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In this study, we applied iron (-oxide) incorporated carbide nanofiber composites as heterogeneous catalysts with wide visible-light absorption ability, catalytic reactivity, and catalytic stability for the highly efficient decomposition performance. Notably, water vapor activated iron (-oxide) incorporated carbide nanofiber catalyst (Act-Fe-CNF) showed high crystalline Fe3O4 phase, saturation magnetization point (17.76 emu/g), and large surface area (508.2 m2/g). In water vapor activation, Fe3C particles inside carbide nanofiber oxidized and aggregated to larger Fe3O4 particles, thereby forming a meso/macroporous structure and improving surface area offering more available active sites for catalytic reactivity. Under both UV-/real solar-light irradiation, it was demonstrated that the Act-Fe-CNF catalysts exhibited unprecedentedly excellent removal capabilities (>98%, [k] = 4.06 h−1) for rhodamine B, leading to complete water purification. Interestingly, the AF-CNFs catalysts also showed strong antimicrobial activities against gram-negative Escherichia coli (E. coli) and gram-positive Staphylococcus aureus (S. aureus) under incandescent-light irradiation. These results indicated that the Act-Fe-CNF catalysts might have utility in important environmental and bio-medical applications.

Recent studies have shown that expanded graphite (EG) is a suitable substrate for combining iron oxide nanoparticles (IONPs). However, the low density and insignificant hydrophobicity of pristine EG hinder its applicability in wastewater treatment systems. Herein, iron oxide (IO)-combined EG nanocomposites (IO/EGs) were prepared using an underwater plasma discharge process, which is a fast and simple method for synthesizing composites. The IO/EGs produced by this method are complex combinations of the FeOOH and γ –Fe2O3 phases, whose compositions vary as the IO precursor content changes between 20 and 60 wt.%. Compared with pristine EG, the IO/EGs with varying IO precursor contents (IOx/EGs) exhibited approximately six times higher surface areas (>100 m2/g), nearly double zeta potential values (>39 mV), and excellent heavy-metal removal efficiencies. The excellent heavy-metal removal efficiencies (>80% within 10 min, [k] = 2.30 h−1, qe; ≥ 125 mg/g) of IO20/EGs are attributed to their high specific surface areas (117.5 m2/g), relatively positive surface potentials (41.76 mV), and abundant reactive active sites (hydroxyl group). Overall, this study demonstrates that the simple and fast combined IOx/EGs are suitable adsorbents for removing heavy metals from polluted solutions.

We have developed a template-free, easily controllable, and simple method for the mass production of hydrogenated iron oxide nanoparticles (NPs). These NPs were formed with a regular spherical shape by underwater plasma discharge treatment at room temperature and atmospheric pressure. The various phases of well-crystallized iron oxide NPs were carefully monitored by controlling the amount of hydrazine. Further, the obtained Brunauer–Emmett–Teller surface area of 67.86 m2/g was much larger than that of a commercial sample (32.40 m2/g), which was further increased to 85.07 m2/g by adjusting the amount of hydrazine. The removal efficiency for heavy metal and organic dyes was obtained to be ~100%, which was 10 times faster than that of the commercial sample. Furthermore, ~100% flocculation efficiency was obtained by using only 6 g/g microalgal cell of the prepared iron oxide, whereas no significant change was observed for commercial iron oxide irrespective of the amount of flocculant. These excellent efficiencies for the removal of pollutant from waste water can be originated in the high specific surface area, relatively positively charged surface, and good crystallinity of the synthesized samples. These indicate that the hydrogenated iron oxide NPs in this study are potentially useful for water purification by serving as an adsorbent, photocatalytic material, and flocculant.

While non-polar nanostructured-GaN crystals are considered as a prospective material for the realization of futuristic opto-electronic application, the formation of non-polar GaN nanocrystals (NCs) with highly efficient visible emission characteristics remain unquestionable up to now. Here, we report the oxygen-incorporated a-plane GaN NCs with highly visible illumination excitonic recombination characteristics. Epitaxially aligned a-plane NCs with average diameter of 100 nm were formed on r-plane sapphire substrates by hydride vapor phase epitaxy (HVPE), accompanied by the oxygen supply during the growth. X-ray photoemission spectroscopy measurements proved that the NCs exhibited Ga-O bonding in the materials, suggesting the formation of oxidized states in the bandgap. It was found that the NCs emitted the visible luminescence wavelength of 400‒500 nm and 680‒720 nm, which is attributed to the transition from oxygen-induced localized states. Furthermore, time-resolved photoluminescence studies revealed the significant suppression of the quantum confined Stark effect and highly efficient excitonic recombination within GaN NCs. Therefore, we believe that the HVPE non-polar GaN NCs can guide the simple and efficient way toward the nitride-based next-generation nano-photonic devices.

