Heat and mass transport at unsteady sublimation of single metal-organic particles in the gas-carrier flow

The results of experimental research and numerical modeling of convective heat and mass transfer during the sublimation of spherical particles of beta-diketonates of metals Cr(acac)3 and Zr(dpm)4 in a high-temperature flow of an inert gas (argon or helium) are presented. The sublimation process is visualized. The temperature and particle size dynamics are obtained. The effect of the carrier-gas properties on the sublimation intensity of the particles with different initial diameters in the temperature range from 200 to 330 ºС is analyzed. It is shown that under the conditions of a high intensity of substance removal from the phase transition surface, the time for complete sublimation of the sample of Cr(acac)3 and Zr(dpm)4 may be less than the time, required to establish an equilibrium temperature between the precursor particle and the vapor-gas flow.Papers presented at the 13th International Conference on Heat Transfer, Fluid Mechanics and Thermodynamics, Portoroz, Slovenia on 17-19 July 2017 .International centre for heat and mass transfer.American society of thermal and fluids engineers

MO CVD of Noble Metals

The state of the art in research and application of processes of chemical vapour deposition of noble metal (Pt, Pd, Rh, Ir, Ru, Au) coatings is considered. Systematization of known experimental data on synthesis, thermal properties and saturated vapour pressure of volatile compounds of noble metals with organic ligands is provided. The processes of CVD of noble metals were analized from general requirements to precursors. It is shown that chelate or mixed-ligand noble metal complexes and, in particular [MATH]-diketonate derivatives due to their thermal properties are the most suitable for deposition of noble metal thick films

Thermal conversions of some Ba, Sr, Ti oxide precursors for CVD

Gas phase composition and conversions under evaporation and thermal decomposition of Sr(dpm)2, Ba(dpm)2, TiO(dpm)2 and Ti(OPri)2(dpm)2 (dpm=C(CH3)3COCHCOC(CH3)3, Pri = CH(CH3)2) which are conventional CVD precursors for BST films have been studied by means of original mass spectrometric technique. Properties and thermal behaviour of these compounds have been compared with respect to CVD precursor. It has been shown that conversions leading to binuclear species formation occur under transportation of TiO(dpm)2 into deposition zone. It has been reported alike decomposition mechanism of Sr and Ba precursors. Influence of oxygen on thermal stability and products of decomposition of the source compound has been shown

Modelling of nanosecond LCVD of 3D metal micropatterns

Modelling of LCVD of metal film micropatterns under the action of a high-power nanosecond pulse UV laser was perfomed on the basis of the analysis of experimental data, calculation of laserinduced temperature field and mass-transport fluxes. It is shown that the reaction zone is limited in time by the laser-induced temperature pulse. It is stated that continuous metal films of uniform thickness are deposited as a result of laser-induced themolysis of the adsorbed layer of the initial molecules, the filling degree of this layer exceeding 1. Spatial and time localisation of the reaction zone is characterised depending on the deposition time at the stages of nuclei formation, formation of a continuous metal film, and increase in its thickness. The conditions to govern the reaction zone localisation are determined

Mass Spectrometric Study of Copper(II) β-Diketonates Vapour Thermolysis Mechanism and Kinetics

Vapour thermolysis processes of copper(II) bis-chelate complexes with different β-diketones in the 160-640°C temperature range were studied by using the high-temperature source of a molecular beam with mass spectrometric recording of the gas phase composition directly at the outlet from the thermal reactor. Schemes of a heterogeneous decomposition of these compounds vapour were suggested on the basis of temperature dependences of the thermolysis gaseous products composition. It was established that the mechanisms of thermal conversion of copper(II) complexes with fluorinated and non-fluorinated ligands were not similar. A comparison of the thermal behaviour of the complexes with fluorinated and non-fluorinated ligands in vacuum, hydrogen and oxygen was carried out. Effective values of kinetic parameters in the Arrhenius equation were calculated for the first-order reaction on initial compound from the temperature dependence of the rate constant. The sequence of copper(II) complexes with β-diketones having different end substituents according to the thermal stability was revealed from the values of the thermal decomposition activation energy

