Fabrication and physical measurement accuracy of nanoscale standard samples for vector beams confocal laser scanning microscopy

Various kinds of super-resolution optical microscope techniques have been developed to break the diffraction barrier in the past decades. Confocal laser scanning microscopy is the super-resolution microscopy. It is widely used due to high resolution and depth selectivity in obtaining images. However, there are neither accurate nor rigorous measurement methods with a nanoscale resolution. In order to measure the resolution of vector beam confocal laser scanning microscopy accurately and rigorously, a nanoscale resolution standard sample is proposed and experimentally realized. This sample is composed of a series of accurate measure patterns and a couple of arrays of triangle finding structures. It allows a wide measurement range between 40 nm to 1000 nm, and provides appropriate measurement steps and high measurement accuracy. The measurement patterns can be efficiently figured out by using the found structures, and their structure line width can be easily calculated. The first standard sample is produced on a piece of amorphous silicon by electron beam lithography and inductive coupled plasma etching technology, and measured by the scanning electron microscopy. According to the test, the sample meets the requirements of accuracy for nanoscale resolution measurement. Optical testing is applied to the sample by a vector beam confocal laser scanning microscope. And the sample shows that the resolution is 96 nm (oil immersion, refractive index 1.52) under the irradiation of 405 nm radially polarized beams, which is far beyond the diffraction barrier. Furthermore, a metal structure standard sample, which is based on a piece of indium tin oxide glass, is produced to improve the signal contrast ratio of the silicon standard sample. The measurement patterns are fabricated by electron beam lithography and electron beam evaporation and made of 10 nm titanium and 100 nm gold. It works for both reflective and transmissive confocal laser scanning microscopy, and would obtain high resolution images with a better contrast ratio. These standard samples are able to test the performance of microscope system efficiently, and provide a more rigorous way to make sub-100 nm resolution measurement and a calibration guidance for point scanning super-resolution microscope. In the meantime, we find that nanoscale opticalimaging is affected not only by sample morphology, but also by the photoelectron property of the sample. Further study is required to understand the underlying mechanism.