Ion Beam Treatment of Functional Layers in Thin-Film Silicon Solar ...

6 Ion beam treatment of the TCO surface
C ra te r d e p th [n m ]
rm s ro u g h n e s s [n m ]
C o rr. le n g th [n m ]
7 5 0
6 0 0
4 5 0
3 0 0
1 5 0
1 0 0
5 0
0
1 2 0 0
1 0 5 0
9 0 0
7 5 0
Z n O , H C l e tc h e d
te x tu re d g la s s s u rfa c e
6 0 8 0 1 0 0 1 2 0 1 4 0 1 6 0
H C l e tc h in g tim e [s ]
a
b
c
Figure 6.14: (a) Crater depth, (b) rms roughness, and (c) lateral correlation length of
800 nm thick wet chemically etched ZnO:Al films (Solid squares) and the
values for the corresponding textured glass (open squares). All lines are
guide for the eyes. The ion source was not tilted during this process.
crater depth and rms roughness for textured glass of 360 nm and 100 nm were obtained.
The lateral correlation length of textured glass is larger than the ZnO:Al films when the
etching time is less than 120 s and smaller than the ZnO:Al film when the etching time
is 150 s. The increase of lateral correlation length might be caused by the elimination
of small craters. The decrease of crater depth and roughness of ZnO:Al films after 100 s
is because the glass has been reached by HCl etching. Since glass is not etched by
HCl solution, the surface becomes smoother for further etching. The textured glass is
smoother than the corresponding ZnO:Al films, which confirms again that the ion beam
etching has smoothening effect.
Fig. 6.15 gives the haze results of the above ZnO:Al films and corresponding textured
glass. The samples with different HCl etching time are shown in the legends. ZnO:Al
films and textured glass are denoted in the figure. Clearly, textured glass have lower
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