Liquid Cobalt (I) Hydride Complexes as Precursors for Chemical Vapor Deposition

Volatile cobalt (I) hydride complexes HCo[R 1 OP(OR 2 ) 2 ] 4 were synthesized, where R 1 = Me, Et, i -Pr, n -Pr, n -Bu, i -Bu, Ph, and benzyl, and R 2 = Me and Et. The cobalt complexes were obtained as liquids as R 1 was lengthened from ethyl to longer chains. The thermal stability of the complex was lowered with bulky R 1, thus, HCo[ n -PrOP(OMe) 2 ] 4 and HCo[ n -BuOP(OMe) 2 ] 4 were distillable but HCo[ i -BuOP(OMe) 2 ] 4 was not. Pure cobalt films of smooth and dense surface morphology were deposited on Si at temperatures as low as 270 °C using the cobalt hydrides as precursors under reduced pressure without employing H 2 .