We report an optimized multi-step chemical vapor deposition process for growing MoS2 thin films. This process enables large-area processing, film patterning simply by using shadow masks, and precise control of the final thickness by changing the initial thickness of the first step of MoO3 film deposition. The structural characterization of the MoS2 films is performed with transmission electron microscopy and X-ray diffraction as a function of film thickness. MoS2 film with a thickness of 3 nm possesses a highly crystalline structure with a spacing of 0.62 nm. The crystallinity and orientation of the films are degraded with increased film thickness. Careful analysis by time-of-flight secondary ion mass spectroscopy reveals that a film with a thickness of 9 nm is not completely sulfurized, and unreacted MoO3 is left at the bottom of the film. These fundamental analyses coincide with the thickness dependence of thin-film transistor (TFT) performance. A TFT with the optimal film thickness of 3 nm achieves high performance, namely a carrier mobility of 0.57 cm2 V−1 s−1 and an on/off ratio of ~ 102.

Transition metal dichalcogenide MoS2 is a two-dimensional material, attracting much attention for next-generation applications thanks to rich functionalities stemming from its crystal structure. Many experimental and theoretical works have focused on the spin-orbit interaction which couples the valley and spin degrees of freedom so that the spin-states can be electrically controllable. However, the spin-states of charge carriers and atomic vacancies in devices have not been yet elucidated directly from a microscopic viewpoint. Here, we report the spin-states in thin-film transistors using operando electron spin resonance spectroscopy. We have observed clearly different electron spin resonance signals of the conduction electrons and atomic vacancies, and distinguished the corresponding spin-states from the signals and theoretical calculations, evaluating the gate-voltage dependence and the spin-susceptibility and g-factor temperature dependence. This analysis gives deep insight into the MoS2 magnetism and clearly indicates different spin-scattering mechanisms compared to graphene, which will be useful for improvements of the device characteristics and new applications. Identifying the properties of spin-states is crucial for understanding the possible magnetic applications of MoS2 thin-film transistors. Here, spin-states of conduction electrons and atomic vacancies in MoS2 are distinguished and investigated under device operation using electron spin resonance.

We identified optimal conditions for the disposal of high concentration of organic contaminants within a short time using a hybrid advanced oxidation process (AOP) combining various oxidizing agents. Plasma-treated water (PTW) containing many active species, that play dominant roles in the degradation of organic substances like hydroxyl radicals, atomic oxygen, ozone, and hydrogen peroxide, was used in this study as a strategy to improve degradation performance without the use of expensive chemical reagents like hydrogen peroxide. In particular, the optimal decomposition conditions using PTW, which were combined with 10 mg/h ozone, 2 g/L iron oxide, and 4 W UV light, demonstrated excellent removal abilities of a high concentration of reactive black 5 (RB5; 100 mg/L, >99%, [k] = 4.15 h−1) and tetracycline (TC; 10 mg/L, >96.5%, [k] = 3.35 h−1) for 25 min, approximately 1.5 times higher than that without PTW (RB5; 100 mg/L, 94%, [k] = 2.80 h−1). These results confirmed that the production of strong reactive hydroxyl radicals from the decomposition process, as well as various reactive species included in PTW efficiently attacked pollutant substances, resulting in a higher removal rate. This suggests that a water treatment system with this optimal condition based on complex AOP systems using PTW could be useful in critical environmental and biomedical applications.

In this paper, it is first reported that gray hydrogenated TiO2 sphere photocatalysts (H-TiO2) with high reactivity to solar light are mass produced within a few minutes using an underwater discharge plasma modified sol-gel method at room temperature and atmospheric pressure. This plasma modified system is an easy one-step in-situ synthetic process and the crystallinity, hydrogenation, and spherical structure of H-TiO2 are achieved by the synergy effect between the continuous reaction of highly energetic atomic and molecular species generated from the underwater plasma and surface tension of water. The resultant H-TiO2 demonstrated high anatase/rutile bicrystallinity and extended optical absorption spectrum from the ultraviolet (UV) to visible range. Furthermore, various defects including oxygen vacancies and hydroxyl species on the TiO2 surface permitted the enhancement of the photocatalytic performance. It was demonstrated that H-TiO2 photocatalysts showed significant degradation efficiencies for reactive black 5 (RB 5), rhodamine B (Rho B), and phenol (Ph) under solar light irradiation, up to approximately 5 times higher than that of commercial anatase TiO2 (C-TiO2), which resulted in good water purification. Notably, it was also possible to cultivate HepG2 cells using such well-purified water (to degrees up to 76%), with minimal cytotoxicity. Considering all these results, we believe that this novel plasma technology is promising for important environmental applications.

