Studies on the Thermal Decomposition Mechanism at Diamond-Silica Interfaces Induced by Localized Laser Vitrification: experimental and ab-initio approach

This study investigates the thermal decomposition mechanisms at silica-diamond interfaces following localized laser vitrification, combining experimental analysis with molecular dynamics simulations. Two types of diamond particles were examined: NV-rich nanodiamonds (180 nm) and monocrystalline synthetic diamonds (154 nm). The samples were fabricated through a challenging process involving vacuum-based CO2 laser vitrification at 5.3 µm wavelength, addressing the inherent processing temperature incompatibility between diamond and silica. Comprehensive characterization using scanning electron microscopy revealed distinct interface regions with defect concentrations up to 10 μm in diameter for monocrystalline particles. Raman spectroscopy and fluorescence analysis demonstrated different decomposition behaviors between used particles, with samples exhibiting characteristic NV center emission at 637 nm. Thermogravimetric analysis coupled with mass spectrometry revealed a multi-step decomposition process, with CO2 release above 300°C and distinct thermal degradation temperatures for each diamond type. Molecular dynamics simulations using the Reax Force Field method elucidated the interface dynamics, revealing that amorphous silica catalyzes CO2 release from carboxylated diamond surfaces. This process generates localized pressure causing surface deformation and eventual glass layer delamination, with the critical temperature depending on diamond crystal face orientation. These findings provide crucial insights into thermal decomposition at silica-diamond interfaces, contributing to the development of hybrid materials for quantum physics applications, particularly in low-loss magnetically sensitive optical fibers for optomagnetometry.