In-doped SnO2 Research Articles

A single In-doped SnO2 submicrometre sized wire as a field emitter

Indium doped tin oxide submicrometre sized wires have been synthesized by thermal evaporation and characterized by field emission (FE) microscopy. The non-linear Fowler–Nordheim plot corresponds to the typical semiconducting behaviour of the emitter. The field enhancement factor has been estimated to be 29 900 cm−1 indicating that electron emission is due to the nanometric features of the emitter. A current density of the order of 6.36 × 103 A cm−2 with an applied electric field of 1 × 104 V µm−1 has been obtained. The long term FE current stability tested at the preset current level of 1 µA exhibits no severe fluctuations.

Synthesis and Characterization of In-Doped SnO<sub>2</sub> (ITO) Nanowires

Large-scale synthesis of In-doped SnO2 (ITO) nanowires was achieved by direct thermal evaporation of a mixture of Sn and In powders at 900°C in an Argon atmosphere. Scanning electron microscopy and transmission electron microscopy observations show that ITO nanowires have diameter ranging from 20 to 100 nm and lengths up to several tens of micrometers. By altered the reaction temperature, we find that the temperature of the reaction is the critical factor for the morphologies and sizes of the ITO nanowires.

Nanocrystalline SnO 2 and In-doped SnO 2 as anode materials for lithium batteries

SnO 2 is one of the promising candidates for the use as anode materials in lithium batteries. This work describes the X-ray absorption near-edge spectra (XANES) and the electrochemical properties of nanocrystalline SnO 2 and In-doped SnO 2 via a soft chemistry route. Both undoped and In-doped systems showed excellent reversibility for Li ions. XANES and HRTEM studies of the samples prepared at various temperatures revealed the effect of low-temperature synthesis on size quantization compared with the samples prepared at higher temperature. The particle size of the synthesized materials were between 6 and 50 nm for the Sn 0.9In 0.1O 2 and SnO 2, respectively. The cycling performances for the In-doped systems were better than that of the undoped SnO 2. In all the cases, there is a large first cycle irreversible capacity, as reported. The variation of electrochemical properties with respect to the In content was studied and discussed.

Preparation and characterization of In-doped p-type SnO2 thin films by solgel dipcoating*

In doped SnO2 thin films were prepared on quartz substrates by sol-gel dipcoating technique.X-ray diffraction results show that In doped SnO2 films a re of rutile structure.Ultraviolet-visible absorption results show that In_do ped SnO2 films have an optical band gap of about 3.8eV. Hall effect measur ement results show that the hole concentration and the mobility are dependent on both the processing temperature and the In/Sn atomic ratio. It is found that 5.25℃ is the optimum processing temperature to get the highest hole concentration . For an In/Sn atomic ratio between 0.05 and 0.20, hole concentration is almo st proportional to the In/Sn ratio.

Specific properties of fine SnO2 powders connected with surface segregation.

The effect of surface segregation in Sb- and In-doped SnO2 fine-grained powders has been analyzed in comparison with single-crystalline samples. The kinetics and thermodynamics of the Sb and In segregation processes were studied as a function of annealing temperature by X-ray photoelectron spectroscopy (XPS) after annealing in an oxygen-containing atmosphere. Significant differences between diffusion and segregation were revealed for doped powders and single crystals, obviously because of simultaneous diffusion and particle-growth processes proceeding during annealing of powders. For doped single crystals the thermodynamic equilibrium is approached after 24 h annealing above 850 degrees C and at 1000 degrees C for Sb and In, respectively. Higher effective activation energies of diffusion are observed for doped powders and the thermodynamic equilibrium is not achieved under technologically relevant annealing conditions. On the basis of dopant profile measurements anomalies in the electrical resistivity at 300 degrees C of Sb-doped SnO2 powders annealed at 700 and 900 degrees C were attributed to an Sb-depleted zone formed beneath the segregated surface during the kinetic regime. To achieve optimum resistivity behavior for commercial application, inhomogeneous doping of powders must be avoided by appropriate preparation steps.

