F. N. Putilin

Sensor properties of Pd-doped SnO2 films deposited by laser ablation

Polycrystalline SnO2 and SnO2 films were surface-doped with palladium using laser ablation. The effect of the energy density of pulsed KrF laser radiation on the plasma generation process and Pd deposition rate was studied, and the depth profiles of Pd in the films were determined. The gas response of the Pd/SnO2 , SnO2, and Pd/SnO2 films was studied between 200 and 380°C using a mixture of 1 vol % H2 with N2 . Surface doping with Pd was found to enhance the hydrogen sensitivity of SnO2 by two orders of magnitude.

Anomalous gas pressure effects in infrared multiphoton dissociation of molecules of the homologous series CnH2n + 1OH (n = 1–4)

Abstract The production of OH radicals in infrared multiphoton dissociation of C n H 2 n + 1 OH ( n = 1–4) homologs has been studied. The OH yield has been found to drop abnormally rapidly with increasing gas pressure of alcohols with n ⩾ 2. Possible reasons for the observed effect, such as redistribution of intramolecular vibrational energy within the electronic ground state and a non-adiabatic vibrational-electronic transition, are discussed.

Pulsed laser deposition of conductive indium tin oxide thin films

Thin indium tin oxide (ITO) films have been grown on quartz glass substrates by pulsed laser deposition. The influence of ablation target composition and deposition conditions on the growth rate, optical transmission spectra, and carrier mobility and concentration of the films has been examined. The average surface roughness of the ITO films grown at substrate temperatures above 300°C is 2 nm. The films grown at an oxygen partial pressure of 5 mTorr using ablation targets with Sn/(In + Sn) = 5% possess high transmission (85-95%) in the visible range and low resistivity (1.8 × 10−4 Ω cm).

Effect of energy density on the target on SnO2:Sb film properties when using a high-speed particle separator

SnO2:Sb thin films are grown by pulsed laser deposition with high-speed particle separation on quartz-glass substrates without post-deposition annealing under different deposition conditions in the range of the energy densities on the target from 3.4 to 6.8 J/cm2. Their optical, structural, and electrical properties are studied. It is found that the energy density on the target affects the SnO2:Sb film conductivity and transmittance. The optimum conditions of film growth by the droplet-free pulsed laser deposition method are determined. A resistivity minimum of 1.2 × 10–3 Ω cm is observed at an energy density on the target of 4.6 J/cm2, a substrate temperature of 300°C, and an oxygen pressure of 20 mTorr in the vacuum chamber during deposition.

Transport properties of thin SnO 2 〈Sb〉 films grown by pulsed laser deposition

Thin SnO2 films grown by pulsed laser deposition have been characterized by X-ray diffraction, optical spectroscopy, and scanning electron microscopy. The carrier mobility and concentration in the films have been determined as functions of target composition (0–8 at % Sb) using Hall effect measurements, and the resistivity of the films has been measured by a four-probe technique. The lowest resistivity (ρ = 2 × 10−3 Ω cm) and the highest transmission (≃ 85%) of the films in the spectral range 400-800 nm have been obtained at a target composition Sb/(Sn + Sb) = 2 at %. The observed variation in the resistivity of the films is determined by changes in carrier concentration to a greater extent than by changes in carrier mobility. X-ray photoelectron spectroscopy results demonstrate that the predominant charge state of the antimony in the films is Sb5+.

Effect of surface modification with palladium on the CO sensing properties of antimony-doped SnO2 whiskers

Antimony-doped tin dioxide whiskers have been prepared by vapor growth in a tube furnace in a flowing mixture of argon and oxygen at a constant evaporation temperature. The antimony concentration was measured by laser mass spectrometry. Palladium was deposited by laser ablation. The palladium-modified whiskers exhibit a sensing response to CO at the level of its maximum allowable concentration in the workplace.

Energy characteristics and deposition rates of metals from vacuum laser plasma on dielectric substrates

The effect of the energy flux density of a pulsed Kr-F laser on the processes of generation of the laser plasma of tin, palladium and platinum and on the deposition rates of metal films on dielectric substrates in laser ablation have been studied. The use of the differential scheme of probing a laser plasma with Faraday cups and time-of-flight mass spectrometry has made it possible to distinguish, in plasma ion signals, the ranges of singly charged and multicharged ions, which differ in kinetic energy. The film deposition rate depends on both the laser energy flux density and the degree of ionization of the laser plasma.

Controlling the phase composition of cadmium sulfide films during pulsed laser deposition

Thin cadmium sulfide films grown by pulsed laser deposition on crystalline and amorphous substrates have been shown to consist of a mixture of a cubic (sphalerite structure) and a hexagonal (wurtzite structure) phase. We have demonstrated the possibility of controlling the percentages of the hexagonal and cubic phases in cadmium sulfide films by varying pulsed laser deposition parameters. Varying the deposition parameters allows one to control the optical and structural parameters and surface morphology of thin cadmium sulfide films.

Hydrogen gas sensitivity of thin films of tin oxide surface doped by platinum laser plasma of different structure and charge composition

The effect of structure and charge composition of Pt laser plasma in the surface doping of SnO2 thin films on their resistive gas sensitivity towards hydrogen has been studied. The structure and charge composition of plasma varied depending on the value and polarity of the potential (UD) of the inhomogeneous electrostatic field generated between a target and plates of a diaphragm located in a vacuum chamber outside the plasma dispersion zone under the action of Kr-F laser radiation on a platinum target. Doping at UD > 0 results in an increase in gas sensitivity of SnO2 films several times greater than doping by quasineutral plasma (UD = 0). The films doped at UD < 0 with surface concentrations of Pt optimum in terms of the maximum gas sensitivity appear to tolerant towards changes in the composition of the gas phase in a temperature range of 50–600°C.

Laser synthesis of metal–metaloxide nanoparticles on carbonic materials in an electric field

Nanoparticles of palladium and its oxides are synthesized on carbonic materials via the laser ablation and deposition of metals in electric fields. Studies of the materials show it is possible to control the crystallinity, size, and chemical state of nanoparticles without changing the laser beam parameters.