Diffusion-Driven Exfoliation of Magneto-Optical Garnet Nanosheets: Implications for Low Thermal Budget Integration in Si Photonics
Diffusion-Driven Exfoliation of Magneto-Optical Garnet Nanosheets: Implications for Low Thermal Budget Integration in Si Photonics
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DOI：
10.1021/acsanm.1c02459
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发表时间：
2021-10
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影响因子：
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通讯作者：
Karthik Srinivasan;Andrew D. Schwarz;Jason C. Myers;N. Seaton;B. Stadler
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作者：
Karthik Srinivasan;Andrew D. Schwarz;Jason C. Myers;N. Seaton;B. Stadler
稀土铁石榴石在集成非互易无源器件如硅光子学中的隔离器和环行器的发展中起着重要作用。不幸的是，片上石榴石的单片集成需要比半导体铸造厂的热预算高得多的退火温度。在这里，我们报告的机械剥离的大面积（0.2 mm × 0.2 mm）的高回转铈掺杂铽铁石榴石（CeTbIG）的纳米片，使应变增强空位扩散过程，遵循纳巴罗-赫林（晶格扩散）模型。由应变速率-应力数据计算的扩散系数（1.13 × 10- 18 m2 s-1）确定铁和稀土阳离子为速率控制晶格扩散剂。横截面扫描透射电子显微镜揭示了剥离间隙位于约30 nm的膜，可比的阳离子扩散长度，这似乎验证了模型。在1550 nm处，饱和磁化强度为18 emu cc-1，法拉第旋转为−2900°cm-1，纳米片的磁性和光学性质与其薄膜值相当。扩散驱动的剥离将打开铸造厂可接受的途径，异质集成的石榴石光子波导和保护设备从高温过程中使用的结晶石榴石薄膜。
Rare-earth iron garnets are instrumental in the development of integrated nonreciprocal passive devices such as isolators and circulators in silicon photonics. Unfortunately, monolithic integration of garnet on-chip requires annealing temperatures much higher than the thermal budget of a semiconductor foundry. Here, we report the mechanical exfoliation of large area (0.2 mm × 0.2 mm) nanosheets of a high-gyrotropy cerium-doped terbium iron garnet (CeTbIG) enabled by a strain-enhanced vacancy diffusion process that follows the Nabarro–Herring (lattice diffusion) model. Diffusivities calculated from the strain rate–stress data (1.13 × 10–18m2s–1) identify iron and rare-earth cations as the rate-determining lattice diffusants. Cross-section scanning transmission electron microscopy reveals an exfoliation gap located ∼30 nm into the film, comparable to the cation diffusion length, which appears to verify the model. With a saturation magnetization of 18 emu cc–1and a Faraday rotation of −2900°cm–1at 1550 nm, the magnetic and optical properties of the nanosheets are comparable to their thin-film values. Diffusion-driven exfoliation will open foundry-acceptable pathways for heterogeneous integration of garnets on photonic waveguides and protect devices from the high-temperature processes used in crystallizing garnet films.