Al-doped SnO2 Research Articles

Effect of single Al2O3 cycle insertion with various positions in SnO2 thin films using atomic layer deposition

We used atomic layer deposition (ALD) to evaluate the effect of single Al2O3 cycle insertion at various locations on SnO2 and Al-doped SnO2 thin film transistors (TFTs). The ALD process was used to deposit the SnO2 thin film in 67 cycles (5 nm thickness). The position of the Al doped layer of Al-doped SnO2 was controlled by inserting a single Al2O3 cycle into the 56th, 34th and 12th cycles out of 67 cycles. The inserted Al doping layer was analyzed by secondary ion mass spectrometry (SIMS). Crystallinity and thickness of SnO2 and Al-doped SnO2 were measured using transmission electron microscope (TEM). Al-doped SnO2 thin films were prepared at different single Al2O3 cyclic positions for use as channel layers. XPS analysis showed that the oxygen vacancies within the film ranged from 32.8% to 41.6%. Also, the carrier concentration varied from 1.44 x 1016 to 2.80 x 1020 cm−3 depending on the Al doping position based on Hall measurements. In addition, the field effect mobility and on/off current ratios ranged from 1.4 to 8.1 cm2/Vsec and from 5.29 x 102 to 1.56 x 107, respectively. Lastly, the threshold voltage varied from −6.56 to 11.60 V. Overall, SnO2 and Al doped SnO2 channel layers deposited using atomic layer deposition were adjusted to exhibit switching characteristics by inserting a single Al2O3 cycle based on position.

Alternative Electron Transport Layer Based on Al-Doped ZnO and SnO2 for Perovskite Solar Cells: Impact on Microstructure and Stability

The stability of perovskite solar cells (PSCs) is currently a hot topic, but the investigation as well as the understanding of the degradation mechanisms remain incomplete. We present the intrinsic...

Electro-optical performance of liquid crystal device based on Al-doped SnO fabricated by sol-gel process

ABSTRACTWe demonstrated uniform LC alignment on IB-irradiated aluminium tin oxide (AlSnO) by controlling the annealing temperature. Physico-chemical analyses were carried out to determine the surface modification and uniform LC alignment mechanism as a function of the annealing temperature. IB irradiation induced the breakdown of the chemical bonds of AlSnO, preserving its anisotropic characteristics along the direction of IB irradiation, allowing for uniform alignment of the LC molecules on the reformed surface. However, at annealing temperatures under the boiling point of the solvent, residual solvent remained on the surface, thereby prohibiting uniform LC alignment. Moreover, we obtained good optical transmittance in the visual region and good electro-optical performance. Therefore, the IB-irradiated AlSnO film annealed above 200°C exhibited good potential as an alternative candidate for LC display applications.

Tailoring the Post-Etching of Room-Temperature-Fabricated H and Ti Co-Doped ZnO Films for Efficient Harvested Light Trapping

Chemical etching is widely applied to texture the surface of sputter-deposited zinc oxide films for efficient light-scattering in silicon thin-film solar cells. Based on experimental findings from our previous studies, two types of experimental techniques, a combination of HCl/NaOH and NaOH/HCl etching modes as well as a multi-step etching process, were considered to improve the light-trapping ability of room-temperature-deposited H and Ti co-doped ZnO (HTZO) films. The effects of the employed experimental procedures on the optical, electrical, and morphological properties of the HTZO films were systematically investigated. After optimization, higher haze values of 96.2%, 90.6%, and 74% at 550 nm, 800 nm, and 1100 nm, as well as a higher average haze value of 90.1% in the range of 400–1100 nm were achieved, which are better than those of the reference conventional HCl-etched Al-doped ZnO (AZO), high-light-trapping AZO, and SnO2:F films. These findings reveal a method to develop high-performance ZnO films for the front electrodes in high-efficiency Si thin-film solar cells.

