Effect of implantation of nitrogen into SIMOX buried oxide on its fixed positive charge density

In order to obtain greater radiation hardness for SIMOX (separation by implanted oxygen) materials, nitrogen was implanted into SIMOX BOX (buried oxide). However, it has been found by the C-V technique employed in this work that there is an obvious increase of the fixed positive charge density in the nitrogen-implanted BOX with a 150 out thickness and 4 x 10(15) cm(-2) nitrogen implantation dose, compared with that unimplanted with nitrogen. On the other hand, for the BOX layers with a 375 nm thickness and implanted with 2 x 10(15) and 3 x 10(15) cm(-2) nitrogen doses respectively, the increase of the fixed positive charge density induced by implanted nitrogen has not been observed. The post-implantation annealing conditions are identical for all the nitrogen-implanted samples. The increase in fixed positive charge density in the nitrogen-implanted 150 nm BOX is ascribed to the accumulation of implanted nitrogen near the BOX/Si interface due to the post-implantation annealing process according to SIMS results. In addition, it has also been found that the fixed positive charge density in initial BOX is very small. This means SIMOX BOX has a much lower oxide charge density than thermal SiO2 which contains a lot of oxide charges in most cases.

Simulation research of nonlinear behavior induced by the charge-carrier effect in resonant-cavity-enhanced photodetectors

In this paper, we have calculated and discussed in detail the nonlinear effect induced by three carrier effects: free-carrier absorption, bandgap filling, and bandgap shrinkage. The central wavelength of response of resonant-cavity-enhanced (RCE) photodetectors shifts according to the change of the refractive index, and the response of a given optical wavelength simultaneously changes.With an increasing As composition of ln(1-x)Ga(x)As(y)P(1-y) and the spacer thickness, the nonlinear effect increases, but the -1-dB input saturation optical power and the -1-dB saturation photocurrent decrease. Bistable-state operation occurs when the input optical power is in the proper bistable region.

Fabrication of ZnO and its enhancement of charge injection and transport in hybrid organic/inorganic light emitting devices

ZnO nanocrystals were synthesized by hydrolysis in methanol. X-ray diffraction and photoluminescence spectra confirm that good crystallized ZnO nanoparticles were formed. Utilizing those ZnO nanoparticles and poly [2- methoxy-5 - (3',7'-dimethyloctyloxy)- 1,4-phenylenevinylene] (MDMO-PPV), light emitting devices with indium tin oxide (ITO)/poly(3,4-oxyethyleneoxy-thiophene):poly(styrene sulfonate) (PEDOT:PSS)/ ZnO:MDMO-PPV/Al and ITO/PEDOT:PSS/MDMO-PPV/Al structures were fabricated. Electrolummescence (EL) spectra reveal that EL yield of hybrid MDMO-PPV and ZnO nanocrystals devices increased greatly as compared with pristine MDMO-PPV devices. The current-voltage characteristics indicate that addition of ZnO nanocrystals can facilitate electrical injection and charge transport. The decreased energy barrier to electron injection is responsible for the increased efficiency of electron injection. (c) 2007 Elsevier B.V. All rights reserved.

Continuous weak measurement and feedback control of a solid-state charge qubit: A physical unravelling of non-Lindblad master equation

Conventional quantum trajectory theory developed in quantum optics is largely based on the physical unravelling of a Lindblad-type master equation, which constitutes the theoretical basis of continuous quantum measurement and feedback control. In this work, in the context of continuous quantum measurement and feedback control of a solid-state charge qubit, we present a physical unravelling scheme of a non-Lindblad-type master equation. Self-consistency and numerical efficiency are well demonstrated. In particular, the control effect is manifested in the detector noise spectrum, and the effect of measurement voltage is discussed.

Mode softening in charge-density excitations of a two-dimensional electron gas driven by Rashba spin-orbit interaction

The electron density response of a uniform two-dimensional (2D) electron gas is investigated in the presence of a perpendicular magnetic field and Rashba spin-orbit interaction (SOI). It is found that, within the Hartree-Fock approximation, a charge density excitation mode below the cyclotron resonance frequency shows a mode softening behavior, when the spin-orbit coupling strength falls into a certain interval. This mode softening indicates that the ground state of an interacting uniform 2D electron gas may be driven by the Rashba SOI to undergo a phase transition to a nonuniform charge density wave state.

Charge-density and spin-density excitations in a two-dimensional electron gas with Rashba spin-orbit coupling

We study theoretically the charge-density and spin-density excitations in a two-dimensional electron gas in the presence of a perpendicular magnetic field and a Rashba type spin-orbit coupling. The dispersion and the corresponding intensity of excitations in the vicinity of cyclotron resonance frequency are calculated within the framework of random phase approximation. The dependence of excitation dispersion on various system parameters, i.e., the Rashba spin-orbit interaction strength, the electron density, the Zeeman spin splitting, and the Coulomb interaction strength is investigated.

Effects of phase-breaking on long-range charge transfer in DNA: Partially-coherent-tunneling model study

The mechanism of hole charge transfer in DNA of various lengths and sequences is investigated based on a partially coherent tunneling theory (Zhang et al., J Chem Phys 117:4578, 2002), where the effects of phase-breaking in adenine-thymine and guanine-cytosine base pairs are treated on equal foot. This work aims at providing a self-consistent microscopic interpretation for rate experiments on various DNA systems. We will also clarify the condition under which the simple superexchange-mediated-hopping picture is valid, and make some comments on the further development of present theory.

