Semiconductor CuO Research Articles

Electrodeposition of 1.4-eV-Bandgap p-Copper (II) Oxide Film With Excellent Photoactivity

A p-type semiconductor CuO film with a bandgap energy of 1.4 eV has been prepared by anodic electrodeposition in a basic aqueous solution containing copper nitrate hydrate and ammonium nitrate at 297 K, and the structural, optical, and electrical characterizations were carried out. The randomly-oriented CuO film prepared on a transparent conductive glass substrate showed electrical characteristics of a 1.26 × 103 Ω cm in resistivity, 2.11 × 1016 cm−3 in carrier concentration, and 0.234 cm2 V−1 s−1 in mobility, and a slight photocurrent generation could be observed during light irradiation. The (002)-oriented CuO film could be prepared on the (111)-oriented Au/Si wafer substrate and possessed an excellent photoactivity of a large photocurrent density and quick response compared to those for the randomly oriented CuO film.

Following Charge Separation on the Nanoscale in Cu2O–Au Nanoframe Hollow Nanoparticles

Cu(2)O-Au nanoframes with different nanolayer thicknesses of Cu(2)O were prepared, and their photocatalytic properties in aqueous solutions were studied. Cu(2)O semiconductor excitation leads to electron-hole separation. In aqueous solution, the hole is known to oxidize water to produce hydroxyl radicals whose concentration (and that of the holes) can be monitored by the rate of the degradation of dissolved methylene blue dye. The exciton lifetime is determined by femtosecond techniques and is determined by electron-hole recombination which depends on the rates of a number of competing processes such as, electron or hole transfer to an acceptor such as a gold nanoframe and/or the electron or hole trapping processes at the Cu(2)O-Au nanoframe interface. We measured the exciton lifetime as a function of the average Cu(2)O-Au layer separation. A good correlation was found between the rate of the photocatalytic degradation of methylene blue and the exciton lifetime. The exciton lifetime is found to increase as the Cu(2)O thickness is increased. This leads to an increase in the electron-hole separation time and thus an increase in the hole (and so the hydroxyl radical) concentration leading to an observed enhanced rate of the dye degradation.

Electrical behavior and Optical Properties of Copper oxide thin Films

In this work the structural, electrical and optical Properties of CuO semiconductor films had been studied, which prepared at three thickness (100, 200 and 500 nm) by spray pyrolysis method at 573K substrate temperatures on glass substrates from 0.2M CuCl2•2H2O dissolved in alcohol. Structural Properties shows that the films have only a polycrystalline CuO phase with preferential orientation in the (111) direction, the dc conductivity shows that all films have two activation energies, Ea1 (0.45-0.66 eV) and Ea2 (0.055-.0185 eV), CuO films have CBH (Correlated Barrier Hopping) mechanism for ac-conductivity. The energy gap between (1.5-1.85 eV).

Electrical behavior and Optical Properties of Copper oxide thin Films

In this work the structural, electrical and optical Properties of CuO semiconductor films had been studied, which prepared at three thickness (100, 200 and 500 nm) by spray pyrolysis method at 573K substrate temperatures on glass substrates from 0.2M CuCl2•2H2O dissolved in alcohol. Structural Properties shows that the films have only a polycrystalline CuO phase with preferential orientation in the (111) direction, the dc conductivity shows that all films have two activation energies, Ea1 (0.45-0.66 eV) and Ea2 (0.055-.0185 eV), CuO films have CBH (Correlated Barrier Hopping) mechanism for ac-conductivity. The energy gap between (1.5-1.85 eV).

Resistive switching mechanism in delafossite-transition metal oxide (CuInO2–CuO) bilayer structure

This study reports reversible and unipolar resistive switching in oxide bilayer structure due to the conversion of rectifying CuInO2–CuO semiconductor heterojunction to metal-semiconductor CuInO2–Cu Ohmic contact. High resolution transmission electron microscopy and conducting atomic force microscopy studies establish that switching occurs due to formation of conducting Cu filaments in CuO layer with CuInO2 layer remaining unaffected. The bilayer structure, with CuO layer acting as the switching element and CuInO2 layer as the resistance controlling element, exhibits improved switching parameters in comparison to single CuO layer.

Influence of silver as an additive on BaTiO 3–CuO thin film for CO 2 monitoring

Abstract Sensitivity of BaTiO 3 –CuO semiconductor thin films to carbon dioxide is analyzed in a concentration range from 500 to 10,000 ppm and at different working temperatures (between 200 and 300 °C). Impedance measurements are performed under the mentioned conditions in order to test the electrical response of BaTiO 3 –CuO samples without additives and with Ag. The results show a sensitivity enhancement both in resistance and capacitance when Ag is added. However, the response and recovery times remain unchanged in the samples with Ag.

Photoelectrochemical characteristics of cells with dyed and undyed nanoporous p-type semiconductor CuO electrodes

Abstract We prepared nanoporous p-type CuO semiconductor electrodes adsorbing various dyes with different HOMO levels and anchoring groups. Solar cells were fabricated by coupling each of the dyed electrodes with a platinum counter electrode and filled with electrolytes containing I−/I3− redox couple. Cathodic photocurrent due to hole injection from the adsorbed dye to the semiconductor was observed. Only the dyes with HOMO and LUMO potentials more positive than valence and conduction band edges, respectively, functioned as sensitizers for p-type dye-sensitized solar cells. Effects of annealing temperature and thickness of the CuO nanoporous membrane on cell performance were investigated as well.

