Study on Structural and Thermal Characteristics of Heteroleptic Yttrium Complexes as Potential Precursors for Vapor Phase Deposition

Abstract

Yttrium oxide (Y2O3) thin films are implemented as a functional component in a broad field of applications such as optics, electronics or thermal barrier coatings. Atomic layer deposition (ALD) is a promising technique to fabricate high‐quality thin films with atomic level precision in which the precursor choice plays a crucial role in process development. The limited number of suitable yttrium precursors available for ALD of Y2O3 has triggered increasing research activity seeking new or modified precursors. In this study, heteroleptic compounds of yttrium bearing the cyclopentadienyl (Cp) ligand in combination with the chelating amidinate or guanidinate ligands were targeted as potential precursors for ALD. In this context, a systematic and comparative study of the structure and thermal characteristics of (bis‐cyclopentadienyl‐(N,N'‐diisopropyl‐2‐methyl‐amidinato)yttrium) [YCp2(dpamd)] 1 and (bis‐cyclopentadienyl‐(N,N'‐diisopropyl‐2‐dimethylamido‐guanidinato)yttrium) [YCp2(dpdmg)] 2 was performed. Complementary characterization tools such as 1H‐NMR, elemental analysis, electron‐impact mass spectrometry (EI‐MS) and single‐crystal X‐ray diffraction (XRD) confirmed the spectroscopic purity and the monomeric nature of the metalorganic compounds. Hirshfeld surface analysis revealed influence of the ligand choice on the intermolecular interactions of the compounds. The important figures of merit for a precursor, namely the thermal properties were investigated via thermogravimetric analysis. Thus, the volatility, transport behavior and thermal stability were examined and compared to their homoleptic counterparts [YCp3], [Y(dpamd)3] or [Y(dpdmg)3].

Rare-Earth–Silyl ate-Complexes Opening a Door to Selective Manipulations

“…Nevertheless, the Y–Cp centroid distances of 5 between 2.38 and 2.39 Å are quite typical. The respective values of Cp 3 Y , are much more diverse, ranging from 2.37 to 2.50 Å. In accordance with the 29 Si NMR signal for the SiMe 2 O unit the Y–O SiMe2 distance of 5 (2.484(2) Å) is larger than in 2Y (2.422(2) Å).…”

Ferromagnetic Europium Sulfide Thin Films: Influence of Precursors on Magneto-Optical Properties

“…Interaction energies were found to be −0.05 eV ( 1 ), −0.10 eV ( 2 ), and −0.92 eV ( 3 ), respectively. DFT calculations show that interaction energies follow the trend of [Eu­(dpfamd) 3 ] < [Eu­(dpamd) 3 ] < [Eu­(dpdmg) 3 ], suggesting that higher steric demand of the ligand results in stronger interactions between the molecules, which confirms findings on comparable Y precursors using Hirshfeld surface analysis …”

“…DFT calculations show that interaction energies follow the trend of [Eu(dpfamd) 3 ] < [Eu(dpamd) 3 ] < [Eu(dpdmg) 3 ], suggesting that higher steric demand of the ligand results in stronger interactions between the molecules, which confirms findings on comparable Y precursors using Hirshfeld surface analysis. 77 Chemical reactions with sulfur were simulated in the gas phase, which allowed us to understand the principal behavior upon reactions of the complexes toward S 8 during sulfidebased CVD processes. In our model, we selected S 2 and S 4 as vaporized co-reactant species, which are known to be formed during thermal heating of elemental sulfur.…”

Atomic layer deposition of dielectric Y2O3 thin films from a homoleptic yttrium formamidinate precursor and water

“…The lower 1 torr vapor pressure temperature for [Y(DPfAMD) 3 ] might be caused by a smaller contribution of van der Waals interactions in the solid state during evaporation due to the small –H substituent in the N–C–N backbone and a lower molecular weight. 30 The superior thermal properties namely, enhanced thermal stability, high volatility and intrinsic reactivity render the yttrium formamidinate [Y(DPfAMD) 3 ] as an interesting and promising alternative precursor to the already established [Y(DPAMD) 3 ] and [Y(DPDMG) 3 ] in ALD processes.…”