Government of the United States of America, as Represented by the Secretary of Commerce

University System of Maryland

Richard E Cavicchi

Stephen Semancik

Michael Gaitan

John S Suehle

Michael R Zachariah

Nim H Tea

Gregory Ernest Poirier

Prahalad Parthangal

Tekin Kunt

Thomas J McAvoy

An in situ approach toward connecting and electrically contacting vertically aligned nanowire arrays using conductive nanoparticles is provided. The utility of the approach is demonstrated by development of a gas sensing device employing the nanowire assembly. Well-aligned, single-crystalline zinc oxide nanowires were grown through a direct thermal evaporation process at 550&#xb0; C. on gold catalyst layers. Electrical contact to the top of the nanowire array was established by creating a contiguous nanoparticle film through electrostatic attachment of conductive gold nanoparticles exclusively onto the tips of nanowires. A gas sensing device was constructed using such an arrangement and the nanowire assembly was found to be sensitive to both reducing (methanol) and oxidizing (nitrous oxides) gases. This assembly approach is amenable to any nanowire array for which a top contact electrode is needed.

Approach to contacting nanowire arrays using nanoparticles

Disclosed is a method for operating a sensor to differentiate between first and second analytes in a sample. The method comprises the steps of determining a input profile for the sensor which will enhance the difference in the output profiles of the sensor as between the first analyte and the second analyte; determining a first analyte output profile as observed when the input profile is applied to the sensor; determining a second analyte output profile as observed when the temperature profile is applied to the sensor; introducing the sensor to the sample while applying the temperature profile to the sensor, thereby obtaining a sample output profile; and evaluating the sample output profile as against the first and second analyte output profiles to thereby determine which of the analytes is present in the sample.

Method for operating a sensor to differentiate between analytes in a

A differential scanning microcalorimeter produced on a silicon chip enables microscopic scanning calorimetry measurements of small samples and thin films. The chip may be fabricated using standard CMOS processes. The microcalorimeter includes a reference zone and a sample zone. The reference and sample zones may be at opposite ends of a suspended platform or may reside on separate platforms. An integrated polysilicon heater provides heat to each zone. A thermopile consisting of a succession of thermocouple junctions generates a voltage representing the temperature difference between the reference and sample zones. Temperature differences between the zones provide information about the chemical reactions and phase transitions that occur in a sample placed in the sample zone.

Micron-scale differential scanning calorimeter on a chip

A design and fabrication methodology, for silicon micromachined micro-hotplates which are manufactured using commercial CMOS foundries techniques with additional post-fabrication processing. The micro-hotplates are adaptable for a host of applications. The methodology for the fabrication of the micro-hotplates is based on commercial CMOS compatible micromachining techniques. The novel aspects of the micro-hotplates are in the design, choice and layout of the materials layers, and the applications for the devices. The micro-hotplates have advantages over other similar devices in the manufacture by a standard CMOS process which include low-cost and easy integration of VLSI circuits for drive, communication, and control. The micro-hotplates can be easily incorporated into arrays of micro-hotplates each with individualized circuits for control and sensing for independent operation.

Micro-hotplate devices and methods for their fabrication

Arrays of microfabricated hotplates have been used as substrate arrays for materials processing on a microscopic scale. Properties of individual elements (pixels) of the array, such as temperature and voltage bias, are controlled by addressing a given pixel with appropriate signals. Materials are deposited onto pixels with individually controlled deposition conditions (pixel temperature, bias). Pixels are also addressed to control properties during post-deposition processing steps such as heating in vacuum or various gases to alter stoichiometry of a single material, or to alloy multiple composition materials. The addressable heating characteristics may also be used for a maskless lithography on pixel elements. The result is an array of separately, but simultaneously, processed films. Properties of film elements may be measured using electrical contact pads. The array of processed films may be used for sensors, electronic devices, greatly accelerated materials development processes, and solid state physics, biology and chemistry studies.

Application of microsubstrates for materials processing

Planar forms of chemically-sensitive materials have been combined, under temperature control, with the pixels of a specially-designed micro-hotplate array to produce a miniature device capable of analyzing chemical mixtures. The device uses integrated multiple elements having different adsorption properties and temperatures to collectively achieve chemical selectivity in sensing. The method of making and using selectively in sensing. The device of the present invention is manufactured by standard CMOS foundry techniques which allow the production of a range of devices that have improved sensing performance.

Temperature-controlled, micromachined arrays for chemical sensor

A planar epitaxial film of tin oxide has low defect density, high purity, crystalline rutile unit cell structure, one crystalline orientation, controlled stoichiometry, extended lateral dimensions, extremely smooth surface morphology, a high degree of atomic order extending to the surface of the film and is colorless and transparent. The film is made by a method which includes reactive sputter deposition. The films can be used in chemical sensors as well as in numerous other applications.

Growing community of inventors

Washington Grove, MD, United States of America

Richard E Cavicchi