Field Emission Electron Spectroscopy Research Articles

Preparation and Characterization of Gd2O3: Er3+ Nanosphere Particles Combinated with Chitosan Gd2O3: Er3+@CS

Nanospherical upconversion luminescence particles (UCLPs) Gd2O3:Er3+ and Gd2O3:Er3+@ chitosan (CS) were prepared by step-by-step precipitation and calcination of the available nitrate rare Earth sales and chitosan. The morphology and composition of as-prepared samples were characterized by field emission electron spectroscopy (FESEM) and Fourier transform infrared (FT-IR) spectroscopy. The synthesized UCLPs were non-agglomerate spheres in uniform nanoscale. The quantitative amount of chitosan was well coated with the gain surface of the UCLPs Gd2O3:Er3+ to obtain Gd2O3:Er3+@CS nanocomposite. The down-conversion luminescent intensity of Gd2O3:Er3+ NSP is lower than Gd2O3:Er3+@CS NSP samples, but luminescent characterizations were non-change. The photoluminescence (PL) of the green emission range of all UCLPs samples with chitosan-coated and -uncoated took the leading position. By using a diode laser excitation with 975 nm of wavelength, the detected intensity of red emission is more remarkably detected than green emissions. The two-photon mechanism for both green and red emissions of nanophosphor was observed. As a result, these might be promising opportunities to conjugate with various bio subjects that could be used in medical applications.

Evaluating Different TiO2 Nanoflower-Based Composites for Humidity Detection.

Unique three-dimensional (3D) titanium dioxide (TiO2) nanoflowers (TFNA) have shown great potential for humidity sensing applications, due to their large surface area-to-volume ratio and high hydrophilicity. The formation of a composite with other materials could further enhance the performance of this material. In this work, the effect of different types of composites on the performance of a TNFA-based humidity sensor was examined. NiO, ZnO, rGO, and PVDF have been explored as possible composite pairing candidates with TiO2 nanoflowers, which were prepared via a modified solution immersion method. The properties of the composites were examined using field emission electron spectroscopy (FESEM), X-ray diffractometry (XRD), transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), current-voltage (I-V) analysis, Hall effect measurement, and contact angle measurement. The performance of the humidity sensor was assessed using a humidity sensor measurement system inside a humidity-controlled chamber. Based on the result, the combination of TiO2 with rGO produced the highest sensor response at 39,590%. The achievement is attributed to the increase in the electrical conductivity, hydrophilicity, and specific surface area of the composite.

A simple, step-by-step approach for the preparation of MoO3@g-C3N4 nanocomposite

We present a simple step-by-step method for the preparation of MoO3@g-C3N4 nanocomposite. Several approaches were used to prepare and characterize the nanocomposite with a weight ratio of MoO3 (0.075). X-ray diffraction measurements have revealed The primary peaks of MoO3 at 13.14°, 23.74°, 26.07°, 27.71°, 29.98°, and 39.33° correspond to the iq (020), (110), (040), (120), (021), and (060) planes, and the g-C3N4 appearing at 27.49° and 12.94° corresponds to the (002) and (100) planes in the MoO3@g-C3N4 nanocomposite. The specific bands for the as-prepared nanocomposite were revealed by Fourier-transform infrared. With the H3 hysteresis loops, the BET isotherm and the BJH technique produced results compatible with Type IV. Furthermore, the results indicated the effective change in surface area, pore-volume, and pore diameter values were larger in the MoO3@g-C3N4 nanocomposite. Diffuse spectroscopy of reflection data revealed more information about the changes that occurred when MoO3 was loaded on the g-C3N4 layers to shift the spectrum to the red extent while decreasing the band gap to 2.63 eV. Furthermore, field emission electron spectroscopy has proven the synthesis of nanocomposite by a dramatic change in the morphological surface as well as a change in the composition of elements that have been demonstrated using the energy-dispersive X-ray spectroscopy methodology. This discovery has improved the form and structure of the MoO3@g-C3N4 nanocomposite

