Sn-doped ZnO Research Articles

Electronic and Optical Properties of Sn-Doped Zno with and without O Vacancy

A systematic study on electronic and optical properties of Sn-doped ZnO with and without O vacancy has been performed using first-principles method. Our results revealed that the band gap of Sn-doped ZnO without O vacancy become narrow, demonstrating as red-shift and the electrons near the Fermi level originates from the delocalized Sn-5s. However, as O vacancy is introduced, Sn-5p states locate near the Fermi level. Furthermore, it is found that the optical absorption edge has been obviously changed after Sn doping in ZnO with and without O vacancy. Interestingly, in the low energy region, one new peak is observed for Sn-doped ZnO with O vacancy, due to the electron transition between Sn-5p and O-2p. The calculated results identify that O vacancy can improve the absorption of the visible light in Sn-doped ZnO.

Efficient UV photosensitive and photoluminescence properties of sol–gel derived Sn doped ZnO nanostructures

In the present work, we report on the UV photosensitivity and photoluminescence properties of Sn-doped ZnO nanostructures fabricated by sol–gel method. The influence of Sn (0, 2 and 5 at.%) on structural, optical and ultraviolet photoconductivity properties has been investigated by X-ray diffraction (XRD), scanning electron microscopy, photoluminescence (PL) and photoconductivity measurements. As evident from XRD, the doping of Sn has a significant impact on the structure of ZnO nanostructures. The energy dispersive X-ray (EDS) analysis for 2 at.% Sn doped ZnO confirms the evidence of Sn in ZnO nanoparticles (NPs). PL spectra of undoped and Sn-doped ZnO samples have strong defects related visible emission, including violet emission at ∼418 nm, blue emission at ∼445 nm, blue–green emission ∼481 nm and green emission ∼525 nm. The introduction of defect levels upon Sn doping facilitates the carrier conduction under UV illumination (λ = 365 nm). Again the extent of Sn is found to affect the UV photoconductivity of nanostructures owing to the increment of resistance of ZnO at higher doping concentration. The variation of photoconductivity of ZnO with Sn concentration is highlighted in terms of appropriate scheme and justifications. Better understanding of the photoconductivity process of ZnO nanostructures upon chemical doping will be useful for the fabrication of realistic optoelectronics devices.

Structure, microstructure and optical properties of Sn-doped ZnO thin films

Transparent and conductive Sn–ZnO films were successfully doped up to higher concentration of 10wt% by spray pyrolysis on glass substrates. Structural, microstructural, and optical characterizations were carried out. All the films crystallise within the würtzite hexagonal structure, confirming successful Sn doping, but with different preferred orientation depending on Sn concentration. Despite these differences, the thin films show enhanced crystalline properties up to 8% of Sn, in agreement with SEM images that reveal grains with regular shape and sharp edges. In disagreements with reported data, the increase in Sn concentration improves the crystalline properties and increases the grain size, i.e. 20–200nm. It is important to note that only at high doping level of 10%, the crystalline properties are slightly degraded. In line with this observation, the Urbach tail energy of 10% film reaches a value of 145meV which is attributed to a disorder in the film structural and crystalline properties. Finally, the optical band gap was found to increase with increasing Sn up to 6% followed with a slight decrease at higher Sn concentration. The shift in the bad gap energy with Sn doping is discussed in terms of widening due to Burstein–Moss effect and narrowing due to many-body effect. It is found that 4% seems to be the optimal doping concentration for Sn-doped ZnO films, with enhanced crystalline and structural properties, and with a transmittance similar or even higher than un-doped ZnO film.

