MICRO-DIFFRACTION WITH MONO-CAPILLARIES, M.J. Fransen, J.H.A. Vasterink, J. te Nijenhuis, pp. 284-289

The use of glass capillaries (the so-called mono-capillaries) as incident beam optical module for X-ray micro-diffraction is evaluated. These mono-capillaries show a gain in intensity with a typical factor of three over traditional pinhole collimators. Procedures to improve the particle statistics of the measurement are discussed. Examples are shown on phase identification and preferred orientation analysis of diamond films grown with a combustion flame and residual stress analysis of a copper damascene structure grown on a silicon substrate. INTRODUCTION When the size of the sample to be investigated is below 1 mm2, the term micro-diffraction is generally used. It is clear that in this situation not only the time for acquiring a diffractogram will increase with respect to a standard sample size, but also the number of crystallites participating in the diffraction process may become too low to meet the isotropy criterion. The recently introduced glass capillaries (the so-called ‘mono-capillaries’) offer a gain in intensity over the traditional pinhole collimators, alleviating at least the first of these problems. In this study we explore the (im)possibilities for micro-diffraction on polycrystalline samples using mono-capillaries. We will discuss ways to overcome the statistical problem of the limited number of crystallites. Application examples of phase analysis, preferred orientation analysis and the determination of residual stress in a thin film are given. PHYSICAL PROPERTIES OF THE MONO-CAPILLARY A mono-capillary is a hollow glass tube used as incident beam X-ray optical module [ 11. The point focus of the X-ray source is used. Photons entering the mono-capillary at a small angle with respect to the inner surface of the capillary are reflected by means of total reflection. In this way, the mono-capillary acts as a wave guide for X-rays. Compared with pinholes, a larger portion of the divergence of the source is used. The divergence of the exit beam is around 0.3”, set by the properties of the glass used. Radiation with a higher energy is absorbed; and thus the white radiation is strongly suppressed by the mono-capillary. The final spot size on the specimen will depend on the inner diameter of the mono-capillary (which can be chosen between 2 mm and 10 pm), the divergence of the exit beam, the distance from the end of the mono-capillary to the sample, the angle of incidence o and the sample tilt angle UT. With a 100 pm mono-capillary, a factor of three in intensity is gained over a pinhole with the same diameter, as measured by recording a rocking curve using a (1 1 1)-oriented Si crystal. Copyright(c)JCPDS-International Centre for Diffraction Data 2001,Advances in X-ray Analysis,Vol.44 1 283 Copyright(c)JCPDS-International Centre for Diffraction Data 2001,Advances in X-ray Analysis,Vol.44 284