[Paper Review] Direct growth of hexagonal boron nitride on photonic chips for high-throughput characterization

Evgenii Glushkov, Noah Mendelson+8 more|arXiv (Cornell University)|Mar 29, 2021

Photonic and Optical DevicesEngineering39 references19 citations

TL;DR

This paper presents a direct growth method for hexagonal boron nitride (hBN) on silicon nitride photonic chips, eliminating the need for transfer-induced contamination. By growing hBN directly on waveguide chips, the authors enable high-throughput, in-situ optical characterization of defects with improved reliability and throughput compared to conventional wet transfer methods.

ABSTRACT

Adapting optical microscopy methods for nanoscale characterization of defects in two-dimensional (2D) materials is a vital step for photonic on-chip devices. To increase the analysis throughput, waveguide-based on-chip imaging platforms have been recently developed. Their inherent disadvantage, however, is the necessity to transfer the 2D material from the growth substrate to the imaging chip which introduces contamination, potentially altering the characterization results. Here we present a unique approach to circumvent these shortfalls by directly growing a widely-used 2D material (hexagonal boron nitride, hBN) on silicon nitride chips, and optically characterizing the defects in the intact as-grown material. We compare the direct growth approach to the standard wet transfer method, and confirm the clear advantages of the direct growth. While demonstrated with hBN in the current work, the method is easily extendable to other 2D materials.

Motivation & Objective

• To eliminate transfer-related contamination in 2D material characterization on photonic chips.
• To enable high-throughput optical characterization of defects in hexagonal boron nitride (hBN).
• To develop a direct growth process for hBN on silicon nitride waveguide platforms.
• To compare the quality and consistency of hBN defects between direct growth and standard wet transfer methods.
• To establish a scalable platform for on-chip characterization of 2D materials beyond hBN.

Proposed method

• Direct chemical vapor deposition (CVD) growth of hexagonal boron nitride (hBN) directly on pre-fabricated silicon nitride photonic chips.
• Use of waveguide-integrated optical microscopy for in-situ, high-throughput defect characterization.
• Comparison of defect signatures (e.g., photoluminescence) between directly grown hBN and conventionally transferred hBN.
• Optimization of growth parameters to achieve uniform, high-quality hBN films on chip-scale platforms.
• Employment of photoluminescence spectroscopy to map and analyze defect states in the hBN layer.
• Validation of structural and optical quality through comparison with standard transfer-based methods.

Experimental results

Research questions

• RQ1 Can hexagonal boron nitride be directly grown on silicon nitride photonic chips without transfer-induced contamination?
• RQ2 How does the defect density and optical signature of hBN compare between direct growth and wet transfer methods?
• RQ3 To what extent does direct growth improve the throughput and reliability of on-chip defect characterization?
• RQ4 Can the direct growth platform be extended to other two-dimensional materials beyond hBN?
• RQ5 What are the key growth parameters that enable high-quality hBN on chip-scale waveguide platforms?

Key findings

• Direct growth of hBN on silicon nitride chips successfully eliminates contamination from transfer processes.
• Defect characterization via photoluminescence shows consistent and high-quality optical signatures in directly grown hBN.
• The direct growth method enables significantly higher throughput for on-chip defect analysis compared to conventional transfer methods.
• The optical properties of hBN, including defect-related photoluminescence, are preserved and comparable or superior to those from transferred samples.
• The method is scalable and readily extendable to other two-dimensional materials for on-chip integration.
• The platform supports reliable, in-situ, and high-throughput optical microscopy of 2D material defects on photonic chips.