Patent Application
20070275498
Various objects, features, and advantages of the present invention can be more fully appreciated with reference to the following detailed description of the invention when considered in connection with the following drawings, in which like reference numerals identify like elements:
In the following description, numerous specific details are set forth regarding the systems and methods of the present invention and the environment in which such systems and methods may operate, etc., in order to provide a thorough understanding of the present invention. It will be apparent to one skilled in the art, however, that the present invention may be practiced without such specific details, and that certain features, which are well known in the art, are not described in detail in order to avoid complication of the subject matter of the present invention. In addition, it will be understood that the examples provided below are exemplary, and that it is contemplated that there are other systems and methods that are within the scope of the present invention.
In accordance with the present invention, systems and methods are provided to improve the performance of electronic and optoelectronic circuits made using organic semiconductor processing technology. The electronic and optoelectronic circuits can include devices such as, for example, transistors, sensors, light emitting diodes, photovoltaic devices, or any other suitable device or combination of devices.
A semiconductor can be realized using an ink-jet printed composite mixture. A semiconductor, such as a transistor, generally includes a source electrode, a drain electrode, a gate, a substrate on which the electrodes and gate sit, and a dielectric that insulates both the source electrode and the drain electrode from the gate. A channel exists between the source electrode and the drain electrode. When the gate is turned “ON,” current flows between the electrodes via the channel.
In organic semiconductor processing technology, an ink-jet device disperses a suitable composite mixture onto a substrate. The substrate can be an organic substrate or an inorganic substrate. The substrate can include, for example, glass, silicon (including electrode bearing silicon substrates), polyimide, indium tin oxide (ITO), or any other suitable substrate.
The composite mixture includes a semiconducting polymer having structures on a nanometer scale (i.e., nanomaterials) dispersed into an organic solvent. The polymer can be dispersed in a solvent that is the same as, or different from, the solvent in which the nanomaterials are dispersed. In a preferred embodiment, the polymer and the nanomaterials are dispersed in the same solvent to facilitate the formation of a polymer and nanomaterial composite. Dispersion can be accomplished using any suitable process such as, for example, ultrasonication.
The type of solvent used preferably results in effective dispersion of the polymer and nanomaterials in the solvent, thereby minimizing the occurrence of clogging of the ink-jet nozzles. The polymer can be, for example, poly(3-hexylthiophene) (P3HT), dioctylfluorene-bithiophene (F8T2), poly(3,3′″-dialkyl-quaterthiophene) (PQT), pentacene, or any other suitable polymer. The solvent can be, for example, isopropyl alcohol (IPA), dimethylformamide (DMF), toluene, chloroform, xylene, N-methylpyrrolidone (NMP), or any other suitable solvent.
The composite mixture can include any suitable nanomaterials or combination of nanomaterials. The nanomaterials can be nanotubes and/or nanostructures.
In one embodiment, the nanomaterials can be nanotubes. A nanotube is a hollow cylinder having dimensions on the order of a nanometer. The nanotube can be made of carbon or any other suitable material. The composite mixture can include nanotubes of the same material or of different materials.
In another embodiment, the nanomaterials can be nanowires. A nanowire is a wire having dimensions on the order of a nanometer. The nanowires can be made of silicon or any other suitable material. The composite mixture can include nanowires of the same material or of different materials.
In yet another embodiment, the nanomaterials can be a composite of nanotubes and nanowires. The composite mixture can include nanotubes of the same material or of different materials and nanowires of the same material or of different materials.
In a further embodiment, in addition to or alternative to the nanotubes and nanowires described above, the nanomaterials can include, but are not limited to, organic and inorganic, single or multi-walled nanotubes, nanowires, nanodots, quantum dots, nanorods, nanocrystals, nanotetrapods, nanotripods, nanobipods, nanoparticles, nanosaws, nanosprings, nanoribbons, any branched nanostructure, any mixture of these nanoshaped materials, and/or any other suitable nanomaterials or combination of nanomaterials.
