AT504162B1 - ORGANIC PLASMON DIODE FOR THE DETECTION OF LIGHT AND LIGHT DISTRIBUTION DISTRIBUTION - Google Patents

Description

(19)

Austrian Patent Office (10) AT 504 162 B1 2008-09-15 (12) Patent specification (21) Application number: A 1423/2006 (51) Int. CI.8: G01N 21117 (2006.01) (22) Date of filing: 2006-08-25 (43) Published: 2008-09-15 AT504 162 B1 2008-09-15 3

(54) ORGANIC PLASMON DIODE FOR DETECTING LIGHT AND LIGHT FIELD DISTRIBUTION (57) The invention relates to a device for detecting light and light field distributions, which has. (a) means (2) for generating surface plasmons (7) by means of light (6), (b) a plasmon conductor (1), (c) a plasmon diode (4) intimately associated with the plasmon conductor (1) for conversion the surface plasmons (7) into a lektrisches signal, and (d) with the plasmon diode (4) in intimate connection means (3) for receiving the electrical energy.

The device according to the invention can be used as a plasma sensor. DVR 0078018 (56)

References: US 2003 / 0206708A1 (73)

Applicant: JOANNEUM RESEARCH RESEARCH SOCIETY M.B.H. A-8010 GRAZ (AT) 2 AT 504 162 B1

The present invention relates to a device for detecting light and light field distributions. The invention uses the excitation and propagation of surface plasmons. The detection of the surface plasmons is carried out with a completely novel monolithically integrable organic diode. The device according to the invention is referred to below as plasmon diode.

In solid state physics, "plasmons" are collective excitations of free electrons in metals to plasma oscillations against the atomic hulls. These are thus density fluctuations of charge carriers.

Surface plasmons (OP) are surface waves in which the longitudinal electronic vibrations are excited parallel to the surface of a metal. The free electrons may e.g. be excited by photoelectric fields. The strength of the electromagnetic fields of this OP is greatest at the surface and decreases exponentially in the two directions normal to the surface.

Direct exposure of smooth metal surfaces to light, however, can not produce OP. Instead, a coupling structure on the smooth metal surface is required. In general, any structure which is capable of disturbing the homogeneity of the metal surface, that is, e.g. the edge of a slit-shaped opening in the metal surface, a roughening of the surface or an Ensenble of nanoparticles or nanowires on the metal surface.

The following plasmonic components are already known in the prior art:

Special coupling structures for excitation of OP by means of light; nanoscopic op waveguides to pass optical signals between active and passive devices;

Mirrors and reflectors;

Lenses;

Beam splitter, and interferometer.

From DE 699 18 488 T2, for example, a surface plasmon sensor of the Otto type is known. This sensor is used for the quantitative analysis of a material in a sample using surface plasmons. In such a plasmon sensor, when a sample is fixed on the sample receiving side of the metal film of sufficient thickness and a light beam is caused to impinge on the one side of a dielectric block opposite to the sample receiving side of the metal film at a specific angle of incidence, vanishing small waves with an electric field distribution of the sample and the metal film, and surface plasmon are excited in the metal film. This allows a quantitative analysis of the material.

From DE 101 51 312 A1 a surface plasmon resonance sensor is known, which comprises a base unit with a light source and an optical sensor unit for exciting surface plasmons, which has a measuring surface formed by a thin metal film which contacts a sample to be measured can be brought.

To exploit the full potential of the technical possibilities which plasmonics can offer, however, further plasmonic components are needed, but above all components with which the OP generated with light or another excitation source can be detected or measured and detected.

Here is where the present invention, whose object is an apparatus for the detection of light and light field distributions, on the basis of the generation and detection of OP, to 3 AT 504 162 B1

To make available.

The device according to the invention for detecting light and light field distributions comprises: (a) means for generating surface plasmons by means of light, (b) a plasmon conductor, (c) a plasmon diode intimately connected to the plasmon conductor for converting the surface plasmons into electrical energy and (d) a means for receiving electrical energy intimately associated with the plasmon diode.

