Highly transparent, conducting, highly oriented, and almost single phase ZnO films have been deposited by simple e-beam evaporation method, and the deposition parameters were optimized. The films were prepared by (a) evaporation of ZnO at different substrate temperatures and (b) evaporation of ZnO at room temperature and subsequent annealing of the films in oxygen ambient at different temperatures. The characterizations of the film were performed by optical absorption spectroscopy (UV-visible), Fourier transform infrared spectroscopy, resistivity measurement, transmission electron microscopy (TEM), photoluminescence, and x-ray diffraction measurement. Absorption spectra revealed that the films were highly transparent and the band gap of the pre- and postannealed films was in good agreement with the reported values. The band gap of the films increases on increasing the substrate temperature as well as annealing temperature, whereas the resistivity of the film decreases with substrate temperature and increases with annealing temperature. Fourier transform infrared spectroscopy of ZnO films confirms the presence of Zn–O bonding. X-ray diffraction, electron diffraction, and TEM images with high resolution and Raman spectra of the films showed the formation of crystalline ZnO having wurtzite structure
Scanning Kelvin probe microscopy has been used to understand the modification of work function of TiO2 with swift heavy ion irradiation. The observed increase in contact potential difference (CPD) indicates a shift in Fermi level towards the valence band, which is due to the development of defects during the bombardment of high energy heavy ions. The change in CPD values on ion irradiation is attributed to electronic excitation induced defect concentration and surface roughness.
Conducting nanowires parallel to each other, embedded in fullerene matrix are synthesized by high energy heavy ion irradiation of thin fullerene film at low fluence (up to 5×1011ions∕cm2). The conductivity of the conducting zone is about seven orders of magnitude higher than that of the fullerene matrix. The conducting nanowires are evidenced by conducting atomic force microscopy. The typical diameter of the conducting tracks is observed to be about 40–100nm. The creation of conducting wires is explained by transformation of fullerene to conducting form of carbon in the ion track, surrounded by the polymerized zone. The polymerization of fullerene is evidenced by Fourier transform infrared spectroscopy.
The present work focuses on photocatalytic performance of Ag-TiO2 systems. Nanocrystalline thin films of TiO2-and Ag-doped TiO2 are grown by sol–gel method, followed by spin-coating technique on Si ⟨100⟩ surface. The crystallinity and crystal size were measured from X-ray diffraction and transmission electron microscopy studies. Lateral distribution of work function (WF) was examined through contact potential difference measurement done by scanning Kelvin probe microscopy. Local WFs of Ag-TiO2 thin films were found to be smaller than that of TiO2, and the minimum WF expected from the polynomial curve fitting was that of pure Ag. The photocatalytic efficiency of these thin films is estimated from photodegradation of methyl orange analyzed by UV–vis spectrophotometer. The photodegradation efficiency of Ag-TiO2 nanocrystalline thin films increases up to a certain dopant concentration of silver, beyond which it decreases. The changes in the photodegradation efficiency of these films are correlated with variation in contact potential difference.
Magnetic measurements using a superconducting quantum interference device and magnetic force microscopy were performed on fullerene films irradiated with 250 keV Ar and 92 MeV Si ions, to compare the effects of electronic excitation and collisional cascade on the magnetization. A ferromagnetic behavior increasing with ion fluence is observed. The magnetization is attributed to (i) the formation of an amorphous carbon network and (ii) the incorporation of oxygen in the irradiated films
Micro-light-emitting diodes (μLEDs) are getting much attention in display industry because of their outstanding optical and electrical characteristics. μLEDs have several advantages over liquid crystal displays (LCDs) and organic lightemitting diodes (OLEDs). μLEDs are showing long lifetimes, high reliability, high power efficiencies, high brightness, and fast response times with tiny pixels. However, for commercial usage, the high production cost and low external quantum efficiency (EQE) are the major hurdles. In this review, we briefly discuss the breakthroughs in μLED technology, fabrication methods, optical/ electrical characteristics, and challenges for display applications. In addition, the development of monolithic μLEDs and general device characteristics combined with various quantum dot patterning processes are systematically discussed. Potential solutions to address these challenges are also presented case by case.
This article reports on the formation and electronic characteristics of conducting carbon nanowires produced by swift heavy ion irradiation of a fullerene thin film. This study shows that it is possible to create arrays of carbon nanowires, which are perfectly parallel to each other and perpendicular to the substrate. As-deposited fullerene films exhibit poor field emission characteristics with breakdown fields as high as 51 V / m, whereas low dose ion irradiated fullerene film produces a threshold field as low as 9 V / m. The present approach of making conducting carbon nanowires by ion irradiation for potential field emitters and large area applications is also discussed.
In the presence of ultraviolet light, TiO 2 photocatalyst finds a lot of applications in degradation of organic and inorganic particles present in environment as well as in water. TiO 2 nanoparticles can not be utilized effectively in presence of solar light since solar radiation has very little contribution in UV region. The photoresponse of TiO 2 can be shifted to the visible region by nitrogen doping. In the nitrogen-doped TiO 2 lattice, the oxygen vacancies are formed below the conduction band in the form of donor energy level. These vacancies increase with increasing nitrogen concentration in TiO 2 , which results in an increase in the trapping rate. This leads to enhancement of photocatalytic activity of nitrogendoped TiO 2 film. Nitrogen doping results in the creation of defects in nitrogendoped TiO 2 , which in other way leads to a modification of the work function of thin films. The observed changes in work function of these films, measured using scanning Kelvin probe microscopy, indicates the shifting of Fermi level with the introduction of defects. The study of work function as well as surface properties of thin films helps in better understanding of the photo activity of nitrogen-doped TiO 2 film.
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