General aspects of surface chemistry of metal β-diketonates

Chemical reactions of metal β-diketonates, which are conventional CVD precursors, on hot surface, have been considered. Extensive experimental data on thermal behaviour of metal β-diketonate vapours obtained by hightemperature mass spectrometry have been generalized. The influence of different gas reagents on thermal stability of the compounds has been discussed. The main mechanisms of the decomposition of compounds under investigation, leading to metal and oxide formation on hot surface, have been established. Application of mass spectrometric data to the optimization of CVD processes (precursor choice, temperature range of deposition) has been shown. A possibility to predict film composition using the data on gaseous decomposition products has been considered

Frontier trends in the prediction of vapour pressure of metal-organic precursors

A quantitative approach to predictions of the volatility of metal-organic precursors has been developed. The proposed concept is based on up-to-date notions concening the character of intermolecular interactions in molecular crystals allowing for the specific features of the molecular and electronic structure of metal-organic precursors. Using the data on the crystal and molecular structure of the metal-organic precursors within the frames of the methods of statistical thermodynamics and molecular physics, we have built the models for calculating the enthalpy and entropy of crystal-vapour phase transitions starting from the potentials OF interatomic interactions. The temperature dependence of vapour pressure has been calculated for various precursors with known crystal and molecular structure. The calculated and experimental data on vapour pressure have been compared. The behaviour peculiarities of thermodynamic functions depending on the features of molecular structure of metal-organic precursors and their packing in crystals have been revealed . Information content and predictability of the proposed model notions for the forecast of vapour pressure for metal-organic precursors have been demonstrated

Mass Spectrometric Study of Thermolysis Mechanism of Metal Acetylacetonates Vapour

The processes of thermal decomposition of aluminium(III) and scandium(III) acetylacetonates (Al(aa)3 and Sc(aa)3) were investigated in the 160-650°C temperature range using a high-temperature molecular beam source with mass spectrometric sampling of the gas phase composition directly at the outlet from the reaction zone. A scheme of thermal decomposition of aluminium(III) and scandium(III) acetylacetonates vapour is suggested. It is established that the common mechanism of thermolysis of these complexes is due to the commonness of electronic structure of ions Mg2+, Al3+, Sc3+ and Hf4+. According to the scheme, the process proceeds along three parallel routes, one of them being possible only for complexes possessing more than two ligands ; in this case the gaseous products resulting from cyclic dimerization of ligand fragments are formed. The influence of oxygen and hydrogen on the composition of the gaseous products and the mechanism of thermolysis of the complexes vapour are also established. From temperature curves, the effective values of kinetic parameters in Arrhenius equation are calculated for the first order reaction

Mechanism of Interaction of Dimethylgold(III) Chelates Vapour with Hot Surface

By the electron impact mass-spectrometric method, the temperature dependence of the gas phase structure was investigated at the thermal decomposition of dimethylgold chelate vapour of the general formula (CH3)2AuL, where L = (RC(X)CHC(Y)R1) ; R = CH3, C(CH3)3 ; R1 = CH3, C(CH3)3, CF3 ; X = O, NH ; Y = O, S) in vacuum and deuterium environment at temperatures up to 350 °C and the saturated vapour pressure by 10-4 - 10-2 Torr. The threshold temperature of the stability of complexes vapour was determined. From the temperature dependence of the rate constant of decomposition processes the effective activation energy was obtained. It was shown that the initial act of the complexes destraction is break of the chelate cycle. The following decomposition process complexes adcorbed at the surface lead to HL, L and CH3 L, methane and ethane by competitive inside-and intermolecular processes. The presence of deuterium (or hydrogen) in the reaction zone couses to decrease onset temperatures for all investigated compounds