The micropatterning of layers of colloidal quantum dots with inorganic ligands using selective wet etching

• Published in: Nanotechnology Vol. 25; no. 17; pp. 175302 - 11
• Main Authors: Hu, Chen, Aubert, Tangi, Justo, Yolanda, Flamee, Stijn, Cirillo, Marco, Gassenq, Alban, Drobchak, Oksana, Beunis, Filip, Roelkens, Günther, Hens, Zeger
• Format: Journal Article
• Language: English
• Published: Bristol IOP Publishing 02.05.2014; Institute of Physics
• Subjects: Applied sciences; Cadmium selenides; Cadmium sulfides; Chemical Sciences; Colloids; Condensed matter: electronic structure, electrical, magnetic, and optical properties; Cross-disciplinary physics: materials science; rheology; Electronics; Engineering Sciences; Etching; Exact sciences and technology; integrated photonics; Intermetallics; layer-by-layer deposition; Ligands; Material chemistry; Materials; Materials science; Micropatterning; Molecular electronics, nanoelectronics; Nanocrystalline materials; nanocrystals; Nanoscale materials and structures: fabrication and characterization; optical lithography; Optical properties and condensed-matter spectroscopy and other interactions of matter with particles and radiation; Optical properties of low-dimensional, mesoscopic, and nanoscale materials and structures; Physics; Quantum dots; Semiconductor electronics. Microelectronics. Optoelectronics. Solid state devices; Inorganic ligand; Quantum dots; Core shell structure; Photoluminescence; Organic ligand; Large scale integration; Quantum yield; Thin films; Selective etching; Photoresists; Dip coating; Photolithography; Nanostructured materials; Sol-gel process
• ISSN: 0957-4484; 1361-6528
• DOI: 10.1088/0957-4484/25/17/175302

The micropatterning of layers of colloidal quantum dots (QDs) stabilized by inorganic ligands is demonstrated using PbS core and CdSe CdS core shell QDs. A layer-by-layer approach is used to assemble the QD films, where each cycle involves the deposition of a QD layer by dip-coating, and the replacement of the native organic ligands by inorganic moieties, such as OH− and S2−, followed by a thorough cleaning of the resulting film. This results in a smooth and crack-free QD film on which a photoresist can be spun. The micropatterns are defined by a positive photoresist, followed by the removal of uncovered QDs by selective wet etching with an HCl H3PO4 mixture. The resulting patterns can have submicron feature dimensions, limited by the resolution of the lithographic process, and can be formed on planar and 3D substrates. It is shown that the photolithography and wet etching steps have little effect on the photoluminescence quantum yield of CdSe CdS QDs. Compared with the unpatterned CdSe CdS QD film, only a 10% degradation in the quantum yield is observed. These results demonstrate the feasibility of the proposed micropatterning method to implement the large-scale device integration of colloidal quantum dots.