Monday, May 15, 2006

US Patent 7042003 - Nanoparticle Light Sensor

Many scientists have considered the use of nanostructured materials as comparable to introducing a new state of matter into industrial processes. While most people are used to thinking of matter as being of one of only four forms (solid, liquid, gas, plasma), nanoparticulate matter may add a fifth category - surface. The surface-to-volume ratio for nanoparticles is so high that completely different behavior may be observed when comparing a material in traditional crystalline solid form and crystalline nanoparticle form. US Patent 7042003, assigned to Samsung, demonstrates one example of the exploitation of this difference. Claim 1 reads-

1. A light receiving element comprising: two electrodes positioned opposite each other; and a light receiving portion interposed between the two electrodes, said light receiving portion comprising interconnected nanoparticles each having a core portion and a shell portion, said core portion of each nanoparticle being composed of a higher band gap material and said shell portion of each nanoparticle being composed of a lower band gap material.

Differing band gap materials placed together are used to form pn junctions- a basic component to electronic and optoelectronic devices. It is common for light sensing devices to employ pn junctions, however typically the pn junctions are formed in different layers on a substrate wafer. The inventors of this patent replace the traditional pn junction structure by an interconnected structure generated by cores and shells of nanoparticles. Improved light receiving efficiency, the ability to detect light from multiple directions or of divergent polarity, and the ability to tune the wavelength of light to be detected (determined by the nanoparticle size) are some of the advantages of this type of light sensor.