A depth-resolved Raman spectroscopy technique was used to study the residual stress profiles in polycrystalline silicon nitride that was irradiated with Xe (167 MeV, 1 × 10¹¹ cm⁻² ÷ 4.87 × 10¹³ cm⁻²) and Bi (710 MeV, 1 × 10¹¹ cm⁻² ÷ 1 × 10¹³ cm⁻²) ions. It was shown that both the compressive and tensile stress fields were formed in the irradiated specimen, separated by a buffer zone that was located at a depth that coincided with the thickness of layer, amorphized due to multiple overlapping track regions. The compressive stresses were registered in a subsurface region, while at a greater depth, the tensile stresses were recorded and their levels reached the maximum value at the end of ion range. The size of the amorphous layer was evaluated from the dose dependence of the full width at half maximum (FWHM) (FWHM of the dominant 204 cm⁻¹ line in the Raman spectra and scanning electron microscopy.

At present, silicon nitride is the only nitride ceramic in which latent ion tracks resulting from swift heavy ion irradiation have been observed. Data related to the effects of SHIs on the nanocrystalline form of Si₃N₄ are sparse. The size of grains is known to play a role in the formation of latent ion tracks and other defects that result from SHI irradiation. In this investigation, the effects of irradiation with high-energy heavy ions on nanocrystalline silicon nitride is studied, using transmission electron microscopy techniques. The results suggest that threshold electronic stopping power, S_et, lies within the range 12.3 ± 0.8 keV/nm to 15.2 ± 1.0 keV/nm, based on measurements of track radii. We compared the results to findings for polycrystalline Si₃N₄ irradiated under similar conditions. Our findings suggest that the radiation stability of silicon nitride is independent of grain size.

Structural effects in nanocrystalline pyrochlore Y₂Ti₂O₇ induced by high energy heavy ions in a wide range of electronic stopping powers were studied by means of high-resolution transmission electron microscopy and molecular dynamics simulation considering the grain size effect. Ion track radii tend to saturate and even decrease at high electron stopping powers (>30 keV/nm) due to the velocity effect. The threshold electronic energy loss to form amorphous tracks in nanoclusters and large (>100 nm) crystals was estimated in the range 10.7–12.8 keV/nm. A strong size dependence was observed for smaller (<50 nm) isolated nanocrystals, with smaller crystals being significantly more sensitive to amorphous track formation.

Depth-resolved Raman piezospectroscopy was used to study residual mechanical stress profiles in polycrystalline silicon and aluminum nitrides irradiated with 710 MeV bismuth ions to fluences of 1×1012, 2×1012, and 1×1013 cm-2. It was found that stress fields of opposite signs are formed in the irradiated Si3N4 layer, separated by a buffer zone located at a depth coinciding with the thickness of the sample layer, amorphized at high ion fluences due to multiple overlapping of track regions. At great depths, tensile stresses witch magnitude reaches their maximum value in the region of the end of the ion range are detected. In contrast to Si3N4, radiation-stimulated changes in mechanical stresses in AlN were within the measurement error throughout the entire thickness of the irradiated layer, except of the near-surface region. The observed effect is associated with the different structural sensitivity of silicon and aluminum nitrides to high-density ionization - the formation of amorphous latent tracks in Si3N4 and their absence in AlN. Методы рамановской пьезоспектроскопии с пространственным разрешением в данной работе были использованы для изучения профилей остаточных механических напряжений в поликристаллических нитридах кремния и алюминия, облученных высокоэнергетическими ионами висмута c энергией 710 МэВ до флюенсов 1 × 1012, 2 × 1012 и 1 × 1013 см-2. По результатам установлено, что в облученном слое Si3N4 формируются поля напряжений различного знака, разделенные буферной зоной, находящейся на глубине, совпадающей с толщиной слоя образца, аморфизованного при высоких флюенсах ионов за счет многократного перекрытия трековых областей. На больших глубинах регистрируются растягивающие напряжения, уровень которых достигает максимального значения в области конца пробега ионов. Показано что, в отличие от Si3N4, уровень радиационно-стимулированного изменения механических напряжений в AlN был в пределах ошибки измерений по всей толщине облученного слоя, только за исключением приповерхностной области. Наблюдаемый эффект связывается с разной структурной чувствительностью нитридов кремния и алюминия к воздействию ионизации высокой плотности – образованием аморфных латентных треков в Si3N4 и их отсутствием в AlN. Кеңістіктік ажыратылымдылығы бар Рамандық пьезоспектроскопия әдістері 1 × 1012, 2 × 1012 және 1 × 1013 см-2 флюенске дейін энергиясы 710 МэВ жоғары энергиялы висмут иондарымен сәулеленген бұл жұмысьа поликристалды кремний мен алюминий нитридтеріндегі қалдық механикалық кернеулердің профильдерін зерттеу үшін пайдаланылды. Сәулеленген Si3 N4 қабатында трек аудандарының бірнеше рет қабаттасуы есебінен иондардың жоғары флюенсі кезінде аморфизацияланған үлгі қабатының қалыңдығына сәйкес келетін тереңдікте орналасқан тректік аймақпен бөлінген түрлі белгілердің кернеу өрістері қалыптасатыны зерттеу нәтижесінде анықталды. Үлкен тереңдікте созылу кернеулері тіркелетіні көрсетілді, олардың деңгейі иондар жүгірісінің соңындағы аймақтағы максималды мәнге жететіні анықталды. Si3 N4 - тен айырмашылығы, AlN - дегі механикалық кернеулердің радиациялық - ынталандырылған өзгеру деңгейі беттік аймақты қоспағанда, сәулеленген қабаттың бүкіл қалыңдығы бойынша өлшеу қатесінің шегінде болды. Байқалатын әсер кремний мен алюминий нитридтерінің жоғары тығыздықтағы ионизация әсеріне әртүрлі құрылымдық сезімталдығымен – Si3 N4 - те аморфты латентті тректердің түзілуімен және олардың AlN-де болмауымен байланысты деген қортынды жасалды.

High-energy (710 MeV) Bi ion track morphology in polycrystalline silicon nitride was investigated during post-irradiation annealing. Using both in-situ and ex-situ transmission electron microscopy, we monitored the recovery of crystallinity within initially amorphous ion track regions. In-situ annealing involved heating samples from room temperature to 1000 °C in 50 °C increments, each held for 10 s. We observed a steady decrease in both the size and number of tracks, with only a small number of residual crystalline defects remaining at 1000 °C. Ex-situ annealing experiments were conducted at 400 °C, 700 °C, and 1000 °C for durations of 10, 20, and 30 min. Complete restoration of the crystalline lattice occurred after 30 min at 700 °C and 20 min at 1000 °C. Due to inherent differences in geometry, heat flow, and stress conditions between thin lamella and bulk specimens, in-situ and ex-situ results cannot be compared. Molecular dynamics simulations further revealed that track shrinkage begins in cells within picoseconds, supporting the notion that recrystallization can start on very short timescales. Overall, these findings demonstrate that thermal recrystallization of damage induced by swift heavy ion irradiation in polycrystalline Si₃N₄ is possible. This study provides a foundation for future research aimed at better understanding radiation damage recovery in this material.