Stanford University radiology instructor Diana Jeong and a team of researchers investigating the interaction between ionizing radiation and matter have made an unexpected discovery. They identified surprisingly strong, instantaneous optical signals in common semiconductors.
Stanford Researchers Uncover Instantaneous Semiconductor Signals
The research relies on ultrafast electrons and laser pulses to capture early radiation-induced light responses.
Overcoming the Scintillator Speed-Versus-Strength Compromise
Ionizing radiation penetrates deep within structures by freeing electrons from atoms. This process allows physicists and medical professionals to peer inside materials and the human body alike. Because this radiation cannot be measured directly, researchers must rely on secondary signals, such as light or electrical discharges, generated when the radiation interacts with matter.
Historically, these secondary signals presented engineers with a frustrating compromise. They were either strong but agonizingly slow to develop, or fast but weak in response amplitude. Standard radiation detectors built today rely primarily on scintillators, which are specialized materials that absorb high-energy radiation and convert it into visible light.
Consider a standard clinical PET scan. Patients receive an injection of a small radioactive tracer. As that tracer decays, it emits positrons that subsequently generate gamma rays, which are ultimately captured by heavy scintillator crystals.
“When the radiation hits the scintillator, it glows,” Diana Jeong explained, describing the mechanics of the process. “That glow has been the standard signal for radiation detection for decades.”
Mapping Early-Stage Ionization With Ultrafast Lasers
Because traditional scintillation glow develops gradually over time, Jeong and her research team set out to systematically investigate optical signal strengths across a diverse range of material classes induced by ionization. They wanted to know if an earlier, much faster light signal existed immediately after ionization—one that could be observed using high-powered ultrafast laser pulses.
By pairing MeV ultrafast electron diffraction (MeV-UED) setups with precise laser diagnostics, the team observed that common semiconductors exhibit surprisingly robust radiation signals right at the point of impact. This upends the long-standing assumption that early-stage ionization signals in non-scintillating materials are too weak to be useful for practical engineering applications.
Bypassing Latency Bottlenecks in Medical and Industrial Systems
Traditional detectors face fundamental limitations in temporal resolution due to the decay time of standard scintillator crystals.
While the research remains focused on foundational material interactions, the identification of strong secondary signals in widely accessible semiconductor substrates lowers the barrier for integrating novel detection layers into existing silicon-based manufacturing pipelines.
Bridging Deep-Penetration Physics and Digital Sensing
By leveraging ultrafast electrons and lasers to study semiconductor ionization dynamics, researchers have found a way around the traditional speed-versus-strength tradeoff in radiation detection.
