Jul 28, 2011
Electron beam lithography forms 2D hybrid photonic crystal slab
New generation materials "under construction" should enhance the performance of photonic devices and broaden their applications, which usually means improving functionality and reducing cost. Tremendous innovations are expected from polymer coatings that exhibit superior functional properties at low cost. One option is to include nanoparticles in the polymer matrix. The challenge is to avoid phase separation, aggregation of nanoparticles and loss of transparency.
Researchers at the Institute of Cybernetics of the Italian National Council of Research (CNR) have prepared a highly transparent and luminescent nanocomposite by incorporating colloidal semiconductor quantum rods of nanometre size into a polymer matrix. Shortly afterwards, the team patterned the nanocomposite to create a novel 2D hybrid photonic crystal (PC) slab.
The highly transparent hybrid organic/inorganic nanocomposite is formed by using inorganic nanorods, core/shell CdSe/CdS quantum rods, as inclusions in an organic polymer matrix. The structure has been prepared as a film in which each domain/inclusion can perform a specific photonic or optoelectronic (combined electronic and photonic) function. A semiconductor nanocrystal-based 2D-PC pattern was uniformly fabricated by electron beam lithography over a large area of 2 × 2 mm2.
To characterize the nanostructures, white light was introduced from an edge of the glass and propagated inside the slab. When it came to investigating the vertical extraction of the light (light propagating in the glass substrate which is extracted by diffraction), the researchers found a very narrow orange emission band with a full width at half maximum (FWHM) of 10 nm. The main peak corresponds to the apparent resonant mode of the PC.
The group's results are extremely appealing in view of the technological impact of hybrid metamaterials such as photonic crystals on the development of new high-performance optical devices such as organic light-emitting diodes, ultra-low threshold lasers and non-linear devices.
Further information can be found in the journal Nanotechnology.
About the author
The study was conducted by research teams of the Italian Institute of Cybernetics "E Caianiello" (ICIB) of CNR in Pozzuoli, the Italian Institute of Technology (IIT) in Genova, and the Institute of Photonics of Ningbo University, China. Lucia Petti is a permanent researcher at the Institute of Cybernetics of the Italian National Council of Research (CNR). She is responsible for the Unit "Nanotechnology and Materials for Composites Devices" of the CNR Department for Materials and Devices. Her current research focuses on photonics, electro- and nonlinear optics with liquid crystals, polymers and organic molecules, and on the fabrication of integrated optical nanodevices by electron beam lithography. Dr Petti conceived of the study, carried out the nanocomposite preparation, the fabrication of the samples, and the SEM characterizations. Massimo Rippa is a postdoc at ICIB. He performed the far field diffraction characterization and the spectra measurements. Prof. Jun Zhou is head of the Institute of Photonics at Ningbo University, China. Dr Liberato Manna is head of the Nanochemistry Facility at the Italian Institute of Technology in Genova (Italy). Dr Manna supervised the synthesis of the colloidal nanorods and provided the TEM characterization. Dr Pasquale Mormile is head of the Photonics Unit at the Institute of Cybernetics of the Italian National Council of Research (CNR). Prof. Zhou and Dr Mormile participated in the design of the study.