Dependence of the sheet resistance of indium-tin-oxide thin films on grain size and grain orientation determined from X-ray diffraction techniques

• Published in: Thin solid films 1999-05, Vol.345 (2), p.273-277
• Main Authors: KULKARNI, A. K, SCHULZ, K. H, LIM, T. S, KHAN, M
• Format: Article
• Language: English
• Subjects: Condensed matter: electronic structure, electrical, magnetic, and optical properties; Condensed matter: structure, mechanical and thermal properties; Cross-disciplinary physics: materials science; rheology; Deposition by sputtering; Electrical properties of specific thin films; Electronic structure and electrical properties of surfaces, interfaces, thin films and low-dimensional structures; Exact sciences and technology; Materials science; Methods of deposition of films and coatings; film growth and epitaxy; Other inorganic semiconductors; Physics; Structure and morphology; thickness; Surfaces and interfaces; thin films and whiskers (structure and nonelectronic properties); Thin film structure and morphology
• ISSN: 0040-6090; 1879-2731
• DOI: 10.1016/s0040-6090(98)01430-8

ITO thin films (100-200 nm) are deposited on glass and plastic (PET and polycarbonate) substrates by r.f. sputtering. Process parameters such as oxygen partial pressure, r.f. power, and post deposition annealing parameters are varied to determine the dependence of the sheet resistance on process parameters. The microstructure of these thin films is determined using an X-ray diffractometer (XRD) and a transmission electron microscope (TEM). The experimentally observed dependence of the sheet resistance on the grain size and grain orientation of these films is correlated to the dependence of the electron mobility on grain boundary scattering. Larger grain sizes ( approximately 25 nm) in ITO films result in lower sheet resistance (250 Omega / square ). This type of large grain size microstructure is produced with moderate r.f. power ( approximately 100 W) and low oxygen partial pressure ( approximately 10%). There is a unique correspondence between grain size and grain orientation. ITO films with a strong peak intensity ratio of (400) orientation to all other orientations ( approximately 0.35) have the largest grain size ( approximately 25 nm) resulting in the lowest sheet resistance (250 Omega / square ) and high transmission ( approximately 86.7%) at lambda identical with 550 nm.