Shigetaka Katori

Fabrication of Silicon Oxide Thin Films by Mist Chemical Vapor Deposition Method from Polysilazane and Ozone as Sources

Silicon oxide thin films were grown from the liquid source, polysilazane, by using mist chemical vapor deposition (CVD) at temperatures of 200–350 °C. The films were grown with a reasonable growth rate of 12 nm/min at the temperature of 200 °C, and they showed resistivity of the order of 1013 Ωcm, although the incorporation of carbon and oxygen remains as a problem to be discussed and solved in the future. The results are encouraging for the future application of mist CVD for the growth of silicon oxide films on plastic substrates.

Ultrasonic Spray-Assisted Solution-Based Vapor-Deposition of Aluminum Tris(8-hydroxyquinoline) Thin Films

Aluminum tris(8-hydroxyquinoline) (Alq3) thin films were fabricated by a vapor-deposition technique from its methanol solution, that is, by the ultrasonic-assisted mist deposition technique. The application of high ultrasonic power to the Alq3–methanol mixture resulted in a stable and transparent solution. Mist particles formed by ultrasonic atomization of the solution were used as the source for vapor-deposition at the substrate temperature of 100–200 °C. Optical absorption and photoluminescence characteristics indicated the formation of Alq3 thin films. The results promise the formation of thin films of a variety of organic materials by the solution-based technique.

Surface Potential Measurement of Tris(8-hydroxyquinolinato)aluminum and Bis[N-(1-naphthyl)-N-phenyl]benzidine Thin Films Fabricated on Indium–Tin Oxide by Kelvin Probe Force Microscopy

To clarify the interfacial properties of an organic light-emitting diode (OLED), we discuss the surface potential of organic semiconductor thin films fabricated on an electrode that was measured by noncontact atomic force microscopy (nc-AFM) and Kelvin probe force microscopy (KFM) utilizing frequency modulation (FM). The organic semiconductor films were deposited on a glass/indium–tin-oxide (ITO) substrate by the vacuum evaporation technique using intersecting metal shadow masks. This deposition technique enables us to fabricate four different areas on the same substrate. The surface potentials of the crossover area of the deposited thin films were investigated by the nc-AFM/KFM technique. The energy band diagram was depicted, and we observed that the charge behavior of the organic semiconductor depended on the material and the structure.

Surface potential measurement of fullerene derivative/copper phthalocyanine on indium tin oxide electrode by Kelvin probe force microscopy

We have investigated the organic semiconductor thin films deposited by vacuum evaporation deposition using intersecting metal shadow masks on indium tin oxide (ITO) electrode/glass substrates to simulate organic solar cells by simultaneous observation with dynamic force microscopy (DFM)/Kelvin-probe force microscopy (KFM). The energy band diagram was depicted by simultaneously obtaining topographic and surface potential images of the same area using DFM/KFM. We considered the charge behavior at the interface having band bending in the phenyl-C61-butyric acid methyl ester (PCBM) film.

Surface potential measurement of fullerene/copper phthalocyanine films on indium tin oxide electrode by Kelvin probe force microscopy

Various organic semiconductor thin films were deposited on an indium tin oxide (ITO) electrode/glass substrate to simulate organic solar cells. The electrical properties at the organic/inorganic and organic/organic interfaces were evaluated by dynamic-mode atomic force microscopy (DFM) together with Kelvin probe force microscopy (KFM). By employing the frequency modulation (FM) method, the DFM/KFM system allows for not only consistent imaging over a wide scanning area, but also highly sensitive detection of the surface potential. The charge carrier behavior at the interface was clarified by simultaneously obtaining topographic and surface potential images of the same area using DFM/KFM and depicting the energy band diagram with band bending in the fullerene (C60) film.

Surface potential measurement of organic thin film on metal electrodes by dynamic force microscopy using a piezoelectric cantilever

We describe applications of a cantilever with a lead zirconate titanate (PZT) piezoelectric film as self-sensing to dynamic force microscopy (DFM) combined with Kelvin probe force microscopy (KFM). We adopted a frequency modulation (FM) detection method not only to stabilize the imaging conditions in our DFM but also to enhance the sensitivity for the detection of electrostatic forces in KFM measurement. We deposited Alq3 [tris (8-hydroxyquinolinato) aluminum] thin films and aluminum (Al) electrode patterns on an indium tin oxide (ITO)/glass substrate by vacuum evaporation using shadow masks. The surface structures and local surface potential of Alq3 films on metals were investigated using our DFM/KFM instrument to study the local electrical properties at the molecule–metal interface. The photosensitive organic material sample can be in a completely dark environment because no optics are required for cantilever deflection sensing in our experimental setup.

Surface potential measurement of n-type organic semiconductor thin films by mist deposition via Kelvin probe microscopy

We partially deposited fullerene (C60) and phenyl-C61-butyric acid methyl ester thin films that are typical n-type semiconductor materials on indium–tin oxide by mist deposition at various substrate temperatures. The topographic and surface potential images were observed via dynamic force microscopy/Kelvin probe force microscopy with the frequency modulation detection method. We proved that the area where a thin film is deposited depends on the substrate temperature during deposition from the topographic images. It was also found that the surface potential depends on the substrate temperature from the surface potential images.