A photolithographic process for the fabrication of short channel solution-processed zinc oxide transistors (ZnO TFTs) was optimized. To avoid damage to the ZnO film by the photolithography, a bottom gate, bottom contact (BG-BC) device structure was adopted. A perhydropolysilazane (PHPS) precursor, thermally annealed and then treated in oxygen plasma, was used as the gate insulator on an aluminum (Al) gate electrode. Al source and drain electrodes, with a minimum channel length of 5 μm were successfully defined using photolithography. A mobility of 1.5×10−2 cm2/Vs, on/off ratio of 106 and good contact between the source and drain (S/D) and semiconductor were achieved for solution-processed ZnO TFTs having various channel lengths, showing no degradation of device properties. The relatively low mobility was attributed to increased roughness of the gate insulator resulting from development during the photolithographic process. These results suggest that short-channel solution-processed ZnO TFTs can be fabricated by adopting optimised photolithographic processes.

In this study, the charge transport mechanism of Pd/Si-based FS-GaN Schottky diodes was investigated. A temperature-dependent current&ndash, voltage analysis revealed that the I-V characteristics of the diodes show a good rectifying behavior with a large ratio of 103&ndash, 105 at the forward to reverse current at &plusmn, 1 V. The interface states and non-interacting point defect complex between the Pd metal and FS-GaN crystals induced the inhomogeneity of the barrier height and large ideality factors. Furthermore, we revealed that the electronic conduction of the devices prefers the thermionic field emission (TFE) transport, not the thermionic emission (TE) model, over the entire measurement conditions. The investigation on deep level transient spectroscopy (DLTS) suggests that non-interacting point-defect-driven tunneling influences the charge transport. This investigation about charge transport paves the way to achieving next-generation optoelectronic applications using Si-based FS-GaN Schottky diodes.

While non-polar nanostructured-GaN crystals are considered as a prospective material for the realization of futuristic opto-electronic application, the formation of non-polar GaN nanocrystals (NCs) with highly efficient visible emission characteristics remain unquestionable up to now. Here, we report the oxygen-incorporated a-plane GaN NCs with highly visible illumination excitonic recombination characteristics. Epitaxially aligned a-plane NCs with average diameter of 100 nm were formed on r-plane sapphire substrates by hydride vapor phase epitaxy (HVPE), accompanied by the oxygen supply during the growth. X-ray photoemission spectroscopy measurements proved that the NCs exhibited Ga-O bonding in the materials, suggesting the formation of oxidized states in the bandgap. It was found that the NCs emitted the visible luminescence wavelength of 400‒500 nm and 680‒720 nm, which is attributed to the transition from oxygen-induced localized states. Furthermore, time-resolved photoluminescence studies revealed the significant suppression of the quantum confined Stark effect and highly efficient excitonic recombination within GaN NCs. Therefore, we believe that the HVPE non-polar GaN NCs can guide the simple and efficient way toward the nitride-based next-generation nano-photonic devices.

