Induced conductivity in sol-gel ZnO films by passivation or elimination of Zn vacancies

Abstract

Undoped and Ga-and Al-doped ZnO films were synthesized using sol-gel and spin coating methods and characterized by X-ray diffraction, high-resolution scanning electron microscopy (SEM), optical spectroscopy and Hall-effect measurements. SEM measurements reveal an average grain size of 20 nm and distinct individual layer structure. Measurable conductivity was not detected in the unprocessed films; however, annealing in hydrogen or zinc environment induced significant conductivity (∼10 −2 Ω.cm) in most films. Positron annihilation spectroscopy measurements provided strong evidence that the significant enhancement in conductivity was due to hydrogen passivation of Zn vacancy related defects or elimination of Zn vacancies by Zn interstitials which suppress their role as deep acceptors. Hydrogen passivation of cation vacancies is shown to play an important role in tuning the electrical conductivity of ZnO, similar to its role in passivation of defects at the Si/SiO2 interface that has been essential for the successful development of complementary metal-oxide-semiconductor (CMOS) devices. By comparison with hydrogen effect on other oxides, we suggest that hydrogen may play a universal role in oxides passivating cation vacancies and modifying their electronic properties. © 2016 Author(s)

Observation of Negative Magnetic Hysteresis Loop in ZnO Thin Films

“…We should consider the possible role of grain boundaries on inducing FM, as our structural characterization of the solgel-doped ZnO films [24] indicates a small grain size of about 20 nm. According to a previous work by Hsu et al [38], FM occurs in polycrystalline ZnO films at high grain boundary densities.…”

“…The films were then annealed in air at 500 or 700°C to form a ZnO structure. More details concerning the synthesis of ZnO films by the sol-gel method and their structural characterization can be found in [24].…”

Synthesis of Conductive Sol-Gel ZnO Films and Development of ZnO Printed Electronics

“…Although there is a lack of ZnO phase formation for ZnO 4 on Kapton and an impurity phase for ZnO 3 on TOPAS, Figure 5. XRD measurements for AZO films annealed in various atmospheres [21].…”

“…Although light from the LED produces localized heating, Table 3. Van der Pauw and Hall effect measurements for ZnO, AZO, GZO, and IGZO thin films grown from ZnO solgel precursors, listing the film type, post-processing conditions, resistivity, mobility, and carrier concentration [20,21].…”

“…Many researchers have successfully fabricated ZnO devices at low cost and relatively low temperature by way of printing sol-gel precursor and other nanoparticlebased inks [11][12][13][14][15][16][17][18][19][20]. In addition, the authors of this chapter have successfully fabricated ZnO transparent conductive oxides (TCOs) using a simple sol-gel, spin coating technique [21]. Research efforts utilizing sol-gel-derived ZnO thin films for device applications have greatly increased, recently [22][23][24].…”