Nanoparticle fabrication
Methods for fabricating at least one nanoparticle include providing one or more substrates and depositing a substance on the one or more substrates. At least one portion of the substance is heated or annealed so the at least one portion beads up on the one or more substrates due to cohesive forces of the substance being greater than adhesive forces between the substrate and the substance. In some methods, a pattern generation process is performed to define the at least one portion. A combination of a substance material for the substance and a substrate material for the one or more substrates may also be selected so that the at least one portion beads up into a predetermined shape. The substance may also be deposited on the one or more substrates with a sub-monolayer thickness or with gaps to further reduce a nanoparticle size.
1. A method for fabricating a nanoparticle on a substrate, the method comprising:
depositing a substance directly onto the substrate by a pattern generation process that defines an at least one portion of the deposited substance having a diameter D and an effective thickness T; and
heating the at least one portion of the substance at a temperature less than the melting temperature of the substance and for a time sufficient so that the at least one portion of the substance beads up on the substrate due to cohesive forces of the at least one portion of the substance being greater than adhesive forces between the substrate and the at least one portion of the substance, thereby forming the nanoparticle on the substrate,
wherein the substance consists of a first metal, wherein the first metal consists of gold, silver, copper, or aluminum, and the substrate consists of a second metal, wherein the second metal consists of platinum or palladium, and
wherein the effective thickness T is selected to provide a nanoparticle diameter d with a reduction factor r of less than about 1.0, and wherein d=r D and r=((3T)/(2D)) 1/3 .
2. The method of claim 1 , wherein depositing the substance includes performing a pattern generation process to define each portion of the at least one portion of the substance to have a size dimension, and wherein heating the at least one portion of the substance reduces the size dimension of each portion of the at least one portion of the substance in forming the at least one nanoparticle.
3. The method of claim 1 , wherein the at least one portion of the substance is heated to bead up into at least one nanoparticle having a spherical shape.
4. The method of claim 1 , further comprising selecting a combination of one substance material and one substrate material so that the at least one portion of the substance beads up into a predetermined shape on the substrate during heating.
5. The method of claim 1 , further comprising selecting a combination of one substance material and one substrate material or a temperature at which to heat the at least one portion of the substance to obtain a contact angle within a predetermined range of angles between the at least one portion of the substance and the substrate during or following heating of the at least one portion of the substance.
6. The method of claim 1 , wherein heating the at least one portion of the substance includes heating the at least one portion of the substance to a temperature between 300 and 500 degrees Celsius.
7. The method of claim 1 , wherein heating the at least one portion of the substance includes heating the at least one portion of the substance and the substrate in an ambient medium, the ambient medium including a vacuum, argon gas, nitrogen gas, air, an oil, a polymer, a metal, or a semiconductor material.