Emergent methods to synthesize and characterize semiconductor CuO nanoparticles with various morphologies – an overview

Nanotechnology can be defined as the science and engineering involved in the design, synthesis and application of materials and devices on the nanometer scale. It is not in itself a single emerging discipline, but rather a meeting of several traditional sciences such as chemistry, physics, materials science, biology and engineering to bring together the required expertise needed to develop these new technologies. The unique properties of nanoscale materials provide benefits in remediation, pollution prevention, and efficient use of resources; however, the greatest contribution to green chemistry is likely to be the new manufacturing strategies available through nanoscience. So, the present review mainly focuses on the synthesis of semiconductor CuO nanomaterials from different starting materials by adopting various routes such as vapor-solid, vapor-liquid-solid, solid-liquid, etc. to reveal the morphological features of the precursor.

Two‐photon coherent control of dark orthoexcitons in Cu2O

AbstractWe investigate experimentally the two‐photon coherence exhibited by optically forbidden exciton states in the bulk semiconductor Cu2O. Two‐photon coherent control is achieved by using phase‐locked optical pulse pairs. Very long dephasing times and a fine energy splittings of the order of µ‐eV are observed. (© 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)

Electronic states and local structures of Cu ions in electrodeposited thin films of Cu and Cu2O from X‐ray absorption spectra

AbstractX‐ray absorption spectra near Cu K edges have been obtained for Cu and Cu2O thin films potentiostatically electrodeposited in an acetate bath. The electronic states of Cu ions and the local structures around these ions are studied using X‐ray absorption near‐edge structure (XANES) and extended X‐ray absorption fine structure (EXAFS) spectroscopy, respectively. The inner strains in micro‐size crystals of the electrodeposited Cu thin film are less than those of a commercial Cu foil. The partial electronic states of Cu ions near the Fermi level (E F) and the local structure around these ions show a systematic transformation from a Cu2O single phase (Phase I), to a Cu2O–Cu intermediate phase (Phase II) and a Cu single phase (Phase III) in thin films electrodeposited on titanium substrates for the deposition potential range of –100 to –900 mV. Phase II consists of independent Cu2O‐like and Cu‐like local structures, but not a Cu2O–Cu complex. Phase II is also characterized by a transition region from the semiconductor Cu2O to the metal Cu for the Cu electronic state having a p‐like character near the Fermi level in the oxygen O‐2p conduction band. (© 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)

Structural and Electrical Characterizations of Electrodeposited p-Type Semiconductor Cu2O Films

The p-type semiconductor cuprous oxide film has been of considerable interest as a component of solar cells and photodiodes due to its bandgap energy of and high optical absorption coefficient. We prepared films on a conductive substrate by electrodeposition at from an aqueous solution containing copper sulfate and lactic acid. The structural and electrical characterizations of the resulting films were examined by X-ray diffraction, X-ray photoelectron spectroscopy, and X-ray absorption measurements, and the Hall effect measurement, respectively. The resistivity varied from , while the carrier density was from and the mobility from , depending on the preparation conditions, i.e., solution pH and deposition potential. The carrier density was sensitive to the atomic ratio of Cu to O in the films and the mobility to the grain size.

Spontaneous Bose coherence of excitons and polaritons.

In the past decade, there has been an increasing number of experiments on spontaneous Bose coherence of excitons and polaritons. Four major areas of research are reviewed here: three-dimensional excitons in the bulk semiconductor Cu2O, two-dimensional excitons in coupled quantum wells, Coulomb drag experiments in coupled two-dimensional electron gases, and polaritons in semiconductor microcavities. The unifying theory of all these experiments is the effect of spontaneous symmetry breaking in the Bose-Einstein condensation phase transition.

Magnetic phase transitions in optical spectrum of magnetic semiconductor CuO

The absorption coefficient in the region of a wide charge-transfer band (3.19 eV) in CuO exhibits anomalously large, up to 8%, changes near two magnetic phase transition temperatures. It can be used for the optical detection of magnetic phase transitions.

New Fine Structures near the Optical Absorption Edge of CuO at Low Temperatures

By using CuO crystals prepared with the floating zone technique, we have observed for the first time an emergence of new fine structures with an energy splitting of 5.86 meV in the optical absorption spectra κ( T ,ν) near the fundamental absorption edge, E G ∼1.60 eV, below 90 K. These results are ascribable either to [1] the direct allowed n = 1 exciton transitions below 90 K at the absorption edge, or [2] the transition due to magnetically ordered localized states such as spin-canted weak ferromagnetic states with a possible splitting due to the exchange interaction E ex =5.86 meV in the hybridized Cu(3d)O(2p) valence electronic system of antiferromagnetic semiconductor CuO.

Nonequilibrium exciton kinetics in Cu2O

Abstract We have observed the energy distribution of nonthermalized excitons in the semiconductor Cu 2 O on a time scale of 10 ps following near-resonant creation by a short (5ps) laser pulse. We see a non-Maxwellian energy distribution with four discrenible hot-luminescence peaks at early times due to emission of both acoustic and optic phonons, which had previously been identified as multi-phonon Raman scattering lines. We fit the energy distribution of the excitons at all times by numerically integrating an exact Boltzmann equation. From this we deduce the deformation potential for acoustic phonon emission, which agrees with the results of hydrostatic-stress and uniaxial-stress measurements, and we deduce the rate for single optic phonon emission, which turns out to be rather slow, about 30 ps.

Effect of Cold Working and Annealing on Oxidation Rates of Copper in Dry Air at Room Temperature

Abstract The effect of plastic deformation and further annealing on the kinetics of growth of thin oxide films on copper at 30 C (86 F) has been investigated. Oxidation rate was found to decrease markedly with increasing deformation. Further annealing showed an increase in the rate, the most pronounced changes occurring during the recrystallization stage. Results are interpreted in the light of Cabrera-Mott theory of growth of very thin oxide films on metals. The change in rate has been related to the concentration of cation vacancies in the Cu2O semi-conductor, which is dependent on the lattice distortion and defect concentration of the substrate metal.