Volatile hafnium(IV) compounds with beta-diketonate and cyclopentadienyl derivatives

Abstract

The volatile hafnium(IV) β-diketonates: Hf(IV) acetylacetonate Hf(acac) 4, Hf(IV) trifluoroacetylacetonate Hf(tfac) 4, dimer of hexafluoroacetylacetonate of Hf(IV) hydroxide Hf 2(OH) 2(hfac) 6, Hf(IV) pivaloyltrifluoroacetonate Hf(ptac) 4 and Hf(IV) 2,2,6,6-tetramethylheptanedionate Hf(thd) 4—as well as two bis-cyclopentadienyl Hf(IV) derivatives Cp 2Hf(NEt 2) 2 and Cp 2HfMe 2 were synthesized. The substances were identified by chemical analyses, melting points, IR, NMR spectroscopy and mass spectrometry. The crystallographic study of Hf(IV) β-diketonates is reported. The thermogravimetric analysis was carried out for all compounds. By the flow method and Knudsen method, the temperature dependences of saturated vapor pressure of Hf(IV) complexes were studied and the standard thermodynamic parameters of vaporization processes Δ H T o and Δ S T o were calculated. Thermodecomposition processes for cyclopentadienyl derivatives in vacuum and in oxygen atmosphere were studied by high temperature mass spectrometry and gas by-products were determined. Hf(thd) 4, Cp 2Hf(NEt 2) 2 and Cp 2HfMe 2 were used for depositing HfO 2 films in different conditions. Data of X-ray diffraction analysis have shown that HfO 2 films were in a monoclinic structure. The specific resistance and permittivity of HfO 2 films was calculated.