We present intrinsic tunneling spectroscopy measurements on small ${\mathrm{Bi}}_2{\mathrm{Sr}}_2{\mathrm{CaCu}}_2{\mathrm{O}}_{8+x}$ mesas. The tunnel conductance curves show both sharp peaks at the superconducting gap voltage and broad humps representing the $c$-axis pseudogap. The superconducting gap vanishes at $T_c$, while the pseudogap exists both above and below $T_c$. Our observation implies that the superconducting and pseudogaps represent different coexisting phenomena.

Intrinsic tunneling spectroscopy in high magnetic field ( $H$) is used for a direct test of superconducting features in the quasiparticle density of states of pure Bi2212 and intercalated ${\mathrm{HgBr}}_2$-Bi2212 high- $T_c$ superconductors. We were able to distinguish with great clarity two coexisting gaps: (i) the superconducting gap, which closes as $H\to H_{c2\mathrm{}}\left(T\right)$, and (ii) the $c$-axis pseudogap, which does not change either with $H$ or with $T$. Strikingly different $H$ dependencies, together with previously observed different temperature dependencies of the two gaps, speak against a superconducting origin of the pseudogap.

Stacked series arrays of intrinsic Josephson tunnel junctions have been fabricated on the surfaces of ${\mathrm{Bi}}_2{\mathrm{Sr}}_2\mathrm{Ca}{\mathrm{Cu}}_2{\mathrm{O}}_{8+\delta }$ single crystals using photolithography and Ar-ion milling together with in situ monitoring of the resulting current-voltage ($I-V$) characteristics. The number of junctions in the stack (along the $c$ axis) is varied from 1-5 to ∼200 in a controlled way. Both Josephson coupling and multiple branches with well developed gap features are seen in the $I-V$ dependences of the arrays at $T\lesssim 90$ K. The gap parameter ${\Delta }_c$ is 10-13 meV at 4.2 K, which is approximately half the value reported in the literature. The temperature dependence of ${\Delta }_c$ deviates strongly from the BCS one. Proximity induced superconductivity of the Bi-O layers may possibly explain both the reduced gap parameter and its temperature dependence.

An improved technique for transferring large area graphene grown by chemical vapor deposition on copper is presented. It is based on mechanical separation of the graphene/copper by H₂ bubbles during H₂O electrolysis, which only takes a few tens of seconds while leaving the copper cathode intact. A semi-rigid plastic frame in combination with thin polymer layer span on graphene gives a convenient way of handling- and avoiding wrinkles and holes in graphene. Optical and electrical characterizations prove the graphene quality is better than that obtained by traditional wet etching transfer. This technique appears to be highly reproducible and cost efficient.