Bidirectional threshold switch（OTS）DeviceIt is a key component in the evolution of memory from two-dimensional to three-dimensional architecture, with its core structure consisting of electrodes/sulfur based thin films/electrodes. Among them, Ge Se sulfur based thin films have become the most popular due to their excellent switching characteristicsOTS material systemHowever, the valence band structure and atomic structure of the system in different compositional intervals, especially in the selenium rich and germanium rich regions, have not been fully revealed. To overcome this challenge, Professor Zhu Min's team from Shanghai Jiao Tong University andThermo Fisher ScientificGe Qingqin and Shi South South cooperation, utilizingThermo Fisher ESCALAB QXi XPS PlatformA systematic study was conducted on the electronic structure and bond type distribution of Ge ₓ Se ₁₋ₓ (x=0-100%) across the entire composition range. Related achievements to“X-Ray Photoelectron Spectroscopy Analysis of Ge-Se Chalcogenides”Title published.

The research team reconstructed and analyzed the energy levels and valence band structure of Ge 3d cores through high-resolution XPS, establishing a quantitative correlation between Ge content changes, coordination environment transitions, and bond redistribution. The research results show that the Ge Se system exhibits three types of structural regions in different composition ranges: the selenium rich region (x<40%) maintains a 4:2 Ge: Se coordination structure; The germanium rich transition region (x=40-60%) exhibits a 3:3 Ge Se coordination competing with the formation of Ge Ge homopolar bonds; The germanium dominant region (x ≥ 70%) exhibits over 72% of the bonds as homopolar Ge Ge bonds.

In addition, the dissociation of selenium chains and the formation of different types of Ge Se bonds and homopolar Ge Ge bonds were also discovered through valence band spectroscopy analysis. These results establish the composition structure relationship in Ge Se chalcogenides, indicating that controlling the doping of Ge can optimize OTS performance through defect mediated bond engineering.

This study not only deepens the understanding of the electronic structure of Ge Se sulfur based materials, but also provides new ideas for the design of high-performance OTS materials and the development of future high-density storage technologies.

Figure 1. Series Ge_xSe_1–xEvolution of Ge3d Core Energy Levels of Thin Films with Composition

Figure 2. Analysis of Ge series by XPS valence band spectrum_xSe_1−xThe valence electron structure of thin films

Figure 3. Comparison of XPS valence band spectra between selenium rich and germanium rich samples

Thermo FisherESCALAB QXi XPS SystemIt played an important role in this study, with its high-resolution and high-sensitivity detection capabilities providing reliable technical support for atomic level structural analysis. These findings not only deepen our understanding of the electronic structure evolution of Ge Se systems, but also provide new ideas and methods for the design of high-performance memory materials in the future. Thermo Fisher Scientific will continue to be committed to providing advanced instruments and solutions for researchers, helping to achieve continuous breakthroughs in scientific research.