Process and apparatus for forming nanoparticles using radiofrequency plasmas
Methods and apparatus for producing nanoparticles, including single-crystal semiconductor nanoparticles, are provided. The methods include the step of generating a constricted radiofrequency plasma in the presence of a precursor gas containing precursor molecules to form nanoparticles. Single-crystal semiconductor nanoparticles, including photoluminescent silicon nanoparticles, having diameters of no more than 10 nm may be fabricated in accordance with the methods.
1. A plasma reactor for producing nanoparticles, comprising:
a plasma reactor chamber having a length extending in a flow direction from an inlet to an outlet;
a source of a continuous precursor monomer gas flow through the plasma reactor chamber along the length of the plasma reactor chamber from the inlet to the outlet which includes a semiconductor containing precursor monomer, the source coupled to the inlet of the plasma reactor chamber;
at least two electrodes, the at least two electrodes arranged in the flow through the plasma reactor chamber perpendicular to the flow direction and spaced apart a distance along the length of the plasma reactor, and the at least two electrodes capacitively couple to the precursor monomer gas in the plasma rector chamber and wherein the gas flow is through the at least two electrodes; and
a high frequency voltage source capacitively coupled to the at least two electrodes which applies a high voltage therebetween and responsively continuously dissociates the semiconductor containing precursor monomer in the plasma reactor chamber to provide precursor species that nucleate and grow into semiconductor nanoparticles, wherein;
the precursor is primarily converted into nonagglomerated semiconductor nanoparticles and the nanoparticles are carried out of the reactor through the outlet in a continuous fashion.
2. The apparatus of claim 1 , including a substrate arranged to receive the semiconductor nanoparticles.
3. The apparatus of claim 2 , wherein the substrate is moved in a continuous or step-wise fashion to produce a film of crystalline nanoparticles on the substrate.
4. The apparatus of claim 1 , wherein the high frequency source generates single-crystal semiconductor nanoparticles from the source of continuous precursor monomer.
5. The apparatus of claim 1 , wherein the high frequency source generates single-crystal semiconductor nanoparticles having an average diameter of no more than about 50 nm from the source of continuous precursor monomer.
6. The apparatus of claim 1 , wherein the high frequency source generates Group IV semiconductor nanoparticles from the source of continuous precursor monomer.
7. The apparatus of claim 1 , wherein the high frequency source generates Group IV semiconductor nanoparticles comprising silicon nanoparticles from the source of continuous precursor monomer.
8. The apparatus of claim 1 , wherein the high frequency source generates semiconductor nanoparticles comprising Group II-VI semiconductor nanoparticles from the source of continuous precursor monomer.
9. The apparatus of claim 1 , wherein the high frequency source generates Group II-VI semiconductor nanoparticles comprising CdSe nanoparticles from the source of continuous precursor monomer.
10. The apparatus of claim 1 , wherein the high frequency source generates semiconductor nanoparticles comprising Group III-V semiconductor nanoparticles from the source of continuous precursor monomer.
11. The apparatus of claim 1 , wherein the high frequency source generates semiconductor nanoparticles comprising photoluminescent nanoparticles from the source of continuous precursor monomer.
12. The apparatus of claim 1 , wherein the at least two electrodes comprise a central high frequency powered capacitively coupled electrode and two ground electrodes on either side of the central high frequency powered electrode.
13. The apparatus of claim 1 , including an orifice and wherein nanoparticles are extracted through the orifice.
14. The apparatus of claim 13 , including a supersonic gas jet and wherein nanoparticles are accelerated by the supersonic gas jet.
15. The apparatus of claim 14 , wherein a substrate is arrange proximate the supersonic gas jet so that nanoparticles are impacted on the substrate with high velocity to form a nanoparticle film.
16. A plasma reactor for producing nanoparticles, comprising:
a plasma reactor chamber having a length extending in a flow direction from an inlet to an outlet;
a source of a continuous gas flow through the plasma reactor chamber along the length of the plasma reactor chamber from the inlet to the outlet which includes a semiconductor containing precursor monomer, the source coupled to the inlet of the plasma reactor chamber;
at least two electrodes arranged the plasma reactor chamber perpendicular to the flow direction and spaced apart a distance along the length of the plasma reactor, and configured to capacitively couple to gas in the plasma rector chamber wherein the gas flow is through the at least two electrodes; and
a high frequency voltage source coupled to the at least one of the two electrodes configured to apply a high voltage therebetween and responsively continuously dissociate the semiconductor containing precursor monomer in the plasma reactor chamber to provide precursor species that nucleate and grow into semiconductor nanoparticles, wherein;
the precursor is primarily converted into nonagglomerated semiconductor nanoparticles and the nanoparticles are carried out of the reactor through the outlet in a continuous fashion; and
wherein the at least two electrodes comprise a composite sheet disposed between an input chamber and an output chamber, the composite sheet comprising an RF powered electrode and a ground electrode separated by a dielectric medium, wherein the composite sheet defines a matrix of holes extending through the composite sheet.