Antimony Doped SnO2 Films Research Articles

Influence of electronic excitations on structural, optical and electrical properties of undoped and antimony doped tin oxide thin films

Study reports on the influence of swift heavy ion irradiation (SHII) induced electronic excitations (EEs) on structural, optical and electrical properties of undoped SnO2 (TO) and antimony doped SnO2 (ATO) thin films. EEs in the thin films were induced by 70MeV Si ion irradiation. It is noticed from the structural analysis that the crystallinity of TO and ATO almost remains unchanged upon Si ion beam irradiation. However, morphological studies by atomic force microscopy and scanning electron microscopy show surface modification upon irradiation. Interestingly, transport measurements show that the pristine ATO film possesses high conductivity which further increases upon irradiation for a fluence of 1×1012ions/cm2, followed with drastic decrease in conductivity and carrier concentration at higher fluences of irradiation. Band gap modification in TO and ATO films are also reported with irradiation fluence and found to be in agreement with quantum confinement (QC) model for TO; while with Burstein-Moss shift (BMS) model for ATO films. However, the modifications at higher fluence can be ascribed to the band tail states due to very high disorder in the lattice as revealed by very high value of Urbach energy in corroboration with transmittance investigations, which also exhibits a significant decrease in transmittance in both films at irradiation fluence ≥1×1013ions/cm2.

Influence of film thickness on structural, optical, and electrical properties of spray deposited antimony doped SnO2 thin films

Transparent conducting antimony doped SnO2 thin films with varying thickness were deposited by chemical spray pyrolysis technique from non-aqueous solvent Propan-2-ol. The effect of film thickness on the properties of antimony doped SnO2 thin films have been studied. X-ray diffraction measurements showed tetragonal crystal structure of as-deposited antimony doped SnO2 films irrespective of film thickness. The surface morphology of antimony doped SnO2 thin film is spherical with the continuous distribution of grains. Electrical and optical properties were investigated by Hall Effect and optical measurements. The average optical transmittance of films decreased from 89% to 73% within the visible range (350–850nm) with increase in film thickness. The minimum value of sheet resistance observed is 4.81Ω/cm2. The lowest resistivity found is 3.76×10−4Ωcm at 660nm film thickness.

Studies on optical properties of antimony doped SnO2 films

Antimony doped tin oxide thin films were grown by spray method on microscope glass substrates. The antimony doping was varied from 0 to 4at%. The structural properties of the films were investigated by X-ray diffraction method. The optical transmittances of thin films were measured with UV-Vis-NIR spectrometer in the 300–2000nm wavelength range. A simple analysis according to Swanepoel's method was applied to derive the real and imaginary parts of the complex index of refraction plus film thickness. The dispersion of refractive index was investigated in terms of the single-oscillator Wemple and DiDomenico model and the important oscillating parameters such as the dispersion energy Ed, the oscillation energy Eo, the high frequency dielectric constant ɛ∞ were determined. The analysis of the refractive index has been carried out to calculate the lattice dielectric constant ɛL and the ratio of carrier concentration to the effective mass N/m*. The real and imaginary parts of the electronic dielectric constant and optical conductivity were analyzed. The optical band gap, Eg values of the films were obtained from the spectral dependence of the absorption coefficient, using the Tauc relation.

Analysis of optical and related properties of tin oxide thin films determined by Drude-Lorentz model

In this paper, optical parameters, such as refractive index n and extinction coefficient κ, of tin oxide thin films determined by fitting the measured and simulated optical reflectance spectra, are presented and analysed. Among the various classical dispersion relations for the dielectric function, we use the Drude model combined with the Lorentzian oscillators to get a good fit of R in the measured spectral range. Results on related parameters such as high frequency dielectric constant, plasma frequency, relaxation lifetime, electron density, film thickness and band gap are discussed. Pure tin oxide films deposited at different temperature exhibit the same reflectance behaviour in the entire range while antimony doped films exhibit a deep minimum of reflectance in the visible domain and a maximum in the infrared domain. The results show also that the refractive index and extinction coefficient of antimony-doped SnO2 films increase with the increase of the Sb/Sn ratios. The dispersion of κ of doped films is higher than that the undoped ones in a wide photon energy spectral range while the dispersion of n exhibit an opposite behaviour. The high frequency dielectric constant ε∞ decreased with increasing percentages of Sb in SnO2 and the optical band gap Eg depend on the doping amount. The deposited films present a great reflection in the NIR wavelength region which may originate from the fact that these layers contain many carriers resulting in a large nonstochiometry in the chemical composition. The optically determined film thickness agrees with that obtained by ellipsometry.

Blue Photoluminescence of Sol-Gel Derived SnO<sub>2</sub>:Sb Films

By varying the antimony dopant level in the sol-gel solutions, we prepared a series of antimony-doped SnO2 films on slide glass with the sol-gel technique. The transmission, absorption, photoexcitation and photoemission spectra were measured for the sol-gel derived antimony-doped SnO2 films. Under the 300 nm excitation, near untraviolet emission at 390nm and blue emission at 460 nm were recorded from thermally annealed antimony-doped SnO2 films. The effect of the ionic dopant on the photoluminescent properties of the antimony-doped SnO2 films are discussed.

Effect of dopant incorporation on structural and electrical properties of sprayed SnO2:Sb films

Antimony-doped tin oxide films were deposited by spray pyrolysis technique. The effect of antimony doping on structural and electrical properties was investigated in detail using the x-ray diffraction technique and room-temperature Hall measurements. Antimony doping did not affect the preferred growth along [200] to a considerable extent. These results were analyzed on the basis of structure factor calculations. From the Hall measurements, the lowest electrical resistivity, i.e., 5.2×10−4 Ω cm was observed for the films with a doping level of 2.3 at. % in the solution. This value of electrical resistivity is the lowest reported so far in the case of spray deposited antimony-doped SnO2 films. The grain boundary and ionized impurity scattering were observed to be prevalent in governing the electronic transport of lightly and heavily doped films, respectively.

Preparation and properties of antimony-doped SnO2 films by thermal decomposition of tin 2-ethylhexanoate

Transparent Sb-doped SnO2 films were prepared at 600° C on glass substrates by thermal decomposition of tin 2-ethylhexanoate and antimony tributoxide. The films 100 to 300 nm thick, which are composed of fine particles, were very smooth. The films showed no preferred orientation. The minimum resistivity (2.1×10−2Ω cm) was attained at a concentration of 8 at% Sb on the substrate precoated with SiO2. The transmission of these films was about 80% over a wavelength range from 0.4 to 2.0 μm.

Deposition of improved optically selective conductive tin oxide films by spray pyrolysis

Antimony-doped SnO2 films with a resistivity as low as 9×10−4 Ωcm were prepared by spray pyrolysis. Structural, electrical and optical properties were studied by varying the antimony concentration, film thickness and deposition temperature. About 94% average transmission in the visible region and about 87% infrared reflectance were obtained for antimony-doped SnO2 films by a systematic optimization of the preparation parameters. As the best combination, an average transmission of 88% in the visible region and an infrared reflectance of 76% was possible for the doped SnO2 films.