The roughness of the surfaces after the etching

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(AFM), with the results shown in Figure 1(a), Figure 1(b) and Table 1. The roughness of the surfaces after the etching procedure was found to be higher than that of the un-etched crystals. These four samples were compared to a commercially available “heatspreader” sample, where the roughness of the surfaces before and after the chemical etch remained same. A multimode q-switched laser was used to damage the diamond surface, operating at an output wavelength of 1064nm and at a pulse duration of ~6.5ns. The laser emission was appropriately attenuated using a half wavelength plate and Glan-Taylor prism and focused onto the surface of a diamond sample at a spot radius (1/e 2 ) of 140μm x 175μm in the horizontal and vertical directions, respectively. For each pulse energy, ten single laser shots were fired onto the diamond surface, with each individual laser pulse incident on a separate point on the diamond, in line with ISO 11254-1 [4]. The energy was incrementally increased using the attenuator, with the value for the LIDT taken as the x-axis crossing of the least squared linear fit (dashed and solid lines in Figure 1(c)) to the data points between and including the last point with a damage probability of zero and the first point with a damage probability of one. The results for diamond surfaces with different values of roughness are summarized in Table 1. Figure 1. (a) AFM image of the unetched surface, (b) of the surface etched with an Ar/Cl plasma, and (c) a typical plot of damage threshold measurements (S ample prepared with 76 grit). (c) (b) (a)
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Table Error! No text of specified style in document. 1. Comparison of surface roughness and laser induced damage threshold of various diamond samples Sample (polish technique /grit size) Roughness before etch (nm) LIDT before etch (Jcm -2 ) Roughness after etch (nm) LIDT after etch (Jcm -2 ) Fine Lap 33 76 151 Heatspreader 142 3.9 1.2 5.6 0.6 ~12.5 23.7±2.0 26.8±1.5 26.7±1.2 ~23 163 33.6 7.3 7.5 0.6 ~19 25.7±2.0 28.3±2.1 25.7±2.9 ~23 An LIDT of ~26Jcm -2 is measured for all samples except the poor optical quality „fine lap” surface . No significant improvement is observed if one side of the samples is etched to remove approximately 5 μ m of material. These results indicate that the laser induced damage threshold of diamond does not vary strongly across the wide range of surface finishes examined here.
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