Study of bismuth alkoxides as possible precursors for ALD

Abstract

While searching for bismuth precursors for thin film preparation by atomic layer deposition (ALD) three bismuth alkoxides Bi(OtBu)3 (1), Bi(OCMe2iPr)3 (2), Bi(OC iPr3)3 (3), bismuth β-diketonate, Bi(thd)3 (4), and bismuth carboxylate, Bi(O2C tBu)3 (5), were synthesized and evaluated. The compounds were characterized by CHN, NMR, MS, and TGA/SDTA. Earlier unknown crystal structures of compounds 1 and 3 were solved. Compound 1 forms dimeric and loose polymeric structures in the solid state while 3 is strictly monomeric. For compound 2 crystals suitable for complete structure solution could not be grown. Crystallization trials of 2 from hexane and toluene resulted in oxygen bridged tetramer [Bi2O(OCMe2iPr)4] 2 (6). Compound 4 has dimeric structure and compound 5 forms loose tetramers as reported earlier. The structure of toluene solvated crystal [Bi(O2CtBu)3]4·2MeC 6H5 (7) was solved. All compounds studied showed relatively good volatility and thermal stability. They were all tested in ALD deposition experiments, in which compound 2 was found to be the most suitable for ALD growth of Bi2O3. It exhibited a clear improvement over Bi precursors studied earlier. © The Royal Society of Chemistry 2010.