The Effect of Al Doping on the Sensitivity of SnO2 Films Prepared by Chemical Spray Pyrolysis

Pure and Al-doped SnO 2 as gas sensors with properties characteristics provoking gas sensitivity were used for measuring CO 2 atmospheres. In this paper we discussed the optical properties of undoped and Al (each 3, 5 and %) doped SnO 2 thin films were synthesized by spray pyrolysis on glass substrate. The samples were characterized using X-ray diffraction (XRD) and gas sensitivity. The XRD analysis reveals that the Al dopants were substituted into rutile SnO 2 nanoparticles without forming any secondary phase. The average particle size of the samples was increasing with increasing Al concentration. From XRD and AFM micrograph it was confirmed, the grain size in the range of 22.4-34.4 nm. The study reveals polycrystalline structure with prominent peaks. In particular, 7% Al-SnO 2 films have a higher sensitivity (30%). Keywords: Structural, gas sensitivity properties, Aluminum (Al) doped , Tin oxide (SnO2) nanocrystal. DOI : 10.7176/APTA/76-02 Publication date :March 31 st 2019

Tin Oxide Based Nano Electroceramics Obtained from Sol–Gel Process: The Modified of the Structural and Opto-Electrical Properties with the Al Doping

Nano electroceramic samples of undoped and Al doped SnO2 were synthesized by the sol–gel calcination process. The structural, morphological, electrical and optical properties of samples were characterized. X-ray diffraction analysis results confirm that all of the synthesized nanopowders are polycrystalline with a tetragonal structure. The crystallite size values of the prepared nanocomposites were calculated in the range of 21.32–34.33 nm. The values of crystallite size indicate that the prepared powders have nanostructure. The grain size and morphological parameters of the undoped and Al-doped SnO2 nanopowders calculated. AFM measurements suggest that Al dopants ratio could be an effect to control surface parameters of the SnO2 nanomaterials. The optical band gap (Eg) of prepared nanomaterials were calculated using Tauc plot method for the various atomic ratios of Al. The calculated Eg values for samples are found to be in the range from 3.51 to 3.69 eV. The electrical conductivity of undoped and Al doped Tin oxide nanopowders were carried out at the temperature range from 290 to 420 K. It demonstrates that the electrical conductivity at room temperature and the activation energy of samples increase with the Al doping. The obtained results suggest that the structural, morphological, optical and electrical properties of SnO2 based nanomaterials can be controlled and changed with Al content.

Charge imbalance induced oxygen-adsorption enhances the gas-sensing properties of Al-doped SnO2 powders

In order to evaluate the effect of Al on the enhancement of the sensor performance of SnO2 prepared at a low sintering temperature, the Al-doped SnO2 powder was prepared by a chemical co-precipitation method and sintered at a temperature of 400 °C. The gas-sensing response to ppm-level ethanol was investigated. The results showed that the gas-sensing response increased with an increase of the Al/(Al + Sn) molar ratio, and exhibited a maximum response at a molar ratio of 19%, then decreased drastically. A new possible influence mechanism is therefore proposed that, with the increase of Al/(Al + Sn) molar ratio, Al3+ ions form at first an interstitial solid solution in the SnO2 lattice, which causes a charge imbalance of the Al-doped SnO2 grains, and enhances the oxygen-adsorption onto the surface of SnO2 grains, thereby resulting in an improvement in the gas-sensing performance. At the molar ratio greater than 19%, excess Al3+ ions deposit on the surface of the SnO2 grains, which reduces the chance of contact between ethanol and the adsorbed oxygen, thereby reducing the gas-sensing performance.

Metal-Oxide Nanoparticles with a Dopant-Segregation-Induced Core–Shell Structure: Gas Sensing Properties

Gas sensors made from high-surface area metal-oxide nanoparticles are susceptible to thermal degradation caused by grain growth and coalescence during service at high working temperature. Therefore, it is crucial to develop an effective strategy to control the rate of grain growth of these nanomaterials without compromising the sensitivity. This paper reports synthesis and characteristics of Al-doped SnO2 nanomaterials with a dopant-segregation-induced core (dopant-free)/shell (dopant-rich) structure to improve the material stability and optimize the gas sensing sensitivity. High-temperature (1100 °C) annealing of a polymer precursor derived Al-doped SnO2 results in the formation of an Al-rich shell because of dopant migration driven by strain and electrostatic interaction energy. Attributed to the solute drag effect, the SnO2 samples with an Al-rich shell show smaller crystallite size and a lower level of coalescence than the pure SnO2, leading to notable enhancement in H2 sensitivity (10×) for the SnO2 ...

