Chemistry of inorganic compounds – Silicon or compound thereof – Elemental silicon
Reexamination Certificate
2006-02-21
2006-02-21
Cooke, Colleen P. (Department: 1754)
Chemistry of inorganic compounds
Silicon or compound thereof
Elemental silicon
Reexamination Certificate
active
07001578
ABSTRACT:
A family of discrete and uniformly sized silicon nanoparticles, including 1 (blue emitting), 1.67 (green emitting), 2.15 (yellow emitting), 2.9 (red emitting) and 3.7 nm (infrared emitting) nanoparticles, and a method that produces the family. The nanoparticles produced by the method of the invention are highly uniform in size. A very small percentage of significantly larger particles are produced, and such larger particles are easily filtered out. The method for producing the silicon nanoparticles of the invention utilizes a gradual advancing electrochemical etch of bulk silicon, e.g., a silicon wafer. The etch is conducted with use of an appropriate intermediate or low etch current density. An optimal current density for producing the family is ˜10 milli Ampere per square centimeter (10 mA/cm2). Higher current density favors 1 nm particles, and lower the larger particles. Blue (1 nm) particles, if any appreciable quantity exist depending on the selected current density, may be removed by, for example, shaking or ultrasound. After the etch, the pulverized wafer is immersed in dilute HF for a short time, while the particles are still connected to the wafer to weaken the linkages between the larger particles. This may be followed by separation of nanoparticles from the surface of the silicon. Once separated, various methods may be employed to form plural nanoparticles into crystals, films and other desirable forms. The nanoparticles may also be coated or doped. The invention produces the family of a discrete set of sized particles and not a continuous size distribution. Particles may be isolated from the family, i.e., it is possible to produce any one of the sizes of particles from the family after the basic method steps have been executed to produce the family of particles.
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M.H. Nayfe
Belomoin Gennadey
Chaieb Sahraoui
Nayfeh Munir H.
Rao Satish
Therrien Joel
Cooke Colleen P.
Greer Burns & Crain Ltd.
The Board of Trustees of the University of Illinois
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