Synthesis, structure and properties of volatile lanthanide complexes containing amidinate ligands: application for Er2O3 thin film growth by atomic layer deposition

Abstract

Treatment of anhydrous rare earth chlorides with three equivalents of lithium 1,3-di-tertbutylacetamidinate (prepared in situ from the di-tert-butylcarbodiimide and methyllithium) in tetrahydrofuran at ambient temperature afforded Ln( t BuNC(CH 3 )N t Bu) 3 (Ln = Y, La, Ce, Nd, Eu, Er, Lu) in 57-72% isolated yields. X-Ray crystal structures of these complexes demonstrated monomeric formulations with distorted octahedral geometry about the lanthanide(III) ions. These new complexes are thermally stable at .300 uC, and sublime without decomposition between 180-220 uC/0.05 Torr. The atomic layer deposition of Er 2 O 3 films was demonstrated using Er( t BuNC(CH 3 )N t Bu) 3 and ozone with substrate temperatures between 225-300 uC. The growth rate increased linearly with substrate temperature from 0.37 A ˚per cycle at 225 uC to 0.55 A ˚per cycle at 300 uC. Substrate temperatures of .300 uC resulted in significant thickness gradients across the substrates, suggesting thermal decomposition of the precursor. The film growth rate increased slightly with an erbium precursor pulse length between 1.0 and 3.0 s, with growth rates of 0.39 and 0.51 A ˚per cycle, respectively. In a series of films deposited at 250 uC, the growth rates varied linearly with the number of deposition cycles. Time of flight elastic recoil analyses demonstrated slightly oxygen-rich Er 2 O 3 films, with carbon, hydrogen and fluorine levels of 1.0-1.9, 1.7-1.9 and 0.3-1.3 atom%, respectively, at substrate temperatures of 250 and 300 uC. Infrared spectroscopy showed the presence of carbonate, suggesting that the carbon and slight excess of oxygen in the films are due to this species. The as-deposited films were amorphous below 300 uC, but showed reflections due to cubic Er 2 O 3 at 300 uC. Atomic force microscopy showed a root mean square surface roughness of 0.3 and 2.8 nm for films deposited at 250 and 300 uC, respectively.

Synthesis and structural characterization of a homoleptic cerium(III) propiolamidinate

“…10 due to the large ionic radii of the lanthanide ions. With values of 54.16(15) and 54.31(17) the NeCeeN angles in 2 are virtually identical with those reported for [MeC(N t Bu) 2 ] 3 Eu (NeEueN: 54.1(3) and 54.7 (3) ) [12]. Quite remarkable are the dihedral angles between the phenyl ring planes and the NeCeN units of the chelating amidinate ligands.…”

“…The effective shielding of the cerium by six isopropyl groups obviously prevents the coordination of additional solvent molecules. The CeeN distances are in the narrow range of 2.487 (5)e2.502 (5) [12]. Thus the overall bond lengths and angles follow the trends which are expected taking into account the ionic radius of six-coordinated Ce(III) of 1.15 Å. Amidinate ligands generally have small NeMeN bite angles typically in the range of 63e65 .…”

Lanthanide N,N-Dimethylaminodiboranates: Highly Volatile Precursors for the Deposition of Lanthanide-Containing Thin Films

“…Quantitative comparisons are difficult, but the Ln(H 3 BNMe 2 BH 3 ) 3 compounds appear to be more volatile than lanthanide complexes of tetramethylheptanedionate, 30 guanidinates, 31 amidinates, 32 and cyclopentadienyls. 33 The sublimation temperatures are as low as (or lower than) those reported for certain lanthanide silylamides (72-102°C at 10 -4 Torr), 34 ether-functionalized -ketoiminates (80-110°C at 10 -4 Torr), 15 and methylborohydrides (100°C in Vacuo).…”

ALD of Scandium Oxide from Scandium Tris(N,N[sup ʹ]-diisopropylacetamidinate) and Water

“…A review of the literature shows several examples of an ALD process that is kinetically slow and the GPC can be increased by either a several orders of magnitude increase in exposure or an increase in temperature. 18,19 The stoichiometry was determined to be Sc 2 O 3.1 from RBS of a 40 nm film grown on a carbon substrate after forming gas anneal. The extra oxygen most likely is in the form of trapped hydroxyl groups, and some remain after the 5 min anneal at 425°C.…”