Synthesis and Thermal Study of Hexacoordinated Aluminum(III) Triazenides for Use in Atomic Layer Deposition

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.

Synthesis, Structure and Thermal Properties of Volatile Indium and Gallium Triazenides

“…The appropriate lithiated 1,3-dialkyltriazenide ligand was prepared in the same manner as that for the aluminium triazenides. 35 Freshly prepared ligand was reacted with either InCl3 or GaCl3 to give compounds 1b-f and 2b-f (Scheme 1). All compounds except 1d and 2d were purified by recrystallisation to give colourless solids.…”

“…THF or 9:1 THF/hexanes -78 °C, 20 min then r.t., 16 h In contrast to their Al(III) analogues, 35 compounds 1b-f and 2b-f had sufficiently rapid exchange to yield time-averaged 1 H NMR spectra at room temperature (see supporting information). The faster exchange for 1a-f and 2a-f is explained by their longer M-N bonds, which allows for faster isomerisation via Rây−Dutt or Bailar twist.…”

“…28,29 The improved volatility of these new compounds over the literature examples can be explained by the higher electron density residing on the triazenide ligand backbone. 35,39,40 Compound 2d showed two distinct mass-loss events and gave ~21% residual mass. Unfortunately, we were unable to obtain satisfactory elemental analysis for 2d and thus the residual mass could be a result of impurities or precursor decomposition.…”

Synthesis, Structure and Thermal Properties of Volatile Group 11 Triazenides as Potential Precursors for Vapor Deposition

“…29,30 Recently, we reported the first examples of volatile group 13 and 14 dialkyltriazenides. [31][32][33][34] The Ga and In triazenides have been used as ALD precursors to afford excellent quality GaN, InN, InGaN and In2O3. 31,32,35,36 With the success of the triazenide ligand to produce volatile and thermally stable group 13 and 14 compounds, we decided to investigate its reactivity with monovalent coinage metals.…”

Synthesis, Characterization, and Thermal Study of Divalent Germanium, Tin, and Lead Triazenides as Potential Vapor Deposition Precursors

“…Recently, we explored the 1,3-dialkyltriazenide ligand for group 13 metals and used the In(III) and Ga(III) 1,3-diisopropyltriazenide precursors for ALD of InN and GaN. 33 − 35 To further explore the 1,3-dialkyltriazenide ligand, we envisaged its ability to stabilize divalent group 14 elements. This would potentially give a new class of tetracoordinated M–N bonded group 14 precursors for ALD.…”