Electrodeposition of 3-D Size-Quantized Cds and CdSe Films

Abstract

CdS and CdSe films electrodeposited from chalcogen-containing non-aqueous electrolytes are shown to possess a nanocrystalline structure and exhibit 3-D quantum size effects. A large variation in optical transmission spectra, due for the most part to this sizequantization, is shown. Photoelectrochemical activity of the as-deposited films is discussed in terms of their nano-structure. Extension of the crystallite size effects to a metalinsulator transition in MoO2 deposited from a similar electrolyte is mentioned.

Nanocrystal size control by bath temperature in electrodeposited CdSe thin films

“…The bandgap values of the films can be obtained by linear extrapolation of the curves to zero absorption. It is found that the bandgap increases as the bath temperature is lowered, which is in agreement with earlier reports by Hodes et al, 27 the estimated bandgap values for the as-prepared films deposited at 180, 160, 150, 140 and 130 uC are 1.75, 1.79, 1.87, 1.96 and 2.03 eV, respectively. In addition, a blue shift in the absorption spectra has also been shown in electrodeposited CdSe and CdS when chloride was used instead of perchlorate, which was attributed to the blocking of nanocrystal growth by the strongly adsorbed halide anion.…”

Semiconductor and ceramic nanoparticle films deposited by chemical bath deposition

“…If the nanocrystals are small enough, which they often are, they exhibit size quantization, the most obvious manifestation of which is an increase in the optical bandgap with decrease in crystal size as was shown first for CBD CdSe 8 and shortly after for PbSe. 9 Subsequently, a wide range of CBD semiconductor films exhibiting size quantization has been reported. However, size quantization is not the only reason for the growing interest in these nanocrystalline films and even somewhat larger crystals, which do not exhibit size quantization, are studied for a range of reasons.…”

Photoelectrochemical Charge Transfer Properties of Electrodeposited CdSe Quantum Dots

“…This difference between the two anions has been reported previously for much thicker films. 13 It is believed to be due to surface capping by adsorbed chloride ions, blocking the growth of the nanocrystals. 14 Nanocrystallite size distributions for all of these films are shown in Figure 2.…”

“…The same trend was noticed in much thicker (> 100 nm) films of CdSe nanocrystals deposited in a similar manner. 13 Possible explanations for this difference are the different surface properties of the two films or bulk recombination in the larger perchlorate-deposited crystals.…”