Kim Ansoon, Filler Michael A, Kim Sehun, Bent Stacey F
Department of Chemistry and School of Molecular Science (BK21), Korea Advanced Institute of Science and Technology, Daejeon 305-701, Republic of Korea.
J Am Chem Soc. 2005 Apr 27;127(16):6123-32. doi: 10.1021/ja042751x.
We have demonstrated the layer-by-layer growth, via a urea coupling reaction between two bifunctional molecules, ethylenediamine and 1,4-phenylene diisocyanate, to form an ultrathin film on Ge(100)-2 x 1 at room temperature under vacuum conditions. The initial adsorption and subsequent growth of each layer was studied with multiple internal reflection Fourier transform infrared (MIR-FTIR) spectroscopy. Ethylenediamine reacts with Ge(100)-2 x 1 to produce a surface-bound amine group which is available for additional reaction. Subsequent exposure of 1,4-phenylene diisocyanate leads to a spontaneous urea coupling reaction between the surface-bound amine and the highly reactive isocyanate functional group. Three bands at 1665, 1512, and 1306 cm(-)(1) are characteristic of a urea linkage and provide evidence of the coupling reaction. The coupling procedure can be repeated in a binary fashion to create covalently bound ultrathin films at room temperature, and in the present work, we demonstrate the successful growth of four layers. In addition, we have found that an initial exposure of 1,4-phenylene diisocyanate to Ge(100)-2 x 1 produces an isocyanate-functionalized surface which, upon exposure to ethylenediamine, also forms urea linkages. This layer-by-layer deposition method provides a strategy with which to design and produce precisely tailored organic materials at semiconductor interfaces.
我们已经证明，在真空条件下，通过乙二胺和1,4-亚苯基二异氰酸酯这两种双功能分子之间的尿素偶联反应，在室温下于Ge(100)-2×1上逐层生长形成超薄膜。利用多重内反射傅里叶变换红外光谱（MIR-FTIR）对每一层的初始吸附和后续生长进行了研究。乙二胺与Ge(100)-2×1反应生成表面结合的胺基，该胺基可用于进一步反应。随后暴露1,4-亚苯基二异氰酸酯会导致表面结合的胺与高反应性异氰酸酯官能团之间发生自发的尿素偶联反应。1665、1512和1306 cm⁻¹处的三个谱带是尿素键的特征，为偶联反应提供了证据。该偶联过程可以以二元方式重复，以在室温下形成共价结合的超薄膜，在本工作中，我们展示了成功生长四层的情况。此外，我们发现，将1,4-亚苯基二异氰酸酯初始暴露于Ge(100)-2×1会产生异氰酸酯官能化的表面，该表面在暴露于乙二胺时也会形成尿素键。这种逐层沉积方法提供了一种在半导体界面设计和生产精确定制有机材料的策略。
