We report ferromagnetism in carbon-doped ZnO. Our first-principles calculations based on density functional theory predicted a magnetic moment of $2.02{\mu }_B$ per carbon when carbon substitutes oxygen in ZnO, and an ferromagnetic coupling among magnetic moments of the carbon dopants. The theoretical prediction was confirmed experimentally. C-doped ZnO films deposited by pulsed-laser deposition showed ferromagnetism with Curie temperatures higher than 400 K. The measured magnetic moment based on the content of carbide in the films [$(1.5–3.0){\mu }_B$ per carbon] was in agreement with the theoretical prediction. The magnetism is due to the Zn-C system in the ZnO environment.

Two-dimensional (2D) materials have been a hot research topic in the last decade, due to novel fundamental physics in the reduced dimension and appealing applications. Systematic discovery of functional 2D materials has been the focus of many studies. Here, we present a large dataset of 2D materials, with more than 6,000 monolayer structures, obtained from both top-down and bottom-up discovery procedures. First, we screened all bulk materials in the database of Materials Project for layered structures by a topology-based algorithm and theoretically exfoliated them into monolayers. Then, we generated new 2D materials by chemical substitution of elements in known 2D materials by others from the same group in the periodic table. The structural, electronic and energetic properties of these 2D materials are consistently calculated, to provide a starting point for further material screening, data mining, data analysis and artificial intelligence applications. We present the details of computational methodology, data record and technical validation of our publicly available data (http://www.2dmatpedia.org/).

We demonstrate, both theoretically and experimentally, that cation vacancy can be the origin of ferromagnetism in intrinsic dilute magnetic semiconductors. The vacancies can be controlled to tune the ferromagnetism. Using Li-doped ZnO as an example, we found that while Li itself is nonmagnetic, it generates holes in ZnO, and its presence reduces the formation energy of Zn vacancy, and thereby stabilizes the zinc vacancy. Room temperature ferromagnetism with $p$ type conduction was observed in pulsed laser deposited ZnO:Li films with certain doping concentration and oxygen partial pressure.