<title>CVD diamond TEM sample preparation by laser machining</title>

Abstract

ABSTRACT The defect structure of diamond films grown by microwave plasma chemical vapor deposition(CVD) in studied by using laser machining to slice thin sections from free standing films ca. 200 micronsthick. This technique has enabled the examination ofthe defects at the nucleation and growth surface ofoptically clear CVD diamond films. A cw Q-switched Nd3/YAG laser was used to slice 1 to 15 micronthick wedges, ca. 3mm in length from 150 to 220 micron thick diamond films. The edges ofthe as cutwedges were thin enough for examination by transmission electron microscopy (TEM). Subsequent ionmilling was used to thin the edges ftirther. Remarkably low defect densities are observed at the growthsurface after 1 50 microns of growth. INTRODUCTION The growth of diamond materials by chemical vapor deposition (CVD) has been an active area ofmaterials science in the last decade. Much progress has been made in the understanding ofthe basicchemical processes by which a metastable material, diamond, is grown under low pressure conditions2.Diamond materials grown by the CVD process are being commercialized and exploited in manytechnological applications, such as cutting tools, thermal management substrate, light and radiationdetectors, optical windows, etc..3 Various commercial companies exist today with capabilities of producingpolycrystalline materials up to 30 cm diameter and several mm thick. As in many other materials systems,defects limit or control many ofthe materials properties. These polycrystalline materials often containcolumner grains with smaller grain sizes on the nucleation surface and much larger grains on the finalgrowth surface and thus many properties are anisotropic. Hence it is necessary to both characterize andunderstand the nature ofthe defects and impurities observed and to learn how to eliminate or control themto improve the desired properties. Transmission Electron Microscopy (TEM) is a powerful technique tostudy the structure and electronic properties of extended defects in bulk materials. TEM requires thepreparation of samples sufficiently thin that 100 to 400 Key electron beams can pass through, typically lessthan 0. 1 to I .0 microns. For many materials this can be accomplished by mechanical polishing followed byion milling. Unfortunately, diamond is the hardest material and hence is the most difficult to polish bytraditional means. This paper focuses on improving the methodology ofthin CVD diamond samples andthe characterizing the extended defects present by TEM.