Nanoscale Electrical Properties of Phase-Separated Thin Film

The performance of novel electronic devices like high-k dielectrics based field effect transistors, flexible organic displays and chemical sensors, active optoelectronic identification devices, organic solar cells, etc. can only be improved by unraveling and controlling the physical-chemical properties of underlying functional materials such as their complex electronic structure. On the other hand, these multicomponent materials are often disordered and show a strong tendency for phase separation on the micro- and nanoscale, which in turn controls their morphology and electronic properties. In particular, peculiar properties of phase-separated domains and interfacial boundaries dominate the carrier generation, trapping and transport through the active layer as well as its contact behavior. Therefore, separating material characteristics into particular components like phase-separated domain and the interfacial boundary is essential to recognize the physics of such devices and of the underlying material. Consequently, spatial resolving techniques are required in order to study, ideally in a non-invasive way, the structural and electrical properties of such materials on the nano- and microscale. Based on detailed nanoscale investigations of representative phase-separated structures relevant for practical application in the future electronics, this project aims to establish a deeper understanding of the interconnect between their electrical and morphological properties, which will contribute to further optimization of their fabrication conditions and corresponding device properties on the macroscopic scale. The structures with different kinds and degrees of phase separation will be investigated in detail using Kelvin Probe Force Microscopy and Conducting Atomic Force Microscopy. These techniques provide in addition to standard topography simultaneously material related electrical information (current, contact potential, electronic work function) and are therefore ideal complementary techniques to measure relative variations in electrical properties of phase-separated thin films on the nanoscale. For quantitative studies, samples will be measured under ultra-high vacuum conditions, in order to avoid the altering of the work function, surface modification and degradation effects during experiments. For detailed studies on the electrical characteristics, two-dimensional (2D) current and work function images as well as local I-V curves will be recorded. 2D maps will provide the information on the electrical sample homogeneity and on the morphology-electrical properties relationship. On the other hand, from local I-V curves, for example, a breakdown voltage for gate dielectrics can be extracted. With obtained breakdown values it will be possible on the one hand to characterize the reliability of the experiment, and on the other hand to obtain additional statistical information on the sample homogeneity. The illumination of the samples during measurement will allow to determine their photovoltaic properties on the nanoscale, which is of great importance for optoelectronic devices.

The performance of novel electronic devices like high-k dielectrics based field effect transistors, flexible organic displays and chemical sensors, active optoelectronic identification devices, organic solar cells, etc. can only be improved by unraveling and controlling the physical-chemical properties of underlying functional materials such as their complex electronic structure. On the other hand, these multicomponent materials are often disordered and show a strong tendency for phase separation on the micro- and nanoscale, which in turn controls their morphology and electronic properties. In particular, peculiar properties of phase-separated domains and interfacial boundaries dominate the carrier generation, trapping and transport through the active layer as well as its contact behavior. Therefore, separating material characteristics into particular components like phase-separated domain and the interfacial boundary is essential to recognize the physics of such devices and of the underlying material. Consequently, spatial resolving techniques are required in order to study, ideally in a non-invasive way, the structural and electrical properties of such materials on the nano- and microscale. Based on detailed nanoscale investigations of representative phase-separated structures relevant for practical application in the future electronics, this project aims to establish a deeper understanding of the interconnect between their electrical and morphological properties, which will contribute to further optimization of their fabrication conditions and corresponding device properties on the macroscopic scale. The structures with different kinds and degrees of phase separation will be investigated in detail using Kelvin Probe Force Microscopy and Conducting Atomic Force Microscopy. These techniques provide in addition to standard topography simultaneously material related electrical information (current, contact potential, electronic work function) and are therefore ideal complementary techniques to measure relative variations in electrical properties of phase-separated thin films on the nanoscale. For quantitative studies, samples will be measured under ultra-high vacuum conditions, in order to avoid the altering of the work function, surface modification and degradation effects during experiments. For detailed studies on the electrical characteristics, two-dimensional (2D) current and work function images as well as local I-V curves will be recorded. 2D maps will provide the information on the electrical sample homogeneity and on the morphology-electrical properties relationship. On the other hand, from local I-V curves, for example, a breakdown voltage for gate dielectrics can be extracted. With obtained breakdown values it will be possible on the one hand to characterize the reliability of the experiment, and on the other hand to obtain additional statistical information on the sample homogeneity. The illumination of the samples during measurement will allow to determine their photovoltaic properties on the nanoscale, which is of great importance for optoelectronic devices.