Preparation of Aligned ZnO Nanorod Arrays on Sn-Doped ZnO Thin Films by Sonicated Sol-Gel Immersion Fabricated for Dye-Sensitized Solar Cell

Aligned ZnO Nanorod arrays are deposited on the Sn-doped ZnO thin film via sonicated sol-gel immersion method. The structural, optical, and electrical properties of the Sn-doped ZnO thin films were investigated. Results show that the Sn-doped ZnO thin films with small grain size (~20 nm), high average transmittance (96%) in visible region, and good resistivity7.7 × 102 Ω·cm are obtained for 2 at.% Sn doping concentration. The aligned ZnO nanorod arrays with large surface area were also obtained for 2 at.% Sn-doped ZnO thin film. They were grown on sol-gel derived Sn-doped ZnO thin film, which acts as a seed layer, via sonicated sol-gel immersion method. The grown aligned ZnO nanorod arrays show high transmittance at visible region. The fabricated dye-sensitised solar cell based on the 2.0 at.% Sn-doped ZnO thin film with aligned ZnO nanorod arrays exhibits improved current density, open-circuit voltage, fill factor, and conversion efficiency compared with the undoped ZnO and 1 at.% Sn-doped ZnO thin films.

Effect of Sn doping on microstructural and optical properties of ZnO nanoparticles synthesized by microwave irradiation method

Pure and Sn-doped ZnO nanostructures have been synthesized by the microwave irradiation method. The influence of Sn loading on the morphology and microstructure was evaluated by using field emission scanning electron microscopy, transmission electron microscopy (TEM), energy-dispersive spectrum analysis techniques, X-ray diffraction, and Fourier transform infrared spectroscopy. A change in the growth pattern, from needle-like particles for pure ZnO to agglomerated spherical crystallites for Sn-doped ZnO, has been observed. TEM observations indicated that the average particle size of the pure ZnO nano needles is in the range of 40–60 nm, whereas on addition of Sn spherical nanoassemblies size lies in the range of 10–21 nm. The pure ZnO and Sn-doped ZnO nanostructures were further characterized for their optical properties by UV–Vis reflectance spectra (DRS) and photoluminescence (PL) spectroscopy.

Structural, Optical, and Improved Field-Emission Properties of Tetrapod-Shaped Sn-Doped ZnO Nanostructures Synthesized via Thermal Evaporation

High-quality tetrapod-shaped Sn-doped ZnO (T-SZO) nanostructures have been successfully synthesized via the thermal evaporation of mixed Zn and Sn powder. The effects of the Sn dopant on the morphology, microstructure, optical, and field-emission (FE) properties of T-SZO were investigated. It was found that the growth direction of the legs of T-SZO is parallel to the [0001] crystal c-axis direction and that the incorporation of Sn in the ZnO matrix increases the aspect ratio of the tetrapods, leads to blue shift in the UV region, and considerably improves the FE performance. The results also show that tetrapod cathodes with around a 0.84 atom % Sn dosage have the best FE properties, with a turn-on field of 1.95 V/μm, a current density of 950 μA/cm2 at a field of 4.5 V/μm, and a field-enhancement factor as high as 9556.

Controllable fabrication and optical properties of Sn-doped ZnO hexagonal microdisk for whispering gallery mode microlaser

We report a controllable method for fabricating hexagonal Sn doped ZnO microdisks. The photoluminescence mechanism of the Sn doped ZnO microdisks is investigated, the defect emission is attributed to the singly charged oxygen vacancy. Under the excitation of a femtosecond pulsed laser with a wavelength of 325 nm, exciton-exciton collision process is clearly demonstrated, and amplified spontaneous emission is further realized under strong excitation. Using the perfect hexagonal symmetric structure of the Sn doped ZnO microdisks, the whispering-gallery mode lasing with high quality factor and fine mode structure is obtained from a single microdisk.

