Environmental Engineering Reference
In-Depth Information
layersgrowonthecathodesurroundedbywetchemicals,unwanted
defects can be removed from the material layer. The best example
is the CdCl
2
treatment of CdS/CdTe solar cells in order to enhance
e
ciency values from
∼
3-5% to
∼
12% [18]. Although there is no
agreedscientificunderstandingofthisprocesstodate,graingrowth,
doping, and defect passivation must be taking place during this
wettreatmentandannealingprocess.Electrodepositionprovidesan
excellent tool for exploring new science and developing electronic
materials, especially for fabricating large-area devices. This method
can also be used to deposit materials on selected parts of electronic
devices or circuitry with any shapes of the substrate.
3.4 Experimental Evidence
3.4.1
Observations in XRD
ElectrodepositionofZnSeandmaterialcharacterisationresultshave
beenreportedindetail[15].ZnSelayersgrownbyelectrodeposition
and MBE have been studied by XRD under the same conditions
for comparison. Figure 3.3 shows such an example, and close
observation of the width of the most intense XRD peaks show
that the crystalline property of the electrodeposited layers seems
comparable, if not superior, to that of MBE-grown layers. It is
also noteworthy that the electrodeposited layers are grown on
polycrystalline indium tin oxide (ITO) substrates when compared
to well-ordered GaAs (100) surfaces provided for MBE-grown ZnSe
layers. Therefore, under optimised and favourable conditions, the
electrodeposition technique is capable of producing high-quality
electronic materials forsome semiconductors.
3.4.2
Observations in XRF
An example of X-ray fluorescence (XRF) results for electrodeposited
CuInSe
2
is shown in Fig. 3.4 [16]. This graph shows the variation
of atomic percentage as a function of growth voltage for a two-
electrode electrodeposition system. These results demonstrate that
