Cuprous Oxide Films Research Articles

Investigation of Thermosonic Wire Bonding Resistance of Gold Wire Onto Copper Pad

This paper discusses the electric performance for thermosonic wire bonding of gold wire onto copper pads. Various methods normally used to improve bondability were investigated including the bare copper pads with argon shielding gas and the copper pads with cupric oxide film, cuprous oxide film, and silver film. The micro-contact theory was used to determine the effective contact area. The circuit contact resistance was measured for each sample and was presented in terms of ultrasound power and effective contact area. The results show that the increase in the effective contact area leads to a lower circuit contact resistance before reaching a minimum value, and further increase in the effective contact area would not have noticeable effect on the resistance.

Amphiphilic molecule controlled synthesis of CuO nano/micro-superstructure film with hydrophilicity and superhydrophilicity surface

This paper described how we obtained cupric oxide (CuO) nano/micro superstructure film with hydrophilicity and superhydrophilicity surfaces by a controllable synthesis of amphiphilic molecule, cetyltrimethylammonium bromide (CTAB) and polyethylene glycol-6000(PEG), via a simple solution-immersion process on Cu foil at room-temperature. A series of control experiments indicated that the concentration of NaOH, the concentration and the species of the amphiphilic molecule had directly influenced the morphology and wettability of the products. Because of their novel structure and wettability, the CuO films could be a promising material for fabricating optical switches, solar cells and catalyst or could be used as a gas-sensing medium. And the wettability of the CuO films may be used in some areas.

Fabrication of cuprous and cupric oxide thin films by heat treatment

Cuprous oxide (Cu 2O) and cupric oxide (CuO) thin films were prepared by thermal oxidation of copper films coated on indium tin oxide (ITO) glass and non-alkaline glass substrates. The formation of Cu 2O and CuO was controlled by varying oxidation conditions such as, oxygen partial pressure, heat treatment temperature, and oxidation time. The microstructure, crystal direction, and optical properties of copper oxide films were measured with X-ray diffraction, atomic force microscopy, and optical spectroscopy. The results indicated that the phase-pure Cu 2O and CuO films were produced in the oxidation process. Optical transmittance and reflectance spectra of Cu 2O and CuO clearly exhibited distinct characteristics related to their phases. The electrical properties indicated that these films formed ohmic contacts with Cu and ITO electrode materials. Multilayers of Cu 2O/CuO were fabricated by choosing the oxidation sequence. The experimental results in this paper suggest that the thermal oxidation method can be employed to fabricate device quality Cu 2O and CuO films that are up to 200–300 nm thick.

무산소동의 표면부식 방지기술 적용에 관한 연구

The protection for copper tarnish was developed by surface treatment method and volatile corrosion inhibiting (VCI) technology. The performance of surface treatment and VCI material is also examined in simulated test environment. Benzotriazole (BTAH) solution that contained molybdate showed best performance than others. Usage of VCI materials with surface treatment was more effective. The protection film foamed on the surface of copper was investigated by auger electron spectroscopy (AES) and X-ray photoelectron spectroscopy (XPS). Molybdate does not participate in the formation of the protective film but promotes the passivation effect. This facilitates the stabilization of the cuprous oxide film, and strengthens the adsorption of BTAH.

Characteristics of p-Cu2O/n-Si Heterojunction Photodiode made by Rapid Thermal Oxidation

Transparent Cuprous oxide film was deposited by rapid thermal oxidation (RTO) of Cu at 500 ℃/45s condition on textured single-crystal n-Si substrate to form Cu₂O/n-Si heterojunction photodiode. The Hall effect measurements for the Cu₂O films showed a p-type conductivity. The photovoltaic and electrical properties of the junction at room temperature were investigated without any post-deposition annealing. I-V characteristics revealed that the junction has good rectifying properties. The C-V data showed abrupt junction and a built-in potential of 1 V. The photodiode showed good stability and high responsivity in the visible at three regions; 525 ㎚, 625-700 ㎚, and 750 nm denoted as regions A, B, and C, respectively.

