Synthesis of ${\mathrm{Bi}}_2$${\mathrm{Sr}}_2$${\mathrm{CaCu}}_2$${\mathrm{O}}_8$/${\mathrm{Bi}}_2$${\mathrm{Sr}}_2$${\mathrm{CuO}}_6$ superlattices with a ${\mathit{T}}_{\mathit{c}}$ enhancement effect

${\mathrm{Bi}}_2$ ${\mathrm{Sr}}_2$ ${\mathrm{CaCu}}_2$ ${\mathrm{O}}_8$(2212)/${\mathrm{Bi}}_2$ ${\mathrm{Sr}}_2$ ${\mathrm{CuO}}_6$(2201) superlattices epitaxially grown in situ by reactive rf magnetron sputtering on heated MgO substrates were studied by x-ray diffraction methods and resistive measurements. The highest ${\mathit{T}}_{\mathit{c}}$(R=0) of 94 K, notably higher than that of single phase 2212 films prepared in the same conditions (${\mathit{T}}_{\mathit{c}}$=75–80 K), was obtained for (2212${)}_{\mathit{m}}$/(2201${)}_{\mathit{n}}$ superlattices where the number m of c-axis half-unit cells are close to unity. We attribute this fact to the metallic nature of the intervening 2201 layer favoring in such a situation an optimal ${\mathrm{O}}_2$ doping of the 2212 layers.