Engagement procedure

The films can be directly glued to the sample holder using double-sided pressure-sensitive adhesive. An equilibration period of ca. 1 h helps to minimize the drift caused by the relaxation of the adhesive. After alignment of the laser and photodiode adjustment (see hands-on example 1), the excitation frequency and amplitude are adjusted to v at 0.85 A0 and 50 nm, respectively. Since the ambient temperature is well below the 7g of PET, we can expect that the surface is not very adhesive, thus this rather small amplitude is sufficient to allow the tip to break away from adhesive interactions with the surface. The engagement procedure and feedback loop adjustment is carried out as described in Chap. 2 and in hands-on example 1. 

The standard TM-AFM procedure discussed in Sect. 3.2 is used (Standard tapping intermittent contact mode set-up). In order to obtain high-resolution images in air, high-aspect-ratio Si-tips with a radius of 10 nm or less is advised (resonance frequency 300-350 kHz). The engagement procedure is carried out as described in Sect. 3.2. Similar to all other experiments the scan size is increased stepwise, while the gains are optimized as described. 

We use a standard tapping/intermittent contact mode set-up, which is assembled as described in Sect. 3.2.1. After inserting the TM cantilever into the cantilever holder, the optical head is mounted, the laser is aligned and the resonance peak is analyzed. The operation frequency and amplitude are adjusted to v at 0.85 Ac and 100 nm, respectively. Prior to engaging, the phase signal is zeroed. The crude and fine engagement procedures are carried out as described in Chap. 2 and Sect. 3.2. After the successful engagement the operation point must be carefully adjusted to maximize the contrast between the EPR and PP phases present (compare... 

The engagement procedure is carried out with minimized forces as described in Sect. 3.2.2. After engagement, the gains and the scan rate must be optimized. It is advisable to image the films in constant force mode with minimized forces in order... 

First, the sensitivity of the optical detection system is calibrated. Hence, the setup is prepared with a neat, pre-cleaned glass slide as sample, as outlined in detail in Sect. 3.3 in Chap. 3 for mounting the dry substrate. A drop of solution is placed onto the sample and the optical head is lowered vertically into its rest position and carefully secured. Once the photodiode differential signal shows a constant value, the engagement procedure as described in hands-on example 3 is carried out. However, to avoid shear forces between tip and sample the scan size is set to 0.0 nm. 

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