Epitaxial Growth and Optical Properties of Laser Deposited CdS Thin Films

In this study, cadmium Sulfide (CdS) thin films were synthesized on quartz substrates using an infrared pulsed laser deposition (IR-PLD) technique under high vacuum (~10−6 Torr) conditions. X-ray diffraction was used to evaluate the structural features. According to X-ray analysis, the deposited CdS films are crystalline and have a favored orientation on a plane (110) of an orthorhombic. The peak intensity and the average crystallite size increases with increasing the film thickness. After annealing at 300 °C, the orthorhombic phase transformed into a predominant hexagonal phase and the same result was obtained by SEM photographs as well. Spectrophotometric measurements of transmittance and reflectance of the CdS films were used to derive optical constants (n, k, and absorption coefficient α). The optical band gap energy was found to be 2.44 eV. The plasma plume formation and expansion during the film deposition have also been discussed. The photocurrent response as a function of the incident photon energy E (eV) at different bias voltages for different samples of thicknesses (85, 180, 220 and 340 nm) have been studied, indicating that the photocurrent increases by increasing both the film thickness and photon energy with a peak in the vicinity of the band edge. Thus, the prepared CdS films are promising for application in optoelectronic field.

Cadmium Sulfide (CdS) Thin Films with Improved Morphology for Humidity Sensing by Chemical Bath Deposition at Lower pH

Cadmium sulfide (CdS), an II–VI group semiconductor material, is one of the most investigated semiconductors in thin film form. In this work, we synthesized CdS thin films with improved film morphology in the presence of ethylene diamine (EA) as the complexing agent by chemical bath deposition (CD) at lower pH. Detailed characterization reveals the presence of cubic phase CdS with a band gap of 2.39 eV with the resultant morphology significantly influenced by the composition of the growth solution. The resultant CdS films finds prospective application as a humidity sensor with a high sensor response of 2.61 corresponding to 80% relative humidity.

CdS/PbSe Heterojunction Made via Chemical Bath Deposition and Ionic Exchange Processes to Develop Low-Cost and Scalable Devices

Complete optoelectronic devices present major difficulties that are caused by aqueous chemical deposition. In this work, a ITO/CdS/PbSe heterostructure was developed, depositing CdS over an ITO-coated substrate via a chemical bath deposition (CBD) technique. The next step involved the growth of a plumbonacrite film over CdS via CBD, where the film acted as a precursor film to be converted to PbSe via ion exchange. The characterization of each material involved in the heterostructure were as follows: the CdS thin films presented a hexagonal crystalline structure and bandgap of 2.42 eV; PbSe had a cubic structure and a bandgap of 0.34 eV. I vs. V measurements allowed the observation of the electrical behavior, which showed a change from an ohmic to diode response by applying a thermal annealing at 150 °C for 5 min. The forward bias of the diode response was in the order of 0.8 V, and the current-voltage characteristics were analyzed by using the modified Shockley model, obtaining an ideality factor of 2.47, being similar to a Schottky diode. Therefore, the reported process to synthesize an ITO/CdS/PbSe heterostructure by aqueous chemical methods was successful and could be used to develop optoelectronic devices.

Epitaxial Growth and Optical Properties of Laser Deposited CdS Thin Films

Cadmium Sulfide (Cds) thin films were synthesized on quartz substrates using infrared pulsed laser deposition (IR-PLD) technique under high vacuum (~ 10− 6 Torr). X-ray diffraction was used to evaluate the structural features. According to X-ray analysis the deposited CdS films are crystalline and have a favored orientation on a plane (110) of an orthorhombic system and the peak intensity and the average crystallite size increases with increasing the film thickness. After annealing at 300oC the orthorhombic phase transformed into predominant hexagonal phase and the same result was obtained by SEM photographs. Spectrophotometric measurements of transmittance and reflectance of the Cds films were used to derive optical constants (n, k and absorption coefficient α). The optical band gap energy was found to be 2.44 eV. The plasma plume formation and expansion during the film deposition have been discussed. The photocurrent response as a function of the incident photon energy E (eV) at different bias voltages for different samples of thicknesses (85, 180, 220 and 340 nm) have been studied, indicating that the photocurrent increases by increasing both the film thickness and photon energy with a peak in the vicinity of the band edge. Thus, the prepared Cds films are promising for application in optoelectronic field.