Tin Interstitials Research Articles

How Halide Alloying Influences the Optoelectronic Quality in Tin-Halide Perovskite Solar Absorbers.

Halide alloying in tin-based perovskites allows for photostable bandgap tuning between 1.3 and 2.2 eV. Here, we elucidate how the band edge energetics and associated defect activity impact the optoelectronic properties of this class of materials. We find that by increasing the bromide:iodide ratio, a simultaneous destabilization of acceptor defects (tin vacancies and iodine interstitials) and stabilization of donor defects (iodine vacancies and tin interstitials) occurs, with strong changes arising for Br contents exceeding 50%. This translates into a decreased doping which is, however, accompanied by a higher density of nonradiative recombination channels. Films with high Br content show a high degree of disorder and trap state densities, with the best optoelectronic quality being found for Br contents of around 33%. These observations match the open circuit voltage trend of tin-based mixed halide perovskite solar cells, supporting the relevance of optoelectronic properties and chemistry of defects to optimize wide-bandgap tin perovskite devices.

Modulation of photoluminescence and optical limiting properties of spray-coated tin oxide thin film through Eu doping

This work reports the effect of Eu doping on the structural, morphological, linear, and nonlinear optical properties of Sn1−xEuxO2 (x = 0 to 0.10) thin films prepared using spray pyrolysis. The films crystallized in tetragonal structure and the crystallite size reduced due to Eu incorporation. The film morphology consisted of evenly distributed dense grains with trapezohedron or bipyramidal shape. The Eu doping reduced the transmittance and energy band gap of the deposited films. The photoluminescence (PL) emission spectra comprised the contributions from both the transitions related to the Eu3+ ions and the defects, such as oxygen vacancies and tin interstitials in the host lattice. The films also showed a near white light emission due to the different defect-related PL emissions. The Z-scan technique revealed the third-order optical nonlinearity shown by the films. Amongst the doped films, Sn0.92Eu0.08O2 films exhibited least optical limiting threshold.Graphical abstract

Effect of erbium on the structural, morphological, and optical properties of SnO2 thin films deposited by spray pyrolysis

In the present work numerous compositions of Er-doped SnO2 thin films were made at 425 °C on a quartz glass substrate using spray pyrolysis method. The powder X-ray diffraction and X-ray photoelectron spectroscopy analysis confirms the tetragonal phase and surface chemical composition of as made Sn1-xErxO2 (x = 0.0, 0.01, 0.02, 0.03, 0.04, and 0.05) thin films. The grain size and RMS roughness of the films were estimated from the AFM measurements and the film surface has a saw-tooth-like morphology. The transmission spectra of the films are fallen in the visible range having between 60% and 80% transmittance with different Er concentration. The optical direct, indirect band gap and phonon energy values have been estimated. The photoluminescence measurements under excitation at 325 nm show three distinct emission peaks, a broad hump positioned at 390 nm, two sharp peaks at 420 nm related to tin interstitials, and a sharp peak at 700 nm related to oxygen vacancies. The Er3+ in SnO2 increased the oxygen vacancies to maintain charge balance and as a result the intensity of emission peaks increases with Er content.

Intrinsic and extrinsic doping contributions in SnO2 and SnO2:Sb thin films prepared by reactive sputtering

SnO2 thin films are considered cheap transparent electrodes, interesting for scalable electronic applications, with intrinsic n-type conductivity related to donor defects like tin interstitials and oxygen vacancies. Besides, SnO2 allows n-type extrinsic doping by pentavalent cations such as Ta or Sb. In the present work, SnO2 and SnO2:Sb films were deposited on unheated soda lime glass substrates by reactive DC sputtering from Sn and Sn:Sb(5%) targets. Their structural, optical and electrical properties have been analyzed comparatively for the layers prepared at different oxygen partial pressures in the sputtering atmosphere, as-grown and after heating in air at several temperatures. Sb doping is proven effective to improve the electrical conductivity of sputtered tin dioxide samples. The contribution of oxygen vacancies is found dependent on the reactive deposition environment, in both pure and Sb-doped films, but subsequent heating can change the proportion and nature of the donor defects. For operation at temperatures above 400 °C, SnO2:Sb shows the best electrical performance and good thermal behavior is also achieved with pure SnO2 layers by adjusting the oxygen content in the sputtering atmosphere.

