Recently, Professor Wang Zenghui and Professor Xia Juan from the University of Electronic Science and Technology of China, along with Professor Zhou Yu from Central South University, collaborated to report on an ultra-high frequency resonant nanopressure sensor based on the non layered two-dimensional material β - In2S3. The sensor achieved excellent sensing performance with a wide range (from 10-3 Torr to atmospheric pressure), high linearity (only 0.0071 nonlinearity), and fast response (intrinsic response time less than 1 microsecond).This achievement was recently published in the InfoMat journal, and the corresponding authors of the paper also include Dr. Zhu Jiankai from the University of Electronic Science and Technology of China (winner of the first Excellent Doctoral Dissertation Award of the China Micron and Nanotechnology Society).

Two dimensional non layered materials have the potential to be applied in nanomechanical structures, and due to their unique physical properties and surface activity, they are expected to further achieve high-performance sensor devices. However, due to the requirements of material stability and conductivity for nanomechanical devices, as well as the difficulty of device preparation, this highly promising application paradigm has not been explored.Recently, the team of researchers utilized β - In2S3, a two-dimensional non layered semiconductor with high carrier mobility and moderate bandgap, to prepare a series of nano electromechanical resonators with operating frequencies in the ultra-high frequency band. The achieved pressure sensing performance is currently the best among similar devices.

 Researchers investigated the elastic characteristics of the device using the dynamic response of a circular nanodrum (Figure 1A − C). The frequency domain dynamic response of the nanoresonator in the ultra-high frequency range was effectively characterized by a self-designed and optimized laser interference displacement measurement system (Figure 1D). To verify the pressure sensing performance of the β - In2S3 nanoresonator, researchers continuously tracked the dynamic response of the device within a wide pressure range of 10-4 Torr to atmospheric pressure, and analyzed the control mechanism of resonance frequency and quality factor.Research has shown that the resonant frequency increases linearly with increasing air pressure, with a response of up to 259.77 ppm/Torr (i.e., each Torr of air pressure change will introduce a frequency offset of up to 2.328 KHz), while the nonlinearity is only 0.0071, revealing the excellent response performance of the sensor (Figure 1E). In addition, the additional air damping introduced by the dissipation factor decreases with increasing air pressure, and theoretical analysis shows that the response speed of the sensor can reach 0.95 microseconds at atmospheric pressure.

Figure 1. (A − C) Schematic diagram of the (A) structure of the two-dimensional β - In2S3 nanomechanical resonator, (B) Microscopic view of the device, and (C) Electron microscopy image; (D) Experimental data of fundamental mode resonance response of resonators (blue line) and model fitting (red line); (E) The resonance frequency and dissipation factor are regulated by the chamber pressure (partial pressure range).

Researchers prepared and tested 24 β - In2S3 nanoresonators with different thicknesses and sizes, operating in a wide frequency range of 8.48 MHz to 89.97 MHz (Figure 2A), and exhibited thickness dependent dissipation mechanisms (Figure 2B). Through theoretical analysis of the intrinsic frequency of resonators, researchers have proposed partition rules for the elastic characteristics of devices corresponding to different device geometries, which have been validated on experimental data.This study also determined the Young's modulus (45 GPa) and built-in stress (within approximately 0.5 N/m) of β - In2S3 material, providing a solid theoretical basis for the design, analysis, regulation, and application of novel nano electromechanical devices based on two-dimensional non layered materials.

Figure 2. Performance and frequency design pattern of β - In2S3 nanoresonator. (A) The measured fundamental mode resonant frequency (scatter) and the frequency design law obtained from theoretical analysis (solid lines and shadows); (B) The relationship diagram between the dissipation factor (Q) extracted from experimental data and device size.