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Articles 2521 - 2528 of 2528

Full-Text Articles in Engineering

Transition Electrolyte Concentration For Bubble Coalescence, Michael Prince, H. Blanch Aug 1990

Transition Electrolyte Concentration For Bubble Coalescence, Michael Prince, H. Blanch

Michael J. Prince

No abstract provided.

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Bubble Coalescence And Break-Up In Air Sparged Biochemical Reactors, Michael Prince, H. Blanch Jul 1990

Bubble Coalescence And Break-Up In Air Sparged Biochemical Reactors, Michael Prince, H. Blanch

Michael J. Prince

No abstract provided.

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On The Electrochemical Etching Of Tips For Scanning Tunneling Microscopy, Nancy Burnham, J. Ibe, P. Bey Jr., S. Brandow, R. Brizzolara, D. Dilella, K. Lee, C. K. Marrian, R. Colton Jun 1990

On The Electrochemical Etching Of Tips For Scanning Tunneling Microscopy, Nancy Burnham, J. Ibe, P. Bey Jr., S. Brandow, R. Brizzolara, D. Dilella, K. Lee, C. K. Marrian, R. Colton

Nancy A. Burnham

The sharpness of tips used in scanning tunneling microscopy(STM) is one factor which affects the resolution of the STM image. In this paper, we report on a direct‐current (dc) drop‐off electrochemicaletching procedure used to sharpen tips for STM. The shape of the tip is dependent on the meniscus which surrounds the wire at the air–electrolyte interface. The sharpness of the tip is related to the tensile strength of the wire and how quickly the electrochemical reaction can be stopped once the wire breaks. We have found that the cutoff time of the etch circuit has a significant effect on the …

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Probing The Surface Forces Of Monolayer Films With An Atomic-Force Microscope, Nancy Burnham, Dawn Dominguez, Robert Mowery, Richard Colton Apr 1990

Probing The Surface Forces Of Monolayer Films With An Atomic-Force Microscope, Nancy Burnham, Dawn Dominguez, Robert Mowery, Richard Colton

Nancy A. Burnham

Using an atomic force microscope (AFM), we have studied the attractive and adhesive forces between a cantilever tip and sample surfaces as a function of sample surface energy. The measured forces systematically increased with surface energy. The AFM is very sensitive; changes in the surface forces (i.e., attraction and adhesion) of monolayer covered samples could be clearly discerned when only the surface group of the monolayer film was changed from -CH3 to -CF3.

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Measuring The Nanomechanical Properties And Surface Forces Of Materials Using An Atomic Force Microscope, Nancy Burnham, Richard Colton Jun 1989

Measuring The Nanomechanical Properties And Surface Forces Of Materials Using An Atomic Force Microscope, Nancy Burnham, Richard Colton

Nancy A. Burnham

An atomic force microscope(AFM) has been configured so that it measures the force between a tip mounted on a cantilever beam and a sample surface as a function of the tip–surface separation. This allows the AFM to study both the nanomechanical properties of the sample and the forces associated with the tip–surface interaction. More specifically, the AFM can measure the elastic and plastic behavior and hardness via nanoindentation,van der Waals forces, and the adhesion of thin‐film and bulk materials with unprecedented force and spatial resolution. The force resolution is currently 1 nanonewton, and the depth resolution is 0.02 nm. Additionally, …

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Electron Beam Effects In The Analysis Of Compound Semiconductors And Devices, Nancy Burnham, Ll Kazmerski, Ab Swartzlander, Aj Nelson, Se Asher Aug 1987

Electron Beam Effects In The Analysis Of Compound Semiconductors And Devices, Nancy Burnham, Ll Kazmerski, Ab Swartzlander, Aj Nelson, Se Asher

Nancy A. Burnham

The effects of electron beams on the analysis of CuInSe2surfaces are examined in this paper. Potential changes in the surface chemistry—including oxidation and desorption—under a range of incident probe conditions, are investigated for possible artifactual information generation. Emphasis is placed on the relationships between beam conditions and oxygen chemisorption and physisorption, since oxygen treatments of devices utilizing this semiconductor are critical to performance. Single crystals and polycrystalline thin films are analyzed and compared to establish the beam‐induced phenomena.

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Electron Energy‐Loss Spectroscopy Study Of Hydrogenated Amorphous Silicon, Nancy Burnham, Rf Fisher, Se Se, Ll Kazmerski Jun 1987

Electron Energy‐Loss Spectroscopy Study Of Hydrogenated Amorphous Silicon, Nancy Burnham, Rf Fisher, Se Se, Ll Kazmerski

Nancy A. Burnham

Electron energy‐loss spectroscopy is used to study hydrogenated amorphous silicon (a‐Si:H). Core‐level and plasma excitations were examined as a function of hydrogen content. This technique and its interpretation reveals a consistent picture of the electron excitations within this important material. The a‐Si:H thin films were fabricated by rf sputtering. Their hydrogen concentrations ranged from 0% to 15%. Hydrogen content was determined by infrared spectroscopy and secondary ion mass spectroscopy. X‐ray photoelectron spectroscopy and inspection of the silicon Auger‐K L L peak confirmed the silicon core levels.

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Scanning Auger Microprobe Studies Of Ball Cratered Cds/Cuinse2 Solar Cells, Nancy Burnham, Ll Levenson, Rj Matson, R Noufi, Ll Kazmerski Apr 1986

Scanning Auger Microprobe Studies Of Ball Cratered Cds/Cuinse2 Solar Cells, Nancy Burnham, Ll Levenson, Rj Matson, R Noufi, Ll Kazmerski

Nancy A. Burnham

CdS/CuInSe2solar cell films are typically several micrometers thick. Composition profiles of these films are usually carried out on fracture cross sections by scanning Auger microscopy or by recording Auger spectra during ion milling. For fracture cross sections, the depth resolution depends on the electron beam diameter and the roughness of the fracture surface. Ion milling is time consuming, and artifacts are caused by ion beam faceting. Ball cratering requires only a fraction of an hour and provides significant magnification of the film cross section. There is sufficient contrast, both in optical and electron microscopy, to distinguish between CdS and CuInSe2 …

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