Yellow emitting Cd doped SnO2 nanophosphor for phosphor converted white LED applications

The optical properties and defect emission of Cd doped (10 and 20 mol%) SnO2 nanoparticles were investigated. The structure and phase purity of the nanoparticles were studied from powder XRD pattern and micro-Raman spectra. XRD pattern revealed the effective substitution of Cd2+ in the Sn4+ sites. The application of microwave for the combustion reaction causes the formation of homogeneous fine particles with crystallite size around 7.5, 6.1 and 7.1 nm for pure SnO2, 10 mol% Cd doped and 20 mol% Cd doped SnO2 nanoparticles, respectively. The influence of fine particle size and doping of Cd2+ ions reduces the optical band gap of SnO2 nanoparticles from 3.08 to 2.98 eV. The existence of surface defects, induced by the smaller size of the particles and the heterovalent doping, was confirmed by the micro-Raman spectral analysis. ESR spectra revealed that there is a significant concentration of singly ionized oxygen vacancies present in undoped as well as Cd doped SnO2 nanoparticles. High surface defects of the nanoparticles give rise to the broad emission band in the wavelength range of 450–625 nm. The surface defects, causes the visible emission, includes the oxygen deficiency produced by the doping of the cation (Cd2+) with low oxidation state than that of host cation (Sn4+), tin interstitials and dangling bonds. The excitation of pure and Cd doped SnO2 nanoparticles with 325 nm laser leads to the emission of yellow light and the emission intensity varied by Cd doping. A wide excitation band (300–400 nm) observed for the emission at 530 nm revealed that visible emission can be obtained by the pure and Cd doped SnO2 nanoparticles under the excitation of UV light. White emission with high CRI of 85.6 and CIE Coordinates of (0.32, 0.30) is achieved by exciting the mixture of blue phosphor with yellow emitting SnO2 nanoparticles using 375 nm LED chip.

Self-accelerated electrochemiluminescence emitters of Ag@SnO2 nanoflowers for sensitive detection of cardiac troponin T

Metal oxide semiconductor nanocrystals (NCs), which emerged as a novel class of electrochemiluminescence (ECL) emitters with low cost and good biocompatibility, have attracted particular research interests in ECL biosensors. However, their analytical applications still remained a substantial challenge of relatively low ECL intensity. Herein, the novel self-accelerated ECL emitters of silver nanoparticles functionalized SnO2 nanoflowers (Ag@SnO2 NFs) were first prepared by in situ generating silver nanoparticles on the surface of SnO2 nanoflowers via silver mirror reaction, which exhibited high-intensity ECL emission with the maximum emission peak at 542 nm in the case of S2O82− as a co-reactant. It was worthy to note that compared with traditional ECL emitters of SnO2 NCs with diameters below 10 nm, the obtained Ag@SnO2 NFs with diameters about 1–2 μM showed a stronger ECL emission. The ECL enhancement was supposed to derive from 1) the strong size effect of flower-like nanostructure aggregating by ultrathin SnO2 nanosheets, which would offer large amount of tin interstitials or oxygen vacancies; 2) the in situ generated silver nanoparticles (Ag NPs) as co-reaction accelerator, which would generate more oxidizing intermediate (▪) to significantly self-promote the ECL emission of Ag@SnO2 NFs. Given these attributes, we developed a sensitive ECL immunosensor for the detection of cardiac troponin T (cTnT) utilizing Ag@SnO2 NFs as efficient signal probes, which showed outstanding sensitivity with a favorable linear range from 1 fg/mL to 100 pg/mL and relatively low detection limit of 0.11 fg/mL. This work efficiently offered insights into the promising applications of Ag@SnO2 NFs as a low toxicity and superior ECL emitter in ECL bioanalysis.

Effects of gas flow rate on the structure and elemental composition of tin oxide thin films deposited by RF sputtering

Photovoltaic technology is one of the key answers for a better sustainable future. An important layer in the structure of common photovoltaic cells is the transparent conductive oxide. A widely applied transparent conductive oxide is tin oxide (SnO2). The advantage of using tin oxide comes from its high stability and low cost in processing. In our study, we investigate effects of working gas flow rate and oxygen content in radio frequency (RF)-sputtering system on the growth of intrinsic SnO2 (i-SnO2) layers. X-ray diffraction results showed that amorphous-like with nano-crystallite structure, and the surface roughness varied from 1.715 to 3.936 nm. X-Ray photoelectron spectroscopy analysis showed different types of point defects, such as tin interstitials and oxygen vacancies, in deposited i-SnO2 films.

Structural and optical properties of (Zn, Co) co-doped SnO2 nano particles

Optical bandgap narrowing is observed in Sn0.94 Zn0.05Co0.01O2, Sn0.92 Zn0.05Co0.03O2 and Sn0.90 Zn0.05Co0.05O2 nanoparticles synthesized by the chemical co- precipitation method. The estimated particle size and optical band gap of Sn0.94 Zn0.05Co0.01O2, Sn0.92 Zn0.05Co0.03O2 and Sn0.90 Zn0.05Co0.05O2 nanoparticles are 16.51, 11.75 and 6.6 nm and 1.45, 1.36 and 0.93 eV, respectively. A red shift is noticed for all samples as compared to band gap value (3.6 eV) for bulk SnO2. Increasing Co content results in decreased particle size, narrowed band gap and enhanced emission intensities in visible range of light. Small sized nano particles have larger surface areas and these large surface areas lead to more defects (oxygen vacancies, tin interstitials). The increasing defects concentration (especially oxygen vacancies, tin interstitials) results to narrow the band gap. With increasing Co content, the particles are in oxygen-poor state indicating the presence of many O vacancies and Sn interstitials. The oxygen content decreases steadily with increasing Co content, with the Sn:O atomic ratio increases suggesting the high density of defects. Large number of defects (oxygen vacancies) creates several donor levels within the forbidden energy gap to narrow the band gap and these defects in the band gap act as luminescent centers to enhance the emission intensities in visible spectrum.

