Abstract
Amidinate and guanidinate ligands have been used extensively to produce volatile and thermally stable precursors for atomic layer deposition. The triazenide ligand is relatively unexplored as an alternative ligand system. Herein, we present six new Al(III) complexes bearing three sets of a 1,3-dialkyltriazenide ligand. These complexes volatilize quantitatively in a single step with onset volatilization temperatures of ∼150 °C and 1 Torr vapor pressures of ∼134 °C. Differential scanning calorimetry revealed that these Al(III) complexes exhibited exothermic events that overlapped with the temperatures of their mass loss events in thermogravimetric analysis. Using quantum chemical density functional theory computations, we found a decomposition pathway that transforms the relatively large hexacoordinated Al(III) precursor into a smaller dicoordinated complex. The pathway relies on previously unexplored interligand proton migrations. These new Al(III) triazenides provide a series of alternative precursors with unique thermal properties that could be highly advantageous for vapor deposition processes of Al containing materials.
Highlights
Aluminum nitride (AlN) is a semiconductor material widely used in current day electronic devices.[1]
Tris(1,3-dialkyltriazenide)aluminum(III) compounds 1−6 were prepared in good yields by reacting the (1,3-dialkyltriazenide)lithium(I) intermediate, generated from an alkylazide[32,33] and alkyllithium, with AlCl3 (Scheme 1)
Synthesis of Tris(1,3dialkyltriazenide)aluminum(III) Compounds 1−6 compounds were purified by recrystallization and were fully characterized by nuclear magnetic resonance (NMR) spectroscopy, elemental analysis (EA), sublimation temperature, and melting point
Summary
Aluminum nitride (AlN) is a semiconductor material widely used in current day electronic devices.[1] This is due to its desirable chemical, optical, and electronic properties, such as high thermal stability, a wide direct band gap, and piezoelectricity.[2] As electronic devices rapidly miniaturize with increasingly complex surface structures, atomic layer deposition (ALD) becomes a vital technique for depositing uniform thin films of high-performance materials for future microelectronics.[3] In ALD, the metal and nonmetal precursors are introduced into the reaction chamber separately, which allows the film mechanism to be governed by two independent and self-limiting half reactions. We reported the first examples of highly volatile homoleptic 1,3-dialkyltriazenide complexes, tris(1,3diisopropyltriazenide)In(III) (In(triaz)3)[30] and Ga(III) (Ga(triaz)3),[31] and their use as ALD precursors These new triazenide precursors underwent gas-phase decomposition at higher temperatures inside the ALD reactor, giving a smaller and more reactive M(III) species. The unique thermal properties of these compounds make them potentially advantageous as precursors for vapor deposition processes
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