Properties of [Mg₂(thd)₄] as a Precursor for Atomic Layer Deposition of MgO Thin Films and Crystal Structures of [Mg₂(thd)₄] and [Mg(thd)₂(EtOH)₂]

Abstract

Complexes [Mg 2 (thd) 4 ] (1) and [Mg(thd) 2 (EtOH) 2 ] (2) (Hthd ) 2,2,6,6-tetramethyl-3,5heptanedione) were prepared and characterized using various techniques, viz. X-ray diffraction, NMR and mass spectroscopy, and thermal analysis. Crystal structures of compounds 1 and 2 were determined. Complex 1 crystallizes as a dimer where three oxygen atoms from three different thd ligands join the Mg atoms together. Crystallization from ethanol results in a monomeric complex having solvent coordinated to Mg. Both complexes volatilize completely, but in 2, coordinated ethanol molecules do not stay intact in the gas phase. Complex 1 was used with H 2 O 2 as precursors in the growth of MgO thin films by atomic layer deposition techniques. A rather constant growth rate of 0.10-0.14 Å/cycle was observed at 325-425 °C.

Synthesis and Structural Characterization of a Novel Magnesium β‐Diketonatoalkoxide Complex: A New Precursor for the MOCVD of MgO

“…Approximately 15 % of the complex evaporates in two stages over the temperature range 100±180 C, corresponding to sequential loss of adducted MeOH ligand. The remaining part of the complex, [Mg(OMe)(thd)] 4 , evaporates in the temperature region 280±340 C (T 50 %~3 10 C), which is slightly higher than the evaporation range of Mg(thd) 2 (200±318 C; T 50 % = 294 C), [7] consistent with a higher degree of association. The evaporation temperature range of 1 is also slightly higher than the evaporation tem- perature of Pb(thd) 2 (280±310 C), the most useful co-precursor for the MOCVD of Pb(Mg,Nb)O 3 .…”

“…These latter bond lengths are consistent with those found in Mg(thd) 2 (phen) (2.011±2.043 ), [18] and Mg(thd) 2 (EtOH) 2 (2.004±2.062 ). [7] The asymmetry in bonding is promulgated throughout the thd ligand, resulting in distinctive differences in nominally equivalent C±C and C±O bonds of between 0.02 and 0.03 (Fig. 3).…”

Polydentate Amines as CVD Precursor Ancillary Ligands. Epitaxial MgO Thin-Film Growth Using a Highly Volatile, Thermally and Air-Stable Magnesium Precursor

“…Residual H 2 O is removed from the colorless solid by drying in a vacuum dessicator over P 4 O 10 , and 1 is subsequently purified via multiple vacuum sublimation (100 C/10 ±4 torr). [24] The average Mg±O distance in 1 for O atoms trans to the amine N atoms (O1A, O1B) is slightly shorter at 2.001(1) than that for the cis O atoms (O2A, O2B) at 2.030(1) , and the average Mg±N distance is 2.282 (2) . Complex 1 was fully characterized by NMR, elemental analysis, single-crystal X-ray diffraction (XRD), and vacuum TGA.…”

“…[24] The average Mg±O distance in 1 for O atoms trans to the amine N atoms (O1A, O1B) is slightly shorter at 2.001(1) than that for the cis O atoms (O2A, O2B) at 2.030(1) , and the average Mg±N distance is 2.282 (2) . [24] In this case, the intrinsic volatility advantages of monomeric complexes are not utilized. As a consequence of the larger ionic radius, the structure of the analogous Ba 2+ complex is eight-coordinate: Ba(dpm) 2 (TMEDA) 2 .…”

The Crystal Structure of Unadducted Strontium bis-Tetramethylheptanedionate: The Standard Precursor for the MOCVD of Strontium-Containing Oxides

“…Consequently, the compounds either oligomerize, or react with solvent or donor impurities such as water. For the alkaline earth M(thd) 2 complexes, the extent of oligomerization depends on the size of the metal atom, and it has been shown that the Mg complexes form dimers, [11] Ca and Sr form trimers, [9,10] whilst the largest metal, Ba, forms tetramers, [9] and even pentamers and hexamers are known. [12±15] The presence of the three six-coordinate Sr atoms in [Sr(thd) 2 ] 3 , compared to the six-, seven-, and eight-coordinate Sr atoms present in [Sr(thd) 2 ] 3 (thdH), [9] explains the high moisture sensitivity of the complex and the difficulties formerly encountered in obtaining anhydrous or solvent-free Sr(thd) 2 .…”