Journal of Electronic Materials, vol.47, no.12, pp.6945-6953, 2018 (Journal Indexed in SCI Expanded)
© 2018, The Minerals, Metals & Materials Society.In this research, bismuth sulfide nanostructures were prepared in the presence of polyvinyl alcohol (PVA) as a capping agent by an ultrasound-assisted method. The x-ray diffraction results show the crystalline phase of the sample and the mean crystalline size estimated by Debye–Scherer’s equation. The UV–Vis absorption spectrum show that the optical absorbance edge of Bi2S3 nanostructure was blue-shifted. The Fourier transform infrared spectra confirm the presence of PVA in the sample and transmission electron microscopy imaging shows that the structures are in nanoscale. The semi-logarithmic forward bias I–V plots have two distinct linear regimes for each temperature which are called low- and moderate-bias regions (LBR and MBR). In order to effectively interpret possible current-conduction/transport mechanisms, the reverse saturation current (Io), ideality factor (n) and zero-bias barrier height (ΦBO) were obtained from the slope and intercept of these plots and they were found to be a strong function of temperature and voltage. The high value of n even at high temperature and the increase of ΦBO with increasing temperature for the two regions is clear evidence of the deviation from thermionic emission (TE) theory. Therefore, ΦBO versus n and q/2kT plots were drawn to get evidence of the Gaussian distribution (GD) of the barrier height (BH) and they show a linear behavior. The mean values of BH (Φ ¯ BO) and standard deviation (σs) were also obtained from the intercepts and slopes of the ΦBO versus q/2kT plots as 1.44 eV and 0.19 V for the LBR and 1.32 eV and 0.18 V for the MBR, respectively. After that, the values Φ ¯ BO and effective Richardson constant (A*) were obtained as 1.29 eV and 267.6 A/(cm K)2 for the LBR and 1.27 eV and 281.7 A/(cm K)2 for the MBR, respectively. Such non-ideal I–V–T characteristics for the Al/(PVA-Bi2S3)/p-Si structure can be successfully explained by the single GD of BH for the LBR and MBR.