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采用直流磁控溅射和在纯氩气中后热处理的方法 ,在LaAlO3 (0 0 1 )衬底上生长出厚度小于 1 0 0nm的Tl2 Ba2 CaCu2 Ox(Tl 2 2 1 2 )超导薄膜 .在 77K和零磁场下 ,1 0 0nm厚的薄膜具有1 0 5 .3K的超导转变温度和 2 .33× 1 0 6A/cm2 的临界电流密度 .这些值与较厚的Tl 2 2 1 2薄膜的最好值相符 .30nm厚的薄膜仍具有大于 1 0 0K的转变温度 ,并具有光滑致密的表面形貌和外延生长的晶体结构 .2 0nm厚的薄膜仍显示出正常态的金属行为和充分的超导转变 .当厚度小于 2 0nm时 ,薄膜的表面形貌和超导电性明显变坏 ,6nm厚的薄膜在 1 5K低温下 ,未发现超导转变 .从这个意义上看 ,2 0nm为我们所研究的Tl 2 2 1 2薄膜的临界厚度 .
A Tl2 Ba2 CaCu2 Ox (Tl2 2 1 2) superconducting thin film with a thickness of less than 100 nm was grown on a LaAlO3 (001) substrate by direct current magnetron sputtering and post-heat treatment in pure argon. At 77 K and zero magnetic field, a 100 nm thick film has a superconducting transition temperature of 105.5 K and a critical current density of 2.33 × 10 6 A / cm 2 These values are comparable to thicker Tl 2 2 1 2 The best values for the films are consistent. The 30 nm thick film still has a transition temperature greater than 100 K and has a smooth and dense surface morphology and epitaxial growth. The 20 nm thick film still shows normal metallic behavior and Sufficient superconducting transition.When the thickness is less than 20 nm, the surface morphology and superconductivity of the films are obviously deteriorated, and the superconducting transition is not found in the 6 nm thick films at the low temperature of 15 K. In this sense, The critical thickness of Tl 2 2 1 2 film for our study.