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

Sebastian M J Beer,Anjana Devi,Constantin Vahlas,Manuela Winter,Annika Krusenbaum

doi:10.1002/ejic.202000436

Sebastian M J Beer, Anjana Devi + Show 3 more

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https://doi.org/10.1002/ejic.202000436

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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].

Highlights

Over the years, rare-earth oxides (REO) have been regarded as a promising class of materials which can be implemented in the form of powders[1] nanoparticles[2] or thin films[3] for a multitude of applications
A variety of vapor phase deposition techniques have been utilized in the past to deposit thin films of Y2O3, RE:Y2O3 and yttria-stabilized zirconia (YSZ), covering physical methods such as molecular beam epitaxy (MBE),[12] sputtering[6c,13] or pulsed laser deposition (PLD).[14]
One representative example is the combination of cyclopentadienyl and amidinate ligands resulting in heteroleptic rare-earth complexes of the type [RE(RCp)2(dpamd)] with R = H, Me, Et, iPr.[27]

Summary

Introduction

Rare-earth oxides (REO) have been regarded as a promising class of materials which can be implemented in the form of powders[1] nanoparticles[2] or thin films[3] for a multitude of applications. One representative example is the combination of cyclopentadienyl and amidinate ligands resulting in heteroleptic rare-earth complexes of the type [RE(RCp)2(dpamd)] (dpamd = N,N′-diisopropyl-2methyl-amidinato) with R = H, Me, Et, iPr.[27] This class of compounds was found to possess beneficial physicochemical properties such as lowering of melting points down to room temperature and high reactivity toward water.

Results

Conclusion