X-ray Version of Davisson-Germer Experiment

Application of unitcell defined boundary conditions leads to the question on the formation of standing waves within unitcell. We design and propose X-ray version of Davisson-Germer experiment as the answer. In the proposed experiment, a tunable synchrotron beam replaces the variable de Broglie wavelength of incident electron beam. Among the two series of Davisson-Germer peaks from original experiments available in literature, first series shown in figure 1 demonstrates standing wave description and the second series shown in figure 2 demonstrates running wave description. Both running waves and standing waves cannot simultaneously exist within the unitcell and the proposed experiment alone can resolve between the two. The experiment can be conducted on a macromolecular crystal also.

Electron Beam Characterization via Infrared Pyrometry of Thin Tungsten Foil

A method is explored for characterizing the energy distribution of an electron beam in vacuum. A thin (125 μm) tungsten foil intercepts the beam causing its temperature to rise. An infrared camera images the opposite side of the foil to map the temperature distribution. To the extent the thermal conduction can be neglected, the temperature distribution serves as a representation of the energy distribution of the incident electron beam. Design of experiments (DOE) methodology is used to develop an equation for predicting the shape of the temperature distribution based on the potential of a single electrostatic lens (−1000 V to 0 V) and that of the tungsten foil (0 V to 2000 V). An assessment of this technique’s utility for future electron beam characterization experiments is included.

Modulated Structure of Bi1.8Sr2.0Rh1.6Ox

We have investigated the modulated structure of the misfit-layered crystal Bi1.8Sr2.0Rh1.6Ox by means of electron diffraction and high-resolution electron microscopy. This compound consists of two interpenetrating subsystems of a hexagonal RhO2 sheet and a distorted four-layered rock-salt-type (Bi,Sr)O block. Both subsystems have common a-, c-axes and β-angles with a = 5.28 Å, c = 29.77 Å and β = 93.7º. On the other hand, the crystal structure is incommensurated parallel to the b-axes, among which b1 = 3.07 Å for the RhO2 sheet and b2 = 4.88 Å for the (Bi,Sr)O block. The misfit ratio, b1/b2 ~ 0.63, characterizes the structural analogue as [Bi1.79Sr1.98Oy]0.63[RhO2]. This compound has two modulation vectors, i.e., q1 = – a* + 0.63b1* and q2 = 0.17b1* + c*, and the superspace group is assigned as the Cc(1β0, 0μ1)-type from the electron diffraction patterns. High-resolution images taken with the incident electron beam parallel to the a- and c-axes clearly show displacive as well as compositional modulations.

Writing Nano-Scale Patterns on Insulators Using Variable Pressure Electron-Beam Lithography

Electron-beam lithography offers very high resolution patterns without the need for masks. Systems based on electron microscopes offer entry into electron-beam lithography at reasonable cost. Such systems are becoming popular in research environments due to their versatility and reasonable cost.While these systems work well they do have problems writing on insulating substrates. The insulating substrate causes charge to build up from the incident electron-beam. As the charge builds up on the surface of the insulator, the incident beam is distorted and moved in x and y. The result is a lack of positioning accuracy on the patterns as well as pattern distortion.