Insituthickness measurements of ultra-thin multilayer polymer films by atomic force microscopy

Abstract

A method for direct in situ thickness measurements of ultra-thin soft polymer films is presented in which an atomic force microscope (AFM) tip is used to create a furrow in the film, whereby the thickness is determined by scanning the sample across the furrow with the AFM. The sample does not need to be moved since the scratching and the measurements are performed with the same apparatus. This `furrow method' is applied to layer-by-layer polymer/polyelectrolyte ultra-thin films onto hydrophilic glass and silicon wafer substrates. This procedure is made possible because the polymeric film is less stiff than the substrates and the silicon tip. Results for 10-12-bilayer films are comparable to those obtained from profilometry, whose accuracy is only reasonable for films with more than ten bilayers. Taken together, the AFM and profilometer results show that film thickness increases linearly with the number of bilayers. Furthermore, the film thickness does not seem to depend on the substrate used but only on the number of bilayers deposited.

Molds and Resists Studies for Nanoimprint Lithography of Electrodes in Low-Voltage Polymer Thin-Film Transistors

“…AFM as in Ref. 13 and an Alpha step 100 profilometer (Veeco) were employed to extract thin-film thickness.…”

Techniques and Challenges for Characterizing Metal Thin Films with Applications in Photonics

“…However, in cases wherein the film is homogeneously deposited across the substrate surface, another method for measuring the thickness with AFM is to scratch the film and measure the depth of the scratch [62]. For sufficiently thin films, the scratch will penetrate down to the substrate and result in an accurate thickness measurement; however, care should be taken with this approach, as an insufficiently deep scratch will not yield a measurement of film thickness, but instead simply a measure of the depth of the scratch in the film.…”

“…Cross-sectional analysis revealed the depth of the furrow, and therefore, the thickness of the film, to be approximately 54 nm. (Reprinted from [62], Copyright IOP Publishing, 1999. ) Film analysis in such a manner will not only reveal the thickness of the film, but also aspects of the transition area, like steepness and film homogeneity.…”

In Situ Measurement of Polymer Layer Thickness in Porous Layer Open Tubular (PLOT) Columns Using Optical Absorbance in the Near-IR Range

“…Several methods exist for the measurement of thin film thickness, ranging from β-and X-ray techniques [24,25], electrical impedance and conductivity [26,27], to tactile methods such as atomic force microscopy (AFM) [28][29][30] and scanning acoustic microscopy techniques [31]. However, it is important to note that the vast majority of these methods are suitable for measurements on planar surfaces.…”