Facile ultrasound-assisted and microwave-assisted methods for preparation of Bi_2S_3-PVA nanostructures: exploring their pertinent structural and optical properties and comparative studies on the electrical, properties of Au/(Bi_2S_3-PVA)-Si Schottky structure

摘要

Polyvinyl alcohol capped Bi_2S_3 semiconductor nanocrystals were prepared by microwave-assisted and ultrasound-assisted methods after heat treatment in open air at 300 ℃ for 1 h. The optical, structural and morphological properties of them have been characterized by XRD, UV-Visible, FT-IR, SEM, TEM techniques. The XRD pattern shows the formation of nano-crystalline Bi_2S_3 and the UV-Vis spectroscopy results show a blue shift of about 1.5 and 1.6 eV for microwave and ultrasound-assisted methods, respectively. These values are due to the confinement of very small nanostructures. In order to determine electrical characteristics, the SBDs measurements of current, capacitance and conductance versus voltage (I-V, C-V, and G/ω-V) were performed at room temperature. Fermi energy level (EF), donor doping atoms (N_D), and barrier height (Φ_B) values were obtained by C~(-2)-V plots at reverse biases. The voltage dependent profile of series resistance (R_s) was extracted by the Nicollian-Brews method. The energy dependent profiles of N_(ss) were also obtained from the forward bias I-V data by considering voltage dependent ideality factor (n) and effective barrier height (Φ_e) for two type diodes. The values of the rectifying ratio (RR) and BH for the ultrasound -assisted interlayer are found greater than the microwave-assisted interlayer. The double-logarithmic I-V plots show three distinct linear regimes which are corresponding to low, intermediate and high forward biases for two structures and in these regions, the dominant current-transport was found via trap-charge limited current and space-charge-limited-current mechanisms, respectively. The value of BH obtained from the forward bias I-V is lower than at about E_F from the reverse bias C-V measurement because of the nature of measurement techniques. These observations of low leakage current and higher RR, R_(sh) and BH for ultrasound-assisted interlayer MPS structure was confirmed that it has good performance when compared to the microwave-assisted interlayer MPS structure.