Dc breakdown conditioning and breakdown rate of metals and metallic alloys under ultrahigh vacuum

The rf accelerating structures of the Compact Linear Collider (CLIC) require a material capable of sustaining high electric field with a low breakdown rate and low induced damage. Because of the similarity of many aspects of dc and rf breakdown, a dc breakdown study is underway at CERN in order to test candidate materials and surface preparations, and have a better understanding of the breakdown mechanism under ultrahigh vacuum in a simple setup. Conditioning speeds and breakdown fields of several metals and alloys have been measured. The average breakdown field after conditioning ranges from $100\text{ }\text{ }\mathrm{MV}/\mathrm{m}$ for Al to $850\text{ }\text{ }\mathrm{MV}/\mathrm{m}$ for stainless steel, and is around $170\text{ }\text{ }\mathrm{MV}/\mathrm{m}$ for Cu which is the present base-line material for CLIC structures. The results indicate clearly that the breakdown field is limited by the cathode. The presence of a thin cuprous oxide film at the surface of copper electrodes significantly increases the breakdown field. On the other hand, the conditioning speed of Mo is improved by removing oxides at the surface with a vacuum heat treatment, typically at $875\ifmmode^\circ\else\textdegree\fi{}\mathrm{C}$ for 2 hours. Surface finishing treatments of Cu samples only affect the very first breakdowns. More generally, surface treatments have an effect on the conditioning process itself, but not on the average breakdown field reached after the conditioning phase. In analogy to rf, the breakdown probability has been measured in dc with Cu and Mo electrodes. The dc data show similar behavior as rf as a function of the applied electric field.

Electronic structure modifications of cuprous-oxide films by ions

We have investigated irradiation effects with 100 keV Ne and N ions on optical properties and atomic structure of cuprous oxide (Cu 2O). Cu 2O films were prepared on MgO substrates at 700 °C by using a RF-magnetron-sputter deposition method. X-ray diffraction shows that the films are polycrystalline with (111) orientation and disordering by ion irradiation has been observed. The composition is found to be nearly stoichiometric before and after ion irradiation by means of Rutherford backscattering spectroscopy. Optical absorbance shows small but visible oscillations in the spectrum near the absorption edge (i.e., in the wavelength of 200 to 500 nm), and ion irradiation reduces the oscillation. Modifications of bandgap and surface morphology under ion irradiation have been described.

Investigation of molybdate–benzotriazole surface treatment against copper tarnishing

AbstractThe synergistic effect of benzotriazole (BTAH) and molybdate on the inhibition of copper tarnish was studied in this paper. The antitarnish treatment of copper was conducted with BTAH solution containing molybdate. The surface morphology observation and composition analysis were investigated by SEM with energy dispersive X‐ray (EDX) spectroscopy. The addition of molybdate improved the protection of BTAH significantly. The BTAH + molybdate treated copper specimen has higher N concentration in its surface. The structure of the protective film was studied by XPS and AES measurements. It was characterized to be a complex of Cu(I)BTA. The antitarnish effect is certified by the formation of the protective Cu(I)BTA film. Molybdate does not participate in the formation of the protective film. The presence of molybdate promotes the passivation of copper. This facilitates the stabilization of the cuprous oxide film, and strengthens the adsorption of BTAH. Copyright © 2008 John Wiley & Sons, Ltd.

Aligned 2-D Nanosheet Cu2O Film: Oriented Deposition on Cu Foil and Its Photoelectrochemical Property

Cuprous oxide (Cu2O) films on Cu foils with a two-dimensional (2-D) nanosheet structure were first synthesized by polyol method with the assistance of acetamide and copper acetate as the copper source. The characterization results show that the prepared Cu2O nanosheets which are aligned on the Cu foils are single crystal with the thickness of ∼20 nm. The addition of acetamide is crucial for the controllable synthesis of 2-D nanosheet structured Cu2O films. Without the presence of acetamide, Cu2O films with granular morphology are formed. The growth mechanism is proposed according to the experimental results. Due to the aligned 2-D structure, the properties of the optical absorption and the charge carrier transportation for the novel Cu2O films are better than that for the Cu2O films with granular morphology. So, the films with 2-D aligned nanosheets morphology outperform the granular morphology in achieving higher photoelectrocurrent efficiency under simulated solar light. It makes the 2-D nanosheet struc...

