Abstract
This work reports mainly on the diffraction phenomena of X-rays in nano-scale waveguides in wide-angle incidence geometry. Through measurements we find that X-ray beam passing through a waveguide is guided along the waveguide without energy loss. We also observe that interference among different modes of wave propagation gives rise to intensity undulation in the transverse 2θ scan.This type of wave guides is different from the conventional types where grazing incidence or normal incidence of X-rays is adopted. In order to bend a wide-angle incident beam along the crystal surface, the (113) reflection of silicon at the 8.8785keV is used. The wave guides are prepared on a [001] Si wafer of 6 inches in diameter and 675 um in thickness. The designed waveguides are along [110] direction. The sizes of the waveguides are 5mm long and 700, 450, 400, and 350nm wide, respectively. The sample wave guides are prepared at the National Nano Device Laboratories (NDL) by etching the Si wafer by 1um in depth. The waveguides are then plated with gold for about 150nm in thickness on the top, the left and right surface and 300nm for the bottom surface.We adopt the dynamical theory of X-ray diffraction in a Cartesian system of coordinates to carry out theoretical calculations. For the (113) surface diffraction, the incident X-ray beam excites eight modes of wave-propagation, thus some of generating eight diffracted beams nearly parallel to the crystal surface. If the angles between the wavevectors of these eight modes and the Si-Au interface are less than 0.460, then total external reflection takes place for these eight diffracted beams. The interference among the eight diffracted beams results in intensity undulation along 2θ direction. This is in good agreement with the experimental result.