The Structure and Composition of Doped Silicon Oxycarbide Microcrystalline Layers Produced by Spatial Separation Techniq
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Mat. Res. Soc. Symp. Proc. Vol. 358 0 1995 Materials Research Society
position of the SiC pattern was not found. The crystals dimensions were inferred using the Scherrer formula [6], showing crystals with average sizes in the range of 100-50 A as po 2 varies from 10-3 to 10-1 mbar, (see figure 1) The crystals volume fraction (fc) was inferred through the ratio between the peak intensity recorded on the pc-films and that one obtained in a c-Si sample [7]. Fig. 2 shows the dependence of Sc and fc on the po 2 , for p-and n-type films. The results show that fc and Sc decrease as po 2 increases, more effectively when PO2 >10-2 mbar. The figure also reveals that Sc and fc are dependent on X, decreasing as X increases, more markedly in the n-type films. This result indicates that 02 works as inhibitor of reach c-Si clusters within the film. The insert of fig. 1 also shows a high resolution crosstransmission micrograph of an n-type 1section __ 22. sample deposited on glass substrate, using X=25% and P0 2=10- 3 mbar. The figure reveals 20__.y . the c-Si planes of Si crystals embedded in the amorphous matrix, with a columnar morphology " ••(200-300 A lateral dimensions) and grains with the dimension around 80 A. The analysis of the same sample deposited on a c-Si substrate was 2.3 performed by TEM. Figure 3 shows the electron diffraction pattern recorded. The bright spot on the 2 (111) diffraction rings show the presence of crystals with average sizes in the range of 500 A, indicating the importance of the substrate structure 60 80 4 20 21ton the crystal's growth process. Here, it is also of SiC thatrevealed, the presence notice important to tfor n-and confirming so not been crystallites have Fig. 1 - X-ray diffraction spectra frnadpdata. X te ay type films prepared at X=40 % and 25 %.The ineprt rnr~pnte n r-nmesretion 'T]E.Inf the n- the X-ray data. ltype-- --------------. sample. /u
.
lic p-type -. 60
) •- W.Sc(X =4- 0% Lit ec(X=25%) lO3
lO2 P02 (mbar)
70
60
40.
40
20 --
60 50
S50
30
fc(X-40%) f c(X=25%):
30 7
, 5o 40
30
20 10r1
20
, .,,= "
103
102 Po2 (mbar)
I10120
Fig. 2 - Dependence of Sc and fc on the P0 2 , for p-and n-type films produced. The film composition and its dependence on oxygen partial pressure The films chemical composition were analysed by ESCA, following the procedure proposed by Watanabe et al [8], (figs 4 a), b) and c)) and IR spectroscopy (fig. 5). The ESCA stoichiometric analysis allows us to determine the different incorporated clusters. For instance, for an n-type film produced using pO2-10"1 mbar, (see fig. 4 a)) the analysis shows that:. Si(26%) + SiC(24%) + SiO2 (15%) + Si130 15 (28 %)+ C(7%) -4 Si56C19 0 25 , supplying so information about how the different clusters are incorporated.
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a) Fig. 3 - Electron diffraction pattern of the same sample produced on a c-Si substrate in the conditions described in the text. The bright spots indicate the presence of Si grains of the order of
0sa1
100
!
500 A.
Changing po 2 from 10-3 to 10-1 mbar t
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