Over the past few decades,angle-resolved photoemission spectroscopy(ARPES)has been one of the important tools to study electronic structure of crystals.In recent years,the spatial resolution of around 150 nm has been ...Over the past few decades,angle-resolved photoemission spectroscopy(ARPES)has been one of the important tools to study electronic structure of crystals.In recent years,the spatial resolution of around 150 nm has been reached through tight focusing of the light spot(nano-ARPES).At present,the lower limit of the spot size of the light on the sample has been reached.Another way to further improve the spatial resolution is through using apertures to only let electrons from a small area of the sample pass.With both back-focal plane and image apertures,the size of the selected area can be as small as 20 nm.Yet,without aberration correction,the maximum opening angle at the sample for 20 nm spatial resolution is usually smaller than 3°,making this method not suitable for nano-ARPES.As shown in this paper,a conventional aberration corrector,which corrects chromatic and third-order spherical aberrations,is not enough either.Only when the fifth-order spherical aberration is also corrected,the opening angle at the sample is large enough for nano-ARPES.In this paper,the design of a time-of-fight PEEM/ARPES/nano-ARPES instrument,which is currently under development at the Quantum Science Center of Guangdong-Hong Kong-Macao Greater Bay Area,is presented.The main point of innovation is a fiveelectrode electron mirror corrector,which is used to correct simultaneously chromatic,third-order and fifth-order spherical aberrations,resulting in 1 nm spatial resolution with~230 mrad aperture angle in PEEM mode.This makes feasible the method of using apertures to improve the spatial resolution of the nano-ARPES mode.A new design of the magnetic prism array(MPA)is also presented,which preserves the rotational symmetry better than the existing designs.展开更多
A design for an efficient monochromatic electron source for Inverse Photoemission Spectroscopy （IPES） apparatus is described. The electron source consists of a BaO cathode, a focus electrostatic lens, a hemispherica...A design for an efficient monochromatic electron source for Inverse Photoemission Spectroscopy （IPES） apparatus is described. The electron source consists of a BaO cathode, a focus electrostatic lens, a hemispherical deflection monochromator （HDM）, and a transfer electrostatic lens. The HDM adopts a “slit-in and slit-out” structure and the degradation of first-order focusing is corrected by two electrodes between the two hemispheres, which has been investigated by both analytical methods and electron-ray tracing simulations using the SIMION program. Through the focus lens, the HDM, and the standard five-element transfer lens, an optimal energy resolution is estimated to be about 53 MeV with a beam flux of 27 μA. Pass energy （P.E.） of 10 eV and 5 eV are discussed, respectively.展开更多
基金supported by Shanghai Tech University and Quantum Science Center of Guangdong-Hong Kong-Macao Greater Bay Area,China(Grant No.SZZX2301006)。
文摘Over the past few decades,angle-resolved photoemission spectroscopy(ARPES)has been one of the important tools to study electronic structure of crystals.In recent years,the spatial resolution of around 150 nm has been reached through tight focusing of the light spot(nano-ARPES).At present,the lower limit of the spot size of the light on the sample has been reached.Another way to further improve the spatial resolution is through using apertures to only let electrons from a small area of the sample pass.With both back-focal plane and image apertures,the size of the selected area can be as small as 20 nm.Yet,without aberration correction,the maximum opening angle at the sample for 20 nm spatial resolution is usually smaller than 3°,making this method not suitable for nano-ARPES.As shown in this paper,a conventional aberration corrector,which corrects chromatic and third-order spherical aberrations,is not enough either.Only when the fifth-order spherical aberration is also corrected,the opening angle at the sample is large enough for nano-ARPES.In this paper,the design of a time-of-fight PEEM/ARPES/nano-ARPES instrument,which is currently under development at the Quantum Science Center of Guangdong-Hong Kong-Macao Greater Bay Area,is presented.The main point of innovation is a fiveelectrode electron mirror corrector,which is used to correct simultaneously chromatic,third-order and fifth-order spherical aberrations,resulting in 1 nm spatial resolution with~230 mrad aperture angle in PEEM mode.This makes feasible the method of using apertures to improve the spatial resolution of the nano-ARPES mode.A new design of the magnetic prism array(MPA)is also presented,which preserves the rotational symmetry better than the existing designs.
基金Supported by National Natural Science Foundation of China(11175239)One Hundred Person Project of Chinese Academy of SciencesInstrument design and development Project of CAS:Spin rosolved Inverse-PES system
文摘A design for an efficient monochromatic electron source for Inverse Photoemission Spectroscopy （IPES） apparatus is described. The electron source consists of a BaO cathode, a focus electrostatic lens, a hemispherical deflection monochromator （HDM）, and a transfer electrostatic lens. The HDM adopts a “slit-in and slit-out” structure and the degradation of first-order focusing is corrected by two electrodes between the two hemispheres, which has been investigated by both analytical methods and electron-ray tracing simulations using the SIMION program. Through the focus lens, the HDM, and the standard five-element transfer lens, an optimal energy resolution is estimated to be about 53 MeV with a beam flux of 27 μA. Pass energy （P.E.） of 10 eV and 5 eV are discussed, respectively.
