ESR and LESR Studies in CVD Diamond
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or the ESR and LESR experiments, free-standing samples were placed in the TE102 cavity of a standard X-band ESR spectrometer. All experiments have been performed at room temperature using 0.07-100 kHz magnetic field modulation, with phase sensitive detection. Samples were illuminated with a Hg/Xe arc lamp for the LESR experiments. Low-pass cut-off optical filters were used to control the photon energy in the LESR experiments. Thermal annealing from 200 to 300 'C was performed with typical heating and cooling times of 60 s in a thermally stabilized oven under air. For the SDC measurements, samples with coplanar contacts were used. The spindependent change of the conductivity was also measured by modulating the magnetic field. RESULTS
CVD-Diamond
• textured
9.3542 GHz
textured H//(1 00)
C
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Fig.I: Typical ESR and LESR spectra for two different types of CVDdiamond films: highly oriented (100) textured (ESR), and non "textured(LESR). Note that for the "former,the anisotropy in the hyperfine constants are clearly observed.
U-1
textured H//(1 10)
I
I
3300
3320
3340
3360
3380
Magnetic Field (G) In Fig. 1, typical ESR and LESR spectra are shown for two types of CVD-diamond films: highly oriented, (100) textured, and non textured (35 ppm N content). The signal consists of two (narrow and broad) central lines and satellite peaks. The broader line has a g-factor of 2.0029 ±t 0.0002 and a peak-to-peak width AH, of 4 ± I G. The narrow line is a triplet composed of a central line with g = 2.0024 ± 0.0001 and AH• = 0.2 ± 0.1 G, and satellite peaks coming from the hyperfine interaction of the electron spin with the 14N nuclei. The broader (g=2.0029) line is present in all samples, independent of nitrogen content, both in the dark (ESR) and under illumination (LESR). Note that this signal consists of a single central line with unresolved shoulders, attributed recently to carbon dangling bonds, hyperfine-coupled to nearby hydrogen nuclei [7,8]. 496
N density (crfi3) 1019
10is CVD-Diamond g=2.0029 -0 9 'E
/
I
1019
I
/" V)
(t.
Fig. 2: Defect density of the C"relateddefect as measured by ESR, for textured and non textured samples, as a function of N
content. The dashed line corresponds to the density of N in the film.
S1018/ M
0 non textured ]0 textured
100 / .............
I-----
10
100
N content (ppm) In Fig. 2 the density of the g=2.0029 defects is plotted against the N content, for textured and non textured samples. As can be seen, optimized deposition conditions that lead to highly oriented, (100) textured samples are related to a decrease by a factor of 10 in the C-related defect density. Note that the density of C-related defects is to a first approximation equal to the density of N in the film (dashed line). This would indicate that N incorporation induces the creation of C-related deep
defects, and thus to achieve a material with low defect density, the incorporated N content must lie below 10 ppm. The detrimental effects of the C-related defects are clearly observed from the spin-depende
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