Emergence of a terawatt scalable photovoltaic (PV) thin film technology is currently impeded by
the limited supply of relatively rare elements like In or Te, which has spurred active research in
recent years on earth-abundant PV materials. Instead of searching for alternative PV materials,
we approach the problem here by...
The thermal conductivity, measured by the 3ω method, of amorphous films of Al₂P₁.₂O₆ (AlPO) deposited on Si substrates by an all-aqueous spin-coating technique is 0.93(3) Wm⁻¹K⁻¹. The thermal conductivity of a degenerately doped n-Si substrate is 85(5) Wm⁻¹K⁻¹ and of a more lightly doped p-Si substrate is 139(7) Wm⁻¹K⁻¹. The...
In situ photoemission spectroscopy experiments are used to characterize the interface between ZnTe and the wide band gap p-type semiconductor BaCuSeF. The contact is characterized by a null valence-band offset, a large conduction-band offset, and a chemically graded interface. By applying the transitivity rule for band offset and on the...
BaCuChF (Ch=S,Se,Te) surfaces and BaCuSeF interfaces with zinc phthalocyanine (ZnPc) were studied by photoelectron spectroscopy. BaCuChF compounds oxidize when exposed to ambient atmosphere. Se capping layers were studied as a means to produce representative surfaces for photoelectron spectroscopic measurements. Decapped BaCuSeF surfaces remain O-free and C-free when the Se layer...
The origin of high hole conduction in BaCuQF (Q=S,Se) was investigated by photoemission
measurements and full-potential linearized augmented plane wave band-structure calculations. In
both compounds, the large dispersion near the top of the valence band is realized by admixed states
of Cu 3d and S 3p or Se 4p orbitals,...
CuCr₁₋ₓMgₓO₂, a wide band gap semiconductor with the delafossite structure, has been synthesized
in bulk and thin-film form. Bulk undoped CuCrO₂ is almost black and has moderate conductivity
with p-type carriers. Upon doping with 5% Mg, the conductivity increases by a factor of 1000. In
films, the best p-type conductivity...
Transport and structural properties of Mg-doped and O-intercalated sintered powders and
polycrystalline films of CuSc₁₋ₓMgₓO[subscript 2+y] are reported. Substitution of Mg for Sc systematically
increases the p-type conductivity in CuSc₁₋ₓMgₓO₂ sintered powders, producing a maximum
conductivity of 0.015 S/cm at x≈0.06. A similar level of conductivity is observed in transparent...
Transparent p – i – n heterojunction diodes are fabricated using heavily doped, p-type CuYO₂ and
semi-insulating i-ZnO thin films deposited onto a glass substrate coated with n-type indium tin
oxide. Rectification is observed, with a ratio of forward-to-reverse current as high as 60 in the range
−4–4 V. The...
Native point defects, defect complexes, and oxygen impurities in BaCuChF were studied using density
functional theory calculations, self-consistent thermodynamic simulations, and various experimental techniques.
Unintentional p-type conductivity in BaCuChF is explained by the presence of copper vacancies with
transition levels in the valence band. These acceptor-like defects are partially compensated...
Double excitonic absorption peaks are observed in textured BaCuSF and BaCuSeF thin films. The excitonic doublet separation increases with increasing fraction of heavy chalcogen in the thin-film solid solutions, in good agreement with the spin-orbit splitting of the valence bands calculated by density-functional theory. In BaCuSF and BaCuSeF, the excitons...
We report measurements of the structural, optical, transport, and magnetic properties of single crystals of the
anisotropic p-type transparent semiconductor CuAlO₂. The indirect and direct band gaps are 2.97 and 3.47 eV,
respectively. Temperature-dependent Hall measurements yield a positive Hall coefficient in the measured range
and an activated carrier temperature...
We have investigated a second-order phase transition of the vortex lattice in thin-film Nd₁.₈₅Ce₀.₁₅CuO[subscript 4-y] from 1 mT to 1 T applied magnetic fields. The dc resistivity-current density data for each field exhibit critical scaling consistent with a second-order vortex-liquid to vortex-solid phase transition. The high-field data support the vortex-glass...
We have measured voltage-current characteristics for YBa₂Cu₃O₇ thin films in magnetic fields from 5
T to ambient, including some in the millitesla range. In all cases, the resistivity —current density isotherms
can be separated into two classes: those which exhibit upward curvature, and have constant
resistivity at low currents, and...
We have measured sweep-rate-dependent magnetization hysteresis curves of thin-film Bi₂Sr₂CaCu₂O[subscript 8+δ] using a Hall probe magnetometer in an unconventional geometry. We find a structure in the response well below the three-dimensional to two-dimensional crossover field. The observed strong enhancement of the perpendicular field component’s creep rate in the presence of...
We have investigated the depinning process of magnetic flux vortices in twinned crystals of YBa₂Cu₃O₇₋δ in intermediate applied magnetic fields parallel to the crystallographic c axis through precise resistivity measurements before and after fast-neutron irradiation. Of particular interest for each field is the power-law dependence of the electric field on...
SnS is a potential earth-abundant photovoltaic (PV) material. Employing both theory and experiment to assess the PV relevant properties of SnS, we clarify on whether SnS has an indirect or direct band gap and what is the minority carrier effective mass as a function of the film orientation. SnS has...
The electronic structure of the oxychalcogenides LaCuOSe and BiCuOSe has been studied using O K-edge x-ray emission spectroscopy, x-ray absorption spectroscopy, and density functional theory, in order to examine the effects of the M³⁺ ion configurations. The known distortion of the BiO layers in BiCuOSe compared to the LaO layers...
Transparent films of CuScO₂₊ₓ have been prepared which show p-type electrical conductivity. The temperature dependence of the conductivity indicates semiconducting behavior with an apparent room temperature activation energy of 0.11 eV. The highest room temperature conductivity observed was 30 S cm⁻1. Films 110 nm thick show 40% transparency in most...
We demonstrate color shifting from the yellow to the red in the electroluminescence from (ZnGa)S:Mn films. We observe threshold voltages down to about 35 V, extremely low for such devices. We discuss the materials characteristics of the phosphor films, and the potential for improvement of the luminous intensity of the...
High electron mobility thin films of In₂₋ₓWₓO₃₊y(0≤x≤0.075) were prepared on amorphous SiO₂ and single-crystal yttria-stablized zirconia (001) substrates by pulsed laser deposition. Mobilities ranged between 66 and 112 cm² /Vs depending on the substrate type and deposition conditions, and the highest mobility was observed at a W-dopant concentration of x~0.03....
Radioactive In has been incorporated into oriented thin films of YBa₂Cu₃O₇₋δ during a thermal coevaporation process. The hyperfme technique of perturbed γγ-angular correlation spectroscopy shows that 60% of the indium substitutes at a single site in the superconductor. We obtain spectra with reasonable statistics from 2 mCi of starting material,...
BaCuQF (Q=S,Se) materials, candidate transparent p-type conductors, were prepared by solid-state reaction, and their bulk electrical and optical properties were evaluated. The room-temperature Seebeck coefficient and electrical conductivity of undoped BaCuQF pellets were +56 μV/K and 0.088 S/cm, respectively, for the sulfide fluoride, and +32 μV/K and 0.061 S/cm, respectively,...