Kim Do Bin Kim, Geunpil Jeong, Hwijoon Sk Mujaffar Hossain Satadeep Bhattacharjee Kwon, Minjae Isaac Lee, Yeunjeong Yang, Chanhee Ham, Yeong Seok Kim, Taek-Soo Moon, Hyowon Park, Inkyu Lee, Seung Cheol Kim, Jinhwan Kim, Jong bum Park, Jae hyun 2026-03-04T07:00:05Z 2026-03-04T07:00:05Z 2026-03-04 2026-04 https://pubs.kist.re.kr/handle/201004/154394 Cubic boron nitride (c-BN) and hexagonal boron nitride (h-BN) are known for their transparency and high 10B density, which provides a large thermal-neutron cross-section, yet their potential for space neutron shielding has not been explored. The fabrication of transparent c-BN films remains challenging, and the chemical vapor deposition growth of h-BN beyond 70 nm, or with precise thickness control and high uniformity, has not been reported except by our group. Here, we present a space window design integrating an h-BN-based neutron shielding layer with advanced ceramic bulletproof layers and a γ-ray shielding layer. By incorporating C and O into h-BN, sp2-sp3 hybridized BN (HBN) reduces the refractive index mismatch with the SiO2 substrate, achieving 90.9% transmission at 550 nm at 11.9 µm thickness and enabling stable, transparent growth up to 79.2 µm with minimized thermal expansion mismatch. The optically optimized HBN (B0.39N0.39C0.06O0.16) shows reduced boron content, but the enriched formation of 63.4% c-BN, with its higher boron density, compensates for this loss. The resultant density is 3.01 g cm−3, evaluated from neutron-shielding probability, and HBN achieves the same neutron-shielding efficiency as h-BN at 3% reduced thickness. English Wiley-VCH Verlag Direct Growth of Transparent Boron Nitride Neutron Shielding Layer for Space Window Article 10.1002/advs.202516390 1 Advanced Science, v.13, no.20 Advanced Science 13 20 N scie scopus 001705412600001 Chemistry, Multidisciplinary Nanoscience & Nanotechnology Materials Science, Multidisciplinary Chemistry Science & Technology - Other Topics Materials Science Article HIGH-PRESSURE THIN-FILMS PLASMA LASER SPECTROSCOPY IRRADIATION PHASE transparent neutron shielding layer transparent sp2-sp3 hybridized boron nitride thermal expansion coefficient direct growth space window