Design And Performance Analysis Of Low-noise Atomic Force Microscopy Scanning Head

Since the beginning of the 21st century,nanotechnology has developed by leaps and bounds.It can not only complete the detection of physical,chemical and biological properties of different materials,but also realize related operations and device processing on the nanoscale,which made improvement in the whole field of science.The research of nanotechnology requires the help of various high-precision instruments.Among them,the atomic force microscopy(AFM)is an important pillar of the flourishing development of nanotechnology and an indispensable research tool for many nanotechnology researchers.The application field of AFM is extremely wide,and it has extremely high adaptability,which can complete the observation of different substances such as insulators,conductors,semiconductors,etc.in the atmosphere,liquid,vacuum and other environments.With the improvement of nanotechnology,the functions of AFM are gradually enriched.In addition to the basic function of directly observing the sample surface morphology on the nanoscale,it can also perform corresponding processing on the nanoscale,and even achieve some special functions such as mechanical property testing of nanostructures and biomaterial research.Compared with the commercial AFM,the self-built AFM system has higher flexibility and openness,and the optical beam deflection detection system used in the traditional commercial microscope has a relatively high noise.At present,few institutions conduct research on this issue.Based on this problem,the design of low-noise AFM system was researched in this paper.The main contents are as follows:(1)The working principle of AFM is introduced in detail,and several current detection methods of the cantilever beam’s tiny deflection and the calibration method of system sensitivity are analyzed and compared,and the design method that the self-built AFM system needs to adopt is clarified.(2)The design theory of the optical beam deflection detection system is derived,and propose a new design scheme that can improve the sensitivity of the system while reducing the overall noise of the system.According to the design scheme,the laser,pre-amplification circuit and signal processing circuit for the optical beam deflection detection system and the overall structure of the AFM system are designed,the testing of self-developed devices and the programming of related programs are completed.(3)The force curve is measured and the system sensitivity is calibrated by using the low-noise AFM system,and combine with the thermal tune method to complete the calibration of the overall noise of the system.The experimental results prove that the low-noise AFM system meets the performance requirements of low noise and high sensitivity.The thermal noise spectrum is used to analyze the noise types and sources of the system,and corresponding solutions are given.(4)Using the calibrated low-noise AFM system to scan different sample surfaces in contact mode and tapping mode respectively.The sample surface morphology data proves that the resolution of the low-noise AFM system can reach below 1nm.In summary,the research work in this paper reduces the overall noise of the AFM system effectively,improves the sensitivity and accuracy of the optical beam deflection detection system,and provides a new way for the independent research of domestic high-precision measuring instruments,which has important theoretical significance and actual application value.