Electrochemically deposited p–n homojunction cuprous oxide solar cells

The electrical properties of both p- and n-type cuprous oxide (Cu 2O) films electrochemically deposited from two electrolyte solutions were examined by current–voltage measurements. The resistivity of p-type Cu 2O varied from 3.2×10 5 to 2.0×10 8 Ω cm, while that of n-type Cu 2O from 2.5×10 7 to 8.0×10 8 Ω cm, depending on deposition conditions such as solution pH, deposition potential and temperature. With optimized deposition conditions for minimum resistivity, p–n homojunction Cu 2O solar cells were fabricated by a two-step deposition process. The p–n homojunction Cu 2O solar cells showed a conversion efficiency of 0.1% under AM1 illumination. The low efficiency is attributed to the high resistivity of p- and n-type Cu 2O, which require doping to reduce.

Cuprous Oxide Films Prepared by Using a Microwave Atmospheric Pressure Plasma Torch

A 2.45 GHz microwave atmospheric pressure torch is employed to prepare cuprous oxide films. The sputtered copper films are firstly deposited on slide glass. After that, the films are annealed in air at 500°C for 12 h, which would directly oxidize into cupric oxide. The annealed films are then treated by atmospheric nitrogen plasma at 800 W for 10 min. The color changed significantly from black to reddish brown after nitrogen plasma treatment. The X-ray diffraction patterns show that annealed films are cupric oxide which is vanished after plasma treatment. The cuprous oxide films appeared after nitrogen plasma treatment. The resistivity of annealed films is 16.7 --cm, which reduce to 2.08 --cm after plasma treatment. The optical band gap of annealed films, cupric oxide phase, is 2.1 eV but the value shifts toward 2.4 eV after plasma treatment. The novel microwave plasma torch posses a fast and easy way to fabricate cuprous oxide films.

Characterization of cuprous oxide films prepared by post-annealing of cupric oxide using an atmospheric nitrogen pressure plasma torch

Cuprous oxide films were prepared by the post-annealing of cupric oxide using an atmospheric pressure microwave plasma torch. Metallic copper films were deposited on glass substrate by magnetron sputtering. Then the films were annealed in air at 500 °C for 12 h, and the formation of cupric oxide observed. The annealed films were further treated by nitrogen plasma at a power of 800 W for 10 and 20 min. The color of the film clearly changed from black to reddish brown over 10 min. X-ray diffraction patterns show that the annealed films were cupric oxide and included cuprous oxide diffraction peaks observed aftert 10 min in nitrogen plasma. The resistivity of annealed films was 16.7 Ω cm, and was reduced markedly to about one order of magnitude under nitrogen plasma. Annealing in air and nitrogen plasma treating shifted the optical band gap from 2.1 eV to 2.4 eV. The relationship between the microstructure and plasma content of the films and their properties is investigated.

Effect of sputtering power on the physical properties of dc magnetron sputtered copper oxide thin films

Cuprous oxide films were deposited on glass substrates using dc magnetron sputtering technique by sputtering of pure copper target in a mixture of argon and oxygen atmosphere under various sputtering powers in the range 0.38–1.50 W cm −2. The influence of sputtering power on the structural, electrical and optical properties was systematically studied. The films were polycrystalline in nature with cubic structure. The films formed at sputtering powers ≤0.76 W cm −2 exhibited mixed phase of Cu 2O and CuO while those formed at 1.08 W cm −2 were single phase Cu 2O. The single-phase Cu 2O films formed at a sputtering power of 1.08 W cm −2 showed electrical resistivity of 46 Ω cm, Hall mobility of 5.7 cm 2 V −1 s −1 and optical band gap of 2.04 eV.

Ferromagnetism in 57Fe‐doped cupric oxide

AbstractFerromagnetic properties were observed at room temperature for 57Fe‐doped cupric oxide (CuO) film and powder samples. Mössbauer spectroscopy measurements on the Fe0.02Cu0.98O samples revealed that the octahedral Cu2+ sites are mostly substituted by Fe3+ ions. Both ferromagnetic and paramagnetic Fe3+ signals were detected. The Fe0.02Cu0.98O samples were found to be ferromagnetic even above the Néel temperature of CuO. A carrier localized around oxygen vacancy can mediate a ferromagnetic coupling among neighboring Fe3+ ions. Additional Li doping into Fe0.02Cu0.98O resulted in an increase of the ferromagnetic strength. Unpaired s1 electron in interstitial Li atom is likely to mediate a ferromagnetic coupling between neighboring spins. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)

Conditions and Mechanism for the Anodic Deposition of Cupric Oxide Films in Slightly Acidic Aqueous Media

