[CON₃H₆BF₄]: An Efficient Metal-Free Borate with Optimized Birefringence Achieved by Structural Design Strategy

Area of Science:

• Crystal engineering
• Materials science
• Optoelectronics

Background:

• Deep-ultraviolet (UV) birefringent materials are critical for deep-UV lithography.
• Maximizing optical anisotropy is key to enhancing material performance.
• Existing materials often require further optimization for deep-UV applications.

Purpose of the Study:

• To design and synthesize a novel deep-UV birefringent material.
• To investigate the structural and optical properties of the new compound.
• To explore a new functional building unit for advanced optical materials.

Main Methods:

• Crystal engineering via amino modulation of a urea template.
• Synthesis of the novel fluoroborate compound [(CON3H6)BF4] (AUBF).
• Characterization of optical properties, including birefringence and UV cutoff edge.

Main Results:

• AUBF was successfully synthesized, featuring a planar deep-UV functional building unit.
• The material exhibits a deep-UV cutoff edge at 196 nm.
• A substantial birefringence of 0.127@546 nm was achieved, comparable to commercial standards.

Conclusions:

• AUBF is the first semi-organic urea-based compound to achieve deep-UV birefringence.
• The study identifies a novel birefringent gene with enhanced optical anisotropy.
• This work provides a strategy for designing new deep-UV birefringent materials through structural regulation.