Flux growth at ambient pressure of millimeter-sized single crystals of LaFeAsO, LaFeAsO$_{1-x}$F$_{x}$, and LaFe$_{1-x}$Co$_{x}$AsO

Millimeter-sized single crystals of LaFeAsO, LaFeAsO$_{1-x}$F$_{x}$, and LaFe$_{1-x}$Co$_{x}$AsO were grown in NaAs flux at ambient pressure. The as-grown crystals have typical dimensions of 3 $\times$ 4 $\times$ 0.05-0.3 mm$^{3}$ with the crystallographic $c$-axis perpendicular to the plane of the plate-like single crystals. Various characterizations confirmed the high quality of our LaFeAsO crystals. Co and F were introduced into the lattice leading to superconducting LaFe$_{1-x}$Co$_{x}$AsO and LaFeAsO$_{1-x}$F$_{x}$ single crystals, respectively. The distribution and control of Co and F dopants will be discussed. - Ames Laboratory is operated for the US Department of Energy by Iowa State University under Contract No. DE-AC02-07CH11358.