Characteristics of ultraviolet-assisted pulsed-laser-deposited Y 2 O 3 thin films
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Characteristics of ultraviolet-assisted pulsed-laser-deposited Y2O3 thin films V. Craciun,a) E.S. Lambers, N.D. Bassim, and R.K. Singhb) Department of Materials Science and Engineering, University of Florida, Gainesville, Florida 32611
D. Craciun Laser Department, National Institute for Laser, Plasma, and Radiation Physics, Bucharest, Romania (Received 11 March 1999; accepted 12 November 1999)
The properties of thin Y2O3 films grown using an in situ ultraviolet (UV)-assisted pulsed laser deposition (PLD) technique were studied. With respect to Y2O3 films grown by conventional PLD under similar conditions but without UV illumination, the UVPLD-grown films exhibited better structural and optical properties, especially for lower substrate temperatures, from 340 to 400 °C. These layers were highly crystalline and textured along the (111) direction, and their refractive index values were similar to those of reference Y2O3 layers. They also exhibited a better stoichiometry and contained less physisorbed oxygen than the conventional PLD-grown layers.
I. INTRODUCTION
Among recently developed techniques for growing thin films, pulsed laser deposition (PLD) has emerged as one of the most promising due to several important advantages.1,2 One particular advantage that helped PLD to gain its widespread acceptance is the use of a relatively low substrate temperature during the growth process. For many advanced technology applications, a further reduction of the process temperatures is highly desirable to prevent harmful film and/or ambient gas–substrate interaction,3,4 unwanted substrate interdiffusion processes, and reevaporation of volatile components.5,6 It is also known from rapid thermal processing of semiconductors that substrate temperature nonuniformity and reproducibility is considerably reduced for processing temperatures below 500 °C.7 Unfortunately, with the exception of very few materials, most high-quality PLD-grown materials still require substrate temperatures in excess of 650 °C. If one wants to lower the substrate temperature without sacrificing the crystalline quality, stoichiometry, and electrical and optical properties, then a nonthermal source of energy or a more reactive gaseous atmosphere should be provided during the growth process. Ion-beam-assisted PLD has been successfully demonstrated for the growth of several materials,8–10 but it is rather expensive and complicated to be easily implemented, especially for reactive PLD. The use of more
a)
Permanent address: Institute of Atomic Physics, Bucharest, Romania. b) e-mail: [email protected] 488
http://journals.cambridge.org
reactive gaseous atmosphere such as N2O, NO2, or ozone has been shown to improve the general properties of the grown layers and allow for a reduction of the substrate temperatures.11–13 Photon-assisted PLD also showed great promise.14–16 This is a process where either a part of the incoming laser pulse used for ablation or a second laser pulse is used to irradiate the growing film.
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