![](media/image1.wmf){width="0.625in" height="0.6111111111111112in"}

the university of north carolina

[at]{.smallcaps}

[chapel hill]{.smallcaps}

Department of The University of North Carolina at Chapel Hill

Physics and Astronomy CB# 3255, Phillips Hall

College of Arts and Sciences Chapel Hill, N.C. 27599-3255

Tel: (919) 962-5002

Email: daxing@physics.unc.edu Fax: (919) 962-0480

Aug. 5, 2003

Dr. Bolko von Roedern

NREL

1617 Cole Blvd.

Golden, CO 80401

Dear Bolko,

Here is the Quarterly Technical Status Report for the period of
April/1/03-June/30/03 on the NREL Subcontract No. ADJ-1-30630-09 with
the University of North Carolina at Chapel Hill. We report the Raman
study of nc-silicon with varied c-Si volume fraction. The work is in
cooperation with NREL, SCM and the Raman lab in our department.

Sincerely,

Daxing Han

cc: Carolyn Lopez (NREL)

Donna Braxton (UNC)

**[Quarterly Technical Status Report]{.underline}**
April/1/03-June/30/03

NREL Subcontract ADJ-1-30630-09 with the University of North Carolina at
Chapel Hill

Bolko von Roedern, NREL Technical Monitor;

Carolyn Lopez, NREL Subcontract Associate;

Daxing Han, principal investigator; Andrea Hilchey, Christopher T
Lawyer, graduate students; and Keda Wang, co-P.I.

Submitted: Aug. 5, 2003

**Is there a correlation between the median component in Raman spectrum
and the (111) side peak in XRD?**

In order to study the above puzzle, a group of samples with varied
hydrogen dilution ratio was deposited at 250°C on SS substrate using
HW-CVD for both Raman and XRD studies. The sample phase was measured
optically. The sample information and Raman results are listed in Table
I.

Table I Sample preparation and Raman results

<table style="width:100%;">
<colgroup>
<col style="width: 12%" />
<col style="width: 11%" />
<col style="width: 13%" />
<col style="width: 8%" />
<col style="width: 6%" />
<col style="width: 9%" />
<col style="width: 8%" />
<col style="width: 9%" />
<col style="width: 9%" />
<col style="width: 11%" />
</colgroup>
<tbody>
<tr class="odd">
<td>Sample ID</td>
<td>R = H<sub>2</sub>:SiH<sub>4</sub></td>
<td><p>Thickness</p>
<p>(Å)</p></td>
<td><p>X<sub>gb</sub></p>
<p>(%)</p></td>
<td><p>X<sub>c</sub></p>
<p>(%)</p></td>
<td><p>X<sub>gb</sub>/X<sub>c</sub></p>
<p>(%)</p></td>
<td><p>Peak<sub>a</sub></p>
<p>(cm<sup>-1</sup>)</p></td>
<td><p>Peak<sub>gb</sub></p>
<p>(cm<sup>-1</sup>)</p></td>
<td><p>Peak<sub>c</sub></p>
<p>(cm<sup>-1</sup>)</p></td>
<td><p>FWHM<sub>c</sub></p>
<p>(cm<sup>-1</sup>)</p></td>
</tr>
<tr class="even">
<td>H1592*</td>
<td>1.2</td>
<td>11854</td>
<td>27</td>
<td>73</td>
<td>38</td>
<td>480</td>
<td>500</td>
<td>513.5</td>
<td>11</td>
</tr>
<tr class="odd">
<td>H1595</td>
<td>1.2</td>
<td>10875</td>
<td>24</td>
<td>67</td>
<td>35</td>
<td>480</td>
<td>503</td>
<td>514.0</td>
<td>11</td>
</tr>
<tr class="even">
<td>H1593</td>
<td>10.2</td>
<td>11591</td>
<td>26</td>
<td>89</td>
<td>29</td>
<td>480</td>
<td>504</td>
<td>517.7</td>
<td>8</td>
</tr>
<tr class="odd">
<td>H1594</td>
<td>18</td>
<td>N/A</td>
<td>12</td>
<td>93</td>
<td>13</td>
<td>480</td>
<td>504</td>
<td>517.8</td>
<td>8</td>
</tr>
</tbody>
</table>

Note: H1592 was set at a low pressure for 7 min, then corrected to the
right pressure for 45 min on top. H1594 can\'t be measured optically
because it is too milky.

Raman measurements were made in backscattered geometry with a JY triple
spectrograph fitted with a liquid-nitrogen cooled CCD detector. The
spectra were collected under ambient conditions using the 514.5-nm line
of an argon-ion laser. The penetration depth of the 514.5-nm light is \~
60 nm for a-Si:H and is larger for µc-Si:H. The spectral resolution was
approximately 0.5 cm^-1^ in a frequency range of 100 to 1000 cm^-1^. The
frequency of the Raman lines were calibrated using the TO mode of a
(111) c-Si wafer at 520 cm^-1^. A low laser power was used to avoid the
possibility of laser-induced crystallization. The incident beam was
approximately three microns in diameter. For each sample, 3 spots were
scanned to check the structural uniformity. The Raman TO models in three
locations of each sample are shown in Fig. 1. The spectra were
deconvoluted into three components: a-Si:H, c-Si and the third component
that we refer to as grain boundaries or small particles of c-Si. The
c-Si volume fraction, the percentage of the grain boundary, the peak
energy and the width of the c-Si peaks are listed in Table I. We have
double-checked the small peak at 496 cm^-1^ of H1593. It was always
there for the four scans. We don\'t know the corresponding structures.

Fig. 1 Raman TO model for H1592, H1595, H1593 and H1594

![](media/image2.wmf){width="5.527777777777778in"
height="4.527777777777778in"}

![](media/image4.wmf){width="5.375in" height="4.583333333333333in"}

The Raman results including the percentage of gb volume fraction,
Xgb/X~c~, the c-Si volume fraction, X~c~, etc. are consistent with the
previous results of H-dilution dependent studies as shown in Fig. 2.

![](media/image6.wmf){width="6.0in" height="6.013888888888889in"}Fig. 2
the percentage of the third component in Raman TO mode as a function of
H-dilution ratio for two groups of films made in 1999 and 2003,
respectively.

In Fig. 3 we show the volume fractions, X~c~, X~gb~, and X~gb~/X~c~ as a
function of H-dilution ratio, R. One can see that at the same R, H1592
shows little bit higher values than those of H-1595, because of the
preparation conditions were slightly different as explained in the note
of Table I. It indicates the strong dependence of the microstructure on
preparation conditions and also the high sensitivity of Raman shift for
the microstructure.

![](media/image7.wmf){width="6.0in" height="6.013888888888889in"}

Fig. 3 The volume fractions as a function of R for the four samples.

Fig. 4 shows the c-Si energy peak position and width as a function of R.
The data imply that the higher the R the larger size of c-Si grains;
meanwhile, the size-disperse may be reduced.

![](media/image8.wmf){width="6.319444444444445in"
height="6.013888888888889in"}

We need to discuss with Don who has the XRD data to figure out if there
is a correlation between the median component in Raman spectrum and the
(111) side peak in XRD, or what kind of structure could be responsible
for those components.