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  • Laser Nanolithography Could Improve Nanomaterials
Jul 2014
SINGAPORE, July 23, 2014 — Laser nanolithography shows potential for improving nanomaterials for electronic and optoelectronic components. Research teams at the National University of Singapore, led by professor Dr. Sow Chorng Haur, used similar techniques to alter the optical properties of a film of molybdenum disulfide (MoS2) and an array of mesoporous silicon nanowires.

Collaborating with researchers from Hong Kong Baptist University, one team generated greenish-blue photoluminescence by fast-scanning a focused green (532 nm) laser beam with power of 5 to 105 mW over a nanowire array.

Micropatterns etched in mesoporous silicon nanowire arrays were invisible under a bright-field optical microscope, as depicted by (a) and (c), but visible under fluorescence microscopy, as depicted by (b) and (d). Courtesy of the National University of Singapore.

The technique was also used to create micropatterns that were invisible under a bright-field optical microscope but visible under a fluorescence microscope.

Using an optical microscope-focused laser beam, the Singapore researchers created microdomains with well-defined structures and controlled thickness on a 2-D film of MoS2, a transition metal dichalcogenide compound. They said the process increased the film’s electrical conductivity by a factor of 10 and its photoconductivity by a factor of five, allowing them to create photodetectors with improved performance.

The approach is simple and low-cost, the researchers said, and its selectivity has advantages over other techniques that modify films in their entirety.

The work was published in ACS Nano (doi: 10.1021/nn501821z) and Scientific Reports (doi:10.1038/srep04940).

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A sub-field of photonics that pertains to an electronic device that responds to optical power, emits or modifies optical radiation, or utilizes optical radiation for its internal operation. Any device that functions as an electrical-to-optical or optical-to-electrical transducer. Electro-optic often is used erroneously as a synonym.
The conductivity increase exhibited by some nonmetallic materials, resulting from the free carriers generated when photon energy is absorbed in electronic transitions. The rate at which free carriers are generated, the mobility of the carriers, and the length of time they persist in conducting states (their lifetime) are some of the factors that determine the amount of conductivity change.
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