Roughness and surface
potential measurements were performed using an Asylum Research MFP-3D
Origin AFM. Roughness measurements were done by scanning three random
positions on each piece of the diced wafer to obtain height, amplitude,
phase, and z-sensor data in air at room temperature by tapping mode.
Images of 2 μm × 2 μm were obtained at a scanning
frequency of 1 Hz using Si probes (f = 150 kHz, k = 8 N/m) from Asylum Research. The rms roughness was obtained
from the images using Igor Pro (version 6.2.2.2).
Surface potential
measurements were performed using the KPFM mode in air at room temperature
with Ti/Ir (5/20)-coated Si probes from Asylum Research (f = 285 kHz, k = 42 N/m). Images of 500 nm ×
500 nm were obtained with a scanning frequency of 1 Hz at three random
positions on each piece of the wafer along the gradient. The samples
were grounded by soldering a copper wire to the wafer surface with
In solder to minimize surface potential drift during the scans, which
was found to be a source of large standard deviations in our previous
work.45 (link) The rms surface potential values
were obtained from the images using Igor Pro (version 6.2.2.2).
potential measurements were performed using an Asylum Research MFP-3D
Origin AFM. Roughness measurements were done by scanning three random
positions on each piece of the diced wafer to obtain height, amplitude,
phase, and z-sensor data in air at room temperature by tapping mode.
Images of 2 μm × 2 μm were obtained at a scanning
frequency of 1 Hz using Si probes (f = 150 kHz, k = 8 N/m) from Asylum Research. The rms roughness was obtained
from the images using Igor Pro (version 6.2.2.2).
Surface potential
measurements were performed using the KPFM mode in air at room temperature
with Ti/Ir (5/20)-coated Si probes from Asylum Research (f = 285 kHz, k = 42 N/m). Images of 500 nm ×
500 nm were obtained with a scanning frequency of 1 Hz at three random
positions on each piece of the wafer along the gradient. The samples
were grounded by soldering a copper wire to the wafer surface with
In solder to minimize surface potential drift during the scans, which
was found to be a source of large standard deviations in our previous
work.45 (link) The rms surface potential values
were obtained from the images using Igor Pro (version 6.2.2.2).
