Structural and optical characterization of CdSe films grown by Chemical Bath Deposition

We present in this work experimental results and their analysis concerning the structuraland optical characterization of cadmium selenide (CdSe) films grown by the Chemical Bath Deposition (CBD) technique, at different bath temperatures T_d : 0≤T_d≤80 °C. Structural characterization was carried out by using X-ray diffraction, whereas optical characterization was done by using optical absorption and photoluminescence spectroscopies. X-ray results showed a change of the crystalline structure as a function of T_d, from the zincblende to wurzite one when T_d increases from 0 to 80 °C. The respective band-gap, E_g, was calculated from the absorption spectrum giving rise to values in the range 1.85 to 2.30 eV, as a function also of T_d. Thses values are higher than the well accepted value of 1.75 eV for the CdSe bulk material. The radiative emission was analyzed throughout the photoluminescence (PL) spectra. All samples showed radiative emission above the band-gap, at room temperature, this radiative emission having a dependence on the pressure inside the cryostat. A quenching of the PL signal is observed when the pressure is decreased at values as low as 60 mTorr.