FABRICATION OF HIGH-RESOLUTION INVERSE PHOTOEMISSION SPECTROSCOPY SYSTEM FOR ORGANIC MATERIALS AND OBSERVATION OF UNICCUPIED ELECTRONIC STATES OF FUNCTIONAL ORGANIC MATERIALS

我们花了2004年和2005年的时间来设计和制造高分辨率的反向光电子能谱系统。首先，研制了用于激励的高分辨率电子枪。采用碳纳米管场发射器件(CNT-FED)作为电子枪的新型电子源。由于CNT-FED发射的电子能量分布较小，制作的电子枪显示出比传统电子源更高的分辨率~0.2 eV。我们采用了两种方法来实现对辐射光子的反向光电子发射探测：(1)制作了带通的SRF_2窗口和KCL镀膜沟道加速器探测器，并通过对不同温度的SRF_2窗口的光谱进行差值测量，成功地获得了小于0.2 eV的高分辨率。(2)设计并制作了用于IPES模式探测的真空紫外光谱仪，该光谱仪由光谱仪和真空紫外椭球镜组成。设计并制作了减少电子轰击样品辐射损伤的样品机械手，并用光电子能谱仪对电子枪的性能进行了检测。在真空紫外区使用同步辐射(IMS-UVSOR BL8B2)对真空紫外谱仪的性能进行了检测。该系统的总能量分辨率从蒸发金膜的费米边缘估计为0.3 eV。利用该系统研究了几种半导体有机材料。我们成功地观察到了锌酞菁(ZnPc)薄膜、全氟化锌酞菁(ZnPc)薄膜、均四甲酸二酐(PTCDA)薄膜、某些离子液体(bmiBF_4和bmiPF_6)以及一些双自由基分子(IDPL和NDPL)薄膜的空态电子状态。

We spent 2004 and 2005 to design and fabricate the high-resolution inverse photoemission spectroscopy system. First, the high-resolution electron-gun for excitation were fabricated. The CNT-field emitter device (CNT-FED) was employed for new-type electron source for the e-gun. Because of smaller energy distribution of electrons emitted from CNT-FED, fabricated e-gun shows higher resolution 〜 0.2 eV than conventional electron sources. We employed two methods to detect the radiated photon by inverse photoemission as following, (1) band-pass typed detector with SrF_2 window and KCL-coated channeltron was fabricated and we succeeded to get high resolution less than 0.2 eV by taking difference between the spectra observed with different temperature of SrF_2 window. (2) We designed and fabricated VUV-spectrometer for IPES mode detection which consists of the spectrometer and VUV-ellipsoid mirror. The sample-manipulator for reduction of radiation damage of the sample by electron impact was designed and fabricated.The properties of the e-gun were checked by photoelectron spectrometer. The properties of VUV-spectrometer were checked by using synchrotron radiation (IMS-UVSOR BL8B2) in VUV region. The total energy resolution of the system was estimated to be about 0.3 eV from the Fermi-edge of evaporated gold film.Studies on several semiconductive organic materials were performed by fabricated systems. We succeeded to observe the unoccupied electronic states of zincphthalocyanine (ZnPc) and perfluorinated ZnPc thin films, perylenetetracarboxylic acid dianhydride (PTCDA) thin films, some ionic liquid (bmimBF_4 and bmimPF_6) and some biradical molecules (IDPL and NDPL) thin films.Manuscripts about fabrication of the new inverse photoemission system for organic materials and observation of unoccupied states of some organic thin films as mentioned above are in preparation now.