Identifying Components in Polymer Films via hyPIRTM Imaging
hyPIRTM (hyperspectral PiFM infrared) image consists of (n x n) pixels of PiFM spectrum. This is a hyPIRTM image (128 x 128 pixels) of 5 nm of PS homopolymer that is spin-coated onto a 2 nm thick PMMA homopolymer on top of silicon substrate. Due to the thin PS layer and its immiscibility with PMMA, PS has dewetted into nanoscale droplets. Up to three distinct region of a hyPIRTM image can be selected to average the spectra for each region. Up to three peaks (blue, red, and green channels) can be selected to display its intensity map. This 2 μm x 2 μm hyPIRTM image took 54 minutes to acquire.
One can also define a line along which a designated number of spectra can be displayed. In this example, six spectra are defined, exported to Excel, and plotted. Considering that each spectrum over the 400 cm-1 range took about 0.2 seconds to acquire, the signal to noise is quite good (from an extremely thin sample).
AFM topography is acquired together with hyPIRTM image. The following images show 3D rendered AFM topography (a), PiFM image at 1495 cm-1 (for highlighting PS, exported from the hyPIRTM image) added as a color map onto the same 3D rendered AFM topography (b), and PiFM image at 1733 cm-1 (for highlighting PMMA, exported from the hyPIRTM image) added as a color map onto the same 3D rendered AFM topography (c).
Sample: 5 nm of PS homopolymer that is spin-coated onto a 2 nm thick PMMA homopolymer on top of silicon substrate. PiFM reveals that PS has dewetted into nanoscale droplets.
One hyPIRTM image is equivalent to 100’s PiFM images taken at different wavenumbers stacked up into a 3D deck (wavenumber = z direction). It contains rich chemical information at nanoscale that would have been difficult if not impossible to acquire until now.