Low temperature detection of ammonia vapor based on Al-doped SnO2 nanowires prepared by thermal evaporation technique

ABSTRACTWith the growth of nanotechnology during the last few decades, development of novel materials, devices, or other structures possessing at least one dimension in nanoscale has found immense attractions for functional applications. The present work reports the in situ synthesis and ammonia-sensing behavior of pure and Al-doped SnO2 nanowires (NWs) to study the effect of Al3+ incorporation on host SnO2 lattice. The Al-doped SnO2 NWs are deposited by a catalyst-free simple evaporation–condensation method. The average diameter of the NWs ranges within 160–250 nm. We investigated sensitivity, repeatability, and response/recovery time of the as-deposited doped sensor. Responses at five different concentrations (10, 25, 50, 100, and 200 ppm) were investigated by varying the temperature (150–300°C range). The minimum and maximum sensitivity for Al-SnO2 NWs was found to be 35% (10 ppm and 150°C) and the maximum as 73% (200 ppm and 300°C), which is considerably higher than the pristine SnO2 nanostructures. The resistance transients were very sharp and prominent, taking less than 6 s for 90% response. The sensitivity of Al-SnO2 NWs to NH3 vapor witnessed a substantial increase due to the creation of additional oxygen vacancies at the surface of SnO2.

Investigation of hydrogen sensing properties of graphene/Al–SnO2 composite nanotubes derived from electrospinning

Graphene-based device/sensor made of multifunctional nanomaterials is an emerging technology due to its huge impact on the engineering materials. Herein, we report the synthesis of pristine SnO2, Al-doped SnO2 (Al–SnO2), and graphene-embedded Al–SnO2 (G–Al–SnO2) nanotubes by one-step electrospinning method and studied their physical and gas sensing characteristics. The synthesized tubular structure was confirmed by scanning electron microscope (SEM) and transmission electron microscope (TEM). Structural, chemical binding, pore size, and chemical composition/elemental states were estimated by the X-ray diffraction, Raman, BET, and X-ray photoelectron spectroscopy, respectively. The performance of the gas sensing based on SnO2, Al–SnO2, and G–Al–SnO2 materials for H2 detection was investigated, and the G–Al–SnO2 composite nanotubes exhibit the superior sensitivity at 300°C. The sensing response reaches about 23.8 at H2 concentration of 100ppm with a shorter response time of about 2.2s and recovery time of about 1.4s. The gas sensing performance of the G–Al–SnO2 nanotubes is much better than that of the pristine SnO2 and Al–SnO2 nanotubes, which is probably attributed to the relatively smaller diameter of about 100nm, better thermal and electronic conductivity, and relatively high oxygen vacancy, induced by graphene and Al-doping. The prepared H2 sensor is a simple, compact and highly sensitive, which holds high promising in many fields.

Growth and Optical Properties Investigation of Pure and Al-doped SnO2 Nanostructures by Sol-Gel Method

SnO2 nanoparticles with different percentage of Al (5%, 15%, and25%) were synthesized by sol-gel method. The structure and nature of nanoparticles are determined by of X-ray diffraction analysis. Also, morphology of the samples is evaluated by SEM. Moreover, the optical properties of the samples are investigated with UV-Visible and FT-IR. The XRD patterns are indicated that all samples and incorporation aluminum ions into the SnO2 lattice have tetragonal rutile structure. The crystalline size of nanoparticles is decreased with increasing the Al percentage. The SEM results confirmed that the size of nanoparticles decreases with increasing the Al percentage. Also, FT-IR and UV-Visible results showed that the optical band gap of nanoparticles increases with the increasing the Al percentage. Finally, we have used the EDX analysis to study the chemical composition of the products. Pure tin and oxygen have been observed. The doped samples showed the existence of Al atoms in the samples of the crystal structure of SnO2.

