Owing to the limited availability of suitable precursors for vaporp hase deposition of rare-earth containing thin-filmm aterials, new or improved precursors are sought after.I nt his study,w ee xplored new precursors for atomic layer deposition(ALD)o fc erium (Ce) and ytterbium(Yb) containing thin films. As eries of homoleptic tris-guanidinate and tris-amidinatec omplexes of cerium (Ce) and ytterbium (Yb) were synthesized andt horoughlyc haracterized. The Csubstituents on the N-C-N backbone (Me, NMe 2 ,N Et 2 ,w here Me = methyl, Et = ethyl) and the N-substituents from symmetrical iso-propyl (iPr) to asymmetrical tertiary-butyl (tBu) and Et were systematically varied to study the influence of the substituents on the physicochemical properties of the resulting compounds. Single crystal structures of [Ce(dpdmg) 3 ] 1 and [Yb(dpdmg) 3 ] 6 (dpdmg = N,N'-diisopropyl-2-dimethylamido-guanidinate) highlightamonomeric nature in the solid-state with ad istorted trigonal prismatic geometry.T he thermogravimetric analysis shows that the complexes are volatile and emphasize that increasing asym-metryi nt he complexes lowers their meltingp oints while reducingt heir thermal stability.D ensityf unctionalt heory (DFT) was used to study the reactivity of amidinates and guanidinates of Ce and Yb complexes towards oxygen (O 2) and water (H 2 O). Signified by the DFT calculations, the guanidinates show an increased reactivity toward water compared to the amidinate complexes. Furthermore,t he Ce complexes are more reactive compared to the Yb complexes,i ndicating even ar eactivity towards oxygen potentiallye xploitable for ALD purposes. As arepresentative precursor,the highly reactive [Ce(dpdmg) 3 ] 1 wasu sed for proof-of-principleA LD depositions of CeO 2 thin films using watera sc o-reactant. The self-limited ALD growth process could be confirmed at 160 8Cw ithp olycrystalline cubic CeO 2 films formed on Si(100) substrates. This study confirmst hat moving towards nitrogen-coordinated rare-earth complexes bearing the guanidinate and amidinate ligands can indeed be very appealing in terms of new precursors for ALD of rare earth based materials.
Atomic / molecular layer deposition (ALD/MLD) process for the fabrication of cerium-based metal-organic hybrid films is demonstrated for the first time. The highly reactive cerium (III) guanidinate precursor [Ce(dpdmg)3] was...
devices has driven academic and industrial research on alternatives such as cobalt (Co) and ruthenium (Ru) to a new dimension. [1,2] These endeavors are based on the inherent limitations of Cu thin films as interconnect in the back end of line (BEOL) and middle of line (MOL) facing scale-down toward 2 nm. At these dimensions, Cu layers are exhibiting lower resistance toward electromigration as well as the tendency toward diffusion under thermal or current-induced stress. [3,4] Both, Co and Ru provide more suited physical, mechanical, and electrical properties. Especially shorter electron mean free paths and higher chemical stability are to be named in this regard. [1,[5][6][7] Recent studies have shown that the chosen metallization approach may decide which of the two is favored: Murdoch and co-workers demonstrated superior performance of Ru thin films in semidamascene structures outperforming those of Cu and Co layers. [8] Beyond great promise for IC applications, Ru catalysts are garnering significant interest, foremost in the context of electrocatalysis for hydrogen production through water splitting. Specifically, their outstanding performance in the oxygen Two novel ruthenium complexes belonging to the Ru(II)(DAD)(Cym) (DAD = diazadienyl) (Cym = cymene) compound family are introduced as promising precursors. Their chemical nature, potential for chemical vapor deposition (CVD), and possibly atomic layer deposition (ALD) are demonstrated. The development of nonoxidative CVD processes yielding high-quality Ru thin films is realized. Chemical analyses are exercised that vitiate the deceptive assumption of Ru(DAD)(Aryl) complexes being zero-valent through clear evidence for the redox noninnocence of the DAD ligand. Two different CVD routes for the growth of Ru films are developed using Ru( tBu2 DAD)(Cym). Ru thin films from both processes are subjected to thorough and comparative analyses that allowed to deduce similarities and differences in film growth. Ru thin films with a thickness of 30-35 nm grown on SiO 2 yielded close-to-bulk resistivity values ranging from 12 to 16 µΩ cm. Catalysis evaluation of the films in the acidic oxygen evolution reaction (OER) results in promising performances based on overpotentials as low as 240 mV with Tafel slopes of 45-50 mV dec −1 . Based on the degradation observed during electrochemical measurements, the impact of OER conditions on the layers is critically assessed by complementary methods.
New metalorganic precursors of cerium and ytterbium have been developed in this systematic study. Among them, a homoleptic guanidinate‐based cerium complex has been demonstrated as a promising precursor for water‐assisted atomic layer deposition of CeO2 thin films. More information can be found in the Full Paper by A. Devi et al. on page 4913.
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