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Die vielfältigen Anwendungen transparenter leitfähiger Oxide (TCO), wie zum Beispiel in Flachbildschirmen, Solarzellen und der Beleuchtungstechnik erfordern die Entwicklung neuartiger TCO-Materialien. Darüber hinaus ist der Einsatz der etablierten TCOs, wie Indiumzinnoxid (ITO) oder Fluor dotiertes Zinnoxid (FTO) zukünftig nur bedingt fortzuführen. Die Verwendung von ITO ist aufgrund des kontinuierlich steigenden Indiumpreises sehr kostenintensiv, während der Einsatz von FTO-Dünnschichten aufgrund des hochgradig toxischen Herstellungsprozesses weltweit umstritten ist. Es konnte gezeigt werden, dass Titandioxid dotiert mit Tantal (TTO) vergleichbare elektrische und optische Eigenschaften, verglichen mit den etablierten TCOs aufweist. Eine wesentliche Herausforderung besteht allerdings darin, TTO-Dünnschichten mittels eines industrienahen kostengünstigen Prozess abzuscheiden. Diese Problemstellung wurde gelöst, indem TTO-Schichten mittels eines 2-stufigen Prozesses, bestehend aus Sputterabscheidung und anschließender Blitzlampentemperung, hergestellt wurden. Die dabei erreichten spezifischen Widerstände im Bereich von 0,001 Ohmcm entsprechen denen, bei Nutzung konventioneller Ofentemperung und sind für zahlreiche Anwendung ausreichend.

Die vielfältigen Anwendungen transparenter leitfähiger Oxide (TCO), wie zum Beispiel in Flachbildschirmen, Solarzellen und der Beleuchtungstechnik erfordern die Entwicklung neuartiger TCO-Materialien. Darüber hinaus ist der Einsatz der etablierten TCOs, wie Indiumzinnoxid (ITO) oder Fluor dotiertes Zinnoxid (FTO) zukünftig nur bedingt fortzuführen. Die Verwendung von ITO ist aufgrund des kontinuierlich steigenden Indiumpreises sehr kostenintensiv, während der Einsatz von FTO-Dünnschichten aufgrund des hochgradig toxischen Herstellungsprozesses weltweit umstritten ist. Es konnte gezeigt werden, dass Titandioxid dotiert mit Tantal (TTO) vergleichbare elektrische und optische Eigenschaften, verglichen mit den etablierten TCOs aufweist. Eine wesentliche Herausforderung besteht allerdings darin, TTO-Dünnschichten mittels eines industrienahen kostengünstigen Prozess abzuscheiden. Diese Problemstellung wurde gelöst, indem TTO-Schichten mittels eines 2-stufigen Prozesses, bestehend aus Sputterabscheidung und anschließender Blitzlampentemperung, hergestellt wurden. Die dabei erreichten spezifischen Widerstände im Bereich von 0,001 Ohmcm entsprechen denen, bei Nutzung konventioneller Ofentemperung und sind für zahlreiche Anwendung ausreichend.

Transparent electrodes are widely used in photovoltaic cells which drives the need for novel cost-efficient transparent conductive materials. The epitaxially grown TiO2 films doped with Nb or Ta show electrical resistivity values comparable to those of the best In2O3:Sn and ZnO:Al films. However, for the most applications the growth of low electrical resistivity polycrystalline TiO2 films is required. In order to address this challenge, we studied the films formed on glass substrates without heating by DC magnetron sputtering of reduced TiO2:Ta ceramic targets followed by vacuum annealing. We present a systematic study of the effect of the process total pressure (Ar+O2) during the deposition on electrical and structural properties of the films after annealing. The optimum total pressure in combination with O2 fine tuning yielded the films with the best free electron mobility of 8 cm²/Vs. Our approach delivered films with an electrical resistivity in the range of 10-3  cm, optical transmittance above 80% for 400nm thick films and electrical activation of Ta dopants up to 80% that is substantially higher than that of Al in ZnO.

Transparent conductive oxides (TCO), mainly In2O3:Sn (ITO), ZnO:Al (AZO) and SnO2:F (FTO) are widely used as transparent electrodes in flat panel displays, thin film solar cells and solid state lighting. The markets for the applications requiring large area electrodes are continuously growing recent years which drives the need for a cost-efficient replacement of conventional TCOs. In addition to a low cost, TiO2 offers unique combination of high refractive index, stability against humidity, the high chemical stability and the non-toxicity. The Nb or Ta doped TiO2 films epitaxially grown on crystalline substrates show electrical and optical properties which are comparable to those of conventional TCOs. However, using expensive crystalline substrates drastically limits applications. It is still a challenge to achieve low electrical resistivity polycrystalline TiO2 films as required for the most applications. Furthermore, it is not possible to get low resistivity in polycrystalline films by direct growth at elevated substrate temperature. Only a two-step approach containing the deposition of amorphous films followed by annealing in vacuum or hydrogen delivers films with resistivity values in the range of 1·10-3 cm. Even in that case, it is known that electrical, optical and structural properties evolution during crystallization, and crystallization itself, is strongly affected by the Ti/O ratio in the as-deposited films. Achieving required Ti/O ratio remains the main challenge. In order to address this problem, we studied the films formed on glass substrates without heating by DC magnetron sputtering of reduced TiO2-x:Ta ceramic targets followed by vacuum annealing. We achieved oxygen fine-tuning using a MS process in conjunction with a plasma feedback system. The optimum total pressure in combination with O2 fine tuning yielded the films with the best free electron mobility of 8 cm²/Vs. Our approach delivered films with an electrical resistivity in the range of 10-3 W

