Table 4.
Few important techniques commonly used to characterize LB films.
| Experimental technique | Information extracted |
|---|---|
| Brewster Angle Microscopy (BAM) | In-situ study of various phases of the thin films at interfaces. It is sensitive to the surface density and to the anisotropy of domains in monolayer. |
| Fluorescence Imaging Microscopy (FIM) | In-situ domain structure study (micrometer range) |
| Surface potential measurement | Polarization, orientation. |
| Infrared reflection absorption spectroscopy, Attenuated total reflection – Fourier transform infrared (ATR-FTIR) | Hydrocarbon chain packing & conformation, degree of ionization of the head groups, H-bonding, chemical and structural changes, molecular orientation. |
| Ellipsometry | Refractive index & thickness measurement (∼2A0) |
| X-ray diffraction/reflection Grazing incidence and small angle – X-ray diffraction |
Inter layer spacing, in-plane lattice structure In-plane/out-of-plane orientation/tilt of hydrocarbon chain. |
| Neutron diffraction | Inter layer spacing. |
| UV-Vis absorption spectroscopy | Electronic transition & orientation. |
| Raman Spectroscopy & Surface-enhanced Raman Scattering/Spectroscopy (SERS) | Identification & orientation, conformation of alkyl chains and head groups, molecular interactions within LB films. |
| Optical harmonic generation (2nd & 3rd order) | Non-linear coefficient, orientation. |
| Optical microscopy Confocal fluorescence |
In-plane structural information. Molecule orientation, lipid domain morphology, grain boundaries, microcollapsed region (lateral resolution of 0.1 μm). |
| Scanning electron microscopy (SEM) Transmission electron microscopy (TEM) |
Surface morphology, domain structure, patterns, pinholes and defects (in-homogeneous crystalline domains, micro-collapse etc) (resolution of 50 nm). |
| Scanning tunnelling microscopy (STM) Atomic force microscopy (AFM) |
Imaging surface in the atomic level, visualisation of defects (grains, pinholes, lateral heterogeneity, disclinations etc), sub-molecular packing (lateral resolution of 0.2 nm). |
| X-ray photoelectron spectroscopy (XPS) or Electron spectroscopy for chemical analysis (ESCA) | Quantitative analysis of chemical composition of the film surface. |
| I – V, C – V, resistivity etc measurement | Electrical behaviour. |
| For further details, the reader can refer to different related books and review papers [34, 35, 36, 50, 51, 52, 53, 54, 55, 56, 57, 58, 59, 60, 61, 62, 63, 64, 65, 66, 67, 68, 69, 70]. | |