摘要:

A photoelectrochemical memory system is created by combining the photochemical trans‐cis isomerization and the electrochemical reduction‐oxidation of azo compounds in LB film. This novel system has the advantages of storge density up to 1012bits/cm2, non‐destructive readout, multiple memory function, rewritability and room‐temperature working condition.

ISSN:0094-243X    

DOI:10.1063/1.42654

出版商:AIP    

年代:1992

数据来源: AIP

摘要:

The properties of photosynthetic reaction centers which make them interesting for technological applications are reviewed. Protein engineering has been used to systematically modify the oxidation potential of the initial electron donor in photosynthesis. The driving force and rates of electron transfer reactions in the reaction center have been altered by application of external electric fields. This leads to changes in the population of various intermediates which is reflected in changes in the absorption properties of the sample. The first example of engineering a new site for covalent attachment of new components to the reaction center is described.

ISSN:0094-243X    

DOI:10.1063/1.42655

出版商:AIP    

年代:1992

数据来源: AIP

摘要:

An overview is given on our attempts to find molecules which can be used for unidirectional transfer of energy or charge and for switching. Results on radical anion salts of Dicyano‐chinone‐diimine (DCNQI), on linear polyenes with substituents on both ends and on photochromic fulgides for switching are summarized.

ISSN:0094-243X    

DOI:10.1063/1.42656

出版商:AIP    

年代:1992

数据来源: AIP

摘要:

Calculations have been performed on models of Langmuir‐Blodgett LB films to explore how molecular nonlinear response expresses itself in film response. The molecules are treated as a string ofsbeads initially arranged normal to the film with their long axes forming a close‐packed hexagonal array, but they are then allowed to tilt away from the vertical. The molecular polarizability &agr; and first hyperpolarizability &bgr; are represented by one‐dimensional models in which the axial components arestimes the perpendicular ones. Because of the layer structure of the films, the dipolar interactions are calculated as planewise sums between one molecule and all the molecules in a given layer. The sums have been calculated for various values ofsas a function of tilt; they are negligible except for interactions of a molecule with its own layer. They have been used to calculate the local electric field, refractive index and quadratic susceptibility &khgr;(2)for thin films. The results show that tilt has a major effect on the pattern of components of &khgr;(2)and hence on measured nonlinear optical behavior. Such information can be used to help guide the design of molecules to achieve desired film properties.

ISSN:0094-243X    

DOI:10.1063/1.42657

出版商:AIP    

年代:1992

数据来源: AIP

摘要:

Using a two‐state model, it was recently shown that there is an optimal combination of donor and acceptor strengths for a given bridge that will maximize the first molecular electronic hyperpolarizability (&bgr;). Implementation of this strategy relies on the realization that molecules with strongly aromatic end groups will not have the correct balance of two limiting charge transfer resonance forms in the ground state to achieve the degree of bond alternation required to optimize the molecular hyperpolarizability. Electric field induced second harmonic generation studies on organic molecules with various bridge structures support our hypothesis.

ISSN:0094-243X    

DOI:10.1063/1.42658

出版商:AIP    

年代:1992

数据来源: AIP

摘要:

Spectral density of the current fluctuations is calculated for the resonant tunneling structure: localized energy level between two bulk electrodes. This structure is molecular‐level counterpart of the system of two small metallic tunnel junctions connected in series (SET transistor). The current fluctuations determine the sensitivity of the structure to variations of the energy of the localized level.

ISSN:0094-243X    

DOI:10.1063/1.42659

出版商:AIP    

年代:1992

数据来源: AIP

摘要:

The conductance of 0.75 &mgr;m long, narrow, high resistance wires has been studied as a function of a voltage imposed upon a closely coupled lateral gate. For all samples with line widths less than 0.12 &mgr;m and resistances greater than 60 k&OHgr; the conductance is observed to oscillate periodically as the voltage on the gate electrode is monotonically changed. The period of oscillation nearly corresponds to the addition or subtraction of one electron to the entire sample. These wires have no apparent tunnel barriers, yet they exhibit all the transport properties found in series arrays of very small tunnel junctions. From measurements of the dc I‐V curves and the temperature dependence of the device characteristics we conclude that the behavior of our devices is consistent with the Coulomb Blockade picture for electrons tunneling in disordered systems. We discuss the potential for using these structures as charge detectors.

ISSN:0094-243X    

DOI:10.1063/1.42660

出版商:AIP    

年代:1992

数据来源: AIP

摘要:

Electronic systems that are large in the sense that they contain a great many devices constitute a unique environment that is described. The essential attributes that enable a device to function properly in that environment are identified. The principles are illustrated with examples of the transistor and other logic devices and applied to recent proposals.

ISSN:0094-243X    

DOI:10.1063/1.42661

出版商:AIP    

年代:1992

数据来源: AIP

摘要:

Mesoscopic physics encompasses a group of ‘‘new’’ phenomena observable in sufficiently small electronic systems. In describing the phenomena one may simply say that the systems are beginning to behave like atoms or molecules rather than bulk systems because of the small system or element size. One looks forward to an electronics based on these phenomena but the effects implementation would be favored by device scale at the level of only a few nanometer. It is of interest therefore whether such size scales are attainable using lithographic means similar at least in principle to those in making ordinary electronic circuits.

ISSN:0094-243X    

DOI:10.1063/1.42665

出版商:AIP    

年代:1992

数据来源: AIP

摘要:

By severely reducing the number of molecules in the illuminated sample, the optical resonances of individual molecules can be resolved in a fluorescence excitation spectrum. Photon correlation and sudden jumps due to spectral diffusion confirm the attribution of the Lorentzian excitation peaks to single molecules. This new spectroscopy displays specific effects whith would be washed out in the average over many molecules. A single molecule is also a truly local probe of its environment, by means of which fundamental studies of the matrix dynamics as well as nanophysics experiments may be undertaken.

ISSN:0094-243X    

DOI:10.1063/1.42666

出版商:AIP    

年代:1992

数据来源: AIP