Laser writing of semiconductor nanoparticles and quantum dots

• Published in: Applied physics letters 2004-12, Vol.85 (24), p.6007-6009
• Main Authors: Bertino, M. F., Gadipalli, R. R., Story, J. G., Williams, C. G., Zhang, G., Sotiriou-Leventis, C., Tokuhiro, A. T., Guha, S., Leventis, N.
• Format: Article
• Language: English
• Subjects: ABSORPTION; AMMONIUM HYDROXIDES; AQUEOUS SOLUTIONS; CADMIUM SULFIDES; HEATING; HYDROPHYLIC POLYMERS; MATERIALS SCIENCE; NEODYMIUM LASERS; PARTICLES; PHOTOLUMINESCENCE; PRECURSOR; QUANTUM DOTS; RAMAN SPECTRA; RAMAN SPECTROSCOPY; SEMICONDUCTOR MATERIALS; SILICA; SILICON COMPOUNDS; SOLVENTS; THIOUREA; TRANSMISSION ELECTRON MICROSCOPY
• ISSN: 0003-6951; 1077-3118
• DOI: 10.1063/1.1836000

Silica aerogels were patterned with CdS using a photolithographic technique based on local heating with infrared (IR) light. The solvent of silica hydrogels was exchanged with an aqueous solution of the precursors CdNO 3 and NH 4 OH , all precooled to a temperature of 5 ° C . Half of the bathing solution was then replaced by a thiourea solution. After thiourea diffused into the hydrogels, the samples were exposed to a focused IR beam from a continuous wave, Nd - YAG laser. The precursors reacted in the spots heated by the IR beam to form CdS nanoparticles. We lithographed features with a diameter of about 40 μ m , which extended inside the monoliths for up to 4 mm . Samples were characterized with transmission electron microscopy and optical absorption, photoluminescence, and Raman spectroscopies. Spots illuminated by the IR beam were made up by CdS nanoparticles dispersed in a silica matrix. The CdS nanoparticles had a diameter in the 4 - 6 nm range in samples exposed for 4 min to the IR beam, and of up to 100 nm in samples exposed for 10 min .