Research On Non-contact 3D Nano-sensing Method Based On Electron Tunneling

At present,China is in a critical historical period of leaping from a big manufacturing country to a powerful manufacturing country.The manufacturing of cutting-edge instruments,such as inertial navigation instruments and high-end equipments such as rocket engines and aero-engines,is developing to a highperformance level.To meet the ever-increasing performance demands,a large number of ultra-precision special shapes and complex structures are used for key components.Under strict quality control requirements,ultra-precision measurement of key dimensions as well as shape and position parameters must be carried out,and at the same time,damage-free and high-efficiency measurement must be ensured.In response to the above-mentioned new requirements,this thesis conducts research on sensing technology of new principle,which not only has high-resolution non-contact sensing capability,but also takes into account the characteristics of no damage,highfrequency response,three-dimensional(3D)isotropy and point aiming,in order to cooperate with the measurement instrument to realize ultra-precision threecoordinate aiming and 3D contour scanning measurement.Quantum technology provides a new way to build a new sensing method that can take into account various advantages and characteristics,and related experimental research on the passivation phenomenon of the tip of scanning tunneling probes leads to a new direction.In this thesis,electron tunneling principle is combined with a spherical electrode structure,in order to achieve a breakthrough in 3D non-contact sensing method,but the following problems remain to be solved:(1)In the metal/air /metal micro-interface formed by a spherical electrode microprobing a measured surface,the electron transport mechanism by which the sensing current generated as well as the model are unclear;(2)The characteristics and laws of non-contact sensing based on the principle of electron tunneling and the structure of spherical electrode need to be further studied.In this thesis,research on the above problems is carried out,and the main tasks completed are as follows:Firstly,the electron transport mechanism and electron tunneling model are studied for the problem of unclear electron transport mechanism and model generated by sensing current in the metal/air/metal micro interface formed by the micro-probing of a spherical electrode on the measured surface.The electron transport mechanism of the current generation in the metal/air/metal microscopic interface is analyzed,and the Fowler-Nordheim tunneling is the main mechanism of the sensing process;based on the classical approximation method to obtain the tunneling current density between atomic pairs,the 3D tunneling process of electrons in the microscopic interface is characterized by the superposition of the current density between atomic pairs of the spherical electrode and the surface of the measured part.Based on the tunneling current density between atomic pairs,the 3D tunneling process of electrons in the microscopic interface is characterized by the superposition of the current density between atomic pairs of the spherical electrode and the measured part surface.This model can effectively characterize the relationship between the electron tunneling sensing current and the gap in the metal/air/metal microscopic interface formed by the spherical electrode micro-targeting the measured surface.Secondly,in order to solve the problem that the characteristics and laws of noncontact sensing based on the electron tunneling principle and spherical electrode structure need to be further studied,study on method characterization and optimal design of non-contact nano-sensing method based on electron tunneling principle and spherical electrode structure are carried out.Based on the proposed electron tunneling sensing current model in the metal/air/metal micro-interface,the relationship between the tunneling current and the aiming gap and its influencing factors have been analyzed,and the influences of spherical electrode size,bias voltage,and potential barrier have been clarified.From the three perspectives of the bias electric field distribution in the micro interface,the surface charge density distribution on the surface of a spherical electrode and the surface current density distribution on the surface of the spherical electrode,the origin and essence of the point-probing characteristic of the sensing method,and a quantitative characterization method based on the current spot is proposed.Based on the analysis and optimization of the sensing characteristic under the guidance of the model,the optimal tunneling boundary condition is constructed and the sensor is successfully developed.Based on the organic combination of the electron tunneling principle and the spherical electrode structure,the non-contact sensing method can realize the point-probing characteristics and the 3D isotropic characteristic on the basis of ensuring the nano-resolution.Finally,the non-contact nano-sensing method based on electron tunneling proposed in this paper is experimentally verified.An experimental system is built under the environment of ultra-precision temperature control and micro-vibration isolation.The characteristic curve is calibrated and the performance of the sensor is tested.The experimental results show that the resolution of the sensor can reach 1nm,and the difference of the 3D anisotropic sensing characteristics are approximately negligible.This thesis explores a non-contact nano-sensing method and technology based on the principle of electron tunneling,which can take into account the excellent characteristics of non-contact measurement,nano-resolution and approximate point aiming,as well as 3D isotropic characteristics.It is suitable for high-precision,damage-free and high-efficiency measurement based on three-coordinate aiming and3 D contour scanning with a ball probe.In cutting-edge instruments such as inertial navigation instruments and high-end equipment such as rocket engines and aeroengines,the high-precision measurement of geometric dimensions and shape/position parameters of key components with special shapes and complex structures provides an effective means of sensing technology.