Grain enlargement of the poly silicon is a key process to improve the electronic properties of microelectronic and photovoltaic devices. We report on lateral dendritic crystal growth in thin silicon films during liquid phase crystallization (LPC) induced by high intensity flash lamp irradiation (FLA). In a series of experiments first a 140 nm SiO2 film and then amorphous silicon of 100 nm thickness were deposited on 500µm thick (100) Si wafers. After that the top silicon film was ion implanted with carbon, first, with the aim to improve the wetting properties of the underlying silicon dioxide by the liquid silicon film during the LPC process. Secondly, due its different solubility in solid and liquid silicon, carbon is responsible for the formation of a laterally depending melting temperature inducing a lateral dendritic growth process. To prove in particular this influence of carbon on the wetting and crystallization process, the flash lamp irradiated structures were studied using XTEM analysis. The pulse annealing process was carried out using the commercial flash lamp annealing tool FLA-50RD of DTF-Technology. The installed set of standard Xenon flash lamps guarantees irradiation densities up to 150 J/cm2 at a pulse length of 20 ms on preheated substrates. As expected, depending on the carbon implantation conditions and the FLA energy densities, the films show, as a result, up to several hundred micrometers extended grains having the characteristic dendritic shape.

Transparent conductive oxides (TCO), mainly In2O3:Sn (ITO), ZnO:Al (AZO) and SnO2:F (FTO) are widely used as transparent electrodes in flat panel displays, thin film solar cells and solid state lighting. The markets for the applications requiring large area electrodes are continuously growing recent years which drives the need for a cost-efficient replacement of conventional TCOs. In addition to a low cost, TiO2 offers unique combination of high refractive index, stability against humidity, the high chemical stability and the non-toxicity. The Nb or Ta doped TiO2 films epitaxially grown on crystalline substrates show electrical and optical properties which are comparable to those of conventional TCOs. However, using expensive crystalline substrates drastically limits applications. It is still a challenge to achieve low electrical resistivity polycrystalline TiO2 films as required for the most applications. Furthermore, it is not possible to get low resistivity in polycrystalline films by direct growth at elevated substrate temperature. Only a two-step approach containing the deposition of amorphous films followed by annealing in vacuum or hydrogen delivers films with resistivity values in the range of 1·10-3 cm. Even in that case, it is known that electrical, optical and structural properties evolution during crystallization, and crystallization itself, is strongly affected by the Ti/O ratio in the as-deposited films. Achieving required Ti/O ratio remains the main challenge. In order to address this problem, we studied the films formed on glass substrates without heating by DC magnetron sputtering of reduced TiO2-x:Ta ceramic targets followed by vacuum annealing. We achieved oxygen fine-tuning using a MS process in conjunction with a plasma feedback system. The optimum total pressure in combination with O2 fine tuning yielded the films with the best free electron mobility of 8 cm²/Vs. Our approach delivered films with an electrical resistivity in the range of 10-3 W

Transparent electrodes are widely used in photovoltaic cells which drives the need for novel cost-efficient transparent conductive materials. The epitaxially grown TiO2 films doped with Nb or Ta show electrical resistivity values comparable to those of the best In2O3:Sn and ZnO:Al films. However, for the most applications the growth of low electrical resistivity polycrystalline TiO2 films is required. In order to address this challenge, we studied the films formed on glass substrates without heating by DC magnetron sputtering of reduced TiO2:Ta ceramic targets followed by vacuum annealing. We present a systematic study of the effect of the process total pressure (Ar+O2) during the deposition on electrical and structural properties of the films after annealing. The optimum total pressure in combination with O2 fine tuning yielded the films with the best free electron mobility of 8 cm²/Vs. Our approach delivered films with an electrical resistivity in the range of 10-3  cm, optical transmittance above 80% for 400nm thick films and electrical activation of Ta dopants up to 80% that is substantially higher than that of Al in ZnO.

Grain enlargement of the poly silicon is a key process to improve the electronic properties of microelectronic and photovoltaic devices. We report on lateral dendritic crystal growth in thin silicon films during liquid phase crystallization (LPC) induced by high intensity flash lamp irradiation (FLA). In a series of experiments first a 140 nm SiO2 film and then amorphous silicon of 100 nm thickness were deposited on 500µm thick (100) Si wafers. After that the top silicon film was ion implanted with carbon, first, with the aim to improve the wetting properties of the underlying silicon dioxide by the liquid silicon film during the LPC process. Secondly, due its different solubility in solid and liquid silicon, carbon is responsible for the formation of a laterally depending melting temperature inducing a lateral dendritic growth process. To prove in particular this influence of carbon on the wetting and crystallization process, the flash lamp irradiated structures were studied using XTEM analysis. The pulse annealing process was carried out using the commercial flash lamp annealing tool FLA-50RD of DTF-Technology. The installed set of standard Xenon flash lamps guarantees irradiation densities up to 150 J/cm2 at a pulse length of 20 ms on preheated substrates. As expected, depending on the carbon implantation conditions and the FLA energy densities, the films show, as a result, up to several hundred micrometers extended grains having the characteristic dendritic shape.