Atomic layer deposition of cobalt(II) oxide thin films from Co(BTSA)2(THF) and H2O

Abstract

In this work, we have studied the applicability of Co(BTSA)2(THF) (BTSA = bis(trimethylsilyl)amido) (THF = tetrahydrofuran) in atomic layer deposition (ALD) of cobalt oxide thin films. When adducted with THF, the resulting Co(BTSA)2(THF) showed good volatility and could be evaporated at 55 °C, which enabled film deposition in the temperature range of 75-250 °C. Water was used as the co-reactant, which led to the formation of Co(II) oxide films. The saturative growth mode characteristic to ALD was confirmed with respect to both precursors at deposition temperatures of 100 and 200 °C. According to grazing incidence X-ray diffraction measurements, the films contain both cubic rock salt and hexagonal wurtzite phases of CoO. X-ray photoelectron

Co(II) Amide, Pyrrolate, and Aminopyridinate Complexes: Assessment of their Manifold Structural Chemistry and Thermal Properties

“…In a next step, we aimed to synthesize Co(II) complexes bearing chelating amido-amine ligands and decided to introduce the two closely related ligands N,N-dimethyl(N'-tert-butyl)ethane-1,2-diamine (H-TBUAEDMA) [27] and N,N-dimethyl(N'-trimethylsilyl)ethane-1,2-diamine (H-TMSAEDMA). [28] Employing a standard salt metathesis route, Co(TBUAEDMA)2 (10) and Co(TMSAEDMA)2 (11) were obtained as black and purple solids from 1:2 reaction of CoCl2…”

“…While Lewis acid base complexation with the chosen Lewis bases failed to yield precursors with improved volatility, they might yet be interesting for CVD applications as thermal instability is introduced. Besides, the initially mentioned successful demonstration of [Co(TMSA)2(THF)] as ALD precursor for CoOx thin films through Iivonen and co-workers [10] still evidences the complexation approach to be viable for the synthesis of enhanced Co(II) ALD precursors. The most pronounced contrast in terms of thermal stability and volatility was observed for the two pyrrolato complexes 8 and 9 as it can be seen in Figure 6 c. While the latter demonstrated clean one-step evaporation with a residual mass of only 5.5 % and an onset temperature of around 203 °C, compound 8 with its non-π-conjugated pyrrole dimethylaminoethyl side chain barely volatilized intactly.…”

“…This is surprising as the two allnitrogen coordinated precursors Co(II) bis-(di-tert-butyl-acetamidinate), [8] and Co(II) bis-(ditert-butyl-diazadienyl) (Co(DAD)2) [9] have led to significant advancements in ALD and material science. While the likely best known Co(II) silylamide [Co(N(SiMe3)2)2]2 in the following referred to as [Co(TMSA)2]2 has not found application in this field yet, the recent usage of its Lewis base coordinated congener [Co(TMSA)2(THF)] in ALD [10] raises the question if all-nitrogen Lewis adducts of the type [Co(TMSA)2L] could be viable precursor candidates. In this regard, it is noteworthy, that a number of Co(II) silylamides and Lewis adducts adapted from them have already been studied in recent years in terms of their structural, electronic and magnetic properties.…”

“…Figure 4: Solid state structures of the title compounds Co(AMPR)2 (8), Co(IMPR)2 (9), Co(TBUAEDMA)2(10) …”

Co(II) Amide, Pyrrolate, and Aminopyridinate Complexes: Assessment of their Manifold Structural Chemistry and Thermal Properties**

“…This is surprising as the two all-nitrogen coordinated precursors Co(II) bis-(di-tert-butyl-acetamidinate), [10] and Co(II) bis-(di-tert-butyl-diazadienyl) [Co(DAD) 2 ] [11] have led to significant advancements in ALD and material science. While the best known Co(II) silylamide [Co(N(SiMe 3 ) 2 ) 2 ] 2 , hereafter called [Co-(TMSA) 2 ] 2 ) has not found application in this field, the recent use of its Lewis base congener [Co(TMSA) 2 (THF)] in ALD [12] suggests that all-nitrogen Lewis adducts of the type [Co(TMSA) 2 L] could be viable precursor candidates. It is noteworthy that a number of Co(II) silylamides and Lewis adducts adapted from them have been studied in recent years in terms of their structural, electronic and magnetic properties.…”