Ethanol Sensing Characteristics of Sn-Doped ZnO Tetrapods Sensor

Sn-doped ZnO tetrapods (T-SnZnO) were successfully synthesized using a simple thermal oxidation reaction method. Zn powder with 20 mol% of Sn powder was used as raw material and synthesized at temperature of 1,000°C under normal atmosphere. FE-SEM images revealed that the T-SnZnO exhibited a four symmetry legs with the length of 1.94±0.42 μm and the width of 260±40 nm. EDS analysis confirmed that the tetrapods contain small amount of Sn. XRD analysis indicated that the tetrapods exhibited a wurtzite hexagonal ZnO structure corresponded to Raman results. The lattice parameters a and c were 3.2494 Å and 5.2057 Å, respectively. The T-SnZnO were fabricated as ethanol sensor and tested with ethanol concentration of 50, 200, and 1,000 ppm at operating temperature between 280°C-340°C by observing I-V curve of the sensors. The sensor response increased as the increasing of the operating temperature and the ethanol concentration. Moreover, the enhancement of ethanol sensor response was observed, and the highest sensor response of 30.4 was detected at 340°C. The sensor response was higher than those of ZnO tetrapods, TiO2-ZnO tetrapods, ZnO nanowires, and TiO2-ZnO nanowires sensors.

Material characteristics and electrochemical performance of Sn-doped ZnO spherical-particle photoanode for dye-sensitized solar cells

The aim of this study was to examine the effects of Sn element on the characteristics and electrochemical properties of ZnO spherical-particle used as dye sensitized solar cells (DSSCs) photoanode. Spherical nanoparticles were synthesized via a polyol mediated precipitation method and four concentrations of Sn–Zn=0, 3, 4, and 5wt.% of photoelectrodes were prepared. Their structures, morphologies, photovoltaic performances and electrochemical properties were studied through XRD, SEM, TEM, J–V, IPCE and EIS. It was observed that the efficiency of dye-sensitized solar cells increased with the addition of Sn element and the SZO4 (Sn–Zn=4wt.%) based DSSC had the highest power energy conversion efficiency of 0.80%, which is greatly increased compared to that of the DSSC based on ZnO (0.28%).

First-principles and experimental studies of the IR emissivity of Sn-doped ZnO

The dielectric function and IR emissivity of Zn1−xSnxO (x=0, 0.0625) were investigated using a first-principles ultra-soft pseudo potential approach based on density functional theory. Pure ZnO and ZnO doped with 6.25 at.% Sn were synthesized by the solid-state reaction method. The crystal structure, morphology, composition, and IR emissivity in the range 3–14μm were characterized by various techniques including X-ray diffraction, scanning electron microscopy, energy-dispersive X-ray spectroscopy, and spectroradiometry. The theoretical and experimental results imply that the IR emissivity of ZnO can be reduced by Sn doping.

Synthesis of tin-doped zinc oxide microrods for gas sensor application

Sn-doped ZnO microrods have been fabricated via the vapor-phase transport method. The as-synthsized samples are characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM) and transmission electron microscopy (TEM). The gas sensors based on the Sn-doped ZnO microrods are very sensitive to ethanol gas, and the sensitivity is about 52.4 against 100ppm ethanol at working temperature of 300°C. The synthesized microrods have high surface-to-volume ratio and large quantity of oxygen vacancy which might be the origin of the high sensitivity for ethanol gas. The results suggest that the Sn-doped ZnO microrods are good candidates for fabricating effective and high performance gas sensors.

Study on Optoelectronic Characteristics of Sn-Doped ZnO Thin Films on Poly(ethylene terephthalate) and Indium Tin Oxide/Poly(ethylene terephthalate) Flexible Substrates

Transparent conductive oxides of Sn-doped ZnO (SZO) films with doping weight ratios of 2.0, 3.0, 4.0, and 5.0 wt % have been deposited on indium tin oxide (ITO)/poly(ethylene terephthalate) (PET) and PET flexible substrates at room temperature by pulsed laser deposition (PLD). Resultant films of SZO on ITO/PET and PET flexible substrates are amorphous in phase. It is found that undoped and SZO films on ITO/PET is anomalously better than films on PET in optical transmittance in the range of longer wavelength, possibly due to the refraction index difference between SZO, ITO films, and PET substrates, Burstein–Moss effect and optical interference of SZO/ITO bilayer films and substrate materials, and furthermore resulting in the decrement of reflection. The lowest electrical resistivity (ρ) of 4.0 wt % SZO films on flexible substrates of PET and ITO/PET are 3.8×10-2 and ρ= 1.2×10-2 Ω·cm, respectively. It is found that electrical and optical properties of the resultant films are greatly dependent on various amount of Sn element doping effect and substrate material characteristics.