Quantum coherence control of solid-state charge qubit by means of a suboptimal feedback algorithm

The quantum coherence control of a solid-state charge qubit is studied by using a suboptimal continuous feedback algorithm within the Bayesian feedback scheme. For the coherent Rabi oscillation, the present algorithm suggests a simple bang-bang control protocol, in which the control parameter is modulated between two values. For the coherence protection of the idle state, the present approach is applicable to arbitrary states, including those lying on the equator of the Bloch sphere which are out of control in the previous Markovian feedback scheme.

A partially incoherent rate theory of long-range charge transfer in deoxyribose nucleic acid

A quantum chemistry based Green's function formulation of long-range charge transfer in deoxyribose nucleic acid (DNA) double helix is proposed. The theory takes into account the effects of DNA's electronic structure and its incoherent interaction with aqueous surroundings. In the implementation, the electronic tight-binding parameters for unsolvated DNA molecules are determined at the HF/6-31G* level, while those for individual nucleobase-water couplings are at a semiempirical level by fitting with experimental redox potentials. Numerical results include that: (i) the oxidative charge initially at the donor guanine site does hop sequentially over all guanine sites; however, the revealed rates can be of a much weaker distance dependence than that described by the ordinary Ohm's law; (ii) the aqueous surroundings-induced partial incoherences in thymine/adenine bridge bases lead them to deviate substantially from the superexchange regime; (iii) the time scale of the partially incoherent hole transport through the thymine/adenine pi stack in DNA is about 5 ps. (C) 2002 American Institute of Physics.

Superconducting charge qubits: The roles of self and mutual inductances

We study the essential roles of self and mutual inductances in superconducting charge qubits and propose a scheme to couple charge qubits by means of mutual inductance. We also show that the Hamiltonians can be exactly formulated in compact forms in the spin-1/2 representation for both single- and double-qubit structures.

First charge collection and position-precision data on the medium-resistivity silicon strip detectors before and after neutron irradiation up to 2x10(14) n/cm(2)

Test strip detectors of 125 mu m, 500 mu m, and 1 mm pitches with about 1 cm(2) areas have been made on medium-resistivity silicon wafers (1.3 and 2.7 k Ohm cm). Detectors of 500 mu m pitch have been tested for charge collection and position precision before and after neutron irradiation (up to 2 x 10(14) n/cm(2)) using 820 and 1030 nm laser lights with different beam-spot sizes. It has been found that for a bias of 250 V a strip detector made of 1.3 k Ohm cm (300 mu m thick) can be fully depleted before and after an irradiation of 2 x 10(14) n/cm(2). For a 500 mu m pitch strip detector made of 2.7 k Ohm cm tested with an 1030 nm laser light with 200 mu m spot size, the position reconstruction error is about 14 mu m before irradiation, and 17 mu m after about 1.7 x 10(13) n/cm(2) irradiation. We demonstrated in this work that medium resistivity silicon strip detectors can work just as well as the traditional high-resistivity ones, but with higher radiation tolerance. We also tested charge sharing and position reconstruction using a 1030 nm wavelength (300 mu m absorption length in Si at RT) laser, which provides a simulation of MIP particles in high-physics experiments in terms of charge collection and position reconstruction, (C) 1999 Elsevier Science B.V. All rights reserved.

A novel DC-DC charge pump circuit for passive RFID transponder

This paper presents a low-voltage, high performance charge pump circuit suitable for implementation in standard CMOS technologies. The proposed charge pump has been used as a part of the power supply section of fully integrated passive radio frequency identification(RFID) transponder IC, which has been implemented in a 0.35-um CMOS technology with embedded EEPROM offered by Chartered Semiconductor. The proposed DC/DC charge pump can generate stable output for RFID applications with low power dissipation and high pumping efficiency. The analytical model of the voltage multiplier, the comparison with other charge pumps, the simulation results, and the chip testing results are presented.

Influence of fluorine on radiation-induced charge trapping in the SIMOX buried oxides

Charge trapping in the fluorinated SIMOX buried oxides before and after ionizing radiation has been investigated by means of C-V characteristics. Radiation-induced positive charge trapping which results in negative shift of C-V curves can be restrained by implanting fluorine ions into the SIMOX buried oxides. Pre-radiation charge trapping is suppressed in the fluorinated buried oxides. The fluorine dose and post-implantation anneal time play a very important role in the control of charge trapping.

A novel low-power input-independent MOS AC/DC charge pump

This paper presents a novel fully integrated MOS AC to DC charge pump with low power dissipation and stable output for RFID applications. To improve the input sensitivity, we replaced Schottky-diodes in conventional charge pumps with MOS diodes with zero threshold, which has less process defects and is thus more compatible with other circuits. The charge pump in a RFID transponder is implemented in a 0.35um CMOS technology with 0.24 sq mm die size. The analytical model of the charge pump and the simulation results are presented.

Photoexcited charge current for the presence of pure spin current

The asymmetric spin distribution in k space caused by the pure spin current (PSC) can introduce a photoexcited charge current (PECC). This provides us a practical scheme for direct detection of PSC. We demonstrate theoretically that the PECC related to the PSC depends sensitively on the wave vector and spin orientation of the carriers, more important, the helicity dependence of this PECC provides us a way to refine it from the helicity independent background current by tuning the polarized laser beams from left to right circular polarization.