Shunji Ido

Effects of Some Additives on Thermoelectric Properties of FeSi2 Thin Films

Effects of some additives (V, Cr, Mn, Co, Ni, Pd, Pt) on thermoelectric properties of FeSi2 thin films were studied. V, Cr or Mn-doped FeSi2 films were of p-type semiconductor and Co, Ni, Pd and Pt-doped FeSi2 films of n-type semiconductor. It was indicated that V or Cr are more suitable additives in thermoelectric properties of p-type FeSi2 than Mn and that Pt is superior to other additives in thermoelectric properties of n-type FeSi2.

The Composition Dependence of Some Electrical Properties of FeSix Thin Films

The composition dependence of the Seebeck coefficients and the microstructures of FeSix thin films were studied. In the region of x 2.08, the Seebeck coefficient is negative. From the results of the d-spacing measurements, it is inferred that the excess Si in the sample with x>2.08 induces structural defects in the FeSi2, which provides the donor.

Composition Dependence of Some Electrical Properties of Fe1-yMySix (M=Cr, Co) Thin Films

The composition dependence of the Seebeck coefficient, electrical resistivity and activation energy associated with acceptor or donor levels of Fe1-yMySix (M=Cr, Co) thin films obtained by rf sputtering were examined. The activation energy associated with defect levels in undoped films were strongly dependent on the composition (x). For Cr-doped or Co-doped films, the activation energy was smaller than that of a undoped film and insensible to x when the impurity density was sufficiently high. It follows that the variation of the defect levels did not influence the activation energy when the impurity levels were shallower than the defect levels. Accordingly, the Seebeck coefficient and electrical resistivity for Cr-doped and Co-doped films are insensible to the composition (x), although they were influenced by the defect density when the electrical polarity of defects and impurities was different.

Computational analyses of a magnetron sputtering system with a ferrromagnetic target

Abstract Computational simulations are applied to the study of the erosion process in a magnetron sputtering system with a ferromagnetic target where the magnetic field analysis was carried out by an FEM code and plasma generation problems are examined by the particle orbit simulations. At first, computational results are compared with the experimental ones in a magnetic field analyses. They show good agreement. Secondly, the magnetic field configuration is modified to expand the lifetime of a target. It is shown that the confinement region of plasma becomes larger by the modification of the target.

Change of Structure and Electrical Properties of FeSi2 Thin Film during Annealing

Changes of structure and electrical properties of FeSi2 thin film by annealing at 380-600°C were studied and the crystallization process of the film was discussed. As a result of annealing, transformation from an amorphous phase to FeSi2 crystal occurred at 380-420°C. FeSi2 crystalline in the film was imperfect and the number of defects decreased with increasing annealing temperature. The electrical resistivity, Seebeck coefficient and activation energy associated with acceptor levels increased with increasing annealing temperature throughout the temperature region. These changes in the electrical properties by annealing were explained by the decrease in the number of defects on annealing. Carrier mobilities in the annealed films at various temperatures were deduced from the results of activation energy measurement.

COMPUTATIONAL STUDIES ON PRIMARY ELECTRON ORBITS IN AN ION SOURCE

The three-dimensional particle orbit simulation is carried out to analyze the plasma generation in a bucket-type ion source. The characteristics of ion source plasma is analyzed when the filament current is changed. When the filament current is increased, the electron is trapped by the magnetic field made by a filament current, and makes less contribution to the plasma discharge. In this study, the filament configurations are studied in viewpoints of efficiency of discharge, where electron emission is examined by tracing electron orbits from and near the filaments. The uniformity of plasma distribution is also studied due to the filament configuration and current.

Three-dimensional magnetic field analyses on the magnetron sputtering system by using Free Mesh Method

A code using the 3-dimensional Finite Element Method (FEM) and Free Mesh Method (FMM) has been developed and applied to the magnetic field analyses in the plasma devices, where a ferromagnetic material is used as a target. An adaptive method is applied to the re-distribution of the nodes. It is shown that this method is useful in the magnetic field analyses.

Computational studies on ion source plasmas of the neutral beam injection system

A three-dimensional particle code taking into account the collision terms between fast electrons and hydrogen molecules is developed, where the elastic, ionization, excitation, and vibrational excitation collisions are calculated. This code is applied to investigate plasma generation and behavior in an ion source of the neutral beam injection system. It is found that the distribution of collision points is affected by grad-B drift when the gas pressure becomes lower. The sheath region around the filament is also taken into account, making it possible to optimize the filament shape and position in a plasma generator.

Computational simulations on electron orbits in the magnetron sputtering plasmas

Abstract Three-dimensional particle orbit simulations are carried out to analyze the electron orbits in a magnetron sputtering system. Collisions between electrons and neutral Ar gas atoms are included using the Monte-Carlo method, Ionization points are related to the plasma generation points and approximate the distribution of plasmas in the magnetron sputtering system. The profiles of plasma distribution correspond to the shape of the magnetic field. The increase of ionization points is obtained by increasing the glow discharge voltage.

Particle orbit simulations on ion loss at the edge of a tokamak with separatrix configuration

Particle orbit simulations are carried out to study the ion orbits and loss at the edge of a tokamak plasma with double null magnetic separatrix. The ion loss conditions are examined as a function of v∥/v0 and the distance of ion launching points from the magnetic separatrix in cases both without and with radial electric field. The simulation results are compared with the theoretical ones. Good agreements and detailed features are obtained in the simulations. As a reference study, the effect of a radial electric field profile similar to that obtained in DIII-D is examined.