Fatimah A. Noor

Electron and hole components of tunneling currents through an interfacial oxide-high-k gate stack in metal-oxide-semiconductor capacitors

Two different components of tunneling current in the TiN/HfSiOxN/SiO2/p-Si(100) metal-oxide-semiconductor capacitor have been presented. The tunneling currents were calculated by taking into account a longitudinal-transverse kinetic energy coupling. The calculated tunneling currents were compared with that measured ones by employing the electron and hole effective masses and phase velocities as fitting parameters. It has been shown that hole tunneling currents dominate at low voltages whereas at high voltages the tunneling currents are mainly contributed by electrons. It has also been found that the effective mass of hole in the HfSiOxN layer is higher than that of electron. The gate electron and substrate hole velocities are 1×105 m/s independent of the HfSiOxN thickness. In addition, it is speculated that the electron and hole effective masses in the HfSiOxN layer perhaps increase as its thickness decreases.

Analysis of electron direct tunneling current through very-thin gate oxides in MOS capacitors with the parallel-perpendicular kinetic energy components and anisotropic masses

An electron direct tunneling current model of n+- poly - Si/SiO2/p - Si(100) metal-oxide-semiconductor (MOS) capacitors has been developed by considering a parallel-perpendicular kinetic energy coupling, which is represented by the gate electron phase velocity, and anisotropic masses under a parabolic E-k dispersion relationship. The electron effective mass in the oxide and the electron phase velocity in the n+ poly-Si gate are the only two fitting parameters to compare calculated tunneling currents to measured ones. It was obtained that the calculated tunneling currents fit well to the measured ones. The electron effective mass in the oxide layer tends to increase with decreasing the oxide thickness. In addition, the gate electron velocity is a constant of 1x105m/s. Moreover, the theoretical model offers a simple treatment and an accurate result in obtaining the tunneling current.

Model of a tunneling current in a p-n junction based on armchair graphene nanoribbons - an Airy function approach and a transfer matrix method

We modeled a tunneling current in a p-n junction based on armchair graphene nanoribbons (AGNRs) by using an Airy function approach (AFA) and a transfer matrix method (TMM). We used β-type AGNRs, in which its band gap energy and electron effective mass depends on its width as given by the extended Huckel theory. It was shown that the tunneling currents evaluated by employing the AFA are the same as those obtained under the TMM. Moreover, the calculated tunneling current was proportional to the voltage bias and inversely with temperature.

Nanocomposite Solar Cells from ''Dirty''TiO{sub 2} Nanoparticles

TiO2 solar cells were fabricated consisting TiO2 layer, TiO2 nanocomposite layers, electrolyte polymer and counter electrode layer. It was found that TiO2 nanocomposite layer that contains metal (Zn) contact could be conductive and make better charge transfer than pure TiO2. Conversion efficiency 1.0% was achieved using TiO2 nanocomposite. It indicates that using of TiO2 nanocomposite is an effective technique for improvement of conversion efficiency.

Comparison of electron transmittances and tunneling currents in an anisotropic TiNx/HfO2/SiO2/p-Si(100) metal—oxide—semiconductor (MOS) capacitor calculated using exponential- and Airy-wavefunction approaches and a transfer matrix method

Analytical expressions of electron transmittance and tunneling current in an anisotropic TiNx/HfO2/SiO2/p-Si(100) metal—oxide—semiconductor (MOS) capacitor were derived by considering the coupling of transverse and longitudinal energies of an electron. Exponential and Airy wavefunctions were utilized to obtain the electron transmittance and the electron tunneling current. A transfer matrix method, as a numerical approach, was used as a benchmark to assess the analytical approaches. It was found that there is a similarity in the transmittances calculated among exponential- and Airy-wavefunction approaches and the TMM at low electron energies. However, for high energies, only the transmittance calculated by using the Airy-wavefunction approach is the same as that evaluated by the TMM. It was also found that only the tunneling currents calculated by using the Airy-wavefunction approach are the same as those obtained under the TMM for all range of oxide voltages. Therefore, a better analytical description for the tunneling phenomenon in the MOS capacitor is given by the Airy-wavefunction approach. Moreover, the tunneling current density decreases as the titanium concentration of the TiNx metal gate increases because the electron effective mass of TiNx decreases with increasing nitrogen concentration. In addition, the mass anisotropy cannot be neglected because the tunneling currents obtained under the isotropic and anisotropic masses are very different.