Notable shift of ultraviolet intensity on Sn-doped ZnO nanostructure fabricated by sol–gel method

Sn-doped ZnO (SZO) thin films are deposited by sol–gel dip-coating method with Sn content at 0 at.% and 1–15 at.% with an increment of 2 at.%. The structure and luminescence of the films are investigated. X-ray diffraction results indicate that all the SZO samples show preferential orientation along the (002) direction, and the scanning electron microscope exhibits that the surface morphology of the films change from nanoparticles to nanorods with increasing Sn concentration. X-ray photoelectron spectroscopy reveals that Sn exists as valence of +4 in the matrix. The photoluminescence peaks at 381 and 398 nm are observed in all the samples. The ratio of intensity of peak at 381 nm to that of peak at 398 nm differed markedly. The intensity of peak at 398 nm might be due to the response for the Sn atoms, while the intensity of peak at 381 nm is probably related to the quantum size effect.

Optoelectronics and formaldehyde sensing properties of tin-doped ZnO thin films

Sn-doped ZnO thin films were deposited on clean glass substrates using the chemical spray pyrolysis technique. XRD analyses confirm stable ZnO hexagonal wurtzite structure of the films with crystallite size in the range of 20–28 nm. The surface roughness of the films increases on Sn doping, which favors to higher adsorption of oxygen species on the film surface, resulting in higher gas response. Optical studies reveal that the band gap decreases on Sn doping. All the films show near band edge emission, and on Sn doping the luminescence peak intensity has been found to increase. Photocurrent in the 1.5 at.% doped film enhances about three times to that observed in the undoped ZnO film. Among all the films examined, the 1.5 at.% Sn-doped film exhibits the maximum response (∼94.5 %) at the operating temperature of 275 °C for 100 ppm concentration of formaldehyde, which is much higher than the response (∼35 %) in the undoped film. The gas response of the film is attributed to the chemisorption of oxygen on the film surface and the subsequent reaction between the adsorbed oxygen species and the formaldehyde molecules.

Microstructural, Optical and Electrical Properties of ZnO:Sn Thin Films Deposited by Sol-Gel Method

Transparent thin films of Sn-doped ZnO (ZnO:Sn) were deposited onto silica glass substrates by the sol–gel method. The effect of different Sn doping on the crystallinity, structural, optical and electrical properties of ZnO:Sn thin films were investigated by XRD, SEM, UV-VIS spectrophotometer and four-point probe method respectively. Among all of ZnO:Sn thin films in this paper, Sn-doped with 2 at.% exhibited the best properties, the surface demonstrate an accumulative crystallization and hexagonal structure, with a high-preferential c-axis orientation, namely an average transmittance of 90% and the resistivity of 19.6 Ω·cm.

Effects of Sn doping on the growth morphology and electrical properties of ZnO nanowires

This study examines the effects of doping ZnO nanowires (NWs) with Sn on the growth morphology and electrical properties. ZnO NWs with various Sn contents (1–3 at.%) were synthesized using the vapor–liquid–solid method. Scanning electron and transmission electron microscopy analyses showed that all of the Sn-doped NWs grew in a bamboo-like morphology, in which stacking faults enriched with Sn were periodically inserted. We fabricated a hybrid film of InZnO sol–gel and Sn-doped ZnO NW networks to characterize the effects of Sn doping on the electrical properties of the NWs. With increasing doping density, the carrier concentration increases significantly while the mobility decreases greatly. The resistivity remains scattered, which suggests that Sn doping in ZnO is not an effective method for the enhancement of conductivity, since Sn does not readily incorporate into the ZnO structure.

