A Versatile Method for Nano‐Fabrication on Diamond Film - Flexible Diamond Metasurfaces as a Demonstration

At a Glance

Metadata	Details
Publication Date	2025-04-19
Journal	Advanced Optical Materials
Authors	Yi‐Cheng Wang, Jixiang Jing, Yumeng Luo, Linjie Ma, Xiaomin Wang
Institutions	Dongguan University of Technology, Southern University of Science and Technology
Analysis	Full AI Review Included

Technical Documentation & Analysis: Versatile Nano-Fabrication on Flexible Diamond Films

This document analyzes the research detailing a novel sugar-transfer method for high-precision nanofabrication on ultrathin, flexible MPCVD diamond films, and outlines how 6CCVD’s advanced diamond materials and customization services can support and scale this technology.

Executive Summary

The research introduces a highly effective, non-conventional method for patterning ultrathin diamond films, overcoming significant limitations associated with standard lithography techniques (EBL, spin-coating) on flexible or low-conductivity diamond substrates.

Novel Methodology: Demonstration of mask-transferring via a sugar medium, enabling high-precision, large-scale, and repeatable pattern definition on diamond films.
Overcoming Limitations: The method successfully mitigates issues inherent to conventional nanofabrication on diamond, including charge accumulation (proximity effect), film fragility (cracking below 1 µm), and geometric fluctuations on flexible substrates.
Material Achievement: Achieved wafer-scale (2-inch) exfoliated diamond films with an ultra-low buried surface roughness (Ra ≈ 1.18 nm), crucial for high-resolution patterning.
Device Demonstration: Successful fabrication of flexible, all-diamond metasurfaces functioning as structural colors on a PET substrate.
Performance Metrics: The metasurfaces exhibited ultra-high reflectance intensity (up to 88.78%) and demonstrated solid stability under mechanical bending/deformation.
Future Impact: This technique unlocks the vast potential of ultrathin diamond films for advanced applications in diamond photonics, next-generation flexible electronics, quantum sensing, and durable display devices.

Technical Specifications

Parameter	Value	Unit	Context
Initial Diamond Thickness	≈600	nm	Grown by MPCVD on Si substrate
Exfoliated Film Size	2	inch	Wafer-scale, freestanding
Buried Surface Roughness (Ra)	≈1.18	nm	Ultra-flat surface used for nanofabrication
As-Grown Surface Roughness (Ra)	44.58	nm	Roughness of the top surface
ICP Etching Gas Flow (O₂)	80	sccm	Inductive Coupled Plasma (ICP) Etching
ICP RF Voltage	200	W	Plasma power setting
ICP Bias Voltage	60	W	Etching control voltage
ICP Cavity Pressure	10	mTorr	Etching environment pressure
Metasurface Period (p) Range	280 to 400	nm	Used for structural color tuning
Metasurface Gap (g) Range	90 to 140	nm	Used for structural color tuning
Maximum Reflectance Intensity	88.78	%	Achieved by the all-diamond metasurface
Sugar Transfer Solidification Temp.	70	°C	Heating oven temperature

Key Methodologies

The research utilized a combination of advanced MPCVD growth, mechanical exfoliation, and a novel sugar-transfer lithography technique followed by plasma etching.

MPCVD Diamond Growth:
- Substrate: 2-inch Silicon (Si) wafer.
- Pretreatment: Hydrogen plasma treatment of the Si surface.
- Seeding: Spin-coating of diamond seeds (<10 nm) dispersed in DMSO/ethanol/acetone mixture.
- Growth Parameters: 3400 W microwave power, 900 °C temperature, 15 sccm methane flow, 40-min growth period, targeting 1 µm thickness.
Edge-Exposed Exfoliation:
- The diamond film was mechanically peeled off the Si substrate using sticky tape, yielding a freestanding, 2-inch film.
- This process exposes the buried surface, which exhibited superior flatness (Ra ≈ 1.18 nm) compared to the as-grown surface (Ra = 44.58 nm).
Mask Preparation (Template):
- A conductive Indium-Tin-Oxide (ITO) film on a PET substrate was used as the template.
- E-beam lithography (EBL) was performed using Hydrogen Silsesquioxane (HSQ) resist to define the desired pattern (e.g., circular pillar arrays, nano-gratings).
- EBL Dose: 750 µJ cm^-2.
Sugar Transfer Process:
- A sugar solution (corn syrup, cane sugar, deionized water) was dropped onto the patterned ITO template.
- The solution was solidified in a heating oven at 70 °C for several hours.
- The solid sugar mask was peeled off the ITO template and gently pressed onto the exfoliated diamond film.
Diamond Etching:
- The pattern was transferred into the diamond film using Inductive Coupled Plasma (ICP) etching.
- Etching Gas: Oxygen (O₂).
- Key Parameters: O₂ flow 80 sccm, RF 200 W, Bias 60 W, Pressure 10 mTorr.
Mask Removal:
- The sugar mask was dissolved using deionized water.
- The final fabricated diamond structure was cleaned using a KOH solution.

