Materials Research Papers: Prof. Glenn H. Chapman
This page contains the paper abstract and full PDF versions of publications
on materials research (Pentenary Semiconductors, CdS) which are not connected
to other projects (see also inorganic thermal
resist papers). Papers in this section are connected to my PhD research
in I(b)-III-V(2) pentenary semiconductors. This work is not part
of my current research. Click on the link to download pdf version.
Papers her are listed in order of publication
Refereed Journal Papers
J.J. Loferski, G.H. Chapman, J. Shewchun, S.D. Mittleman,
E.A. De Meo, R. Arnott, H. L. Hwang, and R. Beaulieu, "Cathodoluminescence
Characteristics of Cu(x)S Films Produced By Different Methods", Solar Energy
Materials, 1, 1, 157- (1979). sem79CdS.pdf
This paper shows how the cathodoluminescence (CL) spectrum of chalcocite
(Cu(2.00)S) films like those in Cu-Cd-S solar cells can be used to
develop information about the opto–electronic properties of the material.
Comparison of the CL spectra of bulk polycrystalline samples known to be
chalcocite with those of thin films produced by sulfurizing thin films
of copper and of thin films produced by the chemical substitution processes
commonly used to fabricate Cu – Cd-S cells, leads to the conclusion that
the CL spectra of the latter may be affected by the presence of Cd as a
dopant. This hypothesis was tested by observing the CL spectra of chalcocite
samples which were doped with various amounts of cadmium. Comparison of
these CL spectra suggest that chalcocite films derived from CdS contain
0.25 and 1.0 wt% Cd. The CL spectra of chalcocite films produced by dipping
CdS crystals into aqueous solutions of cuprous chloride exhibit an ”ageing”
process whose cause has not been identified. Cathodoluminescence was also
observed from thin film and sintered samples containing a tetragonal phase
(not djurleite) having an approximate composition Cu(1.96)S.
G.H. Chapman, J.J. Loferski, J. Shewchun, R. Beaulieu,
and B.K. Garside, "Cu(1-y) Ag(y) In S(2(1-x)) Se(2x) as a Prototype of
the Pentenary Chalcopyrite Semiconductor System for Solar Photovoltaic
Cells", Solar Energy Materials, 1, 2, 451-469 (1979). sem79.pdf
Group III–V mixed alloy quarternary semiconductors, such as Ga(1-y)In(y)As(1-x)P(x),
have been extensively employed in lattice matching different semiconductor
layers (at specified bandgaps) to form heterojunction electro–optical devices.
The feasibility of employing the analogous pentenary alloys, consisting
of the ternary chalcopyrites groups I–III–VI(2), and II–IV–V(2), are being
reported. As a prototype of such alloys, samples of the pentenary Cu(1-y)Ag(y)InS(2(1-x))Se(2x),
have been synthesized and studied. These were prepared by reacting stoichiometric
powder mixtures at about 900C. X-ray diffractometry tests suggest the compounds
maintain complete solid solubility throughout the system in a chalcopyrite
type crystal structure, The alloy’s intrinsic conductivity type appears
to tend towards n-type for silver and sulfer rich compounds, while forming
p-type for copper and selenium rich materials. Using cathodoluminescence
spectra the sample’s bandgap energies were estimated at 300 and 77 K. These
indicate that all the alloys synthesized were direct bandgap semiconductors.
Using least square fits on the data, topological maps of the bandgap and
lattice constants versus composition have been produced.
J. Shewchun, G.H. Chapman, J.J. Loferski, R. Beaulieu,
and B.K. Garside, "The A1(1-y) B1y C3 D6(2x) E62(1-x) Pentenary Alloy Systems
and Its Application to Photovoltaic Solar Energy Conversion", Jour. Appl.
Phys., 50, 6978 (1979). jap79.pdf
This paper reports work on pentenary alloy systems similar to the quarternary
In(1-x)Ga(x)P(1-y)As(y). Such A<I>(1-y)B<I>(y)C<III>D<VI>(2x)E<VI>(2(1-x))
alloys are mixtures of ternary chalcopyrites of the I-III-VI(2) and II-IV-V(2)
variety. These materials are of interest because their use can improve
the performance of heterojunction electr-optic devices such as solar cells.
This improvement arises because the pentenaries can permit different semiconductor
layers to be deposited upon each other such that they are lattice and crystallographically
matched, but at the same time have independently adjustable bandgaps. More
specifically, we have focused on the Cu(1-y)Ag(y)InS(2(1-x))Se(2x) system
which appears to have the best potential of all the possible systems for
solar energy applications. Samples were prepared by reacting stoichiometric
powder mixtures at about 900C. X-ray diffractometry indicated complete
solid solubility over the whole compositional range. Cathodoluminescence
was used to determine band gaps at 300 and 77K and the spectra indicate
that all alloys are direct-band- gap semiconductors. Isolattice constant
and band-gap contour maps for the system have been obtained.
G.H. Chapman, J. Shewchun, J.J. Loferski, B.K.
Garside, and R. Beaulieu, "Lattice Constants and Band-Gap Variations of
the Pentenary Semiconductor Systems Cu(1-y) Ag(y) In S(2(1-x)) Se(2x)",
Applied Phys. Lett., 34, 11, 735- 737 (1979). apl79.pdf
Much interest has been expressed in the ternary I<B>-III-VI(2),
group semiconductors for use in electro-optical devices such as solar cells.
Subsets of these, AgInS(2),AgInSe(2),CuInS(2) and CuInSe(2) have been combined
to form the pentenary alloy system Cu(1-y)Ag(y)InS(2(1-x))Se(2x). With
such an alloy the band gap may be varied while keeping the lattice constant
fixed. Samples were prepared by reacting stoichiometric powder mixtures
at about 900C. X-ray diffractometry tests suggest the alloys maintained
complete solid solubility throughout the system in a chalcopyrite- type
crystal structure. From cathodoluminescence studies on pressed bars of
these powders the band-gap energies were estimated at 300K. These tests
suggest that the alloys are all direct- band-gap semiconductors.
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