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Atomically thin diamond, also called diamane, is a two-dimensional carbon allotrope and has attracted considerable scientific interest because of its potential physical properties. However, the successful synthesis of a pristine diamane has up until now not been achieved. We demonstrate the realization of a pristine diamane through diamondization of mechanically exfoliated few-layer graphene via compression. Resistance, optical absorption, and X-ray diffraction measurements reveal that hexagonal diamane (h-diamane) with a bandgap of 2.8 ± 0.3 eV forms by compressing trilayer and thicker graphene to above 20 GPa at room temperature and can be preserved upon decompression to ∼1.0 GPa. Theoretical calculations indicate that a (−2110)-oriented h-diamane is energetically stable and has a lower enthalpy than its few-layer graphene precursor above the transition pressure. Compared to gapless graphene, semiconducting h-diamane offers exciting possibilities for carbon-based electronic devices. 

The discovery of hydrogen‐induced electron localization and highly insulating states in d‐band electron correlated perovskites has opened a new paradigm for exploring novel electronic phases of condensed matters and applications in emerging field‐controlled electronic devices (e.g., Mottronics). Although a significant understanding of doping‐tuned transport properties of single crystalline correlated materials exists, it has remained unclear how doping‐controlled transport properties behave in the presence of planar defects. The discovery of an unexpected high‐concentration doping effect in defective regions is reported for correlated nickelates. It enables electronic conductance by tuning the Fermi‐level in Mott–Hubbard band and shaping the lower Hubbard band state into a partially filled configuration. Interface engineering and grain boundary designs are performed for H_xSmNiO₃/SrRuO₃heterostructures, and a Mottronic device is achieved. The interfacial aggregation of hydrogen is controlled and quantified to establish its correlation with the electrical transport properties. The chemical bonding between the incorporated hydrogen with defective SmNiO₃is further analyzed by the positron annihilation spectroscopy. The present work unveils new materials physics in correlated materials and suggests novel doping strategies for developing Mottronic and iontronic devices via hydrogen‐doping‐controlled orbital occupancy in perovskite heterostructures.