Tungsten imido complexes as precursors to tungsten carbonitride thin films

Abstract

Thin films of tungsten carbonitride have been formed on glass by low-pressure chemical vapour deposition (LP)CVD at 550 °C from four closely related precursors: [W(μ-N^tBu)(N^tBu)Cl₂(H₂N^tBu)]₂, [W(N^tBu)₂Cl₂(TMEDA)] (TMEDA = N,N,N′,N′-tetramethylethylenediamine), [W(N^tBu)₂Cl₂(py)₂] (py = pyridine) and [W(N^tBu)₂Cl(N{SiMe₃}₂)]. The grey mirror-like films were grown with a nitrogen or ammonia bleed gas. In all cases the chlorine content of the deposited films was less than 1 at% and the oxygen content of the films was lower for those grown using ammonia. Surprisingly, the use of ammonia did not significantly change the carbon content of the resulting films. Despite the coordination environment around the metal being essentially the same and the materials having a comparable volatility, some differences in film quality were observed. The films were uniform, adhesive, abrasion resistant, conformal and hard, being resistant to scratching with a steel scalpel. X-Ray powder diffraction patterns of all the films showed the formation of β-WN_xC_y. As a comparison the aerosol-assisted chemical vapour deposition (AA)CVD of [W(μ-N^tBu)(N^tBu)Cl₂(H₂N^tBu)]₂ was investigated and amorphous tungsten carbonitride films were deposited.