Selective Improvement of NO2 Gas Sensing Behavior in SnO2 Nanowires by Ion-Beam Irradiation.

We irradiated SnO2 nanowires with He ions (45 MeV) with different ion fluences. Structure and morphology of the SnO2 nanowires did not undergo noticeable changes upon ion-beam irradiation. Chemical equilibrium in SnO2/gas systems was calculated from thermodynamic principles, which were used to study the sensing selectivity of the tested gases, demonstrating the selective sensitivity of the SnO2 surface to NO2 gas. Being different from other gases, including H2, ethanol, acetone, SO2, and NH3, the sensor response to NO2 gas significantly increases as the ion fluence increases, showing a maximum under an ion fluence of 1 × 10(16) ions/cm(2). Photoluminescence analysis shows that the relative intensity of the peak at 2.1 eV to the peak at 2.5 eV increases upon ion-beam irradiation, suggesting that structural defects and/or tin interstitials have been generated. X-ray photoelectron spectroscopy indicated that the ionic ratio of Sn(2+/)Sn(4+) increases by the ion-beam irradiation, supporting the formation of surface Sn interstitials. Using thermodynamic calculations, we explained the observed selective sensing behavior. A molecular level model was also established for the adsorption of NO2 on ion-irradiated SnO2 (110) surfaces. We propose that the adsorption of NO2-related species is considerably enhanced by the generation of surface defects that are comprised of Sn interstitials.

Structural and photoluminescence properties of SnO2 obtained by thermal oxidation of evaporated Sn thin films

Tin oxide films have been prepared by oxidation of Sn thin films deposited by thermal evaporation method onto glass substrates. The oxidation of films was done, in air at a temperature of 500 °C, from 20 to 120 min. The oxidized films were characterized by X-ray diffraction (XRD), Rutherford backscattering spectroscopy (RBS), photoluminescence spectroscopy (PL) and surface profilometer. The XRD patterns show that the crystalline structure of the oxidized Sn films improves with the annealing time. The tetragonal SnO2 phase (cassiterite) was obtained after 120 min of annealing with grains sizes between 15 and 20 nm. The thickness of oxide films, as function of the annealing time, follows a parabolic law. The O/Sn atomic ratio increases with the annealing time indicating an improvement of the films quality. Tin interstitials defects density, calculated from PL spectra using Smakula's formula, was found to decrease with the increasing annealing time. Tin interstitials defects density was found proportional to the increasing oxygen density (deduced from RBS). A fit of this proportionality allowed us to quantify the tin cations and oxygen anions diffused through the oxide films.

Growth ambient dependence of defects, structural disorder and photoluminescence in SnO2 films deposited by reactive magnetron sputtering

Abstract The present paper deals with the study of photoluminescence (PL) and the other physical properties (structural, electrical and optical) of SnO2 thin films with controlled disorder and intrinsic defects induced during the reactive magnetron sputtering by changing oxygen flow rate from 12 to 16 sccm. The changes in unit cell volume, near band-edge optical transparency and width of Urbach tail in the films are correlated with the structural disorder and presence of intrinsic defects induced by growth under different oxygen partial pressures. The increased intensity of the PL near UV emission and decrease in the intensity of visible emission peaks with increase in oxygen flow rate is linked with the decrease in oxygen vacancies and tin interstitials in the films. With increasing oxygen content, whereas the electrical resistivity of the films minimizes to a value of 4.3 × 10−2 ohm cm at 14 sccm, the mobility of the films increases to a saturation value 15 cm2 V−1 s−1. The donor-defect concentration linked carrier density is observed to decrease monotonically from 2 × 1019 to 0.6 × 1019 cm−3.

