The influence of a single defect in composite gate insulators on the performance of nanotube transistors

The current through a carbon nanotube field-effect transistor (CNFET) with cylindrical gate electrode is calculated using the nonequilibrium Greens function method in a tight-binding approximation. The obtained result is in good agreement with the experimental data. The space radiation and nuclear radiation are known to cause defects in solids. The theoretical approach is used to calculate the amplitude of the random-telegraph-signal (RTS) noise due to a single defect in the gate oxide of a long channel p-type CNFET. We investigate how the amplitude of the RTS noise is affected by the composite structure of gate insulators, which contains an inner insulator with a dielectric constant larger than 3.9 and an outer insulator with a dielectric constant of 3.9 (as for SiO2). It is found that the RTS amplitude increases apparently with the decreasing thickness of the inner gate insulator. If the inner insulator is too thin, even though its dielectric constant is as large as 80, the amplitude of the RTS noise caused by the charge of Q = +1e may amount to around 80% in the turn-on region. Due to strong effects of defects in CNFETs, CNFETs have a potential to be used for detecting the space radiation or nuclear radiation.Comment: 8 Figure

Intrinsic Regularization Method in QCD

There exist certain intrinsic relations between the ultraviolet divergent graphs and the convergent ones at the same loop order in renormalizable quantum field theories. Whereupon we may establish a new method, the intrinsic regularization method, to regularize those divergent graphs. In this paper, we apply this method to QCD at the one loop order. It turns out to be satisfactory:The gauge invariance is preserved manifestly and the results are the same as those derived by means of other regularization methods.Comment: 18 pages, LaTeX , 7 figures in a separate compressed postscript fil

Organometallic chemical vapor deposition of copper oxide thin films

Copper oxide thin films were prepared by organometallic chemical vapor deposition (OMCVD or MOCVD) technique. This MOCVD process uses copper acetylacetonate (Cu(acac)[subscript]2) as the copper precursor. Spectroscopic (X-ray photoelectron spectroscopy (XPS), Auger electron spectroscopy (AES), and infrared spectroscopy (IR)) and diffraction (X-ray diffraction (XRD)) methods were employed to analyze the chemical composition and oxidation state of copper in these films. According to spectroscopic results, the composition of these MOCVD film primarily depends on the deposition temperature and partial pressures of the reactants. As indicated by XPS and XRD results, Cu[subscript]2O films were prepared at 360°C, with an oxygen partial pressure of 150 torr and copper precursor partial pressure of 0.20 torr. CuO films were grown at temperatures above 420°C, with an oxygen pressure of 190 torr and precursor pressure of 0.20 torr. By using water vapor instead of oxygen as the co-reactant, Cu films were deposited at temperatures above 380°C, with a water vapor pressure of 15 torr and precursor pressure of 0.20 torr. To examine the specific mechanism of precursor decomposition, a molecular vibrational spectroscopic technique, Fourier Transform Infrared spectroscopy (FTIR), was employed to investigate the vapor phase product distribution in the MOCVD effluent stream. Based on FTIR results, a kinetic model was proposed. This model suggests that steric effect from chelating ligands and bond strength sequence in the precursor molecule are the principle factors determining the decomposition products of Cu(acac)[subscript]2 in the MOCVD reactor. Differential scanning calorimetry (DSC) was used to study the pyrolysis pattern of Cu(acac)[subscript]2. Particularly, the impacts of oxygen concentration, carrier gas molecular weight, and heating rate on the pyrolysis of this precursor were studied. From DSC results, it seems that Cu(acac)[subscript]2 undergoes a single-step, exothermic reaction in the ambient with oxygen gas present. In DSC pattern, the exothermic peak height also increased as oxygen concentration increased. The activation energy for the exothermic step was derived by Kissinger equation as 20 kcal/mol. Based on experimental results of deposition, FTIR, and DSC, it seems that a deposition temperature above a critical value is necessary to initiate the decomposition of Cu(acac)[subscript]2 and oxygen can assist this reaction by accelerating the reaction rate

A Robust Quantum Random Access Memory

A "bucket brigade" architecture for a quantum random memory of $N=2^n$ memory cells needs $n(n+5)/2$ times of quantum manipulation on control circuit nodes per memory call. Here we propose a scheme, in which only average $n/2$ times manipulation is required to accomplish a memory call. This scheme may significantly decrease the time spent on a memory call and the average overall error rate per memory call. A physical implementation scheme for storing an arbitrary state in a selected memory cell followed by reading it out is discussed.Comment: 5 pages, 3 figure