Tetragonal SnO2 Phase Research Articles

Growth of Tin Dioxide Nanobelts Via Au-Catalytic VLS Process

Ultra-long (several millimeters) tin dioxide SnO2 nanobelts were prepared by chemical vapor deposition at 850 degrees C. The X-ray powder diffraction (XRD) indicated that the as-prepared sample is tetragonal phase SnO2; field emission scanning electron microscopy (FESEM) reveals the as-prepared SnO2 is uniform nanobelts; transmission electron microscopy (TEM) and high-resolution transmission electron microscopy (HRTEM) studies show the nanobelts is monocrystalline with width of hundreds of nanometers and growth along [101] crystal direction; X-ray energy-dispersive spectrometer (EDS) and photoluminescence (PL) spectrum were used to detail its composition and optical properties. The possible formation mechanism of these ultra-long nanobelts was also proposed on the basis of experiments.

Double dielectric relaxations in SnO2 nanoparticles dispersed in conducting polymer

The tetragonal phase of SnO2 and the conducting form of polyaniline are characterized by x-ray diffraction and Fourier transform infrared spectroscopy. The electrical conductivity and the dielectric properties of tin dioxide (SnO2)-polyaniline hybrid nanocomposites have been investigated as a function of temperature and frequency for different concentrations of polyaniline. Electrical conductivity has been derived from the simple equivalent circuit pertaining to inhomogeneous polycrystalline materials. Grain and grain boundary conductivities follow an Arrhenius type of electrical conduction. The nanocomposites possess an extraordinarily high dielectric constant of about 103. Different conductivities of the grain and grain boundary give rise to a large dielectric constant in nanocomposites. The dielectric loss spectra reveal two peaks in the measured frequency interval for the maximum concentration of the SnO2 nanoparticles. The peaks are ascribed to interfacial polarization and the intrinsic oxygen defects in nanosized SnO2.

Enhancement of Sm3+emission by SnO2nanocrystals in the silica matrix

Silica xerogels containing Sm3+ions and SnO2nanocrystals were prepared in a sol–gel process. The image of transmission electron microscopy (TEM) shows that the SnO2nanocrystals are dispersed in the silica matrix. The X-ray diffraction (XRD) of the sample confirms the tetragonal phase of SnO2. The xerogels containing SnO2nanocrystals and Sm3+ions display the characteristic emission of Sm3+ions (4G5/2 → 6HJ(J = 5/2, 7/2, 9/2)) at the excitation of 335 nm which energy corresponds to the energy gap of the SnO2nanocrystals, while no emission of Sm3+ions can be observed for the samples containing Sm3+ions. The enhancement of the Sm3+emission is probably due to the energy transfer from SnO2nanocrystals to Sm3+ions.

Alcohols and acetone sensing properties of SnO2 thin films deposited by dip-coating

SnO2 thin films were prepared by dip-coating from SnO2 sols of 0.5 and 0.1mol/l. The structure and morphology of the films were analyzed through XRD, UV and AFM methods. The particles in the films were the standard tetragonal phase of SnO2 with spherical morphology. The average size of SnO2 particles was about 87nm (0.5mol/l) and 5nm (0.1mol/l), respectively. The UV absorbance of the films increased linearly with increasing the deposition layers. The sensitivity of thin films to methanol, ethanol, propanol and acetone was detected at room temperature, and the effects of concentration of SnO2 sols on the morphology and sensitivity of the films were investigated as well. With decreasing the sol concentration, the grain size of the particles reduced, the gas sensing properties to acetone and ethanol increased. Such films with small size could detect ethanol as low as 2ppm ethanol. Response and recovery time to methanol, ethanol, propanol and acetone at room temperature were within 30s and 1min, respectively.

Single Crystal SnO2 Zigzag Nanobelts

Zigzag SnO2 nanobelts have been synthesized by evaporating tin grain in air. XRD, SEM, and TEM were employed to characterize the prepared samples. SEM images showed large amounts of zigzag nanobelts with periodic morphology. XRD result showed a pure tetragonal SnO2 phase. HRTEM and SAED revealed a single crystal structure with [010] zone axis on the whole zigzag zone. The zigzag structure is deduced to be formed by shifting the growth direction from [101] to [10] or vice versa. Growing nanobelts along different equivalent directions opens a new avenue for the preparation of novel nanostructured materials.

Synthesis and structural characterization of rutile SnO2 nanocrystals

Nanocrystalline tin dioxide (SnO2) thin films were prepared on glass substrate by pulse laser deposition for the first time. The thin films were characterized for their composition, morphology, and crystalline structure by x-ray diffraction, transmission electron microscopy, and high-resolution transmission electron microscopy. It was found that the thin films consisted only of the tetragonal phase SnO2 with no structural change, and they were well crystallized during deposition. In most cases, SnO2 particles were overlapped, predominantly grown on preferred (101) plane, and connected with two or three neighbors through necks. The average grain size of the as-prepared thin films was about 12 nm. These facts are of great importance for sensor characteristics, since smaller grains and preferred orientation properties provide higher gas sensitivity to the whole thin films. Our findings indicate that the n-type wide-band-gas semiconductor nanocrystalline thin films can be manipulated by using pulse laser deposition techniques, offering new opportunities to control material fabrication.

Atomic Layer Deposition of Epitaxial and Polycrystalline SnO2 Films from the SnI4/O2 Precursor Combination

AbstractThin films of SnO2 have been successfully deposited by atomic layer deposition (ALD) using the SnI4/O2 precursor combination. Depositions were carried out in the temperature range 400–750 °C on SiO2/Si(100) and single‐crystalline α‐Al2O3(012) substrates. The films were found to grow as the tetragonal SnO2 phase (cassiterite), polycrystalline on SiO2/Si(100), and epitaxial on the α‐Al2O3(012) substrates with the in‐plane orientation relationships [010] ∥ [100] and [10$\bar 1$] ∥ [$\bar 1$$\bar 2$1]. In general the growth rate was high, changing from 0.10 nm cycle–1 at 500 °C to 0.12 nm cycle–1 at 750 °C for the α‐Al2O3(012) substrates, and from 0.04 nm cycle–1 at 400 °C to 0.24 nm cycle–1 at 750 °C for the SiO2/Si(100) substrates.

The microstructure and physical properties of thin SnO2 films

Thin polycrystalline SnO2 films were deposited on glass substrates by magnetron sputtering. Electrical, optical, and gas-sensing properties, as well as the structure and phase composition of the films, were studied. The electrical resistance of the films and the concentration and mobility of free charge carriers were determined by the four-point-probe and van der Pauw methods. The band gap and the type of optical transitions in the films were derived from optical absorption spectra. The sensitivity to toxic and explosive gases was measured. The composition, morphology, and crystal structure of the films annealed at 600°C were examined by X-ray diffraction and electron microscopy. The films were found to contain only a tetragonal SnO2 phase and have good crystallinity. The average grain size in the annealed films is 11–19 nm. A model of the electrical conduction in the polycrystalline SnO2 films is discussed.