There are currently several proposals to create molecular electronic devices using
individual organic molecules adsorbed to semiconductor surfaces [1,2]. This endeavor requires a detailed understanding of the nature of the organic/semiconductor interface and the ability to produce adsorbates that are stable during their characterisation by current - voltage (I-V) measurements. Here, we use scanning tunnelling microscopy (STM) and density functional theory (DFT) calculations to study the adsorption of simple ketone molecules (e.g. acetone) to the silicon and germanium (001) surfaces. Our results suggest that bonding of organic molecules to silicon via a carbonyl functional can result in adsorbate structures that exhibit increased stability under I-V characterization. We show bias and time-dependent STM images and their agreement with total energy DFT calculations and simulated STM images. We demonstrate the ability to convert from kinetically-favoured to thermodynamically-favoured adsorbate structures, which can be performed for individual molecules using the highly confined electron beam of the STM tip, or for the entire surface using a moderate thermal anneal. This work has important implications for the creation of robust single-molecule devices on silicon.
[1] N. P. Guisinger, et al., Nano Lett. 4, 55 (2004).
[2] J. L. Pitters and R. A. Wolkow, Nano Lett. 6, 390 (2006).
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