In situ characterization of pulsed-laser-deposition grown Co doped BaFe$_{\mathrm{2}}$As$_{\mathrm{2}}$ on SrTiO$_{\mathrm{3}}$ (001)

We report epitaxial growth of Ba(Fe$_{\mathrm{1-x}}$Co$_{\mathrm{x}})_{\mathrm{2}}$As$_{\mathrm{2}}$ (BFCA) thin films on SrTiO$_{\mathrm{3}}$ (001) substrates using pulsed laser deposition (PLD) technique under ultrahigh vacuum. The growth was performed using a pellet with the optimal Co concentration x$=$0.08. The temperature dependent conductivity of BFCA films was compared with those in the pellet form. The crystallinity was monitored with reflection high-energy electron diffraction during the growth and low energy electron diffraction (LEED) patterns. Optimal growth condition was obtained at the substrate temperature of 700$\pm $20${^\circ}$. The grown sample was immediately transferred to measure the topography and spectroscopy using a scanning tunneling microscope. LEED/STM result reveals modulation of $\sqrt 2 \times \sqrt 2 $ surface reconstruction on the top plane and STM result shows the same structure. The average sizes of terraces were $\approx $10mn with a homogeneous electronic structure. The geometric and electronic structure of BFCA films will be reported.