Growth and Characterization of Indium-Doped Zinc Oxide Thin Films Prepared by Sol-Gel Method

Abstract

Indium-doped ZnO thin films were deposited by sol-gel spin-coating method with various In content. The effects of In content on the structural and optical properties of the indium-doped ZnO thin films were investigated by scanning electron microscopy, X-ray diffraction, and UV-visible spectroscopy. The particle-like surface morphology and the crystallinity of the indium-doped ZnO thin films were affected by change in the In content, especially at the In content of 3 at.%. The values of direct band gap were decreased with increase in the In content. The width of localized states in the optical band gap of the indium-doped ZnO thin films were changed with In content and the Urbach energy (E U ) was changed inversely with optical band gap of the indium-doped ZnO thin films.

Improvement in electrical properties of sol–gel-derived In-doped ZnO thin film by electron beam treatment

“…2a). The red shift of the band gap of the ZnO film induced by In doping is consistent with previous reports [24,39,40] and can be explained by the variation of the Urbach energy, E U [41]. Urbach energy can be calculated using the following formula: Figure 3 shows the Urbach plot of ZnO thin films with different In-doping levels.…”

Optical properties and electrical resistivity of boron-doped ZnO thin films grown by sol–gel dip-coating method

“…The energy band widening of BZO thin films is common phenonmenon and reported in the previous studies [35][36][37]. The shift in the optical band gap is because of the Burstein-Moss shift and the energy band widening (blueshift) effect resulting from the increase in the Fermi level of the conduction bands of degenerate semiconductors [33,38,39]. The donor electrons in the doped semiconductors occupy states at the bottom of the conduction band.…”

“…Therefore, the decrease in the transmittance of the thin film doped with 2.5 at.% B might be attributed to the fact that the higher concentration of B increased the number of ionized impurity in the thin films, thus increasing the degree of light scattering in the thin films. The absorption coefficient (a) for a direct-transition semiconductor material obeys the following relation with respect to the optical band gap (E g ) [33,34]:…”

“…The absorption coefficients for the thin films were obtained using the equation I = I 0 e Àad , where I and I 0 represent the intensities of the transmitted and incident light, respectively. Considering interfaces related to the thin films and the thin films thickness in practical experiments, the transmittance and reflectance of the ZnO-based materials obey the following equation [33]:…”

Sol-Gel Processed Indium-Doped Zinc Oxide Thin Films and Their Electrical and Optical Properties

“…The degree of the blue shift depended on both indium content and vacuum annealing. A recent report [22] on spin-coated (IZO) films has shown that the values of direct band gap decreased with increase in the In content.…”