Silicon computer chips have been the cornerstone of technology for over half a century. Today, the tiniest features on commercially available chips are around 3 nanometers, a remarkable feat considering a human hair is roughly 80,000 nanometers wide. Shrinking these features further is essential to meet our growing demand for more memory and processing power. However, we are approaching the limits of what can be achieved with traditional materials and processes.

Researchers at the U.S. Department of Energy’s Princeton Plasma Physics Laboratory (PPPL) are pioneering the next generation of computer chips. They are leveraging their expertise in physics, chemistry, and computer modeling to explore new materials and processes that can produce chips with even smaller features.

“All of our existing electronic devices use chips made of silicon, a three-dimensional material. Now, many companies are investing in chips made from two-dimensional materials,” explained Shoaib Khalid, an associate research physicist at PPPL. These materials, though existing in three dimensions, are so thin—often only a few layers of atoms—that they are termed 2D. Khalid and his team’s recent paper in the journal 2D Materials delves into the atomic structure variations in transition metal dichalcogenides (TMDs), exploring why they occur and their impact on the material. This knowledge is crucial for refining processes to create next-generation computer chips.

The goal is to design plasma-based manufacturing systems capable of producing TMD-based semiconductors with precise specifications.

A TMD can be as thin as three atoms, resembling a tiny metal sandwich. The “bread” consists of a chalcogen element (oxygen, sulfur, selenium, or tellurium), and the “filling” is a layer of transition metal from groups 3 to 12 in the periodic table. Ideally, the atoms are organized in a precise, consistent pattern, but in reality, small alterations or defects often occur. Interestingly, these defects can sometimes enhance the material’s properties, such as increasing electrical conductivity.

Understanding these defects and their impact is critical. For instance, the team discovered that certain defects involving hydrogen contribute to excess electrons in TMDs, creating negatively charged (n-type) semiconductor material. This insight helps explain previous experimental results and guides future research and manufacturing processes.

The researchers used photoluminescence techniques to analyze TMD defects, identifying the frequencies of light emitted by the material. These frequencies indicate the electron configurations and the presence of chalcogen vacancies. Their findings provide a framework for investigating defects in various TMDs, including molybdenum disulfide.

Khalid stated, “Our work provides a strategy to investigate these vacancies in bulk TMDs. We explained past experimental results in molybdenum disulfide and predicted similar outcomes for other TMDs.”

The results published in the journal offer a guideline for future experiments, detailing the expected light frequencies emitted by five types of TMDs with chalcogen vacancies.

By Impact Lab