Table 2.
Typical and best achieved characteristics of TERS and AFM-IR.
| TERS | AFM-IR | |||
|---|---|---|---|---|
| Typical | Best achieved | Typical | Best achieved | |
| Resolution achieved | 3–5 nm | 0.1 nm | 10–50 nm | 10 nm |
| Sampled depth | A few nm | A few µm | ||
| Typical sample thickness | 20–500 nm | |||
| Sensitivity (smallest sample detected) | Single monolayer | Single molecule | 20 nm thick | Single monolayer |
| Spectral range | 500–1800 cm−1 | unlimited | 900–1900 cm−1 2700–3600 cm−1 | 20000–625 cm−1 (limited by laser range) |
| Typical time for a spectrum | 0.5–10 s | 0.1 s | 1 s- 4 s (QCL) 1 min (OPO) | 0.2 s |
| spectral bandwidth | 500–1800 cm−1 (but spectrometer dependent) | 900–1900 cm−1 | 5000–20000 cm−1 | |
| Spectral resolution | 4–10 cm−1 | 1 cm−1 | 0.5 cm−1 (laser dependent) | |
| Typical hyperspectral imaging & time | 100 × 100 pixels (≈ 1.5 h – 28 h) | - | 100 × 100 pixels (≈ 3 −11 h) | - |
| Typical pixel dwell time | 0.5 s - 10 s (equal to spectral acquisition time) | 10 ms (single wavelength) | 1 ms (single wavelength) | |
| Reproducibility | Tip dependent | Tip independent but dependent on the tip-sample contact mechanics | ||
| Spectral fidelity | High for small molecules, poor for complex biological samples | In first approximation, comparable to FTIR spectra | ||
| Liquid measurement | yes | not typical | achieved | |