Extended Data Table 1 Optimizing fabrication process for monolayer and bilayer Bi-2212 samples

From: High-temperature superconductivity in monolayer Bi2Sr2CaCu2O8+δ

  1. We have systematically investigated the effects of the following key factors on the transport properties of monolayer and bilayer Bi-2212: contact method, air-exposure time and total fabrication time in glove box. We observe that monolayer Bi-2212 is more prone to degradation than is bilayer graphene. In particular, exposure to air is most detrimental to sample quality of the monolayers. Evaporating metal contacts (through shadow mask) also causes considerable degradation. We find that cold-welding indium contacts in the glove box preserves the monolayer sample quality. Here, thin indium foils make stable contacts with a thick flake that is connected to the monolayer, so that the thick flake electrically bridges the indium electrodes and the monolayer (Fig. 1e). The monolayer samples exfoliated from an over-doped crystal (OD55) are slightly over-doped, and their maximum Tc is comparable to the Tc of optimally doped bulk crystals (Fig. 2c).
  2. (#1)–(#5)Transport properties of typical monolayer samples from these categories are shown in Extended Data Fig. 1.
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