An electrodeposition condition to anodically prepare CuO films using slightly acidic solutions of copper acetate (pH 5.5–6.4) is established. The plating solution and solutions with related compositions were investigated using cyclic and linear sweep voltammetry to elucidate the deposition mechanism. The key oxidation reaction that provides for CuO deposition appears to be the oxidation of Cu(II) ions to a Cu(III) species, which subsequently oxidizes water while being reduced to CuO. The solution pH appeared to be critical for these reactions as CuO forms only in solutions with pHs higher than 5.5. The use of acetate ions made it possible to elevate solution pHs to a proper range without chemically precipitating before the initiation of electro- deposition. The resulting films are translucent black and possess smooth surfaces on the microlevel. The as-deposited films are highly crystalline and showed well-defined optical and p-type photoelectrochemical properties that do not improve upon annealing at 300 and . The bandgap and flatband potential are estimated to be and in a solution , respectively.

Chemically deposited electrochromic cuprous oxide films for solar light modulation

Thin cuprous oxide electrochromic films on the transparent conductive electrodes were prepared by chemical electroless method. The films cycled in K +-based electrolyte revealed typical red-ox peaks with higher intensity compared to those in the Li + and the Na +-based electrolytes. The durability of the cuprous oxide due to cycling into LiClO 4 was about 60 cycles. The thermal treatment of the films invoked decrease in red-ox peak intensity, and thus deterioration in the electrochromic properties. The response time of the coloration and bleaching to an abrupt voltage change from −4.5 to +4.5 V and reverse was found to be in the range of about 10 s. The maximum light intensity modulation ability of the films, as the AM1.5 spectrum is taken for an input, was calculated to be about 65%.

Electrochromism of the electroless deposited cuprous oxide films

Thin cuprous oxide films were prepared by a low cost, chemical deposition (electroless) method onto glass substrates pre-coated with fluorine doped tin oxide. The X-ray diffraction pattern confirmed the Cu 2O composition of the films. Visible transmittance spectra of the cuprous oxide films were studied for the as-prepared, colored and bleached films. The cyclic voltammetry study showed that those films exhibited cathode coloring electrochromism, i.e. the films showed change of color from yellowish to black upon application of an electric field. The transmittance across the films for laser light of 670 nm was found to change due to the voltage change for about 50%. The coloration memory of those films was also studied during 6 h, ex-situ. The coloration efficiency at 670 nm was calculated to be 37 cm 2/C.

Innovative wire bonding method using a chemically reacted thin layer for chips with copper interconnects

This paper presents a novel method in which an oxide film is used to facilitate the thermosonic wire bonding of gold wire onto copper pads. A cuprous oxide film is generated by controlling the pH values of the chemical solution. Compared to cupric oxide films, the cuprous oxide film is denser and more brittle and therefore facilitates the bonding process without the need for the elaborate procedures and equipment required by more conventional wire bonding methods.

Mechanisms of carrier generation and transport in Ni-doped Cu 2O

The density and mobility of hole carriers in Ni-doped and undoped cuprous oxide (Cu 2O) films prepared by pulsed laser deposition (PLD) from Ni-doped and undoped CuO targets, respectively, were measured in order to examine the mechanisms of carrier generation and transport in doped films. The temperature dependence of the carrier density of the films revealed that regardless of the Ni content, the activation energies of the acceptor level of the films are 0.22–0.25 eV. The temperature dependence of the mobility of the films changed from −0.58 to ∼0 by doping with Ni. These results evidenced that hole carriers in Ni-doped Cu 2O as well as in undoped Cu 2O were generated by Cu vacancies and were primarily scattered by neutral impurity scattering centers. X-ray diffraction (XRD) measurements of the films showed that the mass fraction of Cu 2O in the films decreased with increasing Ni content, while that of CuO increased. It was also found that the reduction process of CuO to Cu 2O was suppressed by the Ni doping.

Influence of substrate bias voltage on the properties of magnetron sputtered Cu 2O films

Thin films of cuprous oxide (Cu 2O) were deposited on glass substrates at various bias voltages using DC reactive magnetron sputtering technique. The effects of substrate bias voltage on structural, electrical and optical properties were systematically analyzed. The crystallographic structure and orientation of the crystallites were strongly influenced by the bias voltage.