青木 孝憲

Approximately 150 nm-thick Al-doped zinc oxide (AZO) films with c-axis orientation have been prepared on glass substrates by pulsed laser deposition (PLD) using a split target divided into AZO(Al₂O₃ : 1 wt.%) and AZO(Al₂O₃ : 2 wt.%), which resulted in the adjustment of film composition by changing the ratio (trace ratio) of the time required to irradiate each side of the target alternately by an ArF excimer laser (λ= 193 nm). The film deposition took place at a substrate temperature of 230 °C. The trace ratio of 1 : 1 was employed, resulting in the film component of AZO(Al₂O₃ : 1.5 wt.%). In order to improve the film flatness, D.C. voltage of 150 V was applied perpendicularly to the plume generated between the substrate and the target. As a results, fluctuation of film-thickness improved from 7.8 % for the case without applied voltage to 4.7 %, with applied voltage of 150 V. For the AZO film deposited by irradiating a pulsed laser beam of energy density of 1 J/cm² at repetition frequency of 10 Hz, the lowest resistivity was 2.47×10^-4 Ω·cm for the case without applied voltage and 2.59×10^-4 Ω·cm with applied voltage of 150 V. An average transmittance of more than 85 % in the visible range were obtained for the AZO films fabricated with and without D.C. voltage of 150 V applied perpendicularly to the plume, providing useful functionality as TCO films in the visible range.

β-FeSi₂ thin films were grown on Si(111) substrates by pulsed laser deposition (PLD) method using Nd: YAG Laser (λ = 1064 nm, laser energy = 50 mJ, laser energy density = 1.65 J/cm², repetition frequency = 10 Hz). In the fabrication process, three targets of (a) Fe(5N), (b) FeSi₂(3N) and (c) Fe(5N) + FeSi₂(3N) were used. The β-FeSi₂ thin films having best properties of crystallinity were obtained in the case of (c), in which the first layer as the template was formed with the target of Fe(5N) and then, on top of that, the second layer was deposited with the target of FeSi₂(3N). At this time, it was found that by XRD measurement, the degree of crystallinity of the films of the case (c) in which the first layer was introduced as the template improved 1.4 times as much as compared with the case (a), and that by SEM and AFM observations, surface morphologies also improved. Moreover, it was found that by TEM obeservation, the β-FeSi₂ thin grew uniformly along the direction of (220) or (202) from the interface of the Si substrate and the film to the free surface and that by EDS analysis, the compositions of Fe and Si were uniformly distributed.