Takuji Oyama

Low resistance indium tin oxide films on large scale glass substrate

Preparation of low resistance indium tin oxide (ITO) films on large scale glass substrate has been studied for architectural applications. Coatings were carried out by a plasma enhanced deposition technique using sintered ITO pellets as the starting material and high deposition rate of more than 4000 A/min was achieved. Scanning tunneling microscopy observation revealed that surface morphology of the thick (about 1 μm) film was strongly dependent on the substrate temperature. Crystallinity and electrical properties were also dependent on the temperature and closely related to the surface morphology. The films deposited on 125 °C substrate were composed of a mixture of amorphous and polycrystalline phases and showed a hazy appearance caused by light scattering at the rough surface. The polycrystalline ITO films with a clean and transparent appearance as well as the minimum resistivity of 1.7 × 10−4 Ω cm were obtained on 180 °C substrate. Coatings on architectural size glass substrate (1.8 m×3.2 m) were car...

Large scale and low resistance ITO films formed at high deposition rates

Preparation of low resistance indium tin oxide (ITO) films on large scale glass substrates has been studied for architectural applications. Coating was carried out by an inline-type plasma-enhanced deposition system with multiple low voltage electron beam (EB) sources based on arc discharge. When Ar was used as the arc discharge gas, low resistance (1 ≈ 2 Ω sq−1) ITO films were obtained on a large scale (1.8 m × 3.2 m) float glass substrate at high deposition rate (6000 A min−1) and low substrate temperature (<200°C). The minimum specific resistivity of the film was 1.7 × 10−4 Ω cm. In order to increase the deposition rate further, He was used as the arc discharge gas instead of Ar. An extremely high deposition rate of 12 500 A min−1 with sufficient visible transmission and low resistivity was achieved and a minimum sheet resistance of 0.9 Ω sq−1 was obtained. An architectural monolithic electromagnetic interference (EMI) shielding window was realized with the above technology. The glass with a sheet resistance of 5 Ω sq−1 showed an EMI shielding performance of -30 dB at 1 GHz.

A new layer system of anti-reflective coating for cathode ray tubes

A new anti-reflective (AR) coating system, using an absorbing layer, has been developed for cathode ray tubes (CRTs). Theoretical analysis has revealed that the basic system needs only two layers to achieve zero reflection throughout the visible region if an ideal absorbing layer and a transparent layer are combined. The conditions for realizing the ideal AR property with two-layer system has been derived by numerical calculations. TiN x O y was chosen as the actual absorbing layer, while SiO 2 was chosen as the transparent layer. These choices are both based on theoretical and experimental considerations. The oxygen content in the TiN x O y film was found to play an important role on the AR properties, therefore a very thin (around 5 nm) SiN x barrier layer was deposited on the TiN x O y layer to prevent the oxidization of the TiN x O y during the subsequent deposition of SiO 2 . The insertion of such a thin SiN x layer was found to have almost no influence on the optical properties, therefore the system (Glass/TiN x O y /SiN x /SiO 2 ) can be called as two-layer system with a barrier layer. The AR properties and the electromagnetic shielding property (i.e. the electrical conductivity) of the coating was almost the same as the conventional transparent multilayer system which needs more than twice as thick as this system. This coating has been successfully adapted to the panel glass for CRTs on an industrial scale.

Effect of internal stress on adhesion and other mechanical properties of evaporated indium tin oxide (ITO) films

The relationship between various mechanical properties of evaporated indium tin oxide (ITO) films has been investigated. The hardness and internal stress were found to be correlated. This correlation can be expressed as a linear expression similar to that reported for a bulk material. The strength of adhesion to the substrate was observed to be related to the internal stress. This relationship was also linear and could be well interpreted quantitatively by assuming that the stored elastic energy in ITO films was constant during peeling. The coefficient of kinetic friction was found not to be related to any mechanical property. It depended only on the roughness of the film surfaces. A series of Taber abrasion tests revealed that the coefficient of friction was the most important for mechanical durability among factors such as hardness, adhesion, strength, and coefficient of friction.

