Properties of tantalum oxide thin films grown by atomic layer deposition

• Published in: Thin solid films Vol. 260; no. 2; pp. 135 - 142
• Main Authors: Kukli, Kaupo, Aarik, Jaan, Aidla, Aleks, Kohan, Oksana, Uustare, Teet, Sammelselg, Väino
• Format: Journal Article
• Language: English
• Published: Lausanne Elsevier B.V 15-05-1995; Elsevier Science
• Subjects: Condensed matter: electronic structure, electrical, magnetic, and optical properties; Deposition process; Exact sciences and technology; Insulators; Optical coatings; Optical properties and condensed-matter spectroscopy and other interactions of matter with particles and radiation; Optical properties of specific thin films; Oxides; Physics; Structural properties; Oxides; Optical coatings; Structural properties; Deposition process; Tantalum oxides; Deposition rate; XRD; Absorptance; Experimental study; Amorphous phase; Surface states; Thin films; Energy gap; Temperature effects; Morphology; Optical properties; Structure; Tantalum chlorides
• ISSN: 0040-6090; 1879-2731
• DOI: 10.1016/0040-6090(94)06388-5

Thin tantalum oxide films were deposited using atomic layer deposition from TaCl
5 and H
2O at temperatures in the range 80–500 °C. The films deposited at temperatures below 300 °C were predominantly amorphous, whereas those grown at higher temperatures were polycrystalline containing the phases TaO
2 and Ta
2O
5. The oxygen to tantalum mass concentration ratio corresponded to that of TaO
2 at all growth temperatures. The optical band gap was close to 4.2 eV for amorphous films and ranged from 3.9 to 4.5 eV for polycrystalline films. The refractive index measured at
λ = 550 nm increased from 1.97 to 2.20 with an increase in growth temperature from 80 to 300 °C. The films deposited at 80 °C showed low absorption with absorption coefficients of less than 100 cm
−1 in the visible region.