Toroidal Dipole-Induced Photocurrent Enhancement in Si Nanodisk Hexagonal Array below the Band Gap
Toroidal Dipole-Induced Photocurrent Enhancement in Si Nanodisk Hexagonal Array below the Band Gap
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DOI：
10.1021/acsphotonics.2c00660
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发表时间：
2022-09
期刊：
影响因子：
7
通讯作者：
H. Hasebe;Keisuke Moriasa;Kaito Yamashita;H. Sugimoto;M. Fujii
中科院分区：
文献类型：
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作者：
H. Hasebe;Keisuke Moriasa;Kaito Yamashita;H. Sugimoto;M. Fujii
在硅薄膜上形成了六角形的低长宽比硅纳米盘阵列，并研究了其光吸收和光电流特性。数值模拟表明，纳米盘阵列具有环形偶极子模式，该模式将入射光严格限制在纳米盘下方的硅区。当消光系数(κ)很小时，如κ=10~(-2)∼~(10~(-3))时，场限制产生窄带吸收。这表明，利用这些模式可以增强与缺陷相关的亚带隙吸收。制作的器件的透过率谱显示，在亚带隙区域出现了分配给环形偶极子共振的窄的凹陷。在共振波长下，光电流显著增强，增强倍数达到30倍。所观察到的窄带光电探测器可用作工作在近红外范围内的电流检测型折射率传感器。
A hexagonal array of low-aspect-ratio silicon nanodisks is formed on a silicon thin film and the optical absorption and photocurrent properties are studied. Numerical simulations reveal that the nanodisk array possesses the toroidal dipole modes that tightly confine incoming light in a silicon region below the nanodisks. The field confinement brings about narrow-band absorption when the extinction coefficient (κ) is very small, for example, κ = 10–2∼10–3. This suggests that defect-related sub-band gap absorption of silicon can be enhanced by utilizing the modes. Transmittance spectra of fabricated devices reveal that narrow dips assigned to the toroidal dipole resonances appear in the sub-band gap region. At the resonance wavelengths, the photocurrent is substantially enhanced; the enhancement factor reaches 30-fold. The observed narrow-band photodetection can be used as a current-detection-type refractive index sensor operating in the near-infrared range.