Thermal transformations in nanosized MoO3 layers

The degree of the transformation of MoO₃ films (d= 8–130 nm) increased as the duration (1–140 min) and temperature (373–573 K) of thermal treatment grew and as the film thickness decreased under atmospheric conditions. The thermal treatment of MoO₃ films decreased the optical density at λ = 350 nm and caused the appearance of an absorption maximum at λ = 870 nm. A mechanism of thermal transformations of MoO₃ was suggested. The mechanism included the formation of the [(V _a)⁺⁺e] center during the preparation and thermal treatment of MoO₃ films and thermal electron transition from the valence band to the [(V _a)⁺⁺e] center level with the formation of the [e(V_a)⁺⁺e] center.     

Regularities of the formation of the photolysis products in the lead azide-cadmium system

Compared to PbN₆(Ab), the PbN₆(Ab)-Cd system was found to be characterized by a low photolysis rate within the region of intrinsic absorption of PbN₆(Ab) and, at the same time, by a broader range of spectral sensitivity of PbN₆(Ab), up to 510 nm. Preliminary irradiation by 380-nm light resulted in an increase in the photolysis rate. The photolysis rate constants for the PbN₆(Ab)-Cd system were determined. An analysis of the voltammetric characteristics, photocurrent, and contact potential difference made it possible to develop a model of the photolysis of the PbN₆(Ab)-Cd system, including the stages of generation, recombination, redistribution of nonequilibrium charge carriers in the contact field, the photoemission of electrons, formation of the photolysis products, and genesis of the PbN₆(Ab)-Pb(photolysis product)-Cd system. It was demonstrated that the diffusion of anionic vacancies to neutral Pb _n ⁰ sites is the limiting stage of the photolysis of the PbN₆(Ab)-Cd system.     

Photolysis of thallium azide

Preliminary treatment of TlN₃(A) with light (λ = 365 nm, I > 1 × 10¹⁴ quantum cm⁻² s⁻¹) in a vacuum (1 × 10⁻⁵ Pa) at 293 K led to the formation of a new long-wave region of spectral sensitivity. The products of photolysis of TlN₃(A) thallium and nitrogen formed in the stoichiometric ratio on the sample surface. The topography and kinetics of thallium accumulation were determined, and the effective rate constants for photolysis evaluated. Measurements of the contact voltage, current-voltage characteristics, and photocurrent showed that the photolysis of thallium azide resulted in the formation of TlN₃(A)-Tl (photolysis product) microheterogeneous systems. A model of photolysis of TlN₃(A) was suggested. According to this model, photolysis included the generation, recombination, and redistribution of nonequilibrium charge carriers in the contact field and the formation of the end products of photolysis. The limiting stage of photolysis of TlN₃(A) was the diffusion of interstitial thallium cations toward the neutral (T _n Tl _m )⁰ center. Original Russian Text ? E.P. Surovoi, L.I. Shurygina, L.N. Bugerko, N.V. Borisova, 2009, published in Zhurnal Fizicheskoi Khimii, 2009, Vol. 83, No. 4, pp. 784–790.     

Kinetics of thermal transformations in nanosized chromium films

The transformations in nanosized chromium layers at different layer thicknesses (d = 14–154 nm) and thermal treatment temperatures (T = 673–873 K) were studied by optical spectroscopy, microscopy, and gravimetry. The kinetic curves of conversion at different chromium film thicknesses and treatment temperatures are well approximated by the linear, inverse logarithmic, cubic, and logarithmic functions. The contact potential difference for Cr and Cr₂O₃ films and photo-emf for Cr-Cr₂O₃ systems were measured. An energy band diagram of Cr-Cr₂O₃ systems was constructed. A model of thermal transformation was constructed for Cr films that included the stages of oxygen adsorption, charge carrier redistribution in the contact field of Cr-Cr₂O₃, and chromium(III) oxide formation.     

Thermal transformations in nanosized copper layers

The thermal treatment of copper films 3–168 nm thick over the temperature range 373–600 K for 1–120 min was shown to result in the formation of copper(I) oxide. Depending on the initial film thickness and temperature, the kinetic curves of the degree of transformation were satisfactorily described by a linear, inverse logarithmic, parabolic, or logarithmic law. Contact potential difference and photo-electromotive force measurements were used to suggest a model including the stages of oxygen adsorption, charge carrier redistribution in the Cu₂O-Cu contact field (negative on the side of Cu₂O), and copper(I) oxide formation.     

