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ResearchBlogging.org Yttrium-doped Bismuth Strontium Calcium Copper Oxide (BSCCO) films,  specifically Bi 2212, were succesfully deposited with preserved sample concentration using Infrared Pulsed Laser Deposition (IR PLD) as written in a recent publication from the National Institute of Physics, University of the Philippines Diliman [1].  It was also shown that by using appropriate annealing, desired qualities for electronic applications can be obtained.

Y doped Bi 2212 films with different doping compositions deposited by PLD before melting annealing. Photo from de Vero Physica C: Superconductivity 471, 2011

Bi 2212, a member of the BSCCO, is a high Tc superconductor whose critical temperature is around 80 K (-193 ºC) .   There are a lot of methods to produce Bi 2212.  The main concern actually is the ease in which a film can be deposited that still maintains the relative sample/composition of the elements.

In their paper [1], the authors write that they were able to produce stoichiometrically correct Bi 2212 films  using IR PLD without heating the substrate and without using external gases upon deposition.

The main idea of the work according to the authors is to test the IR PLD as a means of depositing stoichiometrically preserved films.  Since the bulk properties of Bi 2212 is already well-known, the deposited film can be bench marked against it.  Hence, testing the effectiveness of the IR PLD.

The deposited films look globular without melting and annealing as shown in the figure on the upper left.  The authors attribute this to the molten particulates that were ejected from the target.  Although the authors observed that the size of these particulates decreases with the increase in Yttrium concentration, they did not offer an explanation.

Y-doped BI-2212 with different doping concentrations after melting and annealing. Photo from de Vero Physica C: Superconductivity 471, 2011

Upon melting at 930 degrees Celsius for 15 minutes and annealing at 850 degrees Celsius for 5 hours, the resulting films are flat and smooth as shown with the figure on the lower right.  Because heat treatment is done after the deposition, there is no depositional flux that interfered to the nucleation and thin film growth. There is also no re-evaporation. These help in maintaining the stoichiometry of  the material.

In their deposited film, heat treatment is needed to produce superconducting films. It was proven that this  do not change the amount of Bi.  EDX measurements  show that the concentration of the  film comes from the depositional flux alone.

The authors conclude that

IR PLD can be a viable technique in producing other high temperature superconductors that cannot be easily and cost-effectively reproducible by current deposition techniques.

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[1] De Vero, J., Blanca, G., Vitug, J., Garcia, W., & Sarmago, R. (2011). Stoichiometric transfer of material in the infrared pulsed laser deposition of yttrium doped Bi-2212 films Physica C: Superconductivity, 471 (11-12), 378-383 DOI: 10.1016/j.physc.2011.03.010

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J. de Vero recently defended his dissertation titled, “Infrared Pulsed Laser Deposition of Superconductor Materials.”

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