ZnO is a promising II-VI semiconductor for UV applications although p-type ZnO is not yet available. Nevertheless it remains an alternative material for GaN and its alloy InGaN. For example, the exciton binding energy of ZnO (60 meV) is higher than that of GaN (21 meV). This allows ZnO to emit light at ambient temperature and interestingly, it increases the device brightness. Besides promising intrinsic properties, light-matter control and especially in the UV relies on the ability of material nanostructuring. We present here two different kinds of top-down process in order to nanostructure ZnO. The first one relies on Electron Beam Lithography (EBL) combined with a lift-off process and inductively coupled plasma (ICP) reactive ion etching (RIE). Nickel (Ni) has been used as a mask in order to have a high selectivity in the presence of C2F6 and O2 ionized gases. The etching rate used was 26nm/s in order to avoid roughness. The second process is called Direct Holographic Patterning (DHP). ZnO thin films have been holographicaly patterned for the first time by direct photodissolution in NaCl solution using laser interference lithography. Application of an electrical potential strongly increases the dissolution rate and decreases the pattern formation time. Both processes will be discussed in terms of their respective potential for light confinement in the UV.
Due to its wide direct band gap and large exciton binding energy allowing for efficient excitonic emission at room
temperature, ZnO has attracted attention as a luminescent material in various applications such as UV-light emitting
diodes, chemical sensors and solar cells. While low-cost growth techniques, such as chemical bath deposition
(CBD), of ZnO thin films and nanostructures have been already reported; nevertheless, ZnO thin films and
nanostructures grown by costly techniques, such as metalorganic vapour phase epitaxy, still present the most
interesting properties in terms of crystallinity and internal quantum efficiency.
In this work, we report on highly efficient and highly crystalline ZnO micropods grown by CBD at a low
temperature (< 90°C). XRD and low-temperature photoluminescence (PL) investigations on as-grown ZnO
micropods revealed a highly crystalline ZnO structure and a strong UV excitonic emission with internal quantum
efficiency (IQE) of 10% at room temperature. Thermal annealing at 900°C of the as-grown ZnO micropods leads to
further enhancement in their structural and optical properties. Low-temperature PL measurements on annealed ZnO
micropods showed the presence of phonon replicas, which was not the case for as-grown samples. The appearance
of phonon replicas provides a strong proof of the improved crystal quality of annealed ZnO micropods. Most
importantly, low-temperature PL reveals an improved IQE of 15% in the excitonic emission of ZnO micropods. The
ZnO micropods IQE reported here are comparable to IQEs reported on ZnO structures obtained by costly and more
complex growth techniques. These results are of great interest demonstrating that high quality ZnO microstructures
can be obtained at low temperatures using a low-cost CBD growth technique.
The PbSe nanocrystals were synthesized without impurity from lead oleate and Se(TOP) by heating in phenyl ether. The particle size increases the synthesis temperature. The PbSe QD / PPA nanocomposite was made with the synthesized PbSe nanocrystals and the amine-containing PPA polymer by using the ligand exchange method. The PbSe nanocrystals were well dispersed in the PbSe QD / PPA nanocomposite. The PbSe QD / PPA nanocomposite film has the broad PL peak around 1300 nm with FWHM of ~ 170 nm. The time constant in the PbSe QD / PPA nanocomposite film is as slow as ~ 150 ns. We investigated the structures of the developed PbSe QD / PPA nanocomposite film as well as their optical properties, and then suggested their photonic applications.