EFFECTS OF WATER PARTIAL PRESSURE ON THE ACTIVATED ELECTRON BEAM EVAPORATION PROCESS TO DEPOSIT TIN-DOPED INDIUM-OXIDE FILMS

The effects of water partial pressure (PH2O) during deposition on the structural and electrical properties of tin‐doped indium‐oxide (ITO) films have been investigated on an activated electron beam evaporation process using an arc plasma generator. The resistivity of the films deposited at 180 °C increased with an increase in PH2O in terms of a decrease both in Hall mobility and carrier density. X‐ray diffraction and scanning electron microscope analyses showed that the ITO films deposited at higher PH2O consisted of a major portion of larger crystalline grains with smaller internal strain and a small portion of amorphous regions which is supposed to be at the interface between the film and the substrate. Plasma diagnostics by optical emission spectroscopy revealed that atomic hydrogen was generated by electron‐impact dissociation of H2O and that the activation of Ar or O2 was suppressed in the higher PH2O process, which resulted in the deposition of less oxidized and lower‐damaged ITO films.

Fabrication of A-Si:H Solar cells on high haze SnO 2 :F thin films

In this work we report on the properties of amorphous silicon (a-Si:H) p-i-n solar cells fabricated on glass substrates covered with extremely high haze fluorinedoped tin oxide (SnO2:F) transparent conductive oxide (TCO) thin films, HU-TCO. The HU-TCO shows high haze value thorough the whole optical region where a-Si:H and microcrystalline silicon (μc-Si:H) solar cells are sensitive. We demonstrate here that open-circuit voltage (Voc) and fill factor (FF) of a-Si:H solar cells fabricated on HU-TCOs does not decrease significantly compared to the cells on conventional pyramidal texture TCOs. We also demonstrate here that Voc and FF of a-Si:H solar cells depend on not only surface morphology of TCOs, but also strongly depend on thickness and deposition conditions of the solar cells.

Light-absorbing wide-band AR coatings on PET films by sputtering

Abstract Wide-band antireflection (AR) coating employing a light-absorbing layer, has been applied to PET film with acrylic anti-abrasion coating. A properly designed RF plasma treatment of the PET substrate before the deposition has been found to play an important role in the improvement of the adhesion at the interface. Ar and N2 were found to be better atmosphere gas species for the RF plasma treatment compared to O2. RF electrode located behind the substrate was found to be in good geometrical arrangement reducing the treatment time to obtain enough adhesion strength. An insertion of a thin SiNx between the AR layers and PET film also improved the adhesion. Using these combined pre-treatments before the deposition of the AR coating, a wide-band AR coating with good mechanical properties has been realized on PET film substrate. This coating also showed a sufficiently low sheet resistance which is often required for the electromagnetic shielding of cathode ray tubes (CRTs).

Improving Mobility of F-Doped SnO2 Thin Films by Introducing Temperature Gradient during Low-Pressure Chemical Vapor Deposition

High mobility is required to suppress free-carrier absorption in the near-infrared (NIR) region. Toward this end, we investigated the properties of a F-doped SnO2 (FTO) film deposited using low-pressure chemical vapor deposition (LPCVD) and found that the optimum deposition temperature varied with film thickness. On the basis of this result, we introduced a temperature gradient into LPCVD, which resulted in an improvement in the mobility of F-doped SnO2 on glass to 77.5 cm2 V-1 s-1.

18.3: A New Layer System for Wideband Anti-Reflection Coatings Designed for CRTs

A new AR coating using an absorbing layer has been developed for CRTs. Theoretical analysis has revealed that basic layer system needs only an “ideal” absorbing layer and SiO2. A Glass/TiNxOy/SiO2 layer system made by DC reactive sputtering exhibited wideband anti-reflection property as well as Iow sheet resistance comparable to conventional transparent multi-layer stacks. SiNx barrier layer inserted between TiNxOy and SiO2 layers made it durable against the heat treatment during CRT manufacturing process, which realized the commercialization of coated panel glass for CRTs with this layer system.

Improved light-trapping effect in a-Si:H / μC-Si:H tandem solar cells by using high haze SnO 2 :F thin films

In this paper we report on the fabrication of amorphous silicon (a-Si:H) / microcrystalline silicon (μc- Si:H) p-i-n tandem solar cells on high haze fluorine-doped tin oxide (SnO2:F) transparent conductive oxide (TCO) thin films, type-HU. The HU-TCO has double texture morphology on its surface and shows high haze value through the whole optical region where the tandem solar cells are sensitive. We demonstrate here that light-trapping effect is improved by using HU-TCO. HU-TCO provided higher short-circuit current than conventional pyramidal TCO when i-layer thicknesses of a-Si:H and μc- Si:H of tandem solar cell were 0.35 and 1.5 µm, respectively. Quantum efficiency of bottom μc-Si:H cell was improved by 1 mA/cm2 by using HU-TCO.