STUDIES ON YBA2CU4O8 THIN-FILMS

YBa2Cu4O8 (Y124) films are successfully grown using sputtering and pul sed laser deposition techniques (PLD). The dependence of 124 phase for mation on the nature of target, substrate temperature and oxygen parti al pressure are studied using both the techniques. Substrate temperatu re between 550-600 degrees C, and oxygen partial pressure between 200- 300 mtorr are found to be optimum range parameters to grow almost sing le phase Y124 films by the pulsed laser deposition technique. For grow th of sputtered Y124 films, around 90 mtorr of Ar + O-2 gas mixture in 3 : 1 ratio and a substrate temperature of 500-550 degrees C are opti mum. Post annealing of sputter deposited films is found to be essentia l. In both the (PLD and sputtering) techniques, chemically coprecipita ted Y124 (unreacted) targets are found to be good for growing insitu Y 124 thin films. The PLD technique produces Y124 films having higher cr itical current density (T-c0 approximate to 78 K and J(c) similar to 1 0(6) A/cm(2) at 65 K) when compared with that of sputter deposited fil ms which have J(c) similar to 10(5) A/cm(2) at 65 K.