Challenges for Pulsed Laser Deposition of FeSe Thin Films

Abstract

Anti-PbO-type FeSe shows an advantageous dependence of its superconducting properties with mechanical strain, which could be utilized as future sensor functionality. Although superconducting FeSe thin films can be grown by various methods, ultrathin films needed in potential sensor applications were only achieved on a few occasions. In pulsed laser deposition, the main challenges can be attributed to such factors as controlling film stoichiometry (i.e., volatile elements during the growth), nucleation, and bonding to the substrate (i.e., film/substrate interface control) and preventing the deterioration of superconducting properties (i.e., by surface oxidization). In the present study, we address various technical issues in thin film growth of FeSe by pulsed laser deposition, which pose constraints in engineering and reduce the application potential for FeSe thin films in sensor devices. The results indicate the need for sophisticated engineering protocols that include interface control and surface protection from chemical deterioration. This work provides important actual limitations for pulsed laser deposition (PLD) of FeSe thin films with the thicknesses below 30 nm.

Stoichiometric Growth of Monolayer FeSe Superconducting Films Using a Selenium Cracking Source

“…The transition temperature T c is usually close to or below that of the bulk and drops further with decreasing film thickness [12]. PLD has not been able to grow superconducting FeSe films thinner than 10 nm and has suffered from difficulties in controlling the film's stoichiometry, nucleation, and bonding to the substrate [13]. So far, FeSe films in a monolayer form have been exclusively grown by MBE using a well-known strategy called "adsorption-controlled growth".…”