The Rules Governing the Formation of Silver Azide Photolysis Products

Irradiation of silver azide at λ = 365 nm (I > 1 × 10¹⁵ quantum cm^?2 s^?1) in a vacuum (1 × 10^?5 Pa) leads to an increase in the rate of photolysis and photoinduced current and the appearance of a new long-wave region of spectral sensitivity. The photolysis products, silver metal and gaseous nitrogen, are formed in a stoichiometric ratio on the surface of silver azide. The rate constants for silver azide photolysis were determined. Measurements of contact potential difference, current—voltage characteristics, photoelectromotive force, and photocurrent showed that AgN₃(A₁)—Ag (photolysis product) microheterogeneous systems were formed in silver azide photolysis. The limiting stage of silver azide photolysis is the diffusion of interstitial silver cations to the (T_nAg_m)⁰ neutral center.     

Thermal transformations in nanodimensional Pb—WO3 systems

Transformations in Pb-WO₃ nanodimensional systems are investigated in dependence on the thickness of the Pb and WO₃ films, temperature, and thermal treatment duration by means of optical spectroscopy, microscopy, and gravimetry. The contact potential difference for Pb and WO₃ films and the photoelectric power of Pb-WO₃ systems is measured. A diagram of the energy bands of Pb-WO₃ systems is constructed. A model of thermal transformation for the WO₃ films in Pb-WO₃ systems is suggested. The model involves the redistribution of equilibrium charge carriers on the contact, formation of the ([(V_a)⁺⁺e]) center during the preparation of a WO₃ film, its transformation into a ([e(V_a)⁺⁺e]) center during the formation of the Pb-WO₃ systems, and thermal ionization of the ([e(V_a)⁺⁺e]) center.     

Kinetic patterns in the formation of nanosized manganese–manganese oxide systems

Transformations in nanosized manganese films are studied by means of optical spectroscopy, microscopy, and gravimetry at different film thicknesses (d = 4–108 nm) and temperatures of heat treatment (T = 373–673 K). It is found that the kinetic curves of conversion are satisfactorily described in the terms of linear, inverse logarithmic, cubic, and logarithmic laws. The contact potential difference is measured for Mn and MnO films, and photo EMF is measured for Mn–MnO systems. An energy band diagram is constructed for Mn–MnO systems. A model for the thermal transformation of Mn films is proposed that includes stages of oxygen adsorption, the redistribution of charge carriers in the contact field of Mn–MnO, and manganese(II) oxide formation.     

Kinetic tendencies of thermal transformations in nanosized Ni–MoO3 systems

The transformations in nanosized Ni–MoO₃ systems were studied by optical spectroscopy, microscopy, and gravimetry depending on the thickness of the Ni (d = 1–40 nm) and MoO₃ (d = 3–50 nm) films, temperature (473–773 K), and thermal treatment time. The contact potential difference was measured for Ni and MoO3 films; photovoltage, for Ni–MoO₃ systems. An energy band diagram of the Ni–MoO₃ systems was constructed. A model of the thermal transformation of MoO₃ films in Ni–MoO₃ systems was suggested, which involves a redistribution of equilibrium charge carriers at the contact, formation of a [(V_а)⁺⁺е] center during the preparation of the MoO₃ film, the transformation of this center into an [е(V_а)⁺⁺е] center during the formation of Ni–MoO₃ systems, and the thermal transition of an electron to the level of the [(V_а)⁺⁺е] center to form an [е(V_а)⁺⁺е] center.

     

Regularities of photostimulated conversions in nanometer aluminum layers

The gravimetric and optical spectroscopic methods reveals that light irradiation with λ = 300–750 nm and intensity I = 6.9 × 10¹⁴–1.1 × 10¹⁶ quanta cm⁻² s⁻¹ for τ = 1–160 min in atmospheric conditions significantly changes the absorption and reflection spectra and mass of aluminum films (d = 2–200 nm). The kinetic curves of the degree of conversion versus aluminum film thickness are satisfactorily described in the inverse logarithmic and parabolic terms. The contact potential difference is measured for Al and Al₂O₃ films along with the photo-EMF of Al-Al₂O₃ systems. The suggested model includes the stages of generation and redistribution of nonequilibrium charge carriers in the contact field of Al-Al₂O₃ systems, oxygen adsorption, Al³⁺ diffusion, and Al₂O₃ formation.