Patterned Nanowires of Se and Corresponding Metal Chalcogenides from Patterned Amorphous Se Nanoparticles

Colloidal self-assembly, involving gravity and evaporation-driven sedimentation was used to achieve selective coverage of amorphous Se (a-Se) nanoparticles on a patterned substrate. The in situ growth of nanowires from a-Se nanoparticles immobilized on featureless substrates and subsequent topotactic reactions into metal chalcogenides were verified. The results show that some a-Se nanoparticles are partially concentrated at the edge of contact and grow into nanowires. Nanaoparticles are found to dewet from the hydrophobic photoresist and assemble into holes, depositing on the exposed hydrophilic Si substrate during slow evaporation and suspension. An initial aging procedure in ethanol at room temperature is expected to activate partial or surface crystallization of a-Se nanoparticles. It is also found that all the transformed nanowires are single crystalline, consistent with X-ray diffraction (XRD) for trigonal Se, orthorhombic Ag2Se, and wurtzite-CdSe.