Characterization and Photoresponse Propreties of Sn-doped ZnO Thin Films

Sn-doped ZnO (SZO) thin films were prepared by sol-gel spin-coating method based on zinc acetate dihydrate (CH3COO)2 Zn H2O, Tin (IV) chloride pentahydrate (SnCl45H2O), 2-methoxyethanol (C3H8O2) and diethanolamine ((HOCH2CH2)2NH, DEA.The solution was prepared with various Sn doping content in ZnO assigned at 2%, 4%, 6%, 8% and 10%. All films were spin-coated on borosilicate substrates and annealed temperature at 550°C for 4h in air. The structural properties of the films were characterized by XRD and SEM and the corresponding results indicated the crystalline structure and surface morphology of the films, respectively. UV-VIS transmission spectra was used to determine optical properties of as-prepared. The increasing Sn doping content into ZnO films results to the enhancement in transparency of the films and the observable alternation in their grain size. The photoilluminated current linearly increases with increasing bias voltage indicating the good Ohmic contact of the device. The photoresponse of the device has significant improvement with increasing Sn doping content.

Spin coated (Mx, Zn1-xO), M= Sn, Al nanofibers investigation

Mx, Zn 1-x O), M= Sn, Al nanofibers properties were investigated. Pure and M-doped zinc oxide films were fabricated onto a glass substrate by a facile and low cost spin coating route. X-rays analysis reveals that films crystallize with a wurtzite structure according to (002) orientation. The transmittance in the visible range was as high as 88 % at 550 nm. The doping increased slightly the transmittance, the as-grown films were high transparent in VIS and IR ranges. The optical band gap was a little bit changed by doping. AFM 3D-views revealed that grains were nanofibers with the size of 18.22, 18.23 and 44.27 nm respectively for pure, Al and Sn-doped ZnO films.

Preparation of semiconductor ZnO powders by sol–gel method: Humidity sensors

Undoped and Sn-doped ZnO nanopowder samples were prepared by the sol–gel method. The crystalline structure and surface morphology of the samples were analyzed by X-ray diffraction and atomic force microscopy. X-ray diffraction results indicate that the samples exhibit a hexagonal crystal structure. Electrical properties of the samples were measured by two probe method. The activation energies of the ZnO samples for low and high temperatures regions were determined. The optical band gaps of the samples were determined by optical absorption method. It was found that the samples have a direct transition optical band gap and the optical band gap values of the ZnO samples were changed with Sn doping. Quartz crystalline microbalance (QCM) technique was employed to investigate sensor features of the ZnO samples. The humidity sensor properties of undoped and Sn-doped ZnO samples based on quartz crystalline microbalance sensors were investigated. The obtained results indicate that the undoped and Sn-doped ZnO nanopowder samples can be used for humidity sensor applications.

Study on the doping effect of Sn-doped ZnO thin films

Tin doped zinc oxide (ZnO:Sn) thin films were deposited onto Pyrex glass substrates by chemical spray pyrolysis technique starting from zinc acetate (CH3CO2)2Zn⋅2H2O and tin chloride SnCl2. The effect of Sn doping on structural, optical and electrical properties was investigated. The atomic percentages of dopant in ZnO-based solution were y=[Sn4+]/[Zn2+]=0%, 0.2%, 0.6% and 1%. It was found that all the thin films have a preferential c-axis orientation. With increase of Sn doping, the peak position of the (002) plane was shifted to the high 2θ values. ZnO:Sn demonstrated obviously improved surface roughness, reduced average crystallite size, enhanced Hall mobility and reduced resistivity. Among all of the tin doped zinc oxide in this study, films doped with 0.6at.% Sn concentration exhibited the best properties, namely a Hall mobility of 9.22cm2V−1s−1, an RMS roughness of 37.15nm and a resistivity of 8.32×10−2Ωcm.