Kunihiro Kashiwagi

Aluminum nitride films by rf reactive ion‐plating

Aluminum nitride films were synthesized successfully on silicon (111) and spinel (111) single crystal surfaces by rf reactive ion‐plating. Aluminum was evaporated from an evaporator in the rf discharge phase of either nitrogen gas or ammonia gas at a pressure of 10−4 Torr (∠10−2 Pa). Film structures were evaluated using reflection high energy electron diffraction (RHEED) and scanning electron microscopy (SEM). The aluminum nitride films synthesized on the spinel (111) surfaces at the substrate temperature of 1000 °C, in the rf discharge phase of both nitrogen gas and ammonia gas, were found to be of single crystal form, having parallel orientation to the substrate surfaces. Aluminum nitride single crystals forming hexagonal pyramids were observed to grow in the perpendicular direction to the substrate surfaces during the study. The growth rate of aluminum nitride film obtained in the ammonia gas discharge, which was about 500 A min−1, was about two times as fast as that obtained in the nitrogen gas discharge.

Hybrid Films Formed from Hexamethyldisiloxane and SiO by Plasma Process

Hexamethyldisiloxane (HMDSO) based films containing silicon monoxide (SiO) were obtained by a plasma process. The HMDSO hybrid films were prepared on the substrates by evaporating SiO during HMDSO plasma polymerization in rf discharge. SiO was evaporated by heating in rf plasma consisting of HMDSO and oxygen at a pressure of the order of 10-4 Torr. The structures of the HMDSO hybrid films thus obtained were analyzed by fourier transform infrared spectroscopy (FTIR) and X-ray photoelectron spectroscopy (XPS) spectra. The structures of the HMDSO hybrid films containing SiO were also analyzed by FTIR. The ratio of Si/C in the hybrid films formed under the HMDSO monomer gas pressure at 7×10-4 Torr were found to be about 1.5 by XPS spectra. The HMDSO hybrid films were found to be pinhole free, and exhibited the characteristics of electrical insulators.

Plasma polymerization of cobalt tetraphenylporphyrin and the functionalities of the thin films produced

Thin films were prepared for the first time from cobalt tetraphenylporphyrin (CoTPP) by plasma polymerization at different r.f. powers. They had cross-linked structures in which the porphyrin ring structure of CoTPP monomer was retained to different extents. Studies by use of a sandwich type device of Au/plasma polymerized CoTPP thin film/ITO glass revealed that plasma polymerized CoTPP thin films had semiconducting characteristics of p-type. The plasma polymerized thin film prepared at an r.f. power of 10 W exhibited better rectification characteristics than those prepared at higher r.f. powers.

Organic films containing metal prepared by plasma polymerization

The organic films containing metal particles were prepared by rf ion plating system. The metal was evaporated during plasma polymerization of organic monomer, in order to make polymer–metal composite materials. The organic films containing metal obtained was observed by transmission electron microscopy to study the structures, and measured by x‐ray photoelectron spectroscopy to find the ratio of components. These films were found to have mixed metal and metal carbide. Moreover, these films showed the characteristics of semiconductorlike electrical properties.

Oxygenation Process of Ti–O Films Formed by Reactive Ion Plating

Ti–O films were deposited under various conditions by RF reactive ion plating. The structures of the TiO2 films were controlled using various parameters such as substrate temperature, RF power, deposition rate, and pressure of reactive gas. By changing the deposition rate at the substrate temperature of 250°C, the crystal structure could be changed from an anatase phase to a rutile phase. In other words, a rutile structure could be deposited even at a low substrate temperature. The emission spectra of ions and excited species in the plasma were measured by optical emission spectroscopy (OES). Relative spectral intensities of these species were studied. The resulting relative relationship of emission intensities of Ti* and O2+ was found to influence reactions in Ti–O film formation.