Abnormal behaviors in electrical transport properties of cobalt-doped tin oxide thin films

Electrical transport behaviors of SnO2-based oxides are absolutely essential, either for the understanding of physiochemical properties, or their practical applications. In this paper, an abnormal change in electrical transport is reported upon cobalt doping. A far-from-equilibrium technique—pulsed spray evaporation chemical vapor deposition (PSE-CVD), is investigated for the fabrication of Sn1−xCoxO2−δ (x = 0–0.18) thin films. Upon cobalt doping, the Hall mobility improves gradually and a ten-fold enhancement was noticed for Sn0.82Co0.18O2−δ relative to pure SnO2 films. This unexpected effect induces a dramatic drop in the electrical resistivity. Post-annealing treatment and XPS investigation indicate that the occurrence of surface-stabilized tin interstitials may be the primary reason for the unusual enhancement in conductivity. Cobalt doping not only generates the interstitial tin cations, but also stabilizes to a great extent their presence at the surface. This study may help to illumine new insight for the understanding of doping strategies, and offer a potential route for transport-related applications.

Nitrogen-doped transparent tin oxide thin films deposited by sputtering

Nitrogen-doped tin oxide thin films prepared by reactive rf magnetron sputtering have been investigated to examine their structural, electrical, and optical properties. Of particular interest was whether the nitrogen doping could create defect levels in tin oxide and change the electrical characteristics of tin oxide. Various N 2/O 2/Ar gas contents were evaluated, and the thin films were characterized by X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), UV/Vis spectrometer, and Hall effect measurements. With nitrogen incorporation in tin oxide, electrical conductivity as high as 134.2 (Ω cm) −1 was achieved due to an increase in carrier concentration. The optical absorption edge moved to a shorter wavelength as the nitrogen content was increased. The XRD and XPS results indicate that the small amount of substitution nitrogen created the second type of defect in addition to oxygen deficiencies and tin interstitials.

Structural and optoelectronic properties of antimony incorporated tin oxide thin films

Thin films of undoped and antimony doped tin oxide (SnO 2 and Sb:SnO 2) prepared by spray pyrolysis technique with different antimony concentrations are found to be polycrystalline with tetragonal crystal structure, having preferential growth along the (2 1 1) and (1 1 2) planes. Randomly oriented needle-shaped polyhedron like grains are observed in the FE-SEM images owing to large scattering effect in the films. From X-ray photoelectron spectroscopy (XPS) measurement, it is observed that films are oxygen deficient. Concentration of Sb in the SnO 2 films is slightly less than that of starting solution. Valence states for Sn, Sb and O, observed from the XPS measurement are Sn 4+, Sb 5+/Sb 3+ and O 2 2 − , respectively. The direct optical band gap ( E g) has increased from 3.55 (undoped) to 3.60 eV with Sb concentration showing formation of degenerate semiconductor. The strong violet and comparatively weak red emissions have observed in room temperature photoluminescence (PL). The origin of various peaks in PL spectra can be assigned to the combined effect of oxygen vacancies, tin interstitials or dangling bonds, singly charged oxygen vacancies, interstitial oxygen and crystal defects present in the films. The films deposited with 2 at.% Sb exhibited lowest value of resistivity (1.22 × 10 −3 Ω cm) and highest value of carrier concentration (5.19 × 10 20 cm −3), mobility (9.83 cm 2 V −1 s −1) and figure of merit (2.11 × 10 −3 Ω −1).

Visible photoluminescence of hydrothermal synthesized Sn1−x Ni x O2 nanostructures

Sn1−xNixO2 nanostructures such as nanocubes, nanospheres and hollow spheres were synthesized by a simple hydrothermal method. Room temperature photoluminescence spectra of the as-synthesized samples display a strong yellow emission at about 600 nm and a weak blue emission at about 430 nm. The as-prepared and annealed Sn1−xNixO2 (x = 0, 0.01, 0.02, 0.04) were characterized by X-ray diffraction, field emission scanning electron microscopy, Raman spectrum, UV–Vis absorption spectra, and room temperature photoluminescence spectra. By investigating the relationship between the Raman band centered at 560 cm−1 and the photoluminescence of the samples, we suggest that the broad yellow emission and weak blue emission primarily originate from singly ionized oxygen vacancies and tin interstitials, respectively.

Luminescence of SnO 2 thin films prepared by spin-coating method

SnO 2 thin films have been grown on soda-lime glass substrate using a simple spin-coating method. The films grown under different calcining temperatures have been characterized using microstructural and luminescent measurements. Room-temperature photoluminescence measurements under excitation at 280 nm show two broad emission peaks, the one peaking at 430 nm can be related to tin interstitials or dangling, and the other at 400 nm can be related to oxygen vacancies in the SnO 2 thin films.

Growth twins in nanocrystalline SnO2 thin films by high-resolution transmission electron microscopy

Growth twins in nanocrystalline SnO2 thin films with grain size 5–50 nm have been investigated by high-resolution transmission electron microscopy. They show the {101}〈101〉 geometry, metal atom mirror symmetry, and slight distortion of oxygen atoms. Multiple twins and step twin boundaries with a density about 1015 m−2 were frequently observed in the films. It appears there are tin interstitials at step twin boundaries and, hence, electronic donors associated with the interstitials.