Recently, industrial wastewater is being discharged in large quantities due to the development of industry and this wastewater contains a various heavy metal ion. Exposure to high levels of trace metal ions [Cd (II), Pb (II), Cu (II)] causes a variety of health and environmental problems. These toxic species accumulated in the human body through the water source have a low rate of clearance. [1,2] To minimize the exposure of humans to these contaminants through effective water quality monitoring, anode stripping voltammetry (ASV) method was used. ASV method has wide linear dynamic range, low detection limit (ppb), multi-element analysis capability and the simplicity of the instrumentation, which is relatively inexpensive and small in size, requires low levels of electrical power and is sufficiently portable to permit its use in the field. So, ASV has been used successfully for the determination of heavy metals in water. The sensitivity of differential pulse anode stripping voltammetry (DPASV) is higher than other classical voltammetry, because of its enhanced faradaic current and decreased non-faradaic charging current. [2] In generally, Ir, Au, Ag and Hg electrodes have been used for stripping analysis of trace metals, but the Ir, Au, Ag electrodes have low sensitivity, Hg electrode have toxicity and volatility. [2] To solve this drawbacks, we fabricate a Boron-doped diamond (BDD) electrodes. BDD electrodes are candidate for use in the detection of a trace heavy metal ions, because these show good electrical conductivity, low background current, and non-toxicity. In this study, BDD electrodes on Si substrate deposited by hot filament chemical vapour deposition (HFCVD) and applied to DPASV measurement. Through the optimization of the deposition condition of BDD electrodes and measurement condition of DPASV, we increased the detection sensitivity of heavy metal ions. The BDD electrode with the optimum boron doping concentration by controlling the boron doping concentration from 100 to 10000 ppm in the deposition process optimization step has excellent durability and selectivity of heavy metal ions. As a result of electrochemical measurement, BDD electrode with 8000 ppm B was displayed high sensitive response and wide potential window range of -1.7 V to 1.6 V with the detection limit of 0.001 mg/L to 0.01 mg/L ±5 % about heavy metal ions [Cd (II), Pb (II), Cu (II)]. [1] M.O. Park et al, Electroanalysis. 2017, 29, pp. 514 – 520 [2] J. –H. Yoon et al, Bull. Korean Chem. Soc. 2010, Vol. 31, No. 1 This study was supported by the Korea Environmental Industry & Technology Institute[grant number 20190027400012] and R&D Center for Green Patrol Technologies through R&D for Global Top Environmental Technologies [grant number 20180018400013] funded by the Ministry of Environment, Republic of Korea (MOE), Figure 1

Si-based optical devices would benefit significantly from large scalable and economic illumination sources. Although we previously demonstrated Si-based homoepitaxial light-emitting diodes (LEDs) with large scalability and highly efficient opto-electrical characteristics, the origin of their high quantum efficiency has not been explored. Here, we reveal the origin of the significantly improved quantum efficiency of InGaN/GaN blue LEDs on Si-based freestanding GaN. In power-dependent photoluminescence measurements, the redshifts and blueshifts with increasing injection power indicate a reduced internal electric field of the devices. Furthermore, time-resolved photoluminescence curves for the Si-based homoepitaxial InGaN/GaN LEDs exhibit much larger decay components, suggesting a reduced piezoelectric polarization field, strong quantum confinement effect, and improved material quality of the LEDs. A significantly improved external quantum efficiency of ~86.4% at 100 A/cm2 of the diodes also confirms the reduced dislocation density and internal electric field in the homoepitaxial device. These findings clearly support that the suppressed structural defects and piezoelectric polarization field are responsible for the remarkable quantum efficiency of the InGaN/GaN blue LEDs on Si-based freestanding GaN.

In this study, we aimed to demonstrate the feasibility of the application of biocompatible liquid type fluorescent carbon nanodots (C-paints) to microalgae by improving microalgae productivity. C-paints were prepared by a simple process of ultrasound irradiation using polyethylene glycol (PEG) as a passivation agent. The resulting C-paints exhibited a carbonyl-rich surface with good uniformity of particle size, excellent water solubility, photo-stability, fluorescence efficiency, and good biocompatibility ( 20% higher than the control cell content). A C-paints concentration of 1–10.0 mg mL−1 induced an approximately >1.8 times higher astaxanthin content than the control cells. The high light delivery effect of non-cytotoxic C-paints was applied as a stress condition for H. pluvialis growth and was found to play a major role in enhancing productivity. Notably, the results from this study are an essential approach to improve astaxanthin production, which can be used in various applications because of its therapeutic effects such as cancer prevention, anti-inflammation, immune stimulation, and treatment of muscle-soreness.

The electrical stability and reliability of molybdenum disulfide (MoS2) thin film transistors (TFTs) were investigated by associating thickness-dependent structural defects with degradation mechanism. Patterned MoS2 films with different thicknesses were fabricated for use as transistor channels via the modified multi-step chemical vapor deposition method. X-ray photoelectron spectroscopic (XPS) analyses revealed that highly layered and stoichiometric MoS2 films of up to ∼3 nm thickness were formed around the surface, whereas Mo metal bonds were dominant around the bottom of the films (9 nm). Variations in transistor properties of the thus prepared MoS2 films were examined by applying positive and negative bias stress (PBS and NBS, respectively). The experimental data indicated that MoS2 TFTs with 3-nm-thick films exhibited stable behavior under both PBS and NBS conditions, whereas those with 9-nm-thick films exhibited clear shifts in electrical performance ( △ V t h △ μ s a t s ). These results, together with XPS analyses, revealed that the instability of the MoS2 TFTs under PBS is dominated by sulfur interstitials, whereas their instability under NBS is caused by oxygen vacancies and metallic Mo defects. Additional details about the correlation between the atomic structural defects, which are generated due to insufficient sulfurization of thick films, and the electrical instability of the MoS2 TFTs were discussed.

