Progress toward an aberration-corrected low energy electron microscope for DNA sequencing and surface analysis

Marian Mankos1, Khashayar Shadman1, Alpha T. N'Diaye2, Andreas K. Schmid2, Henrik H. J. Persson3, and Ronald W. Davis3

Monochromatic, aberration-corrected, dual-beam low energy electron microscopy (MAD-LEEM) is a novel imaging technique aimed at high resolution imaging of macromolecules, nanoparticles, and surfaces. MAD-LEEM combines three innovative electron–optical concepts in a single tool: a monochromator, a mirror aberration corrector, and dual electron beam illumination. The monochromator reduces the energy spread of the illuminating electron beam, which significantly improves spectroscopic and spatial resolution. The aberration corrector is needed to achieve subnanometer resolution at landing energies of a few hundred electronvolts. The dual flood illumination approach eliminates charging effects generated when a conventional, single-beam LEEM is used to image insulating specimens. The low landing energy of electrons in the range of 0 to a few hundred electronvolts is also critical for avoiding radiation damage, as high energy electrons with kilo-electron-volt kinetic energies cause irreversible damage to many specimens, in particular biological molecules. The performance of the key electron–optical components of MAD-LEEM, the aberration corrector combined with the objective lens and a magnetic beam separator, was simulated. Initial results indicate that an electrostatic electron mirror has negative spherical and chromatic aberration coefficients that can be tuned over a large parameter range. The negative aberrations generated by the electron mirror can be used to compensate the aberrations of the LEEM objective lens for a range of electron energies and provide a path to achieving subnanometer spatial resolution. First experimental results on characterizing DNA molecules immobilized on Au substrates in a LEEM are presented. Images obtained in a spin-polarized LEEM demonstrate that high contrast is achievable at low electron energies in the range of 1–10 eV and show that small changes in landing energy have a strong impact on the achievable contrast. The MAD-LEEM approach promises to significantly improve the performance of a LEEM for a wide range of applications in the biosciences, material sciences, and nanotechnology where nanometer scale resolution and analytical capabilities are required. In particular, the microscope has the potential of delivering images of unlabeled DNA strands with nucleotide-specific contrast. This simplifies specimen preparation and significantly eases the computational complexity needed to assemble the DNA sequence from individual reads.

• 以上资料由西亚试剂：http://www.xiyashiji.com/ 提供此产品的详细信息如密度,含量,分子式,分子量等均可在西亚官网查询   
• 相关产品如诺卡氏菌液(-)-樟脑神经鞘磷脂,从牛脑所得 杨梅苷愈创奥IAPN-叔丁基苯硫腈氯化物4-溴苯基五氟化硫色胺盐酸盐4-溴噻吩-2-甲醛纤维素粉 7-(二甲基氨基)-4-三氟甲基香豆素邻硝基苯肼盐酸盐3,3'-二氨基联苯胺四盐酸盐水合物美伐他汀丁卡因阿卡明全氟辛基季胺碘化物布西拉明硫酸多粘菌素B益母草浸膏黄苓干膏 L-2,3-二氨基丙酸盐酸盐黄糊精EB替代品(GoldView)等均有销售.欢迎订购