Exploration On STM Based Spin Noise Spectrometer And Investi Ation On Spin Properties Of Magnetic Molecules

The properties of electron spins have been widely studied in physics,electronics,chemistry and materials science.The ability to measure,control and manipulate a single spin has been highly demanded worldwide.To achieve this goal,one of the schemes is to detect and manipulate spins using scanning tunneling microscopy(STM)because of its high resolution at the single-atom and single-molecule scale and its capability in detecting electronic properties.It has attracted a wide study interest to investigate electron spins of single magnetic atoms or molecules by combining STM with other new techniques.In this thesis,I mainly describe my work on the exploration of a STM-based instrument by combining STM with electron spin resonance(ESR).Using the instrument,I measured the spin signals of magnetic molecules on several surfaces,including the spin procession signals of spin centers on Cr-N codoped rutile TiO2(110)film.Using STM,I studied the adsorption energy of O2 molecule on Fe-and Co-phthalocyanine(MPc)molecules,mainly to detect the spin related adsorption properties.I also prepared endohedral fullerene N@C60 with high purity,and measured the stability of N@C60 on various substrates.In chapter 1,I give the brief introduction about S T M and review the recent progress of STM-based techniques,including spin-polarized STM and STM-ESR.The advantages and the challenges are introduced.In chapter 2,1 describe the exploration on the self-designed low temperature ultra-high vacuum ESR-STM system,including the equipment components and its performance test.In this combined system,the measurement of the electron spin procession signal of single spin center can be performed at 5 K.The spin signal of Cr-N codoped rutile TiO2(110)film have been obtained using the ESR-STM.In chapter 3,I describe the study of the role of spins on the adsorption property of O2 molecules at the metal center(Fe or Co)of MPc.The goal is to detect if the spin selection rule is applicable for understanding the adsorption properties of magnetic O2.The adsorption energies of O2 with triplet states on various magnetic ion center of MPc were measured using STM at 5 K.The measured adsorption energies can be well correlated to the spin selection rule,combining with theoretical calculations and analysis.We find that the spin selection rule basically works in O2 adsorption process,however,there is an exception for O2 on CoPc/Au.Our further analyses show that the d-band center theory may also applicable to describe the system.In chapter 4,O2 molecule adsorbed on FePc molecular layer on Au(111)surface is investigated by spin_polarized STM.I-t spectrums on O2 molecule were obtained by both W tip and Fe-coated spin-polarized tip.Different current levels were observed in I-t spectrums,which may correspond to different adsorption sites of O2 molecule.By analyzing the lifetime of these current levels,we found that it may be affected by the interaction between tunneling electrons and the magnetic moment of O2 molecule.In chapter 5,endohedral fullerene N@C60 was fabricated by nitrogen implantation in solid C60,and enrichment of N@C60 was achieved by high performance liquid chromatography(HPLC).In addition,STM images of N@C60 molecular monolayer on Au(111)surface was obtained,and the dipolar coupling between N@C60 and gold substrate is discussed based on our ESR results.