Direct Laser Patterning of CdTe QDs and Their Optical Properties Control through Laser Parameters

Abstract

Direct laser patterning is a potential and powerful technique to localize nanomaterials within a host matrix. The main goal of this study is to demonstrate that by tuning some parameters of a laser source, like power and laser pulse frequency, it is possible to modify and tune the optical properties of the generated quantum dots (QDs) within a host matrix of a specific chemical composition. The study is realized by using cadmium telluride (CdTe) QD precursors, embedded in polymethylmethacrylate (PMMA) host matrix, as starting materials. The patterning of the CdTe QDs is carried out by using a UV nanosecond laser source at 355. Fluorescence microscopy and photoluminescence spectroscopy, associated with transmission electron microscopy, indicate that it is possible to obtain desired patterns of QDs emitting from green to red of the visible spectrum, due to the formed CdTe QDs. Preliminary highlights of the CdTe QDs’ formation mechanism are given in terms of laser power and laser pulse frequency (repetition rate).

Direct Optical Patterning of Quantum Dots: One Strategy, Different Chemical Processes

“…The direct synthesis of the scQDs by laser [ 102 ] is interesting from the scientific point of view. However, without the setup of an encapsulating agent it is not suitable for market exploitation.…”

“…This technique, often called direct laser patterning [ 101 ], combines the flexibility of the laser technique both at the industrial and technological level with the chemistry and optical properties of the QDs. Indeed, recently it was demonstrated that by changing the laser parameters, like the pulse power and frequency, it is possible to pattern (to grow) the scQDs, modulating their optical properties [ 102 ]. This kind of result has been possible by designing the chemical precursors within the film to be patterned in a proper way.…”

“… ( a ) Synthesis of the cadmium and tellurium precursors, the cadmium carboxylate and TOP-Te, and their chemical reaction during the laser synthesis within the PMMA layer; ( b ) red and green squares formed by CdTe QDs are obtained modulating the laser pulse frequency, dose, and speed. The size of the squares is 1 mm and the image were obtained with the fluorescence microscope exciting the film with UV radiation (Reproduced with permission from [ 102 ]). …”

“…This means including in the chemical formulation the suitable scQDs precursors, polymeric matrix, and other chemicals, allowing the laser-stimulated scQDs' growth (Figure 25a). laser parameters, like the pulse power and frequency, it is possible to pattern (to grow) the scQDs, modulating their optical properties [102]. This kind of result has been possible by designing the chemical precursors within the film to be patterned in a proper way.…”

Direct Laser Writing: From Materials Synthesis and Conversion to Electronic Device Processing

“…[103] Thus, many reports of process-property optimizations use power and speed pairs to determine useful processing windows, in opposition to undesirable outcomes such as ablation or incomplete reactions. [106,[114][115][116][117] A final aspect regarding writing speed is the fabrication and production time. While writing speed has a relevant impact on photon and thermalinduced conversion and synthesis processes, it is relevant to optimize DLW processes for maximum speed, allowing for higher fabrication throughput, contingent that material performance is not compromised.…”