFM component has a Néel temperature higher than room temperature, the spin axis lies parallel to the substrate surface, and the highest magnetic moment m =7 μB/Co at. is obtained when HTT is applied parallel to the substrate surface. Our results show an enhancement of FM moment per Co+2 from 0.06 to 0.42 μB/Co at. for the sample on which HTT was applied perpendicular to the surface. The FM order is attributed to the coupling of Co+2 ions through electrons trapped at the site of oxygen vacancies, as described by the bound magnetic polaron model. Our results suggest that FM order is aligned along [101] direction of Co-doped SnO2 nanocrystals, which is proposed to be the easy magnetization axis.

Physical properties of SnO2: Co thin films prepared by chemical spray pyrolysis

In this research, Co-doped SnO2 thin films were prepared by chemical spray pyrolysis technique using SnCl4.5H2O and CoCl2.6H2O, with impurity percentage are (0%-3%-6%-9%) on glass substrates preheated at (450oC) with spray rate 5sec./1min, and thickness (400nm). The investigation of (XRD) indicates that the (SnO2) films are polycrystalline type of (tetragonal), the optical properties and band gap energy was observed and it`s found varied from (3.361-2.855 eV) when increasing in percentage impurity the energy band gap decreased. The Hall coefficient, concentration and mobility of charge carriers of SnO2:Co films studied, and their results observed that the increase in impurity of cobalt caused increase in electrical properties generally.

An investigation of the Nb doping effect on structural, morphological, electrical and optical properties of spray deposited F doped SnO2 films

F and Nb + F co-doped SnO2 thin films were deposited on glass substrates by the spray pyrolysis method. The microstructural, morphological, electrical and optical properties of the 10 wt% F doped SnO2 (FTO) thin films were investigated specifically for niobium (Nb) doping in the range of 0–4 at.% with 1 at.% steps. As shown by the x-ray diffraction patterns, the films exhibited a tetragonal cassiterite structure with (200) preferential orientation. It was observed that grain sizes of the films for (200) and (301) peaks depended on the Nb doping concentration and varied in the range of 25.11–32.19 and 100.6–183.7 nm, respectively. The scanning electron microscope (SEM) micrographs showed that the FTO films were made of small pyramidal grains, while doubly doped films were made of small pyramidal grains and big polyhedron grains. From electrical studies, although 1 at.% Nb doped FTO films have the lowest sheet resistance and resistivity values, the highest figure-of-merit and optical band gap values obtained for FTO films were 16.2 × 10−2 Ω−1 and 4.21 eV, respectively. Also, infrared reflectivity values of the films were in the range of 97.39–98.98%. These results strongly suggest that these films are an attractive candidate for various optoelectronic applications and for photothermal conversion of solar energy.

Structural, electrical and magnetic studies of Co:SnO2 and (Co,Mo):SnO2 films prepared by pulsed laser deposition

Here we report on the structural, optical, electrical and magnetic properties of Co-doped and (Co,Mo)-codoped SnO2 thin films deposited on r-cut sapphire substrates by pulsed laser deposition. Substrate temperature during deposition was kept at 500°C. X-ray diffraction analysis showed that the undoped and doped films are crystalline with predominant orientation along the [101] direction regardless of the doping concentration and doping element. Optical studies revealed that the presence of Mo reverts the blue shift trend observed for the Co-doped films. For the Co and Mo doping concentrations studied, the incorporation of Mo did not contribute to increase the conductivity of the films or to enhance the ferromagnetic order of the Co-doped films.

Room temperature ferromagnetism of Sn1−xCoxO2−δ films fabricated by sol-gel method

Co-doped SnO2 thin films were fabricated by sol-gel method. All the samples have pure rutile polycrystalline structure and exhibit room temperature ferromagnetism (RTFM). Sn1−xCoxO2−δ films spin coated on Si (111) substrate have larger magnetic moment than those on Si (amorphous) substrate. X-ray photoelectron spectra reveal that cobalt exists as Co2+ in samples and Co57 spin-echo nuclear magnetic resonance experiment did not find Co clusters. Interestingly, the magnetic moment per Co atom decreases with the increase in Co content. The results of the annealing at oxidizing and vacuum atmospheres show that oxygen vacancies play a crucial role in producing ferromagnetism, implying that the origin of RTFM can be understood by a bound magnetic polaron model.