Adsorption and Decomposition Studies of t-Butylamine, Diethylamine, and Methylethylamine on Si(100)−(2 × 1)

• Published in: The journal of physical chemistry. B 2004-02, Vol.108 (5), p.1677-1685
• Main Authors: Wu, Jin-Bao, Yang, Yaw-wen, Lin, Yi-Feng, Chiu, Hsin-Tien
• Format: Article
• Language: English
• ISSN: 1520-6106; 1520-5207
• DOI: 10.1021/jp0349233

We have studied chemisorption and thermal decomposition of tert-butylamine (TBA), diethylamine (DEA), and methylethylamine (MEA) on Si(100)−(2 × 1) with synchrotron-based X-ray photoelectron spectroscopy (XPS) and temperature programmed desorption (TPD). Adsorption at cryogenic temperature leads to molecularly intact chemisorption (dative-bonding via the nitrogen lone pair) and dissociative chemisorption via N−H scission, producing distinct N 1s peaks at binding energies of 401.1 and 398.2 eV, respectively. The corresponding change for C 1s core level is also significant, and a 0.9 eV shift toward lower binding energy is found for DEA, suggesting a high degree of charge redistribution between two adsorption configurations. Upon warming to room temperature, the adsorbed amines almost completely transform into dissociative chemisorbed forms. Thermal decomposition of TBA at elevated temperatures produces desorption species of isobutylene via γ-H elimination, hydrogen cyanide, and H2. In comparison, DEA and MEA decompose thermally to desorb imine via β-H elimination, ethylene via γ-H elimination, hydrogen cyanide, and H2. Eventually, silicon nitride and silicon carbide are formed. Distinct decomposition pathways lead to a C/N ratio variation among the products, with TBA yielding the lowest C/N ratio.