Infrared spectroscopic study of dimethylaluminum-hydride adsorption on oxidized, hydrogen-terminated, and reconstructed Si surfaces

Abstract

Adsorption and decomposition of dimethylaluminum-hydride (DMAH) on various Si(111) and Si(100) surfaces [chemically oxidized, hydrogen-terminated, reconstructed (7×7) and (2×1)] have been investigated at 90 K with a multiple reflection infrared (IR) attenuated total reflection (ATR) method. On the chemically oxidized Si(111) surface, IR absorption due to DMAH increased linearly with DMAH exposure, indicating that DMAH was merely condensed on the surface. Upon DMAH exposure to the hydrogen-terminated Si(111) surface, the stretch band of the surface monohydride (Si–H) diminished immediately, revealing that DMAH reacts with the terminated hydrogens. In contrast, DMAH exposure to the hydrogen terminated Si(100) surface leads to a slight intensity decrease in the bands due to surface hydrides (Si–Hx:x=1–3). On the reconstructed Si surfaces [Si(100)(2×1) and Si(111)(7×7)], IR bands due to DMAH could not be observed during the early stage of DMAH exposure, suggesting that the reactivity of DMAH with the reconstructed surfaces is extremely high. The surface reactivity at 90 K, as judged by IR absorption intensities of the methyl and Al–H groups in DMAH, decreases in the sequence, Si(100)(2×1), Si(111)(7×7), hydrogen-terminated Si(111), and hydrogen-terminated Si(100).