Abstracts Book - IMRC 2018

• SC4-P036
EFFECT OF AMMONIUM HYDROXIDE CONCENTRATION AND THE
DRIP TIME OF THIOUREA ON THE PROPERTIES OF CdS THIN FILMS
DEPOSITED BY CBD
Valeria Detzani Moreno Regino 1 , Fátima Montserrat Castañeda de la Hoya 1 , Carlos Gerardo
Torres Castanedo 2 , Joaquín Márquez Marín 1 , Rebeca Castanedo Pérez 1 , Gerardo Torres
Delgado 1 , Orlando Zelaya Ángel 3
1 Centro de Investigación y de Estudios Avanzados del IPN - CINVESTAV, Unidad Querétaro,
Mexico. 2 King Abdullah University of Science and Technology, Advanced Semiconductor
Laboratory, Saudi Arabia. 3 Cinvestav Zacatenco, Física, Mexico.
Cadmium sulfide (CdS) is a widely studied semiconductor due to its use as n-
type window material in CdTe based solar cells. CdS thin films have been mainly
obtained by chemical bath deposition (CBD) since solar cells with the highest
efficiencies have been obtained them. CBD technique parameters such as bath
temperature (Tb), Cd/S ratio, and pH in the solution have been studied. However,
other ones should have significant effects on the properties of the films. In this
work, CdS thin films were deposited on glass substrates by CBD technique at
constant Tb, 90°C. The reaction was obtained by incorporating cadmium acetate,
ammonium acetate, ammonium hydroxide, thiourea, and deionized water as an
aqueous medium. The optical, electrical and structural properties of the films
were studied by modifying the concentration of ammonium hydroxide and the
time (tg) in which the incorporation of thiourea is carried out (using a constant
drip). Also, the presence of organic impurities and the radiative transitions were
studied by FTIR and photoluminescence, respectively. XRD measurements show
that all the CdS films are polycrystalline cubic zinc-blende with preferred
orientation along the (111) plane. The resistivity of the films increased 10 2 to 10 7
Ω-cm by increasing the concentration of ammonium hydroxide. On the other
hand, films deposited with 20 ml of this reagent at different tg´s, lead to low
resistivity values (~ 10 2 Ω-cm). The transmission spectra of these films show
a slight decrease both when increasing the concentration of ammonium
hydroxide and the tg. The main organic impurity was cyanamide, and its
presence was modified with the variation of the parameters studied. Finally, the
films showed mainly two radiative transitions at 2.27 eV and 1.79 eV attributed
to interstitial cadmium and sulfur vacancy, respectively. For films with the lowest
thicknesses, the band at 2.98 eV associated to nanoparticles was observed with
low intensity.
Acknowledgment: