Research On Development And Application Of FM-KPFM

Scanning probe microscopy(SPM)has been widely used in various fields of scientific research.According to the different signals extracted during the scanning process,SPM derived many branches,which can meet the requirements of the different measurement analysis.In SPM family,Kelvin probe force microscope(KPFM)is used for the measurement of material surface potential.It plays an indispensable role for the work function measurement of conductor and semiconductor materials.Two dimensional heterojunction has attracted considerable interest in applications of functional structures.Measuring difference of work function of semi material by KPFM is an ideal way to discuss the work mechanism of 2D heterojunction.In this thesis,we explore SPM software design and FM-KPFM setup preliminarily.The main contents of the thesis are listed as follows.1.The working principle of KPFM is studied.By comparing the difference between frequency modulation KPFM(FM-KPFM)and amplitude modulation(FMKPFM),the method of combining commercial AFM with lock-in amplifier is proposed to set up a FM-KPFM system.And self-developed KPFM(sKPFM)has been designed and set up.2.The graphene sample is measured by sKPFM.Extra voltage is applied to HOPG to simulation the situation that samples with different work function are measured.The basic function of the test system was verified by experiments.Using commercial instruments and sKPFM to measure two dimensional heterojunction samples,the experimental results verify the correctness of the sKPFM.Measurements of work function difference of the two semi material provide quantitative basis for the application of two dimensional heterojunction in p-n junctions and gas sensors.3.On the basis of the existing AFM software and hardware system of the laboratory,the original software system is improved.The automatic focusing module is improved by using the robert operator with the strongest gradient and the climbing strategy.Template matching is realized by using phase matching algorithm and Fourier transform.TCP/IP communication protocol and custom data analysis method are used to achieve fast communication.