Characterization for the Onset of Crystallization of Amorphous to Microcrystalline Silicon by Optical Spectroscopies Page: 4 of 4
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(a)
(b) 480 520 :m
mmml . mmmi p. ... ... .I m .m.ml 1 ..m.
300 350 400 450 500 550 600
Raman shift (cni )
Fig. 2 Raman spectra (a) for all films listed in Tables II and
III except (b) for #9883 listed in Table II
1 pm for the 325, 488, 514, and 632 nm laser in a-Si:H. As
the examined layer moved to the top surface, the low energy
PL was enhanced. The results imply that the structure tends to
pc as the film grows thicker. Fig. 3(c) shows the PL spectra
for the films deposited with the same H-dilution but varied
deposition rate. The PL intensity decreases as the growth rate
decreases due to pc. Meanwhile, the PL peak energy
decreases from~1.3 to 1.18 eV in sample #12468, that is the
film with highest pc in the TPC measurement[4].
3. Summary
For a number of a/gc films, Raman spectra showed no c-Si
peak. Because that (a) growing near the a- c transition, the
resulting film properties are very sensitive to the film thickness
and substrate material, so the results may not be the same unless
one studies the same piece of sample; and (b) if the c-Si-grain
volume fraction is only a few percentage or the grain size is <3
nm, it is below the technical limitation of Raman[7]. Whereas,
low energy PL enhancement was observed in films containing
small density c-. The electronic density of states measured by
PL and a(E) is more sensitive to the characterization of onset gq.
Furthermore, the excitation wavelength dependence of PL can be
used to study the non-uniformity along the growth direction.
Acknowledgments
The work at UNC and United Solar, was supported by NREL
sub-subcontract under thin film PV partnership, XAK-8-17619-
11, ZAK-817619-09, respectively. Wang is supported by DOE
subcontract DE-AC02-83CH 10093.(a) on ss i
o I on n-ss
- ----- 10306
ft - 10307
(b)
e ,- a325 nm
-' 488 nm
- 'a - - -514 nm
--------- 632 nm
(c)100 W
- ,' 60 W
-4--
- 20 W
0.6 0.8 1.0 1.2 1.4 1.6
Photon Energy (eV)
Fig. 3 PL spectra (a) for the 0.5- m i-layer with and without an n-
layer on ss substrate, (b) dependence on the excitation wavelength
in a 1.4- m thick a-/ c-Si film, and (c) as function of rf power for
H-diluted films 12464, 12466, and 12468 listed in table III.
References
1. S. Guha, J. Yang, D.L Williamson, Y. Lubianiker, J. D.
Cohen, A, H. Mahan, Appl. Phys. Lett., 74, 1860 (1999).
2. J.Koh, A.S. Ferlauto, P.I. Rovira, C,R. Wronski, and R.W.
Collins, Appl. Phys. Lett. 75, 2286 (1999).
3. A.M. Brockhoff, E.H.C. Uiiersma, H. Meiling, F.H.P.M.
Habraken, and W.F. van der Weg, Appl. Phys. Lett. 73,
3244 (1998).
4. Y. Lubianiker, Y. Tan, J.D. Cohen and G. Ganguly, MRS
Symp. Proc.(1999); ICAMS-18 (1999).
5. Daxing Han, Guozhen Yue, J. D. Lorentzen, Jing Lin, H.
Habuchi, and Qi Wang, to be published in J.Appl. Phys. 87,
1882 (2000).
6. XRD was examined by D.L. Williamson.
7 .S. Veprek, F.A. Sarott, and Z. Iqbal, Phys. Rev. B36, 3344
(1987).202
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Yue, G.; Han, D.; Ganguly, G.; Wang, Q.; Yang, J. & Guha, S. Characterization for the Onset of Crystallization of Amorphous to Microcrystalline Silicon by Optical Spectroscopies, article, January 1, 2000; Golden, Colorado. (https://digital.library.unt.edu/ark:/67531/metadc886721/m1/4/: accessed March 28, 2024), University of North Texas Libraries, UNT Digital Library, https://digital.library.unt.edu; crediting UNT Libraries Government Documents Department.