In this study, hierarchically three-dimensional (3D) nanotubular sea urchin-shaped iron oxide nanostructures (3D-Fe2O3) were synthesized by a facile and rapid ultrasound irradiation method. Additives, templates, inert gas atmosphere, pH regulation, and other complicated procedures were not required. Dense 3D-Fe2O3 with a relatively large Brunauer–Emmett–Teller (BET) surface area of 129.4 m2/g was synthesized within 23 min, and the BET surface area was further improved to 282.7 m2/g by a post heat-treatment process. In addition, this post processing led to phase changes from maghemite (γ phase) to hematite (α phase) Fe2O3. Subsequent characterization suggested that the growth mechanism of the 3D-Fe2O3 follows self-assembly and oriented attachment. The prepared 3D-Fe2O3 was applied to wastewater purification. Ultrasound-irradiated 3D-Fe2O3 can eliminate a As(V) and Cr(VI) from water with 25 times faster removal rate by using a one third smaller amount than commercial α-Fe2O3. This was attributed to the inter-particle pores and relatively positively charged surface of the nanostructure. In addition, post heat treatment on ultrasound-irradiated 3D-Fe2O3 significantly influenced the photocatalytic degradation of methylene blue and phenol, with a 25 times higher removal efficiency than that of commercial α-Fe2O3, because of both high BET surface area and good crystallization of the prepared samples.

In this paper, it is first reported that gray hydrogenated TiO

The electrical properties of top-contact pentacene thin-film transistors (TFTs) with a poly(methyl methacrylate) (PMMA) gate dielectric were analyzed in air and vacuum environments. Compared to the vacuum case, the pentacene TFT in air exhibited lower drain currents and more pronounced shifts in the threshold voltage upon reversal of the gate voltage sweep direction, together with a decrease in the field-effect mobility. These characteristic variations were explained in terms of two distinctive actions of polar H2O molecules in pentacene TFT. H2O molecules were suggested to diffuse under the source and drain contacts and interrupt the charge injection into the pentacene film, whereas those that permeate at the pentacene/PMMA interface retard hole depletion in and around the TFT channel. The diffusion process was much slower than the permeation process. The degraded TFT characteristics in air could be recovered mostly by storing the device under vacuum, which suggests that the air instability of TFTs is due mainly to the physical adsorption of H2O molecules within the pentacene film.

We report on the optimization of the plasma treatment conditions for a solution-processed silicon dioxide gate insulator for application in zinc oxide thin film transistors (TFTs). The SiO2 layer was formed by spin coating a perhydropolysilazane (PHPS) precursor. This thin film was subsequently thermally annealed, followed by exposure to an oxygen plasma, to form an insulating (leakage current density of ∼10(-7) A/cm(2)) SiO2 layer. Optimized ZnO TFTs (40 W plasma treatment of the gate insulator for 10 s) possessed a carrier mobility of 3.2 cm(2)/(V s), an on/off ratio of ∼10(7), a threshold voltage of -1.3 V, and a subthreshold swing of 0.2 V/decade. In addition, long-term exposure (150 min) of the pre-annealed PHPS to the oxygen plasma enabled the maximum processing temperature to be reduced from 180 to 150 °C. The resulting ZnO TFT exhibited a carrier mobility of 1.3 cm(2)/(V s) and on/off ratio of ∼10(7).

We report the improvement of the hardness and modulus properties in a silsesquioxane-based soft replica mold by adding thermal initiator, without deteriorating the UV transmittance at the wavelength of 365 nm. It is found that thermal initiator used for this work contributes to improving the hardness and modulus values up to 0.175 and 3.585 GPa, while the UV transmittance value is still above 75%. The optimized soft replica mold built on a flexible plastic substrate allows submicron-scale patterns to be transferred onto a rigid Si substrate by means of UV-NIL process. Consequently, we demonstrate that the developed soft replica mold can be a suitable replacement for typical hard molds, promising further use in mold-based nanolithography for the fabrication of high-resolution nanopatterns over large areas.

