Engineers have been using piezoelectric crystals to generate acoustic ripples, surface acoustic waves (SAWs), that propagate along a material’s surface at gigahertz (GHz) frequencies for decades. These waves are the heartbeat of modern wireless technologies, including high-frequency sensors, hybrid photonic-phononic devices, and even quantum technologies. But piezoelectric materials harbor some endemic challenges: unenviable scaling issues, energy loss, and irreconcilability with silicon itself, the backbone of modern electronics.
Now, researchers from the Indian Institute of Technology Bombay and the Raja Ramanna Center for Advanced Technology have cracked the code. They performed direct, yet inductive, generation of SAWs at both fundamental and higher-order modes using metallic transducers embedded in monolithic silicon, rather than traditional piezoelectric components.
The achievement was tracked using time-resolved extreme-ultraviolet diffraction measurements, a technique precise enough to observe the waves ripple in real time.
Conventional interdigital transducers (IDTs) on piezoelectric materials have historically constituted the norm for SAW technology. Nevertheless, they lose charge transmission at high frequencies because of attenuation: the gradual dissipation of wave energy during propagation. Moreover, their incompatibility with silicon-based fabrication precludes direct integration into mainstream microelectronics.
With wireless communication systems moving to 5G, 6G, mm-wave technologies, and beyond, the quest for compact, low-loss, ultra-high-speed signal-processing devices that can be integrated into or work with existing silicon infrastructure is underway. However, due to increasing demands for rapid communication and quantum-equipped hardware, the generation of these acoustic waves using traditional techniques is being constrained by fundamental physical limits.
Researchers used an ultrafast laser pulse to create thermoelastic stress in nickel transducers on silicon, launching surface acoustic waves that are then “probed” by a beam of extreme ultraviolet light via diffraction. Image credit: Arun Babu
Lead author Arun Babu explains, “The primary reason for SAW devices being built on piezo-actuation is that silicon is incompatible due to its lack of piezoelectricity. To bypass this, the team turned to optical actuation and extreme ultraviolet (EUV) diffraction.”
To circumvent these material restrictions, the research team switched to metallic transducers on silicon. Their experiments, which were corroborated by finite-element simulations, showed that the frequencies and lifetimes of first- and second-order SAWs remain constant over large ranges of operation: 3.5–16.5 GHz for frequency and 14–0.6 nanoseconds for attenuation lifetime.
This enables the generation of long-lived, high-frequency SAWs within a single device architecture, a feat that has previously proven difficult.
They also then showed that attenuation lifetimes (𝜏𝑆) can be tuned by the “duty cycle” of the transducer geometry.
In one such most remarkable instance, they realized a 2nd-order SAW approach to 10 GHz with lifetimes on the order of a few nanoseconds. This tunability leads to applications over a range of instruments, from ultra-sensitive detectors up to quantum systems that require specific acoustic properties.
One of the most remarkable results from the study is that silicon has lower acoustic losses than conventional piezoelectric substrates. This finding contradicts previous beliefs that silicon, often deemed unsuitable for SAW generation, could be a very favorable platform for next-generation acoustic devices.
Why it matters
This work presents a method for implementing high-speed, acoustic-based functionality onto standard semiconductor technology. Monolithic silicon and metallic transducers are used to create the system so it can directly work with the same microchip now found in computing systems as well as automotive systems.
Applications: Quantum devices with phonons (quanta of sound) coupled with photons & electrons, Hybrid photonic-phononic systems opening new signal processing architectures, Sensing covering a wide range, e.g., medical diagnostics and environmental monitoring.
In fact, enabling silicon-based SAW generation bridges a critical gap between the realm of acoustic physics and mainstream integrated circuit technology. In this way, it can provide all-in-one low-loss, high-frequency devices with good access to gender changes of acoustic waves at the nanometer scale.
“Our work provides a timely route toward integrating phononic functionalities within mainstream semiconductor technology,” said Dipanshu Bansal, Associate Professor in the Department of Mechanical Engineering at the Indian Institute of Technology Bombay.
This breakthrough reimagines silicon’s role. Though previously considered acoustically inert to function as a material for these applications, silicon is now shown as a plausible candidate for GHz-scale acoustic waves. Low-intrinsic loss, tunable, and naturally well integrated into existing electronic systems, silicon-based SAWs might become a foundation for scalable architectures to realize next-generation sensing or quantum technologies.
Journal Reference:
- A. Babu, M. Kumar, H. Singhal, A. Ansari, J.A. Chakera, and D. Bansal. “Control of High-Frequency Surface Acoustic Waves via Transducer Geometry and Higher-Order Mode Equivalency.” Nano Letters, 2026. DOI: 10.1021/acs.nanolett.6c01437