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首页> 外文学位 >Synthesis and characterization of group 5 metal complexes containing pyrazolate, amidate, and related ligands as potential precursors for thin film growth by Atomic Layer Deposition.
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Synthesis and characterization of group 5 metal complexes containing pyrazolate, amidate, and related ligands as potential precursors for thin film growth by Atomic Layer Deposition.

机译：包含吡唑酸酯，酰胺酸酯和相关配体的5族金属配合物的合成和表征，这些配合物是通过原子层沉积进行薄膜生长的潜在前体。

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摘要

Atomic Layer Deposition (ALD) is an advanced variant of Chemical Vapor Deposition (CVD) and is used to deposit smooth and conformal thin films for applications in the microelectronics industry. ALD requires metal precursors that are sufficiently volatile and thermally stable at elevated temperatures. Several group 5 ALD and CVD precursors were reported in the literature, which have been used to deposit TaN, NbN, Nb2O5, and Ta 2O5 thin films. Synthesis of low and mid valent group 5 metal ALD precursors might give us access to deposit NbO2, Nb2O 3, Ta2O3, and TaO2 thin films by low temperature ALD pathways upon applying mild oxidation conditions. To this end, attempts were made to synthesize niobium(IV) and tantalum(IV) complexes from pyrazolate, amidate, and alpha-iminoketone ligand systems. Pyrazolate compounds undergo reductive N-N bond cleavage on Nb(IV) and Ta(IV) metal centers and afford six membered metallacycles that are analogous to metallapyrimidines and metallapyrimidiniums. Two other pyrazolate ligands are found to be intact and the final oxidation state of the complexes were +5. Those metallacycles are nearly planer, conjugated, have 6 pi-electrons, and follow the Huckel formalism, hence formally aromatic. In order to estimate the aromaticity of those metallacycles against pyrazoles and pyrimidines, NICS calculations were performed. The metallacycles were found to be aromatic but only weakly aromatic than that of pyrimidines and pyrazoles.;In order to synthesize metal complexes that are in the +4 oxidation state, a novel class of Ta(IV) and Nb(IV) amidate compounds with a variety of substituent groups were synthesized and structurally characterized. All the compounds are monomeric and isolated by sublimation at temperatures between 110-160 °C/0.05 Torr. Several compounds were crystallized in solution and X-ray crystal structures were obtained to address the structural features. TGA/DTA traces, melting points, and decomposition temperatures were used for the thermal stability assessment and preparative sublimation experiments were carried out to estimate the volatility properties. We have identified several compounds that are sufficiently volatile and thermally stable, which can be used as precursors for ALD to deposit group 5 metal oxide thin films.;Due to the fact that the limited availability of group 5 ALD precursors, we have synthesized niobium and tantalum compounds from &agr;-iminoketonate ligands. The six-coordinate niobium and tantalum alpha-iminoketonate complexes were structurally characterized by X-ray crystallography and found that one of the alpha-iminoketone ligands undergo hydrogen abstraction at the alpha-carbon atom. Further evidence of hydrogen atom abstraction was obtained by 1H NMR experiments. In order to understand the reaction mechanism DFT calculations were performed on those compounds, several putative intermediates, and hypothetical gallium alpha-iminoketone analogs. The bond lengths of the possible intermediates and the experimental bond distances were compared and identified a plausible intermediate for the reaction. The resulted complexes were found out to be in the +5 oxidation state and contain two fully reduced alpha-iminoketone ligands and one iminoalkoxi ligand, which is a formal pi-radical monoanion.
机译：原子层沉积（ALD）是化学气相沉积（CVD）的高级变体，用于沉积光滑的保形薄膜，用于微电子行业。 ALD要求金属前驱物在高温下具有足够的挥发性和热稳定性。文献中报道了几种第5组ALD和CVD前体，这些前体已用于沉积TaN，NbN，Nb2O5和Ta 2O5薄膜。中低价5族金属ALD前驱物的合成可能使我们能够在施加温和的氧化条件后通过低温ALD途径沉积NbO2，Nb2O 3，Ta2O3和TaO2薄膜。为此，尝试从吡唑酸酯，酰胺酸酯和α-亚氨基配体系统合成铌（IV）和钽（IV）配合物。吡唑酸盐化合物在Nb（IV）和Ta（IV）金属中心进行还原性N-N键裂解，并提供六元金属环，类似于金属嘧啶和金属嘧啶鎓。发现其他两个吡唑酸酯配体完好无损，配合物的最终氧化态为+5。这些金属环几乎是平面的，共轭的，具有6个pi电子，并且遵循Huckel形式，因此正式为芳族。为了估计这些金属环对于吡唑和嘧啶的芳香性，进行了NICS计算。发现金属环芳烃是芳香族的，但仅比嘧啶和吡唑的芳香族弱。为了合成处于+4氧化态的金属配合物，新型的Ta（IV）和Nb（IV）酰胺化物与合成了各种取代基并对其结构进行了表征。所有化合物均为单体，通过在110-160°C / 0.05 Torr之间的升华进行分离。几种化合物在溶液中结晶，并获得X射线晶体结构以解决结构特征。使用TGA / DTA痕量，熔点和分解温度进行热稳定性评估，并进行制备性升华实验以评估挥发性。我们已经确定了几种具有足够挥发性和热稳定性的化合物，可以用作ALD的前驱物来沉积第5组金属氧化物薄膜。由于第5组ALD前驱物的可用性有限，我们合成了铌和-亚氨基酮酸酯配体中的钽化合物。通过X射线晶体学对六配位的铌和钽的α-亚氨基酮络合物进行结构表征，发现其中一个α-亚氨基酮配体在α-碳原子处发生了氢抽象。通过1 H NMR实验获得了氢原子抽象的进一步证据。为了理解反应机理，对那些化合物，几种推定的中间体和假设的镓α-亚氨基酮类似物进行了DFT计算。比较了可能的中间体的键长和实验的键距，并确定了可能的反应中间体。发现所得的络合物处于+5氧化态，并且包含两个完全还原的α-亚氨基酮配体和一个亚氨基铝氧烷配体，其为正式的自由基单阴离子。

著录项

  • 作者

    Perera, Thuduwage Hiran.;

  • 作者单位

    Wayne State University.;

  • 授予单位 Wayne State University.;
  • 学科 Chemistry General.;Engineering Materials Science.;Chemistry Inorganic.
  • 学位 Ph.D.
  • 年度 2013
  • 页码 122 p.
  • 总页数 122
  • 原文格式 PDF
  • 正文语种 eng
  • 中图分类
  • 关键词

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