We report on the low-temperature formation (180 °C) of a SiO2 dielectric layer from solution-processed perhydropolysilazane. A bottom-gate zinc oxide thin-film transistor has subsequently been fabricated that possesses a carrier mobility of 3 cm2 V s−1, an on/off ratio of 107 and minimal hysteresis in its transfer and output characteristics.

We report the electrical behavior of undoped zinc oxide thin-film transistors (TFTs) fabricated by low-temperature chemical spray pyrolysis. An aerosol system utilizing aerodynamic focusing was used to deposit the ZnO. Polycrystalline films were subsequently formed by annealing at the relatively low temperature of 140°C. The saturation mobility of the TFTs was 2 cm2/Vs, which is the highest reported for undoped ZnO TFTs manufactured below 150°C. The devices also had an on/off ratio of 104 and a threshold voltage of −3.5 V. These values were found to depend reversibly on measurement conditions.

Grain boundaries in polycrystalline pentacene films significantly affect the electrical characteristics of pentacene field-effect transistors (FETs). Upon reversal of the gate voltage sweep direction, pentacene FETs exhibited hysteretic behaviours in the subthreshold region, which was more pronounced for the FET having smaller pentacene grains. No shift in the flat-band voltage of the metal-insulator-semiconductor capacitor elucidates that the observed hysteresis was mainly caused by the influence of localized trap states existing at pentacene grain boundaries. From the results of continuous on/off switching operation of the pentacene FETs, hole depletion during the off period is found to be limited by pentacene grain boundaries. It is suggested that the polycrystalline nature of a pentacene film plays an important role on the dynamic characteristics of pentacene FETs.

Solution-based oxide gate dielectric layers are prepared from metal nitrates using UV-assisted annealing at 150 °C. The leakage current densities of ZrO2 and Al2O3 dielectrics are less than about 10-9 A/cm2 at 1 MV/cm and comparable to those formed by annealing at higher temperatures. High dielectric constants and the low leakage current behavior of the dielectric layers provide excellent ZnO TFT performance, with a field effect mobility of 1.37 cm2/V.s and an off-current density of 10-12 A/cm2. This low fabrication temperature process is compatible with future plastic electronics technology.

The effects of hydrogen plasma treatment on the active layer of top-contact zinc oxide thin film transistors are reported. The transfer characteristics of the reference devices exhibited large hysteresis effects and an increasing positive threshold voltage (VTH) shift on repeated measurements. In contrast, following the plasma processing, the corresponding characteristics of the transistors exhibited negligible hysteresis and a very small VTH shift; the devices also possessed higher field effect carrier mobility values. These results were attributed to the presence of functional groups in the vicinity of the semiconductor/gate insulator interface, which prevents the formation of an effective channel.

We report the light-exposure effects on solution-processed organic thin-film transistors (TFTs) based on a 6,13-bis(triisopropylsilylethynyl)pentacene (TIPS-pentacene) semiconductor. Under light exposure, the increase in drain current and the positive shift of threshold voltage are observed, which are more remarkable for the TIPS-pentacene/cadmium telluride composite TFT. Herein the photosensitivity in these TFTs is explained in terms of photovoltaic and photoconductive effects. Composite semiconductors blended with sensitizers are suggested to enhance the quantum efficiency of organic phototransistors.

The influence of tetrafluoromethane (CF4) gas on the electrical characteristics of monolithic graphene field-effect transistors (FETs) is reported. Compared with the results in nitrogen ambient, FETs in CF4 ambient exhibit a positive shift in the Dirac point voltage and an increase in drain current. These changes are ascribed to the electronegative nature of the fluorine atoms in CF4 gas, which is found to induce p-type doping and excess charge carriers in graphene. The electrical response to CF4 gas exposure demonstrates the feasibility of using monolithic graphene FETs as chemical sensors.

GdVO4 (GVO) thin films were successfully deposited on n-GaN/Al2O3 substrates used as a bottom electrode at 600 °C by radio frequency magnetron sputtering. The GVO films annealed at temperatures up to 800 °C exhibited epitaxial growth but the films annealed above 900 °C showed polycrystalline properties. In the photoluminescence (PL) spectrum, broadband emission was observed at 450 nm for all the films. The auger electron spectroscopy (AES) line-shape of the annealed films was similar to that of the as-deposited film but the Gd/V and Gd/O ratios increased linearly with increasing annealing temperature. The dielectric constant and dielectric loss of the GdVO4 films decreased with increasing annealing temperature with values of 12–26 and 0.04–0.05 at 1 MHz, respectively.