New research has shown that fast electronic processes in two-dimensional materials like graphene can be probed using ion irradiation. A collaboration between researchers at the University of Illinois Urbana-Champaign and the University of Duisburg-Essen has demonstrated that when graphene is irradiated with ions, it generates secondary electrons that provide information about the material’s electronic behavior. The Illinois group performed calculations on high-temperature graphene, while the Duisburg-Essen group experimentally verified the predictions through irradiation. This study, published in Nano Letters, marks a critical step towards using ions for studying 2D materials’ electronic properties.
André Schleife, a professor of materials science & engineering at the University of Illinois, explains that using ions for irradiation can offer advantages over traditional laser light techniques. Ions allow for highly localized, short-time excitations in the material, enabling precise studies of how graphene and other 2D materials evolve over time. When ions collide with a 2D material, energy is transferred to both the atomic nuclei and electrons, resulting in the ejection of secondary electrons. The characteristics of these electrons, such as their temperature and energy distribution, provide valuable insights into the material’s electronic properties.
The study’s lead author, graduate student Yifan Yao, highlights the importance of understanding the delay between ion impact and secondary electron emission. The Illinois group conducted simulations on graphene at absolute zero with no thermal energy and graphene with thermal energy at higher temperatures, representing a first in simulating “hot” graphene. By irradiating graphene with hydrogen ions and studying the release of secondary electrons over time, the computational results aligned well with the experimental results from the Duisburg-Essen group using argon and xenon ions.
Furthermore, the computational study delved into the mechanisms of secondary electron emission and revealed that high-temperature graphene releases more secondary electrons. An analysis of the charge distributions indicated that the atomic nuclei in the material’s lattice, rather than the electrons, are primarily responsible for this process. Schleife notes that beyond precise measurements of 2D materials, ion irradiation holds promise for deliberately introducing defects into materials and manipulating them in the future. However, in the immediate term, this technique has proven effective as a high-precision measurement tool for studying electronic properties.
In conclusion, the research on ion irradiation of two-dimensional materials like graphene offers new avenues for understanding and manipulating their electronic properties. By utilizing ions for irradiation, researchers can achieve highly localized and precise excitations in the material, leading to insights into fast electronic processes. The collaboration between the University of Illinois Urbana-Champaign and the University of Duisburg-Essen has shown the effectiveness of ion irradiation in studying graphene’s electronic behavior and verifying computational predictions. This advancement opens up possibilities for using ion irradiation to manipulate materials in the future and highlights the technique’s potential as a high-precision measurement tool for studying 2D materials.
