Dahlang Tahir

Electronic and optical properties of Cu, CuO and Cu2O studied by electron spectroscopy

The electronic and optical properties of Cu, CuO and Cu(2)O were studied by x-ray photoelectron spectroscopy (XPS) and reflection electron energy-loss spectroscopy (REELS). We report detailed Cu 2p, Cu LVV, O 1s and O KLL spectra which are in good agreement with previous results. REELS spectra, recorded for primary energies in the range from 150 to 2000 eV, were corrected for multiple inelastically scattered electrons to determine the effective inelastic scattering cross section. The dielectric functions and optical properties were determined by comparing the experimental inelastic electron scattering cross section with a simulated cross section calculated within the semi-classical dielectric response model in which the only input is Im(-1/ε) by using the QUEELS-ε(k,ω)-REELS software package. By Kramers-Kronig transformation of the determined Im(-1/ε), the real and imaginary parts (ε(1) and ε(2)) of the dielectric function, and the refractive index n and extinction coefficient k were determined for Cu, CuO, and Cu(2)O in the 0-100 eV energy range. Observed differences between Cu, CuO and Cu(2)O are mainly due to modifications of the 3d and O 2p electron configurations.

Electronic and optical properties of Al2O3/SiO2 thin films grown on Si substrate

The electronic and optical properties of Al2O3/SiO2 dielectric thin films grown on Si(1 0 0) by the atomic layer deposition method were studied by means of x-ray photoelectron spectroscopy and reflection electron energy loss spectroscopy (REELS). The band gaps of the Al2O3/SiO2 thin films before annealing and after annealing were 6.5 eV and 7.5 eV, respectively, and those of the γ-Al2O3 and α-Al2O3 phases were 7.1 eV and 8.4 eV, respectively. All of these were estimated from the onset values of the REELS spectra. The dielectric functions were determined by comparing the effective cross-section determined from experimental REELS with a rigorous model calculation based on dielectric response theory, using available software packages. The determined energy loss function obtained from the Al2O3/SiO2 thin films before annealing showed a broad peak at 22.7 eV, which moved to the γ-Al2O3 position at 24.3 eV after annealing. The optical properties were determined from the dielectric function. The optical properties of the Al2O3/SiO2 thin films after annealing were in good agreement with those of γ-Al2O3. The changes in band gap, electronic and optical properties of the Al2O3/SiO2 thin films after annealing indicated a phase transition from an amorphous phase to the γ-Al2O3 phase after annealing.

Band alignment of atomic layer deposited (ZrO2)x(SiO2)1−x gate dielectrics on Si (100)

The band alignment of atomic layer deposited (HfZrO4)1−x(SiO2)x (x = 0, 0.10, 0.15, and 0.20) gate dielectric thin films grown on Si (100) was obtained by using X-ray photoelectron spectroscopy and reflection electron energy loss spectroscopy. The band gap, valence band offset, and conduction band offset values for HfZrO4 silicate increased from 5.4 eV to 5.8 eV, from 2.5 eV to 2.75 eV, and from 1.78 eV to 1.93 eV, respectively, as the mole fraction (x) of SiO2 increased from 0.1 to 0.2. This increase in the conduction band and valence band offsets, as a function of increasing SiO2 mole fraction, decreased the gate leakage current density. As a result, HfZrO4 silicate thin films were found to be better for advanced gate stack applications because they had adequate band gaps to ensure sufficient conduction band offsets and valence band offsets to Si.

Electronic and optical properties of selected polymers studied by reflection electron energy loss spectroscopy

We have determined the electronic and optical properties of six polymers: Polymethyl-methacrylate (PMMA), polyethylene (PE), polyvinyl chloride (PVC), polyester (PET), polypyrrole (PPY), and polyamide (PA6) for energy losses from 0 to 70 eV by analysis of reflection electron energy-loss spectroscopy (REELS) spectra. We found that the surface was easily damaged by the incident electron beam, in particular for energies above 500 eV. The damage results in new peaks in the bandgap region and the polymers become metallic. Great care was exerted to determine experimental conditions under which these effects are minimized. The REELS spectra were corrected for multiple inelastically scattered electrons with the QUASES-XS-REELS software to determine the effective inelastic-scattering cross sections. From these cross sections, we found that the band gaps for PMMA, PE, PVC, PET, PPY, and PA6 are 5.0 eV, 7.5 eV, 7.0 eV, 3.0 eV, 3.5 eV, and 5.1 eV, respectively. Quantitative analysis of the experimental cross sections...

Dielectric and optical properties of Zr silicate thin films grown on Si(100) by atomic layer deposition

Dielectric and optical properties of (ZrO2)x(SiO2)1−x dielectric thin films, grown on Si(100) by the atomic layer deposition method, were studied by means of reflection electron energy loss spectroscopy (REELS). The quantitative analysis of REELS spectra was carried out by using the quantitative analysis of electron energy loss spectra-e(k,ω)-REELS software to determine the dielectric function and optical properties by using an analysis of experimental REELS cross sections from the simulated energy loss function (ELF). For ZrO2, the ELF shows peaks in the vicinity of 10, 15, 21, 27, 35, 42, and 57 eV. For SiO2, a broad peak at 23 eV with a very weak shoulder at 15 eV and a shoulder at 34 eV were observed, while for Zr silicates (x=0.75 and 0.5), the peak position is similar to that of ZrO2. For Zr silicates with high SiO2 concentration (x=0.25), the peak positions are similar to that of SiO2, but the peak at 42 eV, which is due to excitation of Zr N2,3 shell electrons, still exist. This indicates that the...