Field emission spectroscopy measurements of graphene/n-type diamond heterojunction

In this study, a graphene/n-type diamond heterojunction was fabricated by a wet-transfer process on hydrogen-terminated heavily phosphorus-doped diamond. Ultraviolet photoelectron spectroscopy (UPS) and field-emission electron spectroscopy were conducted to study the band structure of the graphene/n-type diamond heterojunction and its field emission mechanism. UPS suggests that an internal barrier is formed in the diamond by upward band bending near the graphene–diamond interface. The work function of graphene is estimated to be 3.72 eV. Field emission occurs from the Fermi level of graphene at low voltages, and then electron emission from the valence band of diamond starts at increased voltages. The results indicate that electron emission limited by surface termination changes to graphene-oriented emission following the formation of the heterojunction.

R-GO/MWCNTs Nanocomposite Film as Electrode Material for Supercapacitor

We synthesized a reduced graphene oxide (r-GO) multi-walled carbon nanotube (MWCNTs) nanocomposite film via layer by layer (LBL) assembly. This structure was prepared by vacuum filtration and heat-treated at a low temperature of 500°C. The morphology of the sample was determined by field emission electron spectroscopy (FE-SEM). The structural detail and the chemical analysis were characterized by using X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS), respectively. The cyclic voltammetry (CV) curve of r-GO/MWCNTs nanocomposite appeared nearly rectangular in shape. The current density (A/g) was gradually increased by increasing the scan rate of the voltage, as high as a scan rate of 500 mVs-1. At a current density of 10 mAg-1, the specific capacitance of the nanocomposite, estimated by galvanostatic (GA) charge/discharge measurement, is 150 Fg-1. These nanocomposites can be developed for supercapacitor electrodes.

Synthesis, Characterization, and Antibacterial Activity of Silver-Doped Silica Nanocomposite Particles

Silver nanoparticles were adsorbed preferentially on silica surface to form composite particles using a reverse micelle process that stabilizes the silver particles by an anionic sodium bis(2-ethylhexyl) sulfosuccinate (AOT) surfactant in isooctane solvent together with the silica particles in which their surface being mediated by a cationic poly(allylamine hydrochloride) (PAH) polyelectrolyte. The heterogeneous adsorption was rendered by both electrostatic attraction and hydrophilic/hydrophobic interaction, and was carried out in multiple deposition cycles. The resulting nanocomposite particles were characterized by zeta-potential measurement, electron microscopy, X-ray diffractometry, field-emission electron spectroscopy for chemical analysis (ESCA), and inductively coupled plasma analysis, respectively. In addition, antibacterial activity of the composite particles was examined against Escherichia coli (E. coli) in aqueous environment.

Nanotube electronic states observed with thermal field emission electron spectroscopy

We observe nonmetallic electronic states above the Fermi level in single-walled carbon nanotubes by measuring the energy distribution of thermal-field-emitted electrons. This measurement method examines electronic states associated with the nanotube cap or end termination, and with it, we resolve electronic states greater than 3 eV above the Fermi level. The observed emitting states are broad at high temperatures (0.7–1.5 eV full width at half maximum), and the peak positions shift linearly with applied voltage. We present possible mechanisms responsible for these states.

Atom probe and field emission electron spectroscopy studies of semiconductor films on metals

The surface morphology and the electronic states of Ge overlayers deposited on Ir-and Mo-tips were investigated by a combined instrument of an atom probe (AP) and a field emission electron spectroscope (FEES). The overlayers were deposited on the tips while observing field emission microscope (FEM) images of the surfaces. The FEM images of thin Ge overlayers on the Ir-tips show layer-like structures. In field emission electron distribution (FEED) of a Ge overlayer on the Ir-tip, about 5 ML thick, an energy gap near the Fermi level was clearly widened by low temperature annealing. After the thickness was reduced to 3 ML by field evaporation, the energy gap still remained wide. The FEEDs of the Ge overlayers on the Mo-tips exhibit several peaks distinct from those on the Ir-tip. This may be attributed to the local strong electric field surrounding the Ge clusters formed on the Mo-tips.

