There is increasing attention paid to improving transparent conductive electrodes for applications in large area photovoltaic devices and displays that are being developed for energy and electronics. ...To date, transparent and conductive oxides (TCO) based on In
2O
3, ZnO, or SnO
2 are commonly used, but advanced devices require new electrodes with lower resistivities than previously achieved and with optical properties superior to those of the present generation. TCO/metal/TCO multilayer structures have emerged as an interesting alternative because they provide optical and electrical characteristics globally superior to those attainable with a single-layer TCO or metal electrode and can be deposited at low temperatures onto inexpensive plastic substrates. Indeed, the fabrication of thin film devices on flexible substrates has substantial interest for application to lightweight products and implementation of roll-to-roll deposition processes that can significantly reduce production costs. In this sense, organic electronics that require low deposition temperatures have the best chance to be the first transferred from conventional glass to inexpensive plastic substrates. The present critical review summarizes current TCO/metal/TCO research results, first analyzed for materials and thickness selection as a function of the optical transmittance and electrical resistance parameters, and then analyzed according to other important properties such as mechanical reliability and thermal and humidity stability. The review concludes with a brief discussion of the results obtained for TCO/metal/TCO structures applied as electrodes in several organic electronic devices.
This year is the 125th anniversary of the first synthesis of V2O5 gels. The fascinating properties and wide application range of V2O5 thin films have attracted significant attention over the past ...decades. Its wide optical band gap, layered structure, good chemical and thermal stability and excellent thermoelectric and electrochromic properties have made V2O5 a promising material for industrial applications such as gas sensors, electrochromic devices, optical switching devices, and reversible cathode materials for Li batteries. Gels were the first form in which V2O5 was synthesized at the end of the 19th century. Interest started to grow in the 1980s due to the discovery of their semiconducting properties and their use in antistatic coatings in the photographic industry. The rapid development of the sol–gel process brought new interest in V2O5 gels. Following a short discussion of vanadium oxides and V2O5, I summarize all thin film preparation techniques known up to now and use reported optical band gaps to characterize different growth methods. An estimation of the Bohr radius for V2O5 is also presented. This article provides an up-to-date review of more than a century (1885–2010) of research on the growth of vanadium oxide thin films. Nonetheless, due to the huge number of publications in the field, only those are selected and described which, according to the author, contribute the most to the field's further development.
In this work, we study the crystallization and electrical resistivity of the formed oxides in a Cu/SiO2/Si thin film after thermal oxidation by ex-situ annealing at different temperatures up to ...1000°C. Upon increasing the annealing temperature, from the X ray diffractogram the phase evolution Cu→Cu+Cu2O→Cu2O→Cu2O+CuO→CuO was detected. Pure Cu2O films are obtained at 200°C, whereas uniform CuO films without structural surface defects such as terraces, kinks, porosity or cracks are obtained in the temperature range 300–550°C. In both oxides, crystallization improves with annealing temperature. A resistivity phase diagram, which is obtained from the current–voltage response, is presented here. The resistivity was expected to increase linearly as a function of the annealing temperature due to evolution of oxides. However, anomalous decreases are observed at different temperatures ranges, this may be related to the improvement of the crystallization and crystallite size when the temperature increases.
► The crystallization and electrical resistivity of oxides in a Cu films are studied. ► In annealing Cu films, the phase evolution Cu+Cu2O→Cu2O→Cu2O+CuO→CuO occurs. ► A resistivity phase diagram, obtained from the current–voltage response, is presented. ► Some decreases in the resistivity may be related to the crystallization.
Thin films of copper oxide were obtained through thermal oxidation (100–450
°C) of evaporated metallic copper (Cu) films on glass substrates. The X-ray diffraction (XRD) studies confirmed the cubic ...Cu phase of the as-deposited films. The films annealed at 100
°C showed mixed Cu–Cu
2O phase, whereas those annealed between 200 and 300
°C showed a single cubic Cu
2O phase. A single monoclinic CuO phase was obtained from the films annealed between 350 and 450
°C. The positive sign of the Hall coefficient confirmed the p-type conductivity in the films with Cu
2O phase. However, a relatively poor crystallinity of these films limited the p-type characteristics. The films with Cu and CuO phases show n-type conductivity. The surface of the as-deposited is smooth (RMS roughness of 1.47
nm) and comprised of uniformly distributed grains (AFM and SEM analysis). The post-annealing is found to be effective on the distribution of grains and their sizes. The poor transmittance of the as-deposited films (<1%) is increased to a maximum of ∼80% (800
nm) on annealing at 200
°C. The direct allowed band gap is varied between 2.03 and 3.02
eV.
