Protection of Atomically Thin, Flat Metal Layers on the Si(111) Substrate against Thermal Destruction by 7,7,8,8-Tetracyanoquinodimethane Adsorption

The Si(111)-quasi-5.5 × 5.5-In reconstruction that consists of a triple indium layer on the Si(111) substrate and is known to be unstable at room temperature can be protected against thermal destruction up to approximately 150 °C by the adsorption of the 7,7,8,8-tetracyanoquinodimethane (TCNQ) molecules. This is considered because the molecules attach to the edges of the quasi-5.5 × 5.5 domains, which prevent the indium atoms from detaching from them during the heating. Not only the top layer but also the second layer of the quasi-5.5 × 5.5 reconstruction is found to have metastable quasi-5.5 × 5.5 periodicity. The unit lengths of the In-TCNQ surface-confined metal–organic networks with a windmill-like motif formed on the quasi-5.5 × 5.5 domains in the present study are determined to be about 1.2 and 1.5 nm with the angle between them being about 100°.