Method of molecular-scale pattern imprinting at surfaces

Abstract

A method for mask-free molecular or atomic patterning of surfaces of reactive solids is disclosed. A molecular-scale pattern of adsorbate molecules is used in place of the conventional macroscopic “mask”. Molecules adsorb at surfaces in patterns, governed by the structure of the surface, the chemical nature of the adsorbate, and the adsorbate coverage at the surface. The surface is patterned and then marked or imprinted with the pattern by inducing localised chemical reaction between adsorbate molecules and the surface of the solid, resulting in an imprint being formed in the vicinity of the adsorbate molecules. In one aspect of the invention, photoinduced or electron-induced reaction of the patterned adsorbate leads to patterned reaction with the surface. The reaction can take the form of patterned attachment to the surface (patterned “writing” or “doping”) or patterned removal of atoms from the surface (“etching” which takes place in the initial reaction or through subsequent irradiation of the patterned surface). The adsorbate when irradiated with light, electrons or ions imprints a pattern on the substrate by localised reaction. The new method is exemplified by the case of a silicon substrate and chlorobenzene molecules which first adsorb in a pattern on a silicon crystal, and which when irradiated with light or electrons chlorinates the crystal in a similar pattern to that of the adsorbate. The method is suitable for the writing, doping or etching of molecular-scale features. The molecular scale imprinted patterns may be used to produce quantum confinements on the surfaces of nanoscale metal or semiconductor wires or films which will result in diffraction of electrons of selected energies. Variation of voltage or illumination may be used to vary the energy of the electrons.