Au colloid monolayers as templates for nanostructure assembly

A new approach to nanostructure formation based on replication of an existing pattern of colloidal Au nanoparticles is described. The key steps in this strategy involve the coating of a well-defined Au colloid monolayer with an SiO x sol-gel, HF etching until colloidal particles are exposed, and removal of colloidal Au with aqua regia. This process was carried out on a two-dimensional array of 12nm diameter particles on an In-doped SnO 2 (ITO) substrate, and monitored by UV-vis, electrochemistry, and atomic force microscopy (AFM). AFM data indicate the strategy is feasible, with clearly visible differences in surface morphology observed between bare ITO and colloidal Au-depleted, SiO x -coated ITO.

Chemical and Electrochemical Ag Deposition onto Preformed Au Colloid Monolayers: Approaches to Uniformly-Sized Surface Features with Ag-Like Optical Properties

Two approaches to preparation of Ag-clad Au colloid monolayers are described. Each begins with a preformed monolayer of colloidal Au particles on glass, Au-coated quartz, or In-doped SnO2. Chemical reduction of Ag+ from a commercial Ag coating formulation (LI Silver) or electrochemical reduction of Ag+ leads to surfaces for which the amount of Ag deposited can be controlled. On transparent substrates, Ag deposition can be followed in real time by UV−visible spectroscopy. When the substrate is an electrode, electrochemical deposition can be monitored by coulometry; for the chemical process, anodic stripping voltammetry yields accurate values of the amount of Ag present, as confirmed by quartz crystal microgravimetry (QCM). Chemical reduction yields surfaces that are extremely enhancing for surface enhanced Raman scattering (SERS), although the deposition process required must be precisely tuned. In contrast, electrochemical deposition, while affording more accurate control of the reduction rate, produces only mildly enhancing surfaces. Atomic force microscopy (AFM) images of electrochemically-produced surfaces show formation of very large nonuniform Ag particles that are distinct from the Au colloid monolayer, while those prepared by LI Silver show both growth of Ag on Au and formation of smaller colloidal Ag particles attached to Ag-coated Au particles.

Synthesis, Electrooxidation, and Characterization of Bis(diphenylamine)naphthalene Diimide

We have synthesized a new poly(imide) precursor for solution electrodeposition onto conducting surfaces. The new monomer, N,N‘-bis[p-phenylamino(phenyl)]-1,4,5,8-naphthalenetetracarboxylic diimide (DNTD), contains a central naphthalene diimide moiety flanked by two dimerizable diphenylamine groups. DNTD was oxidatively electrodeposited onto Au-, Pt-, and In-doped SnO2 surfaces from DMSO, CH3CN, and CH2Cl2. The cyclic voltammetry is consistent with initial radical cation formation of diphenylamine groups, and then para C−C coupling of radicals to form dimers and higher order oligomers. IR spectroscopy was used to determine the average degree of polymerization and confirm para coupling. The resulting material shows electrochemically reversible 1e-/ and 2e-/monomer unit reduction waves corresponding to the naphthalene tetracarboxylic diimide radical anion and dianion. Also a quasireversible 1e-/ and 2e-/monomer unit oxidation corresponding to the oxidation of diphenylbenzidine unit is shown. Visible−NIR spec...

Hall coefficient measurements for SnO 2 doped sensors, as a function of temperature and atmosphere

The Hall coefficient has been measured for thin (300 nm) r.f. sputtered Al, In-doped SnO 2 and undoped SnO 2 films. Two experiments have been carried out: (i) Hall measurements in a temperature range of 20 to 300 °C in inert (Ar), reductor (H 2 0.2%) and oxidant (O 2 2%) atmospheres. Aged films were also tested in Ar. (ii) Hall measurements as a function of H 2 (0–2%) and O 2 (0–20%) concentrations at fixed temperature. Conduction mechanisms were discussed adjusting temperature dependent results to a grain boundary carried-trapping model. A grain size dependent sensitivity model has been used to explain H 2 and O 2 sensitivities. Combining results from both models, we are able to establish the best conditions for detection of reductor and oxidant gases.

Thin-film In-doped V-catalysed SnO 2 gas sensors

Thin-film In-doped V-catalysed SnO 2 gas sensors are discussed and compared with Pt-catalysed In-doped or undoped SnO 2 gas sensors. The In acceptors are implanted, while the catalysts are directly evaporated onto the active sensor layer. The V/In catalyst/dopant combination leads to thin-film sensors highly sensitive to NO 2, while nearly no cross sensitivity to CO, CO 2, H 2 and CH 4 is detectable. The maximum conductivity change of the V-catalyst In-doped SnO 2 sensor in NO 2-enriched synthetic air occurs at about 200 °C.