Well-Oriented Pyrazine Lines and Arrays on Si(001) Formed by Thermal Activation of Substrate

Abstract

Self-assembled molecular structures formed on a bare Si(001) surface at high temperature have been studied by scanning tunneling microscopy (STM). Linearly arranged pyrazine (C4H4N2) adsorbates were observed that had grown by self-assembly along the Si dimer bond direction on the heated Si(001) substrate. The degree of one-dimensional ordering of the molecules at elevated substrate temperatures (∼60–170 °C) was improved over that at room temperature. In cases of higher pyrazine dosage, well-ordered (2 × 2) molecular arrays were also observed by STM. We found that the molecules tend to adsorb on step edges and defect sites. Utilizing this selective adsorption near the step edge, pyrazine lines were successfully fabricated at regular spacing on the vicinal Si substrate. The local structure of the pyrazine adsorbate on the step edge is the same as that on the terrace. The ordering of molecules on the surface is closely related to the fact that the adsorbate can migrate without decomposition through metastable structures with a N–Si bond on the high-temperature substrate.