Titanium dioxide nanotubes in chloride based electrolyte: an alternative to fluoride based electrolyte

Often, fluoride based electrolyte was applied to synthesize highly ordered titanium dioxide nanotubes. However, in the present work, bundled titanium dioxide nanotubes were fabricated in chloride based electrolyte through electrochemical method. Structural and morphological investigations were carried out on the nanotubes synthesized under different anodization parameters. The growth mechanism of such nanotubes was elucidated and illustrated. The estimated diameter of the as-anodized nanotube was less than 150 nm while the length varied from hundreds of nanometer to microns. X-ray diffraction patterns and Raman spectra have showed anatase and rutile phases of titanium dioxide within the thermally treated samples

Preliminary Studies of Porous GaNbased Dye-Sensitized Solar Cells

This work presents the preliminary studies of porous gallium nitride (GaN) based dye-sensitized solar cells (DSSC). Porous GaN was fabricated using photo-assisted electrochemical etching (PEC), then characterized in terms of its morphological, structural, optical and vibrational aspects. Next, the sample underwent sensitization through immersing in N719 ruthenium based dye for one day. For the DSSC assembly, the dyed porous GaN would serve as anode while platinum (Pt) coated fluorinedoped tin oxide (FTO) glass being the cathode. A thin glass spacer separates the anode/cathode, while triiodide/iodide redox electrolyte would fill the gap between them. Current density-voltage (J-V) curves was obtained under light illumination and used to determine the essential electrical parameters of the DSSC. The open circuit potential <Voc). short-circuit current density (Jsc). and efficiency (TJ) for the aforementioned were 638.8 mV, 0.81 mA/cm2 , and 0.2% respectively. Aside from that, similar works have been repeated here for as-grown GaN, however, the resultant efficiency was ten times lower than that of porous GaN

Preliminary Studies of InGaON Thin Film on Si Substrate Using Simple Growth Technique

In this paper, we present a simple growth setup which is able to grow indium gallium oxynitride (lnGaON). This setup only involves furnace, ammonia gas, as well as gallium (Ga) and indium (In) sources. The characterization results heavily implied the growth of lnGaON on silicon (Si) substrate. Firstly energy-dispersive x-rays (EDX) measurement confirmed the presence of In, Ga, 0 and N. Despite 0 being significant, Fourier transform infra-red (FTIR) spectroscopy and x-rays diffraction (XRD) results revealed the absence of metal oxides signals. Further analysis from both measurements showed the sample contained high In content, with crystalline structure resembled that of lnGaN, and was of (001) dominance

Astronomical Distance Determination in the Space Age: Secondary Distance Indicators

The formal division of the distance indicators into primary and secondary leads to difficulties in description of methods which can actually be used in two ways: with, and without the support of the other methods for scaling. Thus instead of concentrating on the scaling requirement we concentrate on all methods of distance determination to extragalactic sources which are designated, at least formally, to use for individual sources. Among those, the Supernovae Ia is clearly the leader due to its enormous success in determination of the expansion rate of the Universe. However, new methods are rapidly developing, and there is also a progress in more traditional methods. We give a general overview of the methods but we mostly concentrate on the most recent developments in each field, and future expectations. © 2018, The Author(s)

Growth of gallium nitride thin film with the aid of polymethyl methacrylate

Wurtzite structure gallium nitride (GaN) thin film was grown on a c-plane sapphire (0001) substrate through spin coating method followed by nitridation process. Readily available and cheap gallium (III) nitrate hydrate (Ga(NO3)3·xH2O) powder was used as the gallium source. Besides that, ethanol-based precursor solution which has better wetting properties and fast evaporation rate was prepared. In addition, a thin layer of polymethyl methacrylate was introduced as a bonding adhesive layer for the growth of the GaN thin film. X-ray diffraction results indicated that the deposited film consists of nanocrystallite GaN with hexagonal wurtzite structure. Field-emission scanning electron microscopy showed the morphologies of the small and well-defined spherical grains that coated on the substrate. The synthesized GaN thin film demonstrated a pronounced and broad exciton peak at 380 nm in Photoluminescence spectrum. Raman scattering measurements showed two features that correspond to the E2 (high) and A1 (LO) phonon modes of the hexagonal GaN

Properties of Porous InGaNbased Hydrogen Gas Sensor

The research of porous Ill-Nitrides has drawn much attention in the past years. This is due to porous Ill-Nitrides excellent properties such as high surface area to volume ratio, the shift of band gap and efficient luminescence which makes the porous Ill-Nitrides become attractive for the application in optoelectronics and sensing devices. In this work, the development of gas sensors based on PtSchottky contact on porous lnGaN for hydrogen gas sensing ispresented. Porous lnGaN samples were successfully fabricated by UV-assisted electrochemical etching in a diluted solution of KOH. ,........._ From the field emission scanning electron microscopy (FESEM) image, the porous lnGaN sample exhibited rough surface morphology with a high density of pores. Subsequently, for the fabrication of gas sensors, Schottky contacts of using platinum (Pt) that acted as catalytic layer were deposited on as-grown and porous lnGaN samples. The effects of porous structure on the performance of the hydrogen gas sensor was investigated. The PUporous lnGaN gas sensor showed higher sensitivity than the as-grown lnGaN gas sensor upon introduction to 0.1% H2 in N2 at room temperature. The high sensitivity of porous gas sensor was due to thehigh surface to volume ratio of the porous structure. The high sensitivity of hydrogen gas sensor is required to make sure the safety of people, property and environment whenever hydrogen gas is consumed

Highly efficient photoelectrochemical and photocatalytic anodic TiO2 nanotube layers with additional TiO2 coating

In this work, strong beneficial effects of thin and uniform TiO2 coatings within TiO2 nanotube layers for photocurrent generation and photocatalytical degradation of methylene blue are demonstrated for the first time. TiO2 nanotube layers were coated by TiO2 of various thicknesses (from 2.8 nm to 22 nm) using atomic layer deposition (ALD) and compared with TiO2 nanotube layers decorated by TiO2 nanoparticles (using established TiCl4 treatment) and with blank (uncoated) layers. By means of photocurrent measurements and cyclic voltammetry, it is demonstrated that the most efficient charge carrier separation can be achieved for TiO2 nanotube layers with an optimal ALD TiO2 coating thickness ≈11 nm. Significant differences in flatband potentials and carrier density among all nanotube layers were revealed by Mott-Schottky measurements. Photocatalytic decomposition rates for methylene blue solutions were significantly enhanced for ALD TiO2 coated TiO2 nanotube layers compared to their uncoated or TiO2 nanoparticles - decorated counterparts. A perfect agreement in trends was obtained for photocurrent and photocatalytic results

Comment about the use of unconventional Tauc plots for bandgap energy determination of semiconductors using UV–Vis spectroscopy

The Tauc method is the conventional technique for estimating the accurate optical bandgap energy of semiconductors using UV–Vis spectroscopy. The proper bandgap is usually determined by directly extrapolating the linear region of the optical spectrum to the horizontal axis of the Tauc plot αhv1/r vs. hv. However, the use of unconventional Tauc plots, such as α1/r vs. hv, A1/r vs. hv, and FR∞ vs. hv are also found in the literature. This raises a debate as to whether these nontraditional methods can produce the correct bandgap value. These uncommon methods appear frequently even in recent papers published in reputable journals, and therefore, have raised concern to investigate the likelihood of obtaining the correct bandgap value using the unusual methods. Results showed that the plots of α1/r vs. hv, and A1/r vs. hv yielded bandgap values that were consistent with those deduced from the universal Tauc plot, whereas the other methods failed