Increasing performance demands and shorter use lifetimes of consumer electronics have resulted in the rapid growth of electronic waste. Currently, consumer electronics are typically made with ...nondecomposable, nonbiocompatible, and sometimes even toxic materials, leading to serious ecological challenges worldwide. Here, we report an example of totally disintegrable and biocompatible semiconducting polymers for thin-film transistors. The polymer consists of reversible imine bonds and building blocks that can be easily decomposed under mild acidic conditions. In addition, an ultrathin (800-nm) biodegradable cellulose substrate with high chemical and thermal stability is developed. Coupled with iron electrodes, we have successfully fabricated fully disintegrable and biocompatible polymer transistors. Furthermore, disintegrable and biocompatible pseudo-complementary metal–oxide–semiconductor (CMOS) flexible circuits are demonstrated. These flexible circuits are ultrathin (<1 μm) and ultralightweight (∼2 g/m²) with low operating voltage (4 V), yielding potential applications of these disintegrable semiconducting polymers in low-cost, biocompatible, and ultralightweight transient electronics.
Compositional dependences of the optoelectronic properties of sol–gel derived CdO–ZnO composite films with volume ratio of Cd:Zn ranging from 1:0 to 0:1 (with a step of 1/4) have been studied. After ...heat treatments in air the prepared thin films were investigated by studying their structural, morphological, d.c. electrical and optical properties. X-ray diffraction (XRD) results suggest that the samples are polycrystalline and the crystallinity of them increased with Cd ratio. The average grain size is in the range of 20–53
nm. As composition and structure changed due to the Cd volume ratio, the order of the carrier concentration was varied from 10
16 to 10
20
cm
−3 with Cd ratio and the mobility increased from less than 2 to 45
cm
2
V
−1
s
−1. It was found that the transmittance and the band gap decreased as Cd ratio increased. The optical constants of the film were studied and the dispersion of the refractive index was discussed in terms of the Wemple–DiDomenico single oscillator model. The real and imaginary parts of the dielectric constant of the films were determined too. The volume energy loss (VELF) increases more than the surface energy loss (SELF) at their particular peaks. The third-order nonlinear polarizability parameter is higher for CdO–ZnO thin films with higher concentration of cadmium oxide.
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• Physical properties of the sol–gel derived CdO–ZnO nanostructured thin films prepared at different Cd content have been investigated. • The carrier concentration and carrier mobility of the samples were increased with Cd ratio whereas the resistivity was decreased. • The direct optical band gap shifted to the lower energy. • The refractive index and extinction coefficient increase with the increasing of Cd content. • The single-oscillator energy values are correlated with the optical band gap values by an empirical relation:
E
o
≈
2
E
g
. • With the increase in Cd content nonlinear optical susceptibility
χ
(3) increases.
Compositional dependence of the optoelectronic properties of sol–gel derived CdO–ZnO composite films with volume ratio of Cd:Zn ranging from 1:0 to 0:1 (with a step of 1/4) has been studied. After heat treatments in air the prepared thin films were investigated by studying their structural, morphological, d.c. electrical and optical properties. X-ray diffraction (XRD) results suggest that the samples are polycrystalline and the crystallinity of them increased with Cd ratio. The average grain size is in the range of 20–34
nm. As composition and structure changed due to the Cd volume ratio, the order of the carrier concentration was varied from 10
16 to 10
20
cm
−3 with Cd ratio and the mobility increased from less than 2 to 45
cm
2
V
−1
s
−1. It was found that the transmittance and the band gap decreased as Cd ratio increased. The optical constants of the film were studied and the dispersion of the refractive index was discussed in terms of the Wemple–DiDomenico single oscillator model. The real and imaginary parts of the dielectric constant of the films were also determined. The volume energy loss (VELF) increases more than the surface energy loss (SELF) at their particular peaks. The third-order nonlinear polarizability parameter is higher for CdO–ZnO thin films with higher concentration of cadmium oxide.
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