Thin Film Synthesis of Superconductors with Unusually High Vapor Pressures

New ways of synthesizing thin films using a modified a Pulsed Laser Deposition system. This will permit us to deposit at high vapor pressures and obtain thin film superconductors which have not been available.  Personnel-   T. H. Geballe, Gertjan Koster, Ivan Bozovic(Oxxel) and one visiting student joining in October.

Many superconductors of the high Tc family have been only obtained by synthesis in bulk form at extreme pressures. or by complicated multistep depostitions and annealing processes. These superconductors are interesting because of the novel sequencing of the CuO2 layers and their unusually high Tcs. We have developed a novel technique based upon pulsed laser deposition which will permit thin films to be deposited under pressures of the order of tenths of an atmosphere which is 100 times the standard conditions.   High oxygen and/or ozone pressures will be used to stabilize high pressure phases such as YBa2Cu4O8 (the "248" phase)[1], and the Cu-1234 phase [2].  These phases in bulk are distinguished, respectively,  by being very stable and stoichiometric, and by having unusually high Tc's.   The system will also be used to synthesize films where the cations are volatile such as MgB2 and the Hg-cuprates.

[1] K. Char, M. Lee, R.W. Barton, A.F. Marshall, I. Bozovic, R.H. Hammond, M.R. Beasley, T. H. Geballe, A. Kapitulnik and S.S. Laderman, Phys. Rev. B 38 (1988) 834. see also J. Valo and M. Leskela, A. Narlikar ed., Studies of High Temperature superconductors (Nova Science Pub. Inc.,  NY, 1997)
[2] e.g., J. Akimoto, K. Tokiwa, A. Iyo, H. Ihara, H. Hayakawa, Y. Gotoh and Y. Oosawa, Physica C 279 (1997) 181 and references therein.