Ion-Beam-Induced White Luminescence of CaF2 Implanted with Both Eu and Tb Ions

A study on luminescence induced by Ar-ion bombardment of ion-implanted CaF2 has been conducted. Ion implantations of Eu and Tb ions in CaF2 single crystals ware carried out at fluences of 1×1014-1×1015 ions/cm2 at 100 keV at room temperature. The luminescence spectra from the Eu-implanted specimen mainly consist of two peaks: one is at ~430 nm due to Eu2+ and the other is at ~600 nm due to Eu3+. The main peak of ~545 nm owing to Tb3+ appears in Tb-implanted CaF2. The luminescence spectra from CaF2 implanted with both Eu and Tb ions mainly show three peaks at ~430, ~545 and ~600 nm, which are close to the wavelengths of the three primary colors. Ion implantations of both Eu and Tb ions result in white luminescence which is visible to the naked eye, with control of the fluences of Eu and Tb ions.

Zinc-Oxide Film Synthesized by ECR Oxygen Plasma

ZnO films were deposited using an evaporation system with an oxygen ECR plasma. The ECR plasma was produced in an octapole magnetic field with 2.45 GHz microwave. The deposited ZnO films, which have 3.3 eV band gap, were obtamed without heating (55°C). Deposition was carried out on substrates set in two regions to examine the effect of ion irradiation; one region was in the octapole field (ion rich atmosphere) and the other was the area outside of it (ion poor atmosphere). The deposition in the ion poor atmosphere gave high quality films. The film structure was analyzed by means of optical spectrophotometer, RHEED, SEM and X-ray diffraction.

Negative effect of crystallization on the mechanism of laser damage in a HfO2/SiO2 multilayer

Elucidation for the mechanism of laser damage is indispensable to realize a high resistance mirror for the ultra-short pulse high intense lasers of the next generation. In this study, the surface and a section of a laser-damaged area of a laser mirror were observed with a laser microscope and a transmission electron microscope (cross-sectional TEM), respectively. A grain boundary of HfO2 microcrystal was observed in the damaged area. This observation, and an evaluation of the mirrors damage resistance showed that the formation of crystals in the multilayer mirror is one of the major determinants of damage resistance.

Optical Thin Film Coating Having High Damage Resistance in Near-Stoichiometric MgO-Doped LiTaO3

Currently, High power and compact red, green, and blue (RGB) lasers are being considered for use in large screen laser televisions and reception-lobby projectors. Among these three laser sources, green semiconductor lasers are expensive and exhibit inferior performance in terms of the semiconductor material used, making it difficult to achieve a high output. In this study, we examined the use of our coating on MgO-doped LiTaO3, using a mirror coated with a multilayer film. Over a substrate, a Ta2O5 film was used to coat a high-refractive-index film layer, and a SiO2 film was used to coat a low-refractive-index film layer. To improve reflectivity, we designed the peak of the electric field intensity to be in the film layer with the low refractive index. As a result, the film endurance of 100 J/cm2 was obtained by one-on-one testing. With the nonlinear crystal material, the mirror without our coating exhibited a damage threshold of 33 J/cm2; however, after coating, this mirror demonstrated a higher damage threshold of 47 J/cm2. Thus, the film we fabricated using this technique is useful for improving the strength and durability of laser mirrors.

The surface modification effect by irradiation of a surface wave excited hydrogen plasma onto zinc oxide thin films

[Outline] We investigate about the increase of conductivity of zinc oxide thin films by irradiating a surface wave excited hydrogen plasma. [Experiment] Zinc oxide thin films are irradiated by surface wave hydrogen plasma generated by means of microwave. The changes of the conductivity of the thin films are evaluated by using a resistivity meter. The zinc oxide thin films used here have the thickness of 1500Aring which is formed by the reactant ion plating method. Diagnosis of a film is thicknessmeter. The surface of thin films and the chemical bond state of the depth direction are measured by XRD and XPS, SIMS. The XRD and XPS, SIMS are utilized to observe the crystal and chemical structures. Transmissivity is measured by spectrophotometer. [Result] The surface resistance changes from infinite to 3.0 times 10 2[/sq], without losing transparency by irradiating hydrogen microwave surface wave plasma at a zinc oxide thin film