6CCVD Solutions & Capabilities

The successful fabrication of high-performance, flexible diamond metasurfaces relies critically on the quality, thickness control, and surface finish of the initial MPCVD diamond film. 6CCVD is uniquely positioned to supply the necessary materials and engineering support to replicate, scale, and advance this research.

Applicable Materials

To replicate the ultra-flat surface quality (Ra ≈ 1.18 nm) required for high-resolution EBL mask patterning, 6CCVD recommends the following materials, ensuring superior surface integrity without relying on the buried surface of an exfoliated film:

Material Grade	Key Feature	Application Relevance
Optical Grade SCD	Highest purity, lowest defects. Polished to Ra < 1 nm.	Ideal for high-performance photonics, metasurfaces, and quantum sensing applications requiring minimal scattering loss.
High-Purity PCD	Scalable, cost-effective for large areas (up to 125 mm). Polished to Ra < 5 nm.	Suitable for scaling up the structural color display demonstration and large-area flexible electronics where the Ra ≈ 1.18 nm target is critical.
Boron-Doped Diamond (BDD)	Electrically conductive.	Essential for future extensions of this work into diamond electronics (transistors, P-N junctions) or for eliminating charge accumulation during direct EBL/lithography without needing the sugar-transfer method.

Customization Potential

6CCVD’s in-house capabilities directly address the material requirements and potential scaling challenges identified in the research:

Surface Engineering (Polishing): The paper highlights the necessity of an ultra-flat surface (Ra ≈ 1.18 nm). 6CCVD guarantees Ra < 1 nm for Single Crystal Diamond (SCD) and Ra < 5 nm for inch-size Polycrystalline Diamond (PCD), providing the required foundation for high-fidelity nano-fabrication.
Custom Dimensions and Thickness: While the paper used 2-inch films, 6CCVD offers PCD plates/wafers up to 125 mm in diameter, enabling significant scaling of the flexible display technology. We provide precise thickness control for both SCD and PCD from 0.1 µm to 500 µm, allowing researchers to optimize film fragility and flexibility for specific device designs.
Metalization Services: For researchers extending this work into active devices (e.g., quantum sensors, electronics), 6CCVD offers internal, clean-room metalization capabilities, including Au, Pt, Pd, Ti, W, and Cu deposition, avoiding the chemical contamination issues mentioned in conventional methods.
Substrate Flexibility: 6CCVD can supply SCD or PCD films pre-grown or prepared for transfer onto custom flexible substrates, streamlining the process for flexible and wearable display applications.

Engineering Support

6CCVD maintains an in-house team of PhD-level material scientists and engineers specializing in MPCVD diamond growth and processing.

Process Optimization: Our team can assist researchers in optimizing diamond film specifications (e.g., thickness, doping level, orientation) to ensure compatibility with advanced post-processing techniques like the sugar-transfer method and subsequent ICP etching.
Material Selection for Advanced Projects: We provide consultation on material selection for similar Diamond Photonics and Quantum Sensing projects, ensuring the chosen diamond grade meets the stringent requirements for low defect density and high optical transparency (UV to IR).
Global Logistics: We offer reliable global shipping (DDU default, DDP available) to ensure timely delivery of custom diamond materials worldwide.

For custom specifications or material consultation, visit 6ccvd.com or contact our engineering team directly.

View Original Abstract

Abstract Diamond exhibits unique performance across a wide range of applications due to its enormous presentable properties in electronic, photonic, and quantum fields. Yet heterogeneous integration of diamonds for on‐chip functionalities, like 2D materials, remains challenging due to the hard acquisition of scalable, transferable, and ultrathin diamond samples. Recently, edge‐exposed exfoliation is demonstrated as an effective way to produce wafer‐scale, freestanding, and ultrathin diamond films. However, the incompatibility of the newly developed diamond film with conventional nano‐fabrication methods makes it difficult to fabricate diamond film into practical devices. Herein, the mask‐transferring by sugar is demonstrated as a versatile method for pattern‐definition on diamond films, which shows satisfying geometrical resolution and accuracy comparing to conventional approaches. Additionally, based on this method, the flexible all‐diamond metasurfaces functioning as structural colors are achieved, which indicates its wide potential for fabricating more diamond‐related devices.

Tech Support

Original Source

DOI: https://doi.org/10.1002/adom.202403429