Enhanced critical current density of MgB2 thin films deposited at low temperatures by ZnO seed impurity

• Published in: Current applied physics 2018, 18(6), , pp.762-766
• Main Authors: Pham, Duong, Van Ngoc, Huynh, Jung, Soon-Gil, Kang, Dae Joon, Kang, Won Nam
• Format: Article
• Language: English
• Subjects: Critical current density of MgB2; HPCVD; MgB2 thin films; ZnO-doped MgB2; 물리학
• ISSN: 1567-1739; 1878-1675
• DOI: 10.1016/j.cap.2018.03.008

We report a facile method to enhance the critical current density (Jc) of superconducting MgB2 thin films. MgB2 thin films were deposited on zinc acetate dehydrate (Zn(CH3COO)22H2O) spin-coated Al2O3 (000l) substrates by using a hybrid physical-chemical vapor deposition system at low temperatures. Synthesis of MgB2 at low temperatures can reduce the substitution of Zn into the Mg site, hence avoiding the reduction of superconducting critical temperature. MgB2 thin films grown on ZnO-buffered layers showed a significant enhancement of Jc in the magnetic field due to the creation of additional pinning sources, namely point defects and grain boundaries. Broad peaks were observed in the magnetic field dependence of the flux pinning force density, indicating competition of different pinning sources. •The high quality of MgB2 films were synthesized successful at a temperature as low as 480 °C by optimizing the condition of a hybrid physical-chemical deposition.•The MgB2 films with ZnO impurity layer show a significant enhancement of Jc compared to the pristine film, and the film with 23 nm of ZnO shows the best performance of Jc.•The critical temperature Tc was decreased under the effect of ZnO impurity, but this decreasing is less than that of other methods (like Carbon substitution or SiC impurity).•The flux pinning forces show the improvement of pinning sources, i.e., grain boundary and point pinning in ZnO impurity films. The pinning sources composed by the ZnO are effective for flux pinning at both 5 K and 20 K.