Tunneling spectra and superconducting gaps observed by scanning tunneling microscopy near the grain boundaries of FeSe0.3Te0.7 films

Abstract

We used STM to study the tunneling spectra of FeSe 0.3 Te 0.7 films with two orientations of ab-planes and the connection ramp between them. We have discovered that, using pulse laser deposition (PLD) method, the a-and b-axis of the FeSe 0.3 Te 0.7 film deposited on Ar-ion-milled Magnesium Oxide (MgO) substrate are rotated 45° with respect to those of MgO, while the a-and b-axis of the film grown on pristine MgO substrate are parallel to those of MgO. With photolithography and this technique, we can prepare FeSe 0.3 Te 0.7 film with two kinds of orientations on the same MgO substrate, and the connection between them forms a ramp at an angle about 25° to the substrate plane. In the planar region with either 0° or 45° orientation, we have observed tunneling spectra with a superconducting gap about 5 meV and 1.78 meV respectively. However, a much larger gap about 18 meV has been observed in the ramp region. Furthermore, we have also observed a small zero-bias conductance peak (ZBCP) inside the large gap at T = 4.3K. The ZBCP becomes smaller and disappear with increasing temperature to 7 K. The possible causes of such large gap and the ZBCP will be discussed.

Study of Structural Properties of Ni3Pb2S2 Films

“…For example, the obtained films could be characterized by using several techniques such as spectroscopic ellipsometry 1,2 , Raman Spectroscopy [3][4][5] ,electrochemical impedance spectroscopy [6][7][8] ,profilometer 9,10 , R u t h e r fo r d backscattering spectrometry [11][12][13][14] , scanning tunneling microscopy [15][16][17] , and atomic force microscopy [18][19][20] . These films exhibit excellent chemical, optical, physical and electrical properties.…”