A diagnostic study of the field emission characteristics of individual micro-emitters in CVD diamond films

Details are given of an experimental study of the characteristics of field-induced electron emission from 15 mm diameter CVD diamond films deposited on an Mo substrate. Three dedicated techniques have been used to characterize the electron emission process: (i) the 'transparent anode imaging' technique for recording the spatial distributions of emission sites and the total current-voltage (I-V) characteristic, (ii) the 'anode probe hole' technique for measuring the I-V characteristic of individual sites, and (iii) 'field emission electron spectroscopy' for studying the energy distribution of emitted electrons. Finally, the physical implications of the findings from the electron energy spectroscopy measurement are discussed.

Atom-probe and field emission electron spectroscopy studies of ordered structures and electronic properties of Ge overlayers on Ir-tips

The combined instrument of an atom probe (AP) and a field emission electron spectroscope (FEES) was employed to investigate the crystallinity and the surface electronic state of Ge overlayers deposited on Ir tips. The crystallinity of Ge overlayers deposited at 300 and 420 K, and those annealed after the deposition, is better than that of the overlayers deposited at 50 K. The surface electronic state of the well-crystallized Ge overlayer is semiconductive at the thickness of ≈4 ML. When the degree of crystallinity is rather low or Ir atoms exist in the Ge overlayer, even a thick overlayer exhibits metallic surface electronic states. When an Ir atom exists on the overlayer surface, a small peak appears at ≈ 0.3 eV below the Fermi level in the field emission electron distribution (FEED), indicating a local state of the Ir atom.

Structurally induced FEES from nanotips: implications for scanning tunneling spectroscopy

Recent theoretical studies and experimental data show the existence of energy levels at the apex atom of nanotips. We report here experimental measurements, by field emission electron spectroscopy (FEES), of strong modifications of the local density of states for varying atomic configurations of the nanotips. The local density of states specific to each protrusion must then be considered in interpreting scanning tunneling microscopy and scanning tunneling spectroscopy experiments with atomic resolution instead of the commonly used free-electron model.

Structurally induced FEES from nanotips: implications for scanning tunneling spectroscopy

Recent theoretical studies and experimental data show the existence of energy levels the apex atom of nanotips. We report here experimental measurements, by field emission electron spectroscopy (FEES), of strong modifications of the local density of states for varying atomic configurations of the nanotips. The local density of states specific to each protrusion must then be considered in interpreting scanning tunneling microscopy and scanning tunneling spectroscopy experiments with atomic resolution instead of the commonly used free-electron model.

High resolution tunneling microscopies: from FEM to STS

Field emission microscopy, field ion microscopy and scanning tunneling microscopy realized atomically high resolutions utilizing electron tunneling and confining a tunneling region into an atomically small spot. These microscopies have other unique features: the energy analyses of tunneling electrons by a field emission microscope (FEM) and a scanning tunneling microscope (STM), i.e., field emission electron spectroscopy (FEES) and scanning tunneling spectroscopy (STS), respectively, and the mass analysis of individual surface atoms by a combined instrument of a field ion microscope (FIM) and a mass spectrometer, the atom-probe (A-P). FEES and STS provide information on the electronic states of specimen surfaces and the A-P clarifies the surface composition in atomic dimensions. The present study suggests that the unification of A-P/FEES and STM/STS would lead to a new approach for reliable ultramicroscopic analysis of solid surfaces.

ULTRAMICROANALYSIS UTILIZING ELECTRON TUNNELING

The field emission microscope(FEM), the field ion microscope (FIM) and the scanning tunneling microscope(STM) are the high resolution microscopes utilizing electron tunneling. Field emission electron spectroscopy(FEES), the atom-probe(A-P) and scanning tunneling spectroscopy(STS) were developed from FEM, FIM and STM, respectively. The atomic arrangement, composition and electronic states of the Si micro-cluster on a Mo surface and the atomic step on the Si(001) plane were investigated at the level of individual surface atoms.