The influence of doping power on the properties of Al-doped SnO2 films deposited by reactive magnetron co-sputtering

ABSTRACTAl-doped SnO2 films were deposited by reactive magnetron co-sputtering on Si (100) and glass substrates using Al and SnO2 target. The structure, surface morphology, electrical, optical and photoluminescent properties of films were investigated. With the increase of doping power, the shift of peaks was observed in XRD spectrum, indicating that Al atoms have been incorporated into SnO2 lattice successfully. Meanwhile, the grain size of the Al-doped SnO2 thin film is much smaller than that of the un-doped SnO2 thin film. The average transmittance of the films decreases from 83% to 75% as the doping power increases from 0 W to 60 W. Moreover, the intensity of the photoluminescence gets weaker due to the decrease of oxygen vacancy.

Performance Enhancements in p-Type Al-Doped Tin-Oxide Thin Film Transistors by Using Fluorine Plasma Treatment

This letter reports on a tin oxide (SnO) thin-film transistor (TFT) with p-type conduction that uses aluminum (Al) doping in the SnO active channel layer. Performance enhancements were further achieved by applying fluorine plasma treatment on the p-type Al-doped SnO channel layer. The effects of the fluorine plasma treatment were also investigated.By tuning the power of the fluorine plasma treatment on the p-type Al-doped SnO channel layer, the optimal TFT device showed a very high on/off current ratio of 2.58×10 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">6</sup> and a low threshold swing of 174 mV/decade, which could be attributed to the passivation effect of the plasma fluorination on the dominant donor-like traps at the SnO/HfO <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> interface, as reflected by the suppression of the hysteresis phenomenon, the low density of interface traps, and the small subthreshold swing. The results indicate that the p-type Al-doped SnO TFT device with fluorine plasma treatment has considerable potential for application in future high-performance displays.

Catalyst-free growth of Al-doped SnO2 zigzag-nanobelts for low ppm detection of organic vapours

In this effort, we report on development of specific sensors dedicated for detection of two of these volatiles, namely ethanol and acetone, below the prescribed statutory limits. Single crystalline Al-doped SnO2 zigzag nanobelt structures were deposited on Si substrate by a catalyst-free thermal evaporation method. The Al-doped SnO2 zigzag nanostructures exhibit high sensitivity and repeatability together with coveted features like fast response and excellent stability. Structural attributes involving the crystal quality and morphology of Al-doped SnO2 zigzag nanobelts were analyzed using X-ray photoelectron spectroscopy (XPS), scanning electron microscopy and transmission electron microscopy. The microscopic images revealed formation of randomly oriented ‘zigzag-like’ nanobelts with characteristic width between 60nm and 200nm and length of 50–300µm. The Al-doping was observed to have a discerning effect in enhancing the sensitivity in comparison to the pristine nanowires by creating excess oxygen vacancies in the crystal lattice, confirmed through XPS and PL spectra.

Experimental Observation and Computer Simulation of Al/Sn Substitution in p-Type Aluminum Nitride-Doped Tin Oxide Thin Film

In this study, the Al3+–Sn4+ substitution reaction in the AlN-doped SnO2 thin films is confirmed by photoluminescence and X-ray photoelectron spectrum analysis. Also, both Al3+–Sn4+ and N3––O2– substitution reactions are verified by computational simulation, Vienna ab initio simulation package (VASP). The computational simulation shows that both Al and N impurity dopants generate an unoccupied band at the upper valence band maximum, which produces holes within the upper valence band region. Both Al3+–Sn4+ and N3––O2– substitution reactions contribute to the p-type conversion of AlN-doped SnO2 thin films. Annealing AlN-doped SnO2 (Al content is 14.65%) thin films at high-temperature (larger than 350 °C), N outgassing would occur and cause the p-type conduction of the annealed AlN-doped SnO2 thin films back to n-type conduction. Yet, in this work, we found that the Al3+–Sn4+ substitution reaction in the high Al-doping concentration of Al-doped and AlN-doped SnO2 (the Al content is between 29% and 33.2%) thi...