The invention is based on the recognition that OPs can be converted into an electrical signal when they are introduced into a plasmon diode.

A preferred embodiment is characterized in that the plasmon diode consists of at least one thin layer, the physical properties of which are changed by the action of plasmons, wherein the change of the physical properties is tapped via two electrodes attached directly to this thin layer and the thin layer an organic material, organic molecules, a polymer material, an inorganic material or an organic-inorganic hybrid material.

The plasmon diode may further consist of a series of thin layers, the thin layers of organic materials, of polymeric materials, of organic molecules, of inorganic materials, of at least one organic layer and further polymer layers, of at least one polymer layer and other organic layers at least one organic layer and further inorganic layers, of at least one polymer layer and further inorganic layers, of at least one inorganic layer and further organic layers, of at least one inorganic layer and further polymer layers, of at least one organic-inorganic hybrid material layer and further organic layers, of at least one organic-inorganic hybrid material layer and other polymer layers, or consist of at least one organic-inorganic hybrid material layer and other inorganic layers.

The thin layers are preferably structured on the plasmon diode.

The device according to the invention is preferably on a rigid or flexible substrate.

The invention further relates to the use of the device according to the invention for the detection of surface plasmons.

A preferred embodiment of the plasmon diode according to the invention will be described in more detail with reference to the accompanying figure. 1.- production

FIG. 1 shows schematically a cross section through a plasmon diode according to the invention. Reference numeral 1 denotes a metal film. He can e.g. consist of silver and have a thickness of about 100 nm. This metal film also represents the base electrode of the diode. Instead of a metal, it is also possible to provide a semiconductor or any other plasma-conducting material.

The coupling-in structure for the light is designated slot 2 in the metal film 1. As a coupling structure, however, any local disturbance of the homogeneity of the metal film, such as: a 4 AT 504 162 B1

Kante, an ensemble of nanoparticles, nanowires, etc. act.

The reference numeral 3 also shows a metal film. This metal film 3 acts as a top electrode of the diode and may be e.g. also consist of a silver layer with a thickness of about 100 nm.

Reference numeral 4 denotes a layer sequence consisting of one or more organic thin films. This layer sequence serves as the active layer of the plasmon diode (Schottky diode, pn diode).

The reference numeral 5 designates a substrate which carries the metal film 1. This substrate may e.g. be made of glass. Instead of the glass substrate, any carrier material with appropriately applied primer layers can be used. Arrows 6 and 7 denote incident light and propagating OP, respectively.

The plasmon diode shown in FIG. 1 can be manufactured as follows:

The plasmon diode is manufactured in sandwich structure. One or more organic thin films are contacted by two electrically conductive electrodes. The starting point for the fabrication of the diode is, for example, a glass substrate. For structuring the individual components of the plasmon diode various structuring methods, such as photolithography, electron beam lithography, FIB (focused ion beam), lift-off technique, etc. can be used. The application of the organic and metallic thin layers takes place e.g. by vacuum sublimation in appropriate evaporator plants or by spinncoats or inkjet printen of polymer materials. 2.- Function of the plasmon diode according to the invention

The function of the plasmon diode according to the invention is now the following:

When an edge of the slit 2 is irradiated with light 6, surface plasmons 7 are generated on the metal film 1, which propagate in the arrow direction on the surface of the metal film 1 and run into the interface between the metal film 1 and the semiconductor 4.

There, they generate electric charges with the electromagnetic plasmon field in the organic semiconductor layer 4, which can be tapped off at the base electrode 1 and at the cover electrode 3. This is schematically indicated by the ammeter A.

The electrical current tapped at the plasmon diode is directly proportional to the local light field intensity at the coupling-in structure, which was realized by a slot.

As experimental evidence for the conversion of surface plasmons into electricity by means of a plasmon diode, spatially resolved measurements of the plasmon current (2D plasmone current scan) were performed.

For this purpose, according to FIG. 2, a HeNe laser beam (wavelength 633 nm) is focused onto the substrate plane with a microscope objective (100 ×, numerical aperture 0.75), which produces a laser focus with a diameter of approximately 1.5 μm. The plasmon diode is piezoelectrically moved relative to the focus spot in the x and y directions and the plasma generated current is recorded and displayed simultaneously with the location coordinates.

