| dc.description.abstract | This thesis reports the experimental and modeling research carried out on eld and
thermal emission from knife-edge structures. Field emission arises from electron emission
from a surface under the in
uence of intense electric elds by the process of
quantum mechanical tunneling through the potential barrier at the material-vacuum
interface. The eld emission experiments were done on the Madison Cathode Experiment
(MACX) setup with cathodes fabricated with raised vanes or knife-edges.
Measurements of emission current as a function of applied voltage, anode-cathode
spacing and temperature were recorded using an ampli er developed for these experiments
and analysis of the experimental data was done using Fowler-Nordheim theory
as well as thermal- eld emission processes. Cathode parameters such as work function
( ), eld enhancement factor ( ) and the e ective emitting area (A) are extracted for
the copper knife edge (CKE) cathodes making use of thermal and eld emission data.
The ranges of cathode parameters thus obtained are, 2.96{4.7 eV, 400{440
and A 6.3{6.66 10 7 m2. Evidence of space charge limited emission current is also
obtained for these CKE cathodes. Investigations of eld emission from lanthanum
hexaboride (LaB6) thin lms ( 300 nm) sputter deposited on these CKE cathodes
with a titanium adhesion layer on copper are also reported. These thin lms of LaB6
have a low work function ( 2:6 eV) and are expected to enhance the emission current
density from the CKE cathodes. However, the experiments obtain a lower emission
current density than bare copper and nonlinear eld emission current variations from
these LaB6 lms at elevated temperatures ( 200deg). A hypothesis based on electron
transport in the copper metal and the LaB6 thin lm is presented to explain these
observations. In conclusion, some future experiments are suggested to further investigate
eld emission from CKE cathodes as well as eld emission properties with
di ering LaB6 thickness thin lms on CKE structures. | en |