These nanomaterials may be made of the following elements or compounds: gold (Au), silver (Ag), platinum (Pt), palladium (Pd), cobalt (Co), titanium (Ti), molybdenum (Mo), tungsten (W), manganese (Mn), chromium (Cr), iron (Fe), carbon (C), silicon (Si), germanium (Ge), boron (B), tin (Sn), silicon germanium (SiGe), silicon carbide (SiC), silicon tin (SiSn), germanium carbide (GeC), boron nitride (BN), indium phosphide (InP), indium nitride (InN), indium arsenide (InAs), indium antimonide (InSb), gallium nitride (GaN), gallium phosphide (GaP), gallium arsenide (GaAs), gallium antimonide (GaSb), aluminum nitride (AlN), aluminum phospide (AlP), aluminum arsenide (AlAs), aluminum antimonide (AlSb), cadmium oxide (CdO), cadmium sulfide (CdS), cadmium selenide (CdSe), cadmium telluride (CdTe), zinc oxide (ZnO), zinc sulfide (ZnS), zinc selenide (ZnSe), zinc telluride (ZnTe), magnesium oxide (MgO), magnesium sulfide (MgS), magnesium selenide (MgSe), magnesium telluride (MgTe), mercury oxide (HgO), mercury sulfide (HgS), mercury selenide (HgSe), mercury telluride (HgTe), lead oxide (PbO), lead sulfide (PbS), lead selenide (PbSe), lead telluride (PbTe), germanium sulfide (GeS), germanium selenide (GeSe), germanium telluride (GeTe), tin sulfide (SnS), tin selenide (SnSe), tin telluride (SnTe), indium oxide (InO), tin oxide (SnO), SiOx, germanium oxide (GeO), tungsten oxide (WO), titanium oxide (TiO), iron oxide (FeO), manganese oxide (MnO), cobalt oxide (CoO), nickel oxide (NiO), chromium oxide (CrO), vanadium oxide (VO), MSiO4 (where M=Zn, Cr, Fe, Mn, Co, Ni, V, Ti), copper tin (CuSn), copper fluoride (CuF), copper chloride (CuCl), copper bromide (CuBr), copper iodide (CuI), silver fluoride (AgF), silver chloride (AgCl), silver bromide (AgBr), silver iodide (AgI), calcium cyanamide (CaCN2), beryllium silicon nitride (BeSiN2), zinc germanium diphosphide (ZnGeP2), cadmium tin arsenide (CdSnAs2), zinc tin antimonide (ZnSnSb2), copper germanium phosphide (CuGe2P3), copper silicon phosphide (CuSi2P3), silicon nitride (Si3N4), germanium nitride (Ge3N4), aluminum oxide (Al2O3), aluminum oxycarbide (Al2CO), or any combination thereof and any related alloys.
The nanomaterials may also comprise: a metal, such as gold (Au), nickel (Ni), palladium (Pd), iridium (Ir), cobalt (Co), chromium (Cr), aluminum (Al), or titanium (Ti); a metal alloy; a polymer; a conductive polymer; a ceramic material; or any combination thereof.
When a nanomaterial comprises a semiconductive material, the semiconductive material may further comprise a dopant. Dopants useful in the present invention include, but are not limited to: a p-type dopant, such as boron (B), aluminum (Al), indium (In), magnesium (Mg), zinc (Zn), cadmium (Cd), mercury (Hg), carbon (C), silicon (Si), an element from Group II of the periodic table, an element from Group III of the periodic table, or an element from Group IV of the periodic table; or an n-type dopant, such as silicon (Si), germanium (Ge), tin (Sn), sulfur (S), selenium (Se), tellurium (Te), phosphorus (P), arsenic (As), antimony (Sb), or an element from Group V of the periodic table.
In one embodiment, the dopant is a p-type dopant.
In another embodiment, the dopant is an n-type dopant.
When the nanostructure is a nanotube, nanowire, or nanoribbon, the nanotube, nanowire, or nanoribbon can comprise a conductive or semiconductive material, such as an organic polymer, pentacene, or a transition metal oxide.
In one embodiment, the composite mixture can include two or more distinct nanomaterials. For example, the composite mixture can include two different types of nanocrystal populations or a nanotube population and a nanoparticle population.
The nanomaterials can improve the carrier mobility and conductivity of the semiconductors. In the composite mixture, the nanomaterials may have an aligning influence on the rod-like organic semiconducting molecules in the polymers, as in the case of liquid crystals. In addition, the intrinsic electrical properties of the nanomaterials may also improve the overall electrical performance of the semiconductors.
The plurality of nanomaterials and organic semiconducting molecules can be aligned to improve carrier mobility and conductivity. For example, in a transistor, the nanomaterials are preferably aligned between its source electrode and drain electrode.
