Scalable Production of Ultraflat and Ultraflexible Diamond Membranes

Academic Background

Diamond, as a material with exceptional physical properties, holds significant potential in various fields such as electronics, photonics, mechanics, thermotics, and acoustics. However, despite substantial progress in diamond research over the past decades, the large-scale production of high-quality ultrathin diamond membranes remains a significant challenge. Traditional methods for producing diamond membranes, such as laser cutting and chemical vapor deposition (CVD), can produce high-quality single-crystal diamond (SCD) but face limitations in industrial-scale applications, particularly in producing large-area, ultrathin, and ultraflat diamond membranes. These limitations have hindered the widespread adoption of diamond materials in semiconductor technologies.

To address this issue, researchers have been exploring new production methods to achieve large-area, ultrathin, ultraflat, and transferable diamond membranes. This paper presents a simple, scalable, and reliable method based on edge-exposed exfoliation, successfully producing large-area (2-inch wafer), ultrathin (sub-micrometer thickness), ultraflat (sub-nanometer surface roughness), and ultraflexible (360° bendable) diamond membranes. This breakthrough opens new possibilities for the commercialization of diamond materials in electronics, photonics, and other related fields.

Paper Source

This paper is a collaborative effort by a team from multiple research institutions, with primary authors including Jixiang Jing, Fuqiang Sun, Zhongqiang Wang, and others, affiliated with the University of Hong Kong, Peking University Dongguan Institute of Optoelectronics, Southern University of Science and Technology, and other institutions. The paper was published in Nature on December 19-26, 2024, under the title Scalable production of ultraflat and ultraflexible diamond membrane.

Research Process

1. Growth and Exfoliation of Diamond Membranes

The research team first grew diamond membranes on silicon (Si) substrates using microwave plasma chemical vapor deposition (CVD). By controlling the growth time, diamond membranes of varying thicknesses were obtained. To facilitate exfoliation, the researchers cropped the edge of the silicon wafer to expose the diamond-substrate interface. Subsequently, transparent tape was used to peel the diamond membrane from the substrate, successfully obtaining a 2-inch diamond membrane.

2. Characterization of Membrane Quality

The exfoliated diamond membranes underwent a series of quality characterizations. Raman spectroscopy, X-ray photoelectron spectroscopy (XPS), and X-ray diffraction (XRD) analyses showed that the exfoliated diamond membranes exhibited optical, electrical, and thermal properties comparable to those of standard single-crystal diamond. Additionally, atomic force microscopy (AFM) measurements revealed that the surface roughness of the exfoliated diamond membranes was below 1 nanometer, making them suitable for precise micro- and nanofabrication.

3. Flexibility Testing

The research team also tested the flexibility of the diamond membranes. Experiments demonstrated that a 4-micrometer-thick diamond membrane could be bent 360° and wrapped around cylinders of different radii. By attaching the diamond membrane to a flexible polydimethylsiloxane (PDMS) substrate, the researchers demonstrated its potential in strain sensing applications.

4. Optimization of Exfoliation Parameters

To optimize the exfoliation process, the research team developed a homemade exfoliation device capable of precisely controlling the peeling speed and angle. Through experiments and theoretical simulations, the researchers found that the peeling angle and membrane thickness were critical factors affecting the quality of exfoliation. Within the optimal operating window, crack-free diamond membranes could be consistently produced.

Main Results

1. Production of High-Quality Diamond Membranes: The research team successfully produced large-area, ultrathin, ultraflat, and transferable diamond membranes with surface roughness below 1 nanometer, suitable for precise micro- and nanofabrication.
2. Flexibility Applications: The diamond membranes exhibited excellent flexibility, withstanding over 10,000 deformation cycles, demonstrating their potential in flexible electronics and strain sensing applications.
3. Optimization of Exfoliation Parameters: Through experiments and theoretical simulations, the researchers identified the optimal peeling angles and membrane thicknesses, providing guidance for the large-scale production of crack-free diamond membranes.

Conclusion

This paper presents a simple, scalable, and reliable method based on edge-exposed exfoliation, successfully producing large-area, ultrathin, ultraflat, and transferable diamond membranes. This method opens new possibilities for the commercialization of diamond materials in electronics, photonics, and other related fields. The results show that the exfoliated diamond membranes exhibit optical, electrical, and thermal properties comparable to those of standard single-crystal diamond, along with excellent flexibility, making them suitable for precise micro- and nanofabrication and flexible electronics applications.

Research Highlights

1. Innovative Exfoliation Method: This paper introduces, for the first time, a method based on edge-exposed exfoliation, successfully achieving the production of large-area, ultrathin diamond membranes.
2. Production of High-Quality Membranes: The exfoliated diamond membranes exhibit ultra-low surface roughness and excellent flexibility, making them suitable for precise micro- and nanofabrication and flexible electronics applications.
3. Application Potential: This method provides new possibilities for the commercialization of diamond materials in electronics, photonics, and other fields, potentially accelerating the advent of the diamond era.

Other Valuable Information

This research not only provides a new method for the production of diamond materials but also offers a reference for the exfoliation and transfer of other two-dimensional materials. Additionally, the research team demonstrated the potential applications of diamond membranes in flexible electronics, strain sensing, and quantum technologies, providing new directions for future research.

Through this study, significant progress has been made in the large-scale production and application of diamond materials, which are expected to play a greater role in electronics, photonics, and other fields in the future.