Electronic and optical properties of Fe, Pd, and Ti studied by reflection electron energy loss spectroscopy

We have studied the electronic and optical properties of Fe, Pd, and Ti by reflection electron energy-loss spectroscopy (REELS). REELS spectra recorded for primary energies in the range from 300 eV to 10 keV were corrected for multiple inelastically scattered electrons to determine the effective inelastic-scattering cross section. The dielectric functions and optical properties were determined by comparing the experimental inelastic-electron scattering cross section with a simulated cross section calculated within the semi-classical dielectric response model in which the only input is Im(−1/e) by using the QUEELS-e(k,ω)-REELS software package. The complex dielectric functions e(k,ω), in the 0–100 eV energy range, for Fe, Pd, and Ti were determined from the derived Im(−1/e) by Kramers-Kronig transformation and then the refractive index n and extinction coefficient k. The validity of the applied model was previously tested and found to give consistent results when applied to REELS spectra at energies betwee...

Band alignment of atomic layer deposited (HfZrO{sub 4}){sub 1−x}(SiO{sub 2}){sub x} gate dielectrics on Si (100)

The band alignment of atomic layer deposited (HfZrO{sub 4}){sub 1−x}(SiO{sub 2}){sub x} (x = 0, 0.10, 0.15, and 0.20) gate dielectric thin films grown on Si (100) was obtained by using X-ray photoelectron spectroscopy and reflection electron energy loss spectroscopy. The band gap, valence band offset, and conduction band offset values for HfZrO{sub 4} silicate increased from 5.4 eV to 5.8 eV, from 2.5 eV to 2.75 eV, and from 1.78 eV to 1.93 eV, respectively, as the mole fraction (x) of SiO{sub 2} increased from 0.1 to 0.2. This increase in the conduction band and valence band offsets, as a function of increasing SiO{sub 2} mole fraction, decreased the gate leakage current density. As a result, HfZrO{sub 4} silicate thin films were found to be better for advanced gate stack applications because they had adequate band gaps to ensure sufficient conduction band offsets and valence band offsets to Si.

Stopping powers and inelastic mean free path of 200eV-50keV electrons in polymer PMMA, PE, and PVC.

The stopping power (SP) and inelastic mean free path (IMFP) of three polymers: polymethyl methacrylate (PMMA), polyethylene (PE), and polyvinyl chloride (PVC) for electron energies from 200eV to 50keV have been determined based on dielectric models. The energy loss function (ELF) is the main input in the calculation of the SP and IMFP for the dielectric models. ELF in this study was determined from a previously published quantitative analysis of reflection electron energy loss spectroscopy (REELS) spectra. The SP of PMMA, PE and PVC decreases and the IMFP increases with increasing electron energies up to 50keV. For comparison, data from the National Institute of Standards and Technology (NIST) database for electron energies from 10 to 50keV were used and show that SP in this study is lowered by 10-15%. The obtained IMFP for PE was compared with those calculated using the TPP2M predictive equations and shows that a reasonable agreement with a root-mean-square (rms) is 7.01Å. The present approach has high potential for the experimental determination of SP and IMFP from the REELS spectra.

Nanocomposites Fe/Activated Carbon/PVA for Microwave Absorber: Synthesis and Characterization

Nanocomposites, activated carbon/polyvinyl alcohol (AC/PVA) filled with Fe to form Fe/AC/PVA, were characterized by using X-ray fluorescence (XRF), X-ray diffraction (XRD), Fourier transform infrared (FTIR), and vector network analyzer (VNA). The crystal orientations from Fe are (104), (110), and (200) and the bonding formations of AC are O-H, C-H, and C=C show existence in nanocomposites, which may be due to the Fe that has been filled the pore of AC via a chemical bond. 20% AC (3 mm in thickness) in nanocomposites shows higher performance absorption for C-band (4.65 GHz) with maximum reflection loss of −32.5 dB.

Comparison of sensitivity and resolution load sensor at various configuration polymer optical fiber

This study uses a load sensor with a macro-bending on polymer optical fiber loop model which is placed between two plates with a buffer spring. The load sensor with light intensity modulation principle is an infrared LED emits light through the polymer optical fiber then received by the phototransistor and amplifier. Output voltage from the amplifier continued to arduino sequence and displayed on the computer. Load augment on the sensor resulted in an increase of curvature on polymer optical fibers that can cause power losses gets bigger too. This matter will result in the intensity of light that received by phototransistor getting smaller, so that the output voltage that ligable on computer will be getting smaller too. The sensitivity and resolution load sensors analyzed based on configuration with various amount of loops, imperfection on the jacket, and imperfection at the cladding and core of polymer optical fiber. The results showed that the augment on the amount of load, imperfection on the jacket an...