To utilize the full potential of semiconductor materials in device applications including solar cells, LEDs, and lasers, the ability to precisely and controllably tune the charge carrier concentration and hence the doping density is crucial. The conventional methods such as impurity doping with thermal diffusion or ion implantation, have been successfully implemented for doping bulk semiconductors for decades. In spite of the maturity of doping with traditional methods, it has remained a long-standing challenge to introduce impurity doping successfully into organic and new generation of semiconductors, such as conducting polymers and quantum dots. Additionally, the prospect of new technologies and the shrinkage in the device dimensions to nanoscale have stimulated researchers to search for alternative methods for achieving doping of such semiconductor materials reliably. Electrochemical doping is arguably the most powerful and versatile method for doping porous semiconductor materials, in which the charge carrier concentration can be precisely and controllably modulated as a function of applied potential by an external voltage source. Unfortunately, when the doped semiconductor film is disconnected from the voltage source, the electrochemically injected charges leave the film spontaneously in a matter of seconds to few minutes. In that regard, the stability of injected charges as well as the immobilization of external dopant ions need to fixed for achieving stable electrochemical doping of such semiconductor films to be used in device applications. The research carried out in this thesis is aimed to enhance the stability of injected charges and the fixation of dopant ions with photopolymerization treatment at room temperature in electrochemically doped quantum dots and conducting polymers. This was attempted by understanding the underlying mechanism of electrochemical doping in such porous films and eliminating or minimizing possible causes for instability with the final goal of producing stable doped of semiconductor films.@en

The increasingly complex nanoscale three-dimensional and multilayered structures utilized in nanoelectronic, catalytic, and energy conversion/storage devices necessitate novel substrate-selective material deposition approaches featuring bottom-up and self-aligned precision processing. Here, we demonstrate the area-selective atomic layer deposition (AS-ALD) of two noble metals, Pt and Pd, by using a plasma-polymerized fluorocarbon layer as growth inhibition surfaces. The contact angle, x-ray photoelectron spectroscopy (XPS), and scanning electron microscopy measurements were performed to investigate the blocking ability of polymerized fluorocarbon (CFx) layers against ALD-grown metal films. Both Pt and Pd showed significant nucleation delays on fluorocarbon surfaces. Self-aligned film deposition is confirmed using this strategy by growing Pt and Pd on the microscale lithographically patterned CFx/Si samples. CFx blocking layer degradation during ozone exposure was analyzed using XPS measurements, which confirmed the oxygen physisorption as the main responsible surface reaction with further hydroxyl group formation on the CFx surface. Our work reveals that the CFx layer is compatible with an ozone coreactant until the blocking polymer cannot withstand oxygen physisorption. Our results could potentially be used to investigate and develop radical-assisted AS-ALD processes for a wider selection of materials.@en

Quantum dots (QDs) are considered for devices like light-emitting diodes (LEDs) and photodetectors as a result of their tunable optoelectronic properties. To utilize the full potential of QDs for optoelectronic applications, control over the charge carrier density is vital. However, controlled electronic doping of these materials has remained a long-standing challenge, thus slowing their integration into optoelectronic devices. Electrochemical doping offers a way to precisely and controllably tune the charge carrier concentration as a function of applied potential and thus the doping levels in QDs. However, the injected charges are typically not stable after disconnecting the external voltage source because of electrochemical side reactions with impurities or with the surfaces of the QDs. Here, we use photopolymerization to covalently bind polymerizable electrolyte ions to polymerizable solvent molecules after electrochemical charge injection. We discuss the importance of using polymerizable dopant ions as compared to nonpolymerizable conventional electrolyte ions such as LiClO4 when used in electrochemical doping. The results show that the stability of charge carriers in QD films can be enhanced by many orders of magnitude, from minutes to several weeks, after photochemical ion fixation. We anticipate that this novel way of stable doping of QDs will pave the way for new opportunities and potential uses in future QD electronic devices. @en