Reactive pulsed laser deposition and laser induced crystallization of SnO₂ transparent conducting thin films

Abstract

Transparent conducting SnO₂ thin films with a thickness between 1000–2000 Å were deposited on glass, quartz and silicon substrates using standard pulsed laser deposition techniques with two different targets (Sri and SnO₂) and with three different laser wavelengths (1.06, 0.532 and 0.266 μ) from a Q-switched Nd: YAG laser. Tin dioxide films with optical transmission over most of the visible spectrum exceeding 80% were obtained using a Sn target and a background oxygen pressure of 20 Pa. The electrical resistivity (ρ) depended strongly on the substrate temperature during deposition, with the lowest values ofρ of about 10⁻² Ω-cm obtained when the substrate was maintained at 400°C during deposition. Using SnO₂ targets, predominantly amorphous phase SnO₂ films were deposited on Si substrates and then transformed into polycrystalline Sn₃O₄ by laser induced crystallization (λ = 1.06 μm). Whereas these later films were essentially non-conducting as deposited (ρ > 400 Ω-cm), the electrical resistivity was permanently reduced after laser induced crystallization by a factor greater than 1000 to a value of approximately 4 × 10⁻¹ Ω-cm.