Investigating the influence of Al-doping and background humidity on NO&amp;lt;sub&amp;gt;2&amp;lt;/sub&amp;gt; sensing characteristics of magnetron-sputtered SnO&amp;lt;sub&amp;gt;2&amp;lt;/sub&amp;gt; sensors

Abstract. Elevated temperatures and humidity contents affect response, lifetime and stability of metal-oxide gas sensors. Remarkable efforts are being made to improve the sensing characteristics of metal-oxide-based sensors operating under such conditions. Having versatile semiconducting properties, SnO2 is prominently used for gas sensing applications. The aim of the present work is to demonstrate the capability of the Al-doped SnO2 layer as NO2 selective gas sensor working at high temperatures under the presence of humidity. Undoped SnO2 and Al-doped SnO2 (3 at. % Al) layers were prepared by the radio frequency (r.f.) reactive magnetron sputtering technique, having an average thickness of 2.5 μm. The sensor response of Al-doped SnO2 samples was reduced in the presence of background synthetic air. Moreover, under dry argon conditions, Al doping contributes to obtain a stable signal and to lower cross-sensitivity to CO in the gas mixtures of CO + NO2 at temperatures of 500 and 600 °C. The Al-doped SnO2 sensors exhibit excellent chemical stability and sensitivity towards NO2 gas at the temperature range of 400–600 °C under a humid environment. The sensors also showed satisfactory response (τres = 1.73 min) and recovery (τrec = 2.7 min) towards 50 ppm NO2 in the presence of 10 % RH at 600 °C.

Tuning band gap and ferromagnetism in epitaxial Al-doped SnO2 films by defect engineering

The role of acceptor and donor defects in epitaxial Al-doped SnO2 films were systematically investigated. Al doping introduces acceptor defects (AlSn) at low doping concentration while donor ones (Ali) in a concentration range from 8 to 10at%. The band gap is firstly narrowed by hole-doping and then widened by electrons introduced by oxygen vacancies and Ali. Air-annealing absorbs oxygen and makes Al ions transformed from AlSn to Ali, corresponding to a decrease (increase) in the band gap when most Al ions occupy the substitutional (interstitial) sites. The saturation magnetization of the films is enhanced by AlSn doping, with the maximum value in the Sn0.98Al0.02O2 film. The magnetic moment is contributed by the localized holes introduced by AlSn. The existence of the ferromagnetism induced by holes in the film with oxygen vacancy gives a new insight into the behavior of defects in SnO2.

Al-Doped SnO2 Flower-Like Microspheres with Hierarchical Nanorods Synthesized by Hydrothermal Method and H2 Sensing Property

Al-Doped SnO₂ Flower-Like Microspheres with Hierarchical Nanorods Synthesized by Hydrothermal Method and H₂ Sensing Property

Evolution of the doping regimes in the Al-doped SnO2 nanoparticles prepared by a polymer precursor method

In this study, we report on the structural and hyperfine properties of Al-doped SnO2 nanoparticles synthesized by a polymer precursor method. The x-ray diffraction data analysis carried out using the Rietveld refinement method shows the formation of only rutile-type structures in all samples, with decreasing of the mean crystallite size as the Al content. A systematic study of the unit cell, as well as the vicinity of the interstitial position show strong evidence of two doping regimes in the rutile-type structure of SnO2. Below 7.5 mol% doping a dominant substitutional solution of Al+3 and Sn4+-ions is determined. However, the occupation of both substitutional and interstitial sites is determined above 7.5 mol% doping. These findings are in good agreement with theoretical ab initio calculations.

Al-doped SnO2 hollow sphere as a novel anode material for lithium ion battery

SnO2 hollow spheres are doped with different contents of Al (1, 1.5, 2at.%) by a one-step hydrothermal reaction. X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), field emission scanning electron microscopy (FESEM) and Brunauer–Emmett–Teller (BET) are utilized to characterize the structures, components, chemical environments, morphologies and specific areas of the as-prepared samples. The investigation in cycling performances demonstrates that 1.5at.% Al-doped SnO2 hollow spheres exhibit the best cycling stability, with a specific capacity of 443mAhg−1 and coulombic efficiency of 99.1% after 50cycles at 0.1C, much higher than those of the pristine SnO2 hollow spheres and the other Al-doped samples. The improved electrochemical performances of Al-doped SnO2 hollow spheres are attributed to the increase of electronic conductivity and lithium ion diffusion coefficient, and therefore, enhance the reversible capacity and cycling properties.