Michio Watamori

Oxygen content of indium tin oxide films fabricated by reactive sputtering

Indium tin oxide (ITO) films, which are transparent conductive films, have been widely used in optoelectronic applications. A high quality film with correct stoichiometric composition is essential for its applications, such as a flat panel display. However, it is difficult to estimate the absolute oxygen concentration. There are few studies of oxygen depth profiling for ITO films. We have investigated a relationship between the oxygen content of ITO films and the electrical properties under various deposition conditions. The absolute oxygen concentration has been determined by 16O(α,α)16O resonant backscattering of a 3.045 MeV 4He2+ ion beam. It has been found that there is a correlation between the depth profile of oxygen concentration of ITO films and the film properties. In the case of the ITO film fabricated at room temperature, a large deficiency of oxygen can be seen at the surface of the film. When the film was formed at 400 °C, no deficiency of oxygen at the film surface was observed. The observed...

The effects of oxygen content on electrical and optical properties of indium tin oxide films fabricated by reactive sputtering

Abstract We have investigated the depth profile of the oxygen content of indium tin oxide (ITO) films fabricated by reactive sputtering. The oxygen content was determined by means of 16O(α,α)16O resonant backscattering. The effect of the oxygen partial pressure of reactive gas on the oxygen content of the films was investigated. From the depth profile of oxygen, it was found that the oxygen compositions of the films, especially in the surface region, changed with the oxygen partial pressure. Also it was found that the electrical and optical properties of the ITO films changed with the oxygen partial pressure. The correlation between the oxygen content and the electrical and optical properties is discussed.

Methodology for Accurate Oxygen Distribution Analysis and Its Application to YBa2Cu3Ox Thin Films Using 16O(α, α)16O 3.045 MeV Resonance Reaction

The enhancement factor of oxygen of 16O(α, α)16O resonance for a Rutherford backscattering cross section has been investigated using SiO2 films of various thicknesses. A new procedure to accurately extract the resonant oxygen height from a raw spectrum has been proposed. With this procedure, the dependence between the film thicknesses and resonant signals has been investigated, and was found to agree well with a computer simulation within experimental error. Using the enhancement factor, the depth dependence of oxygen concentration in the YBa2Cu3Ox /MgO systems has been estimated accurately. Estimations of the accuracy of elastic backscattering analysis are also given.

Depth profiling of oxygen content of indium tin oxide fabricated by bias sputtering

Abstract Depth profiling of oxygen in indium tin oxide (ITO) films, fabricated by a hot cathode Penning discharge sputtering (HC-PDS) on glass substrates with negative substrate voltage in Ar atmosphere has been investigated using a high-energy ion beam. The substrate bias voltage was changed from −100 to 0 V. The oxygen content in the deposited film changed with substrate bias voltage. It was considered that Ar ion bombardment affected the change in oxygen composition. Correlation between oxygen content and the electrical and optical properties will be discussed.

Reconstruction and growth of Ag on hydrogen-terminated Si(111) surfaces

Abstract Initial stage of Ag film formation on hydrogen-terminated Si(111) surfaces at room temperature (RT) and high temperatures has been investigated by scanning tunneling microscopy. Ag atoms formed clusters on the hydrogen-terminated Si(111) at all temperatures, though the size and number were different in each case. When Ag was deposited at RT, relatively large and uniform Ag clusters were formed on the surface, compared with Ag deposition on a clean Si(111)-7×7 surface. On increasing the deposition temperature to 200 and 300°C, the size of Ag clusters became larger and the number of Ag clusters became less. When the surface where Ag was deposited on the hydrogen-terminated Si(111) at RT was annealed at 350°C, shallow and deep areas of 3 − Ag structure appeared, due to hydrogen desorption. We demonstrate the usefulness of hydrogen termination for Ag deposition on the Si surface to fabricate flat and uniform thin films.

High-Energy Ion Beam Analysis of YBa2Cu3Ox Thin Films

The composition and crystalline structure of high-Tc superconducting YBa2Cu3Ox thin films formed on MgO(100) and Si(100) substrates have been investigated by Rutherford backscattering and channeling techniques. Y, Ba, Cu contents have been analyzed by employing a high-energy (over 4.5 MeV) 4He ions and large scattering angle (near 170°) condition, where Y, Ba and Cu peaks are clearly separated from each other. Oxygen concentration has been obtained through the use of low primary energy (below 2.5 MeV) and small scattering angle (below 150°) conditions, where the O peak is separated from the background. The crystalline quality of the films has also been investigated by ion channeling techniques.

Depth Profiling of Oxygen Concentration of Indium Tin Oxide Films Fabricated by Reactive Sputtering.

Depth profiling of the oxygen concentration of indium tin oxide (ITO) films on glass substrates has been investigated using a high-energy ion beam. Hot-cathode Penning-discharge sputtering (HC-PDS) in the mixed gases of argon and oxygen was applied to fabricate the films. It is found that there is a correlation between the depth profile of oxygen concentration and the electrical properties. The effect of partial pressures of oxygen gas on the depth profile of the oxygen concentration and on electrical properties is discussed.

High-energy ion channeling study of the atomic displacement of Si(111) surfaces induced by Ag thin films

Abstract We have investigated, using high energy ion channeling technique, atomic displacements of Si(111) substrates carrying Ag deposits (less than 5 monolayers) of two different morphologies: an epitaxial Ag(111) film formed by deposition at room temperature and an ordered adsorbed structure of Si (111)( 3 × 3 ) R 30°- Ag formed by deposition at 400 °C. It has been found that there is a definite difference in the vertical displacement of Si atoms between these two surfaces, while there is no difference in the lateral displacement. The room temperature deposition of Ag of about 1 monolayer significantly relaxes substantial vertical displacement of the 7 × 7 surface, while the deposition at higher temperature, in contrast, enhances it slightly. Based on a Monte Carlo simulation of ion channeling intensities, the range of possible lateral displacements of Si atoms is determined for various Si (111)( 3 × 3 ) R 30°- Ag structure models proposed so far.

Ion channeling study of SrTiO3 substrates and As-deposited YBa2Cu3Ox thin films

The crystalline quality (perfection or imperfection) of SrTiO3 substrates and subsequent as-deposited YBa2Cu3Ox superconducting films has been investigated by a high-energy ion channeling technique. Analysis was performed as a function of depth, especially at 3 typical depth regions (surface, inside, interface), to clarify junction ordering features between substrates and films. Based on ion channeling measurements, it has been found that (1) disorders of substrates affect crystalline quality of films greatly at the interface regions, (2) the film reorders over a proper amount of YBa2Cu3Ox disordered layers (as in buffer layers), (3) the film consists of an almost single domain. The crystalline quality of some SrTiO3 substrates widely used in Japan has also been investigated and the common characteristics of distortions along the c-axis have been found.

Structural study of SrTiO3(100) surfaces by low energy ion scattering

Abstract We have studied the atomic structure of the SrTiO 3 (100) surface annealed at 600°C in ultrahigh vacuum (UHV) by using time-of-flight impact collision ion scattering spectroscopy (TOF-ICISS) and low energy electron diffraction (LEED). Considering its perovskite structure, the SrTiO 3 (100) surface consists of a SrO-terminated surface, a TiO 2 -terminated surface or a mixture of these surfaces. From the results of TOF-ICISS and LEED experiments, we have found that the SrTiO 3 (100) surface annealed at 600°C is an ordered surface (1 x 1 structure) and consists of a mixture of SrO-terminated and TiO 2 -terminated surfaces.