• Refine Query
  • Source
  • Publication year
  • to
  • Language
  • No language data
  • Tagged with
  • 1
  • 1
  • 1
  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
1

Alkali metal beams from solid state electrochemical sources

Roy, Stephen Campbell January 1995 (has links)
All solid state electrochemical cells capable of producing beams of lithium, sodium and potassium in ultrahigh vacuum have been developed and investigated. The evolution of alkali metal vapour has been demonstrated by deposition of the metal on a substrate during polarisation of the cell followed by ex-situ analysis of the metal using laser ionisation mass analysis (LIMA). The electrochemistry of alkali metal evolution from these unusual solid state cells has been investigated using cyclic voltammetry, chronoamperometry and AC impedance measurements at pressures of 10−3 mbar and 10−8 mbar (UHV). It has been found for all three sources that the mechanism at relatively high pressure involves the nucleation and growth of liquid alkali metals or compounds containing alkali metals on the working electrode prior to their evaporation. In UHV the mechanism for potassium and sodium emission appears to involve the transfer of atoms directly into the gas phase whereas lithium exhibits nucleation and growth. In order to obtain a more complete characterization of the electrochemical mechanisms a spectro-electrochemical technique involving the simultaneous mass spectrometric analysis of the evolved vapour under UHV conditions along with cyclic voltammetry was developed. The formation of p-type ZnSe is essential to the fabrication of blue light emitting diodes and semiconductor lasers but has long represented a major problem in optoelectronics. This work shows that the potassium source can be used to p-dope ZnSe during growth of the material by molecular beam epitaxy (MBE). Efforts directed to the preparation of n-type diamond using a lithium source in microwave enhanced chemical vapour deposition (MWECVD) apparatus have demonstrated that the source can introduce lithium to diamond, although full semiconductor characterization of this material has yet to be made.

Page generated in 0.6732 seconds