A Theoretical Study on the Performance of SnO2/SiO2/n-Si Solar Cells

The performance of SnO2/SiO2/n-Si solar cells was studied by considering various transport mechanisms including minority-carrier diffusion, carrier recombination, and tunneling through insulating layer. The tunneling current through the SiO2 layer was obtained by employing the Airy-wavefunction approach. The efficiency was calculated to determine the performance of the cells under AM1 illumination for different values of insulating layer thickness, interface state density, hole life-time, doping density of silicon substrate, and cell thickness. It was shown that the efficiency increases as the insulating layer becomes thinner due to the decrease of short-circuit current. It was also shown that the efficiency increases as the doping density increases up to 6x1022/m3 and it then decreases for higher doping densities. As the interface state density decreases, the efficiency becomes higher. In addition, the increases in the hole lifetime and cell thickness enhance the efficiency of the solar cell.

Introducing Organization Parameter for Self‐Organized Nanoparticles

We introduced a parameter to distinguish how well (the quality) of organization of nanoparticles in self‐organized samples. This parameter measures how far the deviation of real particle positions in the sample with respect to positions of particles forming a perfect lattice of the corresponding packing structure. The perfect lattice was developed by taking the lattice site as the average distance between contacting particles in the sample.

The effects of insulator thickness and substrate doping density on the performance of ZnO/SiO2/n-Si solar cells

ABSTRACT The insulator layer and the substrate material play an important role in determining the performance of metal-insulator-semiconductor type solar cells. Here, the effects of insulator layer thickness and substrate doping density on the efficiency of a ZnO/SiO2/n-Si solar cell were studied. Semi-analytical calculations wer performed to obtain the current–voltage dark current, efficiency, and current–voltage characteristics of the cell. An efficiency of 20% was obtained with an insulating layer thickness of around 19 Å. It was also found that the efficiency started to decrease when an insulator layer thicknesses greater than the optimum thickness was used. Furthermore, the efficiency of the cells decreased with increasing substrate doping density, and the maximum efficiency was obtained with a substrate doping density of 6 × 1022 m−3. By optimizing the insulating layer thickness and substrate doping density an efficiency of 20% was achieved at a cell thickness of 25 μm.

Modelling of Drain Current in Tunnelling Field-Effect Transistor Based on Strained Armchair Graphene Nanoribbons

A tunnelling field-effect transistor (TFET) based armchair graphenenanoribbons (AGNRs) with variation of uniaxial strain has been modeled. Bandgap of strained AGNR estimated by an extended tight binding method is applied to obtain electrical characteristics of a TFET under the quantum capacitance limit device approximation. Furthermore, the electron transmittance is calculated by utilizing the WKB (Wentzel–Kramers–Brillouin) approach. The obtained transmittance is then used to calculate the drain current by employing the Landauer formula. The results show that strain parameter has significant effect on the current. In other words, the electrical characteristics of AGNR TFET can be tuned by the strain of AGNR.

Molecular dynamics simulation of graphene growth at initial stage on Ni(100) facet for low flux C energy by CVD

In this study, atomic simulation for graphene growth on Ni (100) at initial stage via chemical vapor deposition method has been developed. The C-C atoms interaction was performed by Terasoff potential mean while Ni-Ni interaction was specified by EAM (Embedded Atom Modified). On the other hand, we used very simple interatomic potential to describe Ni-C interaction during deposition process. From this simulation, it shows that the formation of graphene is not occurs through a combined deposition mechanism on Ni substrate but via C segregation. It means, Ni-C amorphous is source for graphene growth when cooling down of Ni substrate. This result is appropriate with experiments, tight binding and quantum mechanics simulation.