Optical phonon cascade emission by photoelectrons at a p-GaN (Cs,O)–vacuum interface

The capability to obtain symmetrical images at voltages as low as 200 eV and beam currents less than 9 pico amps is believed to be advantageous for metrology and study of dielectric or biological samples. Symmetrical images should allow more precise and accurate line width measurements than currently achievable by traditional secondary electron detectors. The low voltage and current capability should allow imaging of samples which traditionally have been difficult because of charging or electron beam damage.The detector system consists of a lens mounted dual anode MicroChannel Plate (MCP) detector, vacuum interface, power supplies, and signal conditioning to interface directly to the video card of the SEM. The detector has been miniaturized so that it does not interfere with normal operation of the SEM sample handling and alternate detector operation. Biasing of the detector collection face will either add secondaries to the backscatter signal or reject secondaries yielding only a backscatter image. The dual anode design allows A−B signal processing to provide topological information as well as symmetrical A+B images.Photomicrographs will show some of the system capabilities. Resolution will be documented with gold on carbon. Variation of voltage, beam current, and working distance on dielectric samples such as glass and photoresist will demonstrate effects of common parameter changes.

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Double longitudinal-optical phonon intrawell depopulated terahertz quantum cascade structures: Electron transport modeling using a density matrix method

Applied Physics Letters ◽

10.1063/5.0052598 ◽

2021 ◽

Vol 118 (24) ◽

pp. 241107

Author(s):

Will Freeman

Keyword(s):

Electron Transport ◽

Density Matrix ◽

Optical Phonon ◽

Matrix Method ◽

Longitudinal Optical ◽

Transport Modeling ◽

Longitudinal Optical Phonon ◽

Quantum Cascade ◽

Quantum Cascade Structures

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Long-wavelength dielectric properties and infrared active optical phonon modes of molecular beam epitaxy ScxAl1−xN determined by infrared spectroscopic ellipsometry

Applied Physics Letters ◽

10.1063/5.0027364 ◽

2020 ◽

Vol 117 (23) ◽

pp. 232107

Author(s):

Alyssa L. Mock ◽

Alan G. Jacobs ◽

Eric N. Jin ◽

Matthew T. Hardy ◽

Marko J. Tadjer

Keyword(s):

Dielectric Properties ◽

Molecular Beam Epitaxy ◽

Spectroscopic Ellipsometry ◽

Optical Phonon ◽

Molecular Beam ◽

Phonon Modes ◽

Long Wavelength ◽

Infrared Spectroscopic

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Polar Optical Phonon Instability and Intervalley Transfer in Gallium Nitride

MRS Proceedings ◽

10.1557/proc-512-549 ◽

1998 ◽

Vol 512 ◽

Cited By ~ 2

Author(s):

B. E. Foutz ◽

S. K. O'leary ◽

M. S. Shur ◽

L. F. Eastman ◽

B. L. Gelmont ◽

...

Keyword(s):

Gallium Nitride ◽

Analytical Model ◽

Optical Phonon ◽

Room Temperature ◽

Phonon Scattering ◽

Polar Optical Phonon ◽

Scattering Mechanism ◽

Loss Mechanism ◽

One Dimensional ◽

Optical Phonon Scattering

ABSTRACTWe develop a simple, one-dimensional, analytical model, which describes electron transport in gallium nitride. We focus on the polar optical phonon scattering mechanism, as this is the dominant energy loss mechanism at room temperature. Equating the power gained from the field with that lost through scattering, we demonstrate that beyond a critical electric field, 114 kV/cm at T = 300 K, the power gained from the field exceeds that lost due to polar optical phonon scattering. This polar optical phonon instability leads to a dramatic increase in the electron energy, this being responsible for the onset of intervalley transitions. The predictions of our analytical model are compared with those of Monte Carlo simulations, and are found to be in satisfactory agreement.

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