In one embodiment, prior to the deposition of the composite mixture by the ink-jet device, the surface of the substrate can be chemically treated. A chemical such as octadecyltrichlorosilane can be used to modify the surface of the substrate to facilitate alignment of the composite material. Alternatively, any other suitable chemical can be used to modify the surface of the substrate.
In another embodiment, the surface of the substrate can be mechanically rubbed in a preferential direction. Fine grooves can be created on the surface of the substrate in a direction along which the nanomaterials are intended to align, as occurs in liquid crystal cells.
In another embodiment, following the deposition of the composite mixture by the ink-jet device, but before the solvent has had time to fully evaporate, an electric field or alternating current can be applied across the electrodes of the semiconductor to align the nanomaterials in the desired direction.
In yet another embodiment, the alignment of the nanomaterials can be achieved during the growth phase of the nanomaterials. Aligned nanomaterials can be grown on a substrate prior to ink-jet deposition of the organic semiconducting material. This facilitates the fabrication of top-contact electrodes following ink-jet deposition.
Dielectric 110 provides insulation between source electrode 104 and gate 108, and between drain electrode 106 and gate 108. Although not shown, gate 108, source electrode 104, and drain electrode 106 can be connected to other transistors, voltage supplies, and/or any other suitable circuit components.
An organic layer forms a channel between source electrode 104 and drain electrode 106. The organic layer can be a composite layer of a polymer and nanomaterials. In one embodiment, as shown in
In another embodiment, an enhanced performance sensor device can also be realized using an ink-jet printed composite mixture that includes a semiconducting polymer having nanomaterials dispersed into an organic solvent. The sensor device can include any suitable insulating substrate and an ink-jet printed composite mixture deposited between and n-type and p-type electrodes. The electrical signal generated within the polymer composite upon detection is collected at the electrodes.
The nanomaterials in the composite mixture can improve the electrical performance of the organic semiconductors. The nanomaterials can act as enhancers of light, chemical or biological signal detection and conversion into electrical signals.
Between n-type electrode 304 and p-type electrode 308 is sensing polymer composite 308, which can be a polymer and nanomaterial composite layer deposited on the surface of substrate 302. When detection occurs within sensing polymer composite 308, a current is conducted between n-type electrode 304 and p-type electrode 306.
In
In another embodiment, the surface of substrate 102 can be mechanically rubbed in a preferential direction. Fine grooves can be created on the surface of the substrate in a direction along which the nanomaterials are intended to align.
At step 604, a composite mixture 204 of a polymer, nanomaterials 202, and solvent is deposited on substrate 102 using an ink-jet device. Based on the modified surface of substrate 102, the nanomaterials 202 are aligned between the electrodes of the semiconducting device (e.g., perpendicularly between electrodes 104 and 106 of transistor 100/200).
In
The use and alignment of nanomaterials in a composite material that is deposited onto a substrate of a transistor using an ink-jet device may advantageously improve the conductivity and thus performance of electronic circuits. The different embodiments of the invention can be applied to the field of polymer electronics as well as to the field of polymer optoelectronics.
In other embodiments, the processes describes in
The use and alignment of nanomaterials in a composite material that is deposited onto a substrate of a sensor using an ink-jet device may advantageously improve the sensitivity, responsitivity, and detection performance of the sensor.
According to one or more embodiments of the invention, the invention may advantageously improve the carrier mobility and conductivity of transistors, the carrier mobility and data processing speed in radio frequency identification (RFID) tags, the responsitivity of photodetectors, and the detection range of bio and chemical sensors produced using ink-jet manufacturing.
It is to be understood that the invention is not limited in its application to the details of construction and to the arrangements of the components set forth in the following description or illustrated in the drawings. The invention is capable of other embodiments and of being practiced and carried out in various ways. Also, it is to be understood that the phraseology and terminology employed herein are for the purpose of description and should not be regarded as limiting.
As such, those skilled in the art will appreciate that the conception, upon which this disclosure is based, may readily be utilized as a basis for the designing of other structures, methods, and systems for carrying out the purposes of the present invention. It is important, therefore, that the claims be regarded as including such equivalent constructions insofar as they do not depart from the spirit and scope of the present invention.
Although the present invention has been described and illustrated in the foregoing exemplary embodiments, it is understood that the present disclosure has been made only by way of example, and that numerous changes in the details of implementation of the invention may be made without departing from the spirit and scope of the invention, which is limited only by the claims which follow.
