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Surface characterization of semicond...

Liu, Zhi.

Surface characterization of semiconductor photocathode structures.

Record Type:	Electronic resources : Monograph/item
Title/Author:	Surface characterization of semiconductor photocathode structures.
Author:	Liu, Zhi.
Description:	116 p.
Notes:	Adviser: R. F. W. Pease.
Notes:	Source: Dissertation Abstracts International, Volume: 66-01, Section: B, page: 0452.
Contained By:	Dissertation Abstracts International66-01B.
Subject:	Engineering, Electronics and Electrical.
Online resource:	http://pqdd.sinica.edu.tw/twdaoapp/servlet/advanced?query=3162342
ISBN:	0496962299

Surface characterization of semiconductor photocathode structures.
Liu, Zhi.

Surface characterization of semiconductor photocathode structures. - 116 p.

Adviser: R. F. W. Pease.

Thesis (Ph.D.)--Stanford University, 2005.

A much-improved InGaN photocathode that was activated with Cs only exhibited an energy spread of &sim;300meV FWHM and a lifetime longer than 1 week at 2 x 10-9 Torr vacuum.

ISBN: 0496962299Subjects--Topical Terms:

226981
Engineering, Electronics and Electrical.

Surface characterization of semiconductor photocathode structures.
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100 0 $a Liu, Zhi. $3 237458
245 1 0 $a Surface characterization of semiconductor photocathode structures.
300 $a 116 p.
500 $a Adviser: R. F. W. Pease.
500 $a Source: Dissertation Abstracts International, Volume: 66-01, Section: B, page: 0452.
502 $a Thesis (Ph.D.)--Stanford University, 2005.
520 # $a A much-improved InGaN photocathode that was activated with Cs only exhibited an energy spread of &sim;300meV FWHM and a lifetime longer than 1 week at 2 x 10-9 Torr vacuum.
520 # $a Achieving a clean, stoichiometric and repeatable GaAs(100) surface was the first step in this study. Based on the knowledge obtained from synchrotron radiation photoelectron spectroscopy, we successfully developed and optimized a reliable surface cleaning technique for our GaAs photocathodes.
520 # $a Energy distribution curve measurements of GaAs(100) and GaN(0001) NEA surfaces were performed under laser illumination. We found that the main contribution to the total emitted current of NEA GaAs and GaN surfaces was due to the electrons that were lost an average 140meV and 310 meV respectively in the near surface region prior to emission into vacuum. This energy loss is due not to the scattering through Cs or Cs/O layer; In GaN, it is probably due to a Gunn-like effect involving inter-valley phonon scattering within the band-bending region. We observed a highly directional emission profile from GaAs cathodes (electrons emitted within a semi-angle of 15° relative to the surface normal). In practice, it is expected that the highly directional photoemission will be characteristic of all NEA photocathodes.
520 # $a The fully activated photocathode and its decay under different vacuum conditions were investigated. The NEA activation layer is about 1 nm thick and was very vulnerable to oxygen in the system. A revised double dipole structural model was proposed to explain how the Cs/O co-deposition could produce a NEA surface. We found the chemical changes of oxygen species in the activation layer caused the initial quantum yield (QY) decay of the cathode. Further exposure to oxygen oxidized the substrate and permanently reduced the QY to zero.
520 # $a The need for a high performance photocathode in the electron beam lithography and microscopy is well established. Previous research demonstrated high brightness (1 x 108 A/cm2-sr at 3 KeV), and an energy spread as low as 50meV at room temperature for a GaAs based negative electron affinity (NEA) cathode in a sealed-off tube. However the GaAs cathodes suffer rapid decay in an open vacuum system.
590 $a School code: 0212.
650 # 0 $a Engineering, Electronics and Electrical. $3 226981
650 # 0 $a Engineering, Materials Science. $3 226940
650 # 0 $a Physics, General. $3 227017
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710 0 # $a Stanford University. $3 212607
773 0 # $g 66-01B. $t Dissertation Abstracts International
790 $a 0212
790 1 0 $a Pease, R. F. W., $e advisor
791 $a Ph.D.
792 $a 2005
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