From technological and physical points of view, the studies of ferromagnetic films carried out most intensively in the 1960's are reviewed. By indicating the problems left unsolved, as well as the technological development made in this field, we show examples of the research characterizing the usefulness of 2-dimensional magnetic materials.
Switching characteristics as well as pre-breakdown characteristics were investigated in thin film of an amorphous semiconductor having the composition of As30-Te48-Ge10-Si12. Sandwich type samples with electron-blocking Au and electron-injecting Al electrodes were mainly used for the experiment. It was found that both electrodes play an important role for conduction in the pre-breakdown state and for switching phenomena. A model was proposed for the switching mechanism, which also includes pre-breakdown carrier transport mechanism. According to the model, in the pre-breakdown state, electrical conduction is predominantly a one-carrier, space charge limited current caused by injected electrons, while injection of holes could not be observed. When the electron space charge density in the film reaches a critical value, however, hole injection begins and this causes switching action. From the view point of this model, threshold voltage, threshold current, delay time before switching and stored charge density of electron are evaluated as function of geometrical factors such as film thickness or electrode area. It was concluded that the model proposed here satisfactorily explains several features of the switching characteristics in thin film of an amorphous semiconductor.
Sn-doped In2O3 films for applications as selective transparent films for solar thermal conversion are fabricated by RF sputtering with O2-Ar mixture. The optical and electrical properties of the films are measured for various oxygen concentration in sputter gas and substrate temperature. It is found that oxygen concentration plays an important role in determining the physical properties of the films, and that 2_??_3% oxygen concentration results in films, having desirable optical properties for selective transparent films at the substrate temperature of 400°C. The influence of annealing temperature on the film properties is also discussed.