Method of producing compound nanorods and thin films

Abstract

A method of producing compound nanorods and thin films under a controlled growth mode is described. The method involves ablating compound targets using an ultrafast pulsed laser and depositing the ablated materials onto a substrate. When producing compound nanorods, external catalysts such as pre-deposited metal nanoparticles are not involved. Instead, at the beginning of deposition, simply by varying the fluence at the focal spot on the target, a self-formed seed layer can be introduced for nanorods growth. This provides a simple method of producing high purity nanorods and controlling the growth mode. Three growth modes are covered by the present invention, including nanorod growth, thin film growth, and nano-porous film growth.

1 . A pulsed laser deposition system for producing compound nanorods, comprising:
 a pulsed laser system generating pulses having pulse durations in the range from 10 fs to 100 ps, and providing adjustable pulse energy in a range from below an ablation threshold of a target material to several times above an evaporation threshold of the target material; and   a chamber containing background gases comprising oxygen and nitrogen, wherein the system produces ablated portions of target material comprising nanoparticles and vaporized target material with different respective laser fluence values applied to the target material.   
   
   
       2 . A device comprising nanorods made by a non-catalytic process including the steps of
 ablating a target material with laser pulses, the laser pulses comprising at least one pulse having a pulse duration in the range from about 10 fs to 100 ps and providing a fluence substantially lower than a plasma threshold of the target material, the fluence sufficiently low such that at least a large portion of ablated material comprises nanoparticles;   forming a seed layer on a substrate by depositing at least a portion of the nanoparticles on a substrate;   ablating a target material with laser pulses, at least one pulse having a pulse duration in the range from about 10 fs to 100 ps and providing a sufficiently high fluence such that the ablated material comprises substantially vaporized target material; and   forming the nanorods on the seed layer by depositing at least a portion of the vaporized target material on the seed layer.