Physical Properties of Endohedral Metallo fullerenes at solid, thin film and nano-scale.

在固体、薄膜和纳米尺度上研究了内嵌金属富勒烯和高级富勒烯的结构和电子性能。通过同步辐射x射线衍射图的Rietveld改进，确定M@C_<82>（Dy，Ce和Pr）和C_<82>的晶体结构为简单立方（Pa3）。在150 K左右，M@C_<82>的晶体发生了一级结构相变。在C_<84>晶体中掺杂金属Rb，制备了Rb_<8.8(7)>C_<84>， x射线衍射图显示为Pa3的简单立方结构。温度相关ESR谱显示Rb_<8.8(7)>C_<84>具有金属行为。对M@C_<82>、C_<82>和C_<84>的电阻率和光吸收光谱分析表明，这些化合物不是金属，而是具有小间隙的普通半导体。电阻率估计的间隙为光学间隙的1/2。因此，由电阻率估计的间隙为迁移率。制备了M@C_<82>、C_<82>、C_<84>和C_<88>的薄膜场效应晶体管（fet）。这些FET具有n沟道常导FET特性。C_<88>场效应晶体管的场效应迁移率达到~ 10^<-2> cm^2 V^<-1> s^<-1>，在富勒烯场效应晶体管中居第二位。内嵌金属富勒烯和更高富勒烯的正常开启特性源于在薄膜所有区域流动的大体积电流。扫描隧道显微镜（STM）显示M@C_<82>的局部结构清晰图像，包括内部结构。STM充分研究了M@C_<82>在定义明确的Si(111)-（7 × 7）表面上的生长，发现M@C_<82>为Stranski-Krastanov型生长。第一层中M@C_<82>的分子通过C原子与Si原子悬空键之间的化学键在Si表面紧密结合。第一层以上的M@C_<82>分子通过分子间的范德华力聚集。将覆盖多层M@C_<82>的Si衬底在200℃下退火，形成了M@C_<82>的密排结构。通过STM尖端的场蒸发，在单分子精度上实现了C_<60>致密层中C_<60>分子的去除和移动。STM尖端的精确射击使人们能够绘制纳米级的字符、图片和由分子大小的空隙组成的图案。由于该技术技术简单，可自由控制，且孔洞尺寸为1nm，因此广泛应用于纳米级制造。从而获得了许多关于内嵌金属富勒烯和高级富勒烯的结构和物理性质的信息，并在此基础上尝试了在薄膜场效应晶体管和分子电子学方面的应用。少

The structures and electronic properties of endohedral metallofullerenes and higher fullerenes have been studied at solid, thin-film and nanometer scale. The crystal structures of M@C_<82>(Dy,Ce and Pr) and C_<82> have been determined to be simple cubic (Pa3) by Rietveld refinements for X-ray diffraction patterns with synchrotron radiation. The first-order structural phase transition was observed for the crystals of M@C_<82> around 150 K. Furthermore, Rb_<8.8(7)>C_<84> was prepared by doping Rb metal into the crystals of C_<84>, and the X-ray diffraction pattern showed the simple cubic structure of Pa3. The temperature-dependent ESR spectra suggested a metallic behavior for Rb_<8.8(7)>C_<84>.The resistivity and optical absorption spectra for M@C_<82>,C_<82> and C_<84> showed that these compound are not metals but normal semiconductors with small gap. The gap estimated from resistivity was 1/2 of the optical gap. Therefore the gap estimated from resistivity was concluded to be mobility … More gap. The thin-film field-effect transistors (FETs) have been fabricated with M@C_<82>,C_<82>,C_<84> and C_<88>. These FETs showed n-channel normally-on FET properties. The field-effect mobility of C_<88> FET reached to 〜10^<-2> cm^2 V^<-1> s^<-1>, whose value was the second highest value among the fullerene FETs. The normally-on properties for endohedral metallofullerens and higher fullerenes originate from high bulk current which flow in all region of thin films.The scanning tunneling microscope(STM) showed clear images of local structures of M@C_<82> inclusive of internal structures. The growth of M@C_<82> on well-defined Si(111)-(7 x 7) surfaces has been fully studied by the STM, and the Stranski-Krastanov type growth was found for M@C_<82>. The M@C_<82> molecules in the first layer are strongly bound on the Si surface through the chemical bond between C atoms and dangling bonds of Si adatoms. The M@C_<82> molecules above the first layer aggregate by van der Waals force between molecules. The close-packed structures of M@C_<82> have been formed by annealing the Si substrates covered with multilayer of M@C_<82> at 200℃.The removals and movements of C_<60> molecules in the close-packed layer of C_<60> have been achieved at single molecular precision by field evaporation with the STM tip. The pin-point shooting from the STM tip enables ones to draw nano-scale characters, pictures and patterns consisting of molecular size voids. Because of technical simplicity, the free controllability, and 1 nm size of voids, this technique is widely applicable to nanoscale manufacture. Thus much information of the structures and physical properties of endohedral metallofullerens and higher fullerenes has been obtained, and the applications towards thin-film FET devices and molecular electronics have been tried based on the obtained information. Less