Fig. 3 shows in the image (a) a light micrograph and in the image (b) the 2D plasmone current scan of the plasmon diode. The plasmon coupling structures consist of 3 slots (A) and alternatively a slot (B) in the silver film. In the field of plasma

Claims (4)

5 AT 504 162 B1 nenblock structure (BS), the silver film was completely removed. The area B2 in the right part of Fig. 3 (a) represents the plasmon diode with its edge. The large bright area B1 (center and left) represents the silver film, which acts as a plasmon diode as well as a plasmon diode. The plasmon coupling structures were realized by 130 nm wide slots in the silver film. We distinguish two separate regions (A and B): Region A consists of three 25 μm long parallel slits with a distance of 614 nm, which corresponds exactly to the plasmon wavelength under the given circumstances. Area B consists of a slot with a length of 50 pm. The structure designated BS acts as a plasmone block structure. A rectangular area (5 x 25 pm) of the silver film was completely removed for this purpose. The width of 5 pm of this structure guarantees that no plasmons can cross over from the left to the right side. This ensures that this structure actually works as a plasmone blocker. The 2D plasmon current scan in Fig. 3 (b) can now be interpreted as follows: direct exposure of the smooth silver surface to light can not produce OP, thus most of the 2D plasmon current scan appears dark (corresponding to very low Values of the plasmone current). The plasmon coupling structure consisting of the 3 slots in the silver film (region A) gives the highest plasmon current values, which is in line with expectations, since the distance of the slots was optimized with respect to the light-plasmon coupling efficiency. The upper part of the coupling structure consisting of a slot (region B) appears bright, the lower part of this coupling structure provides no contrast, since the Plasmo nenblockstruktur there prevents a Plasmonenausbreitung from the coupling structure to the diode out. The fact that the lower region of the coupling-in structure from region B does not produce a signal at the plasmon diode clearly proves that the plasmon diode only detects surface plasmons. Thus, non-plasmonic effects as sources of the measured current can be reliably excluded. If the slit 2 is scanned by a 3D light field, the current to be picked up at the plasmon diode delivers a 3D profile of the light field distribution. The degree of resolution of this measurement method is essentially predetermined by the width of the coupling-in structure. 1. A device for detecting light and light field distributions, which comprises: (a) a means (2) for generating surface plasmons (7) by means of light (6), (b) a plasmone conductor (1), (c) one with plasmon diode (4) intimately connected to the plasmon conductor (1) for converting the surface plasmons (7) into an electrical signal, and (d) means (3) intimately connected to the plasmon diode (4) for receiving the electrical signal, characterized in that the plasmon diode (4) consists of at least one thin layer whose physical properties are changed by the action of plasmas, wherein the change in physical properties is picked up by two electrodes (1; 3) attached directly to this thin layer and the thin layer of an organic material, of organic molecules, of a polymer material, of an inorganic material or of an organic h-inorganic hybrid material. 2. Device according to claim 1, characterized in that the plasmon diode (4) consists of a sequence of thin layers, wherein the thin layers of organic materials, from polymer materials, from organic molecules, from inorganic materials, from at least an organic layer and further polymer layers, at least one polymer layer and further organic layers, at least one organic layer and further inorganic layers, at least one polymer layer and further inorganic layers, at least one inorganic layer and further organic layers, at least one inorganic layer and further polymer layers, of at least one organic-inorganic hybrid material layer and further organic layers, of at least one organic-inorganic hybrid material layer and further polymer layers, or of at least one organic-inorganic hybrid material erialschicht and other inorganic layers. 3. Device according to claim 1, characterized in that the thin layers of the plasmon diode (4) are structured, in particular by photolithography, electron beam lithography, FIB (focused ion beam) or lift-off technique. 4. The device according to claim 2, characterized in that the thin layers of the plasmon diode (4) are structured, in particular by photolithography, electron beam lithography, FIB (focused ion beam) or lift-off technique. For this purpose 2 sheets of drawings