**4. Conclusion**

weight of the gas that will affect the collision with ablated species. The growth was performed by PLD using a 355 nm laser at a substrate temperature of 250°C. The results show that nanostructures growth was dependent critically on the background pressure (**Figure 8**), similar

**Table 4.** Resistivity, carrier density, and Hall mobility of commercial ITO and ITO samples grown in Ar and He ambient.

**Carrier density (×1020 cm−3)**

**Hall mobility**

**(cm2 /Vs)**

in Ar, XRD diffraction patterns corresponding to (222), (400), (440), and (622) orientations of cubic bixbyite structure of ITO were detected. As the pressure of Ar increased, the (400) diffraction peak became relatively stronger, indicating the increase in crystalline orientation.

**Figure 9.** Optical transmittance of commercial ITO and ITO samples grown in Ar and He background gases [39].

[37]. ITO nanowires were obtained in both gases. For ITO deposited

to those reported in N2

**ITO samples Resistivity**

**(×10−4Ω cm)**

Commercial ITO 1.97 18.7 16.6 Ar (30 mTorr, 250°C) 1.61 10.5 36.7 Ar (40 mTorr, 250°C) 2.09 6.65 44.9 He (250 mTorr, 250°C) 9.37 13.2 5.06 He (1000 mTorr, 250°C) 1.91 6.91 4.75 He (2000 mTorr, 250°C) 7.75 9.50 8.78

98 Applications of Laser Ablation - Thin Film Deposition, Nanomaterial Synthesis and Surface Modification

Laser ablation of ITO target was studied in various aspects. Pulsed laser ablations by 193, 248, or 355 nm lasers in low vacuum conditions afforded the deposition of high-quality ITO films at relatively low temperatures. This was largely ascribed to the production of homogenous, energetic, and atomized plasma plume. The effects of substrate temperature, background gas pressure, in particular the O2 on the electrical and optical properties of ITO films have been presented and discussed. In addition to the normal consensus that ITO depositions are to be performed in O2 to preserve the stoichiometry of the final films, pulsed laser ablation of ITO target, when performed in various gases such as Ar, He, or N2 , could promote the growth of ITO nanostructures. At optimized pressure, the gas-phase condensation successfully induced nucleation and growth of the nanostructures such as nanorods and nanowires on glass substrate at relatively low substrate temperature.
