High quality YBCO films grown over large areas by pulsed laser deposition

Abstract

High quality films of YBCO have been grown in situ by pulsed laser deposition (PLD) on small samples as well as both 5 cm (2 in.) and 7.6 cm (3 in.) diam (100) LaAlO3 and 5 cm (100) NdGaO3 substrates. Films grown on small LaAlO3 and NdGaO3 substrates display critical temperatures Tc in excess of 89 K while critical current densities Jc of 5 MA/cm2 at 77 K have been obtained. Films grown on 5 cm diam substrates display Tc’s in excess of 89 K, and Jc’s in excess of 2 MA/cm2 at 77 K. Also, a patterned three-piece strip line resonator (1.56 GHz fundamental frequency) fabricated using samples cut from a 5 cm diam LaAlO3 substrate yielded a microwave surface resistance Rs of 700 μΩ at 77 K when scaled to a frequency of 10 GHz. Substrates were radiatively heated without the use of absorbing layers such as nickel or thermally conductive layers such as silver paint or indium, thus making backside film deposition a clean and simple process. YBCO films grown on the backside of small LaAlO3 substrates (previously coated with 5000 Å of YBCO) display Tc’s ≳88 K with no significant degradation in the front side film properties. Furthermore, recent results of backside PLD of YBCO onto three-inch diameter LaAlO3 substrates have yielded films on both surfaces with Tc’s ≳86 K, and Jc’s ≳2 MA/cm2. The novel features of the large area PLD system will be described, and the uniformity for a number of important electrical and physical film properties will be reported.