Solid-state dewetting refers to the spontaneous transformation, occurring over time and under specific annealing conditions, of ultra-thin solid films into three-dimensional structures. Initially considered undesirable, this phenomenon has been harnessed for various applications over the past three decades, ranging from light manipulation to biological filtering. In this study, we investigate the controlled dewetting instability of monocrystalline semiconductor thin films such as silicon, silicon-germanium and amorphous germanium atop silicon oxide. We examine different dewetting arrangements, including spontaneous void growth, controlled dewetting through edge retraction, and a spinodal-like mechanism. To further our understanding, we develop a novel, cost-effective, and time-efficient dewetting mechanism using rapid thermal annealing. This method allows us to investigate the dewetting of amorphous germanium thin layers. By employing this technique, we successfully produce dewetted disordered crystal Ge islands on large areas, exhibiting nearly-hyperuniform patterns with diverse shapes and densities. To evaluate the light manipulation properties of the dewetted framework, we transferred it, via degassed assisted patterning, to the back-contact of ultrathin solar cell to perform light-trapping and enhance the solar-cell efficiency.
Solid-state dewetting è il fenomeno fisico che descrive la capacità di un film sottile, instabile in particolari condizioni di pressione e temperatura, di agglomerarsi in strutture tridimensionali. Seppur tale fenomeno fosse inizialmente considerato svantaggioso per le nanotecnologie, oggi esso trova applicazione in diversi ambiti che spaziano dalla fotonica alla microfluidica. Questa ricerca si focalizza sull'analisi e comprensione del dewetting di film semiconduttori ultra-sottili (silicio, germanio e leghe di silicio-germanio) che evolvono tramite void-growth, edge retraction o tramite un meccanismo spinoidale. E' stato implementato un metodo innovativo che richiede l’uso di macchine di rapid thermal annealing, rapido e a basso costo, al fine di studiare il dewetting di materiale amorfo. Grazie a questa procedura sono state ottenute strutture di amorfo germanio spazialmente disposte in modo quasi-iperuniforme di densità e dimensione controllabile che non richiedono l’uso di costose tecniche litografiche. Al fine di mostrare le potenzialità di questa tecnica e aprire la strada ad ulteriori applicazioni nel light management, le geometrie quasi-iperuniformi sono state replicate tramite degassed assisted patterning sul back-contact di celle solari ultra-sottili al fine di effettuare light-trapping e migliorarne l’efficienza.
Instability investigation of thin solid films via solid-state dewetting
Barri, Chiara
2022/2023
Abstract
Solid-state dewetting refers to the spontaneous transformation, occurring over time and under specific annealing conditions, of ultra-thin solid films into three-dimensional structures. Initially considered undesirable, this phenomenon has been harnessed for various applications over the past three decades, ranging from light manipulation to biological filtering. In this study, we investigate the controlled dewetting instability of monocrystalline semiconductor thin films such as silicon, silicon-germanium and amorphous germanium atop silicon oxide. We examine different dewetting arrangements, including spontaneous void growth, controlled dewetting through edge retraction, and a spinodal-like mechanism. To further our understanding, we develop a novel, cost-effective, and time-efficient dewetting mechanism using rapid thermal annealing. This method allows us to investigate the dewetting of amorphous germanium thin layers. By employing this technique, we successfully produce dewetted disordered crystal Ge islands on large areas, exhibiting nearly-hyperuniform patterns with diverse shapes and densities. To evaluate the light manipulation properties of the dewetted framework, we transferred it, via degassed assisted patterning, to the back-contact of ultrathin solar cell to perform light-trapping and enhance the solar-cell efficiency.